# SCM Minimax S45 Bandsaw Teardown & Overhaul



## Sideways (16 Jan 2022)

This thread is to share a (hopefully quick) overhaul of a secondhand Minimax S45 bandsaw in real time.
I'm working on this with my buddy Deema and our aim for the saw is to give it a good clean, a thorough mechanical overhaul and ensure the electrics are safe and robust.

We both share the view that the Minimax bandsaws are a quality tool. Simple and robust.
The S45 is the smallest in this range.
Minimax were founded in the 70's and offered innovative machines aimed at advanced amateurs and small professionals. They have been very successful from the early days and since 1986 as part of SCM.

Here are a bunch of images of this used saw as we were getting started. Maybe Deema will be able to chip in a full length shot but I was more interested in recording details for reassembly....

The saw has a stong frame






Plenty of paint, resin and sawdust coating the machine




but trunnions are very solid




and dust extraction is concentrated where it will do most good - as the blade enters the lower wheel case



.
Love the improvised brush 

Solid cast band wheels





And simple substantial guides


----------



## Sideways (16 Jan 2022)

We stripped the machine down to the frame and put in the hours to clean it. Under the dirt, the paintwork is in very good condition overall. It's a quality white enamel so it would be a waste to strip it and repaint. The top left corner of the saw has however taken a knock at some point and the upper door has a dent. It's fully functional still so we will have to decide whether this is acceptable or if we can improve it.
All bearings will be replaced. The wheels have been pulled off and the motor disassembled so that we can identify the bearings and order replacements. New belt will be fitted. Everything cleaned, reassembled and adjusted.
Here is the inside of the motor. It's in excellent condition.




The front bearing where the spindle is loaded : some wear can just be felt compared to the rear bearing which always lasts longer in normal use but it has a lot of life left. We'll replace both as routine.
Originals were good branded NSK bearings. The replacements will be SKF from choice but NSK, FAG, and the other big name brands are all safe choices.
The rotor is nicely made and you can see the balancing. The rotor is cast with projections front and back. Washers are placed over these to add weight where it is needed and the stems swaged over to keep them permanantly in place. Like car wheel balancing but these are never intended to come off.




The spindle looks brown but this is just rust, resin and sawdust. Easily cleaned before the new bearings are fitted.

Here is the frame of the saw after cleaning and with the doors popped back on for safekeeping


----------



## deema (16 Jan 2022)

The paint used on these saws is IMO excellent, the reason for starting off with this statement is because the saw looks rather sorry for itself. However, we know what a few hours work can do, and this saw will look great again without a repaint. So, this is the saw in it’s as purchased spleder.








The ‘trick’ of cleaning tge paint is finding solvents to remove the black permanent marker and sprayed on red identifier as well as any over sprayed paint without stripping the original paint. the SCM paint is very robust, and makes it relatively easy to remove the ‘graffit’.


----------



## deema (16 Jan 2022)

Whilst Sideways took the saw apart, every nut and bolt removed, I was busy taking the motor apart. The fan is usually the most tricky bit to remove. It’s incredibly easy to break them, and they must be intact to correctly cool the motor. We usuallt gently warm up just the centre of the plastic fan to make it ever so slightly soft and to expand the plastic. A little gently plying usually gets them off. You can source new fans when occasionally they don’t want to play.

A puller is needed to remove the pulley after first extracting tge locking grub screw.










I mark the front and rear motor caps and their respective locations on the motor housing using a centre punch. This is to ensure I put them back together in the exact same orientation and alignment.








The motor bearings will be replaced with new SKF bearings and the whole thing will be cleaned. The paint is in excelkent condition, nothing a bit of elbow grease won’t sort out. Hopefully the bearings will arrive quickly, I have some others that should have been on next day delivery that I’m still waiting for over a week later.


----------



## Ttrees (16 Jan 2022)

@Sideways and @deema
Love looking at the details which you folks put into your threads.
A question if I may, as I haven't got a good look at the wheels of a Centauro to see if the bore of the wheels was non shouldered, like on my machine.
I have to make a new spacer for mine, and was wondering if the s45 has the same setup as this, as in 
Whether the spacer is made of plastic or metal, if it's as deep, 
if it fits snugly on the shaft, and if it's the thickness is matching the inner race.

Thanks
Tom


----------



## deema (16 Jan 2022)

Hi Ttrees, the S45 doest have a spacer, it uses two circlips to act as hard stops for the two bearings in each wheel hub,
Here is the schematic


----------



## deema (16 Jan 2022)

The tyres on this saw look virtually brand new, it’s been sat for a long time without being used as the belt was literally triangular having taken a set. A new A37 best us now in order. The A signifies the belt section, which is 13mm wide and 8mm deep, it’s a v section.

The pictures are all from the ’original’ condition. It’s only by completely disassembling the saw can you verify the condition of everything, make sure everything is working properly so that you can set it back up correctly to ‘as new’ condition. Clearly there is going to be some ‘patina‘ from it being use.

Bottom driven wheel.




Top wheel.


----------



## Sideways (16 Jan 2022)

I snapped these as the wheels sat on the floor after removal.
Both were pulled forwards off their shafts with a a three legged puller.
The rims have been part drilled to remove weight as required to balance them.
One photo is down into the hub of (possibly) the top wheel. You can see the two circlips and the ball bearing at the bottom
One photo shows the spindle of the lower wheel with a bearing remaining after the wheel was pulled off.
Last shot is the belt code ...


----------



## Ollie78 (17 Jan 2022)

Looks like a good one.


----------



## ndbrown (17 Jan 2022)

My first bandsaw was a Minimax S45, a truly excellent machine. The earlier white machines had a 250mm depth of cut (my one), later ones had 300mm before they went to the MK2 current shape. These are at the lighter end of industrial so they are really at the heavy end of hobby. Often go for a lot less than they are worth as they are overlooked by the hobbiest in favour of the much lighter build Startrite range. Agree, the epoxy powder coated paint is extremely durable. All the bandsaw most hobbiest will ever need in a fairly compact footprint. Hugely rigid frame for its size.
Nigel


----------



## mindthatwhatouch (17 Jan 2022)

What perfect timing, watching with interest.

I lucked out on one a few years ago (really cheap) that had motor issues. A little time with some wire and a soldering iron fixed that, and I've been using it since. 
I've finally got round to trying to clean it up a bit and improve the dust collection and guides. Unlike yours, on mine the factory fitted dust extraction is at the base of the cabinet which really does nothing other than catch a bit of dust. The previous owner has added a port near the top which is better but still feel I can improve it further. Really like to change the guides for rollers. particularly the lower one which has cool blocks type of holder, still has the pieces of wood that the last owner fitted!

Not convinced the brush is improvised, mine is identical.


----------



## Sideways (17 Jan 2022)

Some less dramatic progress today.

First the door interlock. This little hinged section sits between the top and bottom doors. It overlaps tabs on both and has a tongue that goes into a locking solenoid. This is wired up so that the saw won't run with the the doors to the bandsaw wheels open.





A wire brush in the drill press it good for removing surface rust and grime from components, so several pieces have been brushed, subjected to diesel and scotchbrite to loosen resin, etc.
Here are the trunnion castings after a good clean.








And fitted




















It is very easy to disassemble a "Kipp" or Bristol locking lever handle, so they get opened up and the sawdust removed with a fine wire brush


----------



## Sideways (17 Jan 2022)

The lower guide set is badly encrusted in resin. This has had a partial clean but I'm going to try CMT Orange spray on it.














The upper guide wasn't so crusty so that has already come up very nicely
I'm deliberately showing several views so that you can see how these are put together, mounted, easily dismantled and adjusted.











In the image below, we are looking vertically downward between the side guides. You can see how the outer part of the rear guide's face will stop the back of the blade from moving rearward.




With flash off the gap between the blade guides is more obvious. The guides are set just a paper thickness from the side of the blade when it use. We'll set these up once the saw is reassembled with a blade.


----------



## Sideways (17 Jan 2022)

Last parts to show today are parts of the rack + upper blade guard. I'm loosely assembling these on the bench as they are cleaned.
The rack is in perfect condition and has been left bolted to the support tube.
The two adjacent parts bolt to it and are part of the upper blade guard. See the slot where the blade slides in.
Two pairs of holes are lined up, this is how these components are bolted together. The smaller of the sliding pieces remains inside the upper band wheel box at all times. The rack and blade guard wind down when cutting thinner stock
This view is from the side as if I were are the spine of the saw looking out at the blade





Here the same pieces with the blade guides added and seen from operators position





The rack is wound up and down by a pinion. This is screwed onto the knob spindle and locked with a grubscrew.















All for now. Time to go soak those lower guides overnight ...


----------



## FlatlandsF7a (18 Jan 2022)

mindthatwhatouch said:


> What perfect timing, watching with interest.
> 
> I lucked out on one a few years ago (really cheap) that had motor issues. A little time with some wire and a soldering iron fixed that, and I've been using it since.
> I've finally got round to trying to clean it up a bit and improve the dust collection and guides. Unlike yours, on mine the factory fitted dust extraction is at the base of the cabinet which really does nothing other than catch a bit of dust. The previous owner has added a port near the top which is better but still feel I can improve it further. Really like to change the guides for rollers. particularly the lower one which has cool blocks type of holder, still has the pieces of wood that the last owner fitted!
> ...



Perfect for me too, very interested to see this thread develop. Just to second that it would be great to see clear details of the lower guides, as mine are also the 'cool block' and single rear thrust bearing version (yellow S45, Pre 1995 is all I know, as it has a dealer sticker phone number without the extra '1' in the number!), and I'd be intersted to upgrade if that would be worthwhile (although I'm not sure there's space.

Also to confirm that my brush is identical as well, so definitely not improvised. My dust collection port is in the ideal location though, and a wee bit of plywood makes the extraction excellent, except for large blade rip cuts where the grid can get clogged.


----------



## Hornbeam (18 Jan 2022)

The GL456 guides work really well and are very simple to set up. N=My only issue is that you cant buy just the wear parts but have to buy the guide sub assembly


----------



## Ttrees (18 Jan 2022)

Could make your own if you felt the replacement shaft and rollers were too costly.





Centauro Classico Band Saw


I'm debating the purchase of a 24" Centauro Classico industrial band saw. Don't know anything about the brand but it's a solid looking machine. All I have been able to find on the net is it's made in Italy. No reviews of any kind. Any guidance will be appreciated. Thanks, Steve




www.ncwoodworker.net


----------



## Sideways (18 Jan 2022)

Interesting thread there Ttrees, thanks.
The lower guide here is really well gummed up. CMT orange didn't do a lot to unglue it, not really any better than diesel. It may be cellulose thinners next at this rate.
Nevertheless, the guides I can get hold of are very little worn on this saw. No slop. A little axial movement. I can't pull them apart by hand though Deema says the similar looking ones on his Felder bandsaw do dismantle.
You can clearly see the bronze bush looking at the join between barrel and disc


----------



## FlatlandsF7a (19 Jan 2022)

Sideways said:


> Interesting thread there Ttrees, thanks.
> The lower guide here is really well gummed up. CMT orange didn't do a lot to unglue it, not really any better than diesel. It may be cellulose thinners next at this rate.
> Nevertheless, the guides I can get hold of are very little worn on this saw. No slop. A little axial movement. I can't pull them apart by hand though Deema says the similar looking ones on his Felder bandsaw do dismantle.
> You can clearly see the bronze bush looking at the join between barrel and disc
> View attachment 127330



Do you happen to have a figure for the clearance below the table for the lower guides on your machine? 

Mine (the cool-block type) seem to be pretty squeezed in, so I wonder if the clearance below the table and above the machine frame is the same. My upper side guides feel pretty chunky, and it would be a challenge to squeeze them in under the table I think!


----------



## Sideways (19 Jan 2022)

It was a little tricky to maneouver the lower guides out after unbolting them.
When I reassemble, i'll take you some photos with a rule in the frame so we can see the clearances.


----------



## Sideways (21 Jan 2022)

Clean up continued today.

Acetone and a wire brush eventually dissolved the resin and got the lower guides apart.





It helps to unbolt the two barrels from the carrier.




When you reassemble, the thumbscrew with a flattened end is used to clamp the rear guide as this may need adjusting more often. A capscrew with a coned tip is used to secure the mounting bar which has a V groove to match and prevent rotation.









The discs do indeed pull out of the plain bearings (probably oilite) once they're no longer gummed up with sawdust and resin.

When bolting the barrels back onto the frame, gently wind in the side guides until they touch and hold these square while you tighten up the capscrews. If you don't do this, it's possible for the guides to twist while you tighten up the bolts.






The band wheels after wire brush to remove the sawdust. Good condition. Tyres still sound. Need just a few minutes with some scotchbrite and metalguard to remove the fine rust from the machined surfaces.









Plated metalwork was cleaned with a brush, acetone as needed, and wiped over with metalguard for some extra protection. These parts are the fence, bracket and the support for the upped band wheel which is adjustable for tilt and height (tension).


----------



## Sideways (21 Jan 2022)

The table was also cleaned.
First scrape with a blade to remove resin, paint and rust, then medium or fine scotchbrite lubricated with wd40.









Our preference is to do as little as possible to machine tables. We are not looking to interfere with flatness. A couple of rounds was enough, the first wipe down showed the stubborn rust spots and rings that needed some more attention.










After cleaning, seal the surface with metalguard which must be left to evaporate off,










then polish and do the same with machine wax. Any will do, but the liberon version contains anti rust additives and buffs to a nice hard, low friction finish after it has been left to dry.


----------



## deema (26 Jan 2022)

A quick shot of the underside of the table. These are good thick tables, and are nicely ribbed. SCM take the time to actual paint the underside properly. The mating surfaces to the quadrants for tilting the table are machines surfaces.


----------



## deema (26 Jan 2022)

The top wheel assembly is simple and rugged for what it does. There are two steel channels, made from very decent wall thickness steel that are held together by a rod that is secured by a circlip on either end. The shaft for the upper wheel is bolted to this arrangement.





The two wheels are cast iron, and carry a flat tyre, rather than a crowned tyre. There are two bearings separated by a circlip at the back of each bearing. The bearings are pressed into the wheel hubs initially before being pressed into the shafts. This is one job where I believe it’s necessary to have a proper press, rather than ‘tapping’ the bearings onto the shafts.







The lower wheel sits on a shaft that needs to be removed for both pressing it back into the wheel, and also when ever the belt is changed. This is the only part of the design I don’t like. The hub is pulled back into the body of the saw by a bolt and large washer. The shaft and hence the wheels alignment is made by adjusting 4 bolts around the circumference of the shaft at the 12, 3, 6 and 9 o’clock positions. To remove the shaft the easiest way is to take off the pull back bolt, and then mark the shaft orientation with respect to the 4 alignment bolts. I centre punched it at 12 oclock, I then slacken two of the 4 adjuster bolts. I do this so that when I put it back the chancers are by realigning the shaft and tightening up the two bolts it will need almost no adjustmen.
Shaft and pull back bolt / washer.




The aligning bolts




The inside where the lower shaft comes through




Pressing the lower shaft back into the wheel




Lower wheel put back, note, you have to fit the belt at this stage.




Motor just poked back in and the belt out on both pulleys.


----------



## deema (26 Jan 2022)

The lower wheel hub back showing the aligning bolts tightened back up.




The wheels are retained on the shaft by a M6 cap head screw and washer. We tend to chase most threads to be sure that they arnt full of foreign bodies.


----------



## deema (26 Jan 2022)

The blade guide assembly is again a well made unit. First of all the raise and lower gear is put back in. This is threaded and also (bad design) retained by a grub screw that impacts the threads. I ran a die down the M12 threads to allow the cig to run back on smoothly. 



An angle plate is bolted next to the guide, which has a spring that acts on a stud to push the guide hard against one side.




The blade guards bolt on next. They are held by two fiddly cal head screws. You can’t fit this with the upper wheel installed…..ask me how I know!


----------



## Jitter (26 Jan 2022)

What a superb overall on the SCM you are both doing. Thanks both Deema and Sideways for such great work and detailed information about this bandsaw. I can’t thank you enough!

I am going to do your cast top cleaning methods on the Wadkin UOS, some great advice there and great pictures to show how it transforms.

A question I have-
Do you recommend releasing tension on the blade when it is not in use? (for this particular machine) 

As a newbie to bandsaws and most other workshop machines, my questions will most likely be boring to the many knowledgeable people on the forum. I apologise in advance


----------



## Ttrees (26 Jan 2022)

deema said:


> View attachment 127981


@deema 
This is a most fascinating thread to see the in's and out's of a Centauro machine.
I've been looking into various designs of non shoudered bores in the last few weeks, and very thankful I can see an alternative way of doing things, should things not go to plan.

Could you tell me if that big skookum boss has some relief machined into it, so it only makes contact with the inner race, or if it's machined with a perfectly square shoulder.
No rush, yet to make some tooling to turn this on my wood lathe.


----------



## deema (26 Jan 2022)

Hi Ttrees, the boss on the spindle is larger than it needs to be as it only contacts the inner race of the bearing. I suspect the large size it to ensure it contacts the body of the machine with a good land area when pulled back.
I think the boss may well be a separate part that has been pressed onto the smaller diameter spindle. It had by eye a square face with no apparent radius at the inner intersection.

The wheels pressed into it, so without destroying the bearings, I can’t take a photo of the other side for you.


----------



## Ttrees (26 Jan 2022)

No bother Deema, I was presuming this, and was going to aim for no bevel/chamfer first.
I have plenty spare old bearings from the machine to find out.
Likely it might take me a few tries anyway.

Thanks for taking the time to make this thread.
Tom


----------



## Sideways (27 Jan 2022)

Jitter said:


> A question I have-
> Do you recommend releasing tension on the blade when it is not in use? (for this particular machine)


I'm nearly as much a newbie as you are when it comes to bandsaws, I've overhauled a Startrite and a Kity before this, fettled, setup and used just a few more. So take this with a pinch of salt...

Unless it's a weak saw carrying the maximum width blade at full tension, I very much doubt that the frame of a bandsaw is bothered whether it's under tension or not. The S45 is a strong saw with a really good frame. Nothing to worry about there.

The possible benefits of releasing tension on the blade are taking pressure off
1. the bandsaw tyres
2. the top and bottom wheel bearings
from the blade sitting under tension in one position. This could conceivably encourage some sort of micro pitting on the ball races and certainly it could imprint on the tyres over time.

Depending on how much pressure is dialled in, there's an argument that a spring can lose it's tension over time. Metal behaves like elastic up to a point and I doubt that the spring is at any risk, but if you run a 20mm+ blade under high tension, then maybe there's something to consider.
Lastly, if creep and fatigue failure does happen to snap your bandsaw blade while it's sitting there tight but not being used, it makes a hell of a bang ! It might startle you into spilling your tea  

If I had a saw that was in daily use, I'd take the tension off going into weekends or holidays. I wouldn't bother overnight but I'd not criticise anyone who did. They probably know better than me.
If I used a bandsaw occasionally as an amateur, I'd leave the tension off until I wanted to use it, and take the tension back off at the end of that day.

Experienced users, please come and set us both straight ....


----------



## TRITON (27 Jan 2022)

You're making an excellent job of that. A big job, and doing all the parts is testimony to yourself and your skills. 

My only niggle is you haven't painted it in some gaudy colour


----------



## Jester129 (27 Jan 2022)

@TRITON, that comes when he asks me what colour I want it, as he's kindly giving it to me, aren't you Deema (please!) ?


----------



## deema (27 Jan 2022)

Jester129 said:


> @TRITON, that comes when he asks me what colour I want it, as he's kindly giving it to me, aren't you Deema (please!) ?


I’m so sorry, you were pipped to the post by another member of this forum. It is detained to fly north when we have it finished.


----------



## deema (27 Jan 2022)

Not a hugely productive day today. The new owner asked for a mains cable 5m long…….and as is typical we had just 4m left……not a big deal, we had anticipated supplying a cable of circa 3m, so hadn’t ordered a new real. Rather than relying on the unreliable post we popped to the local electrical distributor to pick up some additional cable. We selected a particular type of cable for this saw, Sideways will explain the rational as he is in charge of the rewiring of the machine. We always replace all the cables in a machine, with age they become brittle and for us it’s a false economy for the new owner if it isn’t rewired throughout.


----------



## deema (27 Jan 2022)

The tension in the blade is created by a draw bolt compressing a spring, pulling the wheel up. It’s a very simple and very effective way of doing it. Some saws have the spring below the wheel, and others above. Out of preference I prefer the spring above. The gauge for the tension on this saw is rather unusual, it’s a clear perspex cup, with markings on it indicating the correct position for the tension handle to be wound down to for different blade widths. The cup rotates to show different tension points. Simple and effective. However, the cup on this saw, when we relieved it of all the grime is actually crazed, it’s not broken, but somehow it’s crazed.

The photo shows the cleaned blade tensioning system after cleaning up installed. You can see how crazed the cup is making it difficult to see where the markings are. You can just make out the red markings of the tension setting.





I took the whole assembly apart, the bits I’m showing are just for the cup.
The large circlip just provides a seat for the cup to sit upon. The Perspex tube just sits on top of the circlip and fits snuggly around the stem of the metal body (it sits around the fat end). It’s not a push fit, and you should be able to rotate it easily. This one was full of sawdust and was wedged on. I suspect saw dust got down between the perspex and metal body and with temperature changes caused the crazing as it slowly descended into the crack between the two.




Well, that’s not good enough for us, we want the machines we restore to look and function as close to new as possible. I’ve ordered a new Perspec cup, an original table insert (as it was missing, we will make one ourselves, but it’s nice for the new owner to have an original) and a wheel brush from SCM spares in the UK. They have a minimum order value of £70 excluding VAT, and these items met that the criteria! The only downside is they won’t be delivered until early March. We will be delivering the machine before that and will send the new bits to him afterwards.


----------



## Sideways (27 Jan 2022)

The saw is to be powered from a transwave 3ph converter and it is possible that it will be plugged in and out somewhat regularly if other machines share the Transwave.
This influenced the choice of a power cable.
If the saw was to be permanently wired in, or only occasionally moved, then SY flexible cable with a protective wire braid would be a good choice.
The downside of SY, is that it is rather stiff and unwieldy. An alternative is to use a high grade rubber flex. Code H07RNF identifies premium abrasion resistant rubber cables that are also oil and chemical resistant. These are excellent cables. More costly than SY and long lived.


----------



## Sideways (27 Jan 2022)

The saw has a simple pushbutton start switch and a latching off / emergency stop switch fitted in a box below the table.
The originals were in sound condition so were cleaned up and reused.





The advantage of fitting controls in a sealed enclosure is dust resistance. Cable glands and a rubber seal around the box combine with industrial style switches which have rubber O rings around their mounting holes.





The industrial switches are typical of the type. Made in three parts there is a button or switch up front, a mid section that secures the switch to the panel, and clip on blocks at the back that do the electrical switching. The contact blocks on these switches screw firmly to the metal section rather than using spring clips.













Notice in the bottom image the contact blocks are labelled NO (normally open) green, and NC (normally closed) red. In most typical setups, the green contact block is clipped onto a green start button or rotary start switch. The red block onto a momentary stop switch or emergency stop button.

An important point to note. These switches operate a control circuit only. Power goes to the motor through a large 3 phase relay aka "contactor" that sits in a box on the back of the saw. The pushbuttons and the safety relay in the next post work at 3 phase mains voltage but carry only the small current that flows through the operating coil of the contactor.

FOOTNOTE: One small detail nagged at me and had to be put right after the event.
You may notice that the industrial switches in this control box have metal frames and bezels around the buttons. That is a nice quality detail, but used here in a plastic enclosure, an unlikely but hazardous fault could arise. IF a live wire were to come loose from one of the switches because of vibration, fatigue or a mistake in tightening the terminal screws, AND IF that loose wire happened to touch part of the metal clamp / frame on one of the switches, then that part and the metal bezel around the switch on the outside could become live at 240V.

Normally this would never happen because the enclosure would be metal and grounded. The frame and bezels of the switches make a good electrical contact with the box and are also grounded. In a plastic enclosure this can't happen. We needed to go back and explicitly earth the bodies of the switches as a safety measure against 3 pieces of bad luck coinciding.


----------



## Sideways (27 Jan 2022)

The next element of the wiring is the safety switch monitoring the upper and lower bandsaw wheel covers. When both doors are secured shut by a hinged bracket made for this purpose, a metal tongue or "actuator" is pushed into the slot in the red end. This closes the switch.





Notice the simple box joint between the red and black parts of the switch. This can be separated and the red end rotated to point the actuator slot in 4 different directions to suit the application. A replacement switch might have the slot pointing the wrong way, but the red end is easily unscrewed and turned through 90 degree steps.

The safety switch is wired in series with the stop switch. Both of them have Normally Closed contacts and allow a small control current to flow while the motor is running. If the tongue is pulled out of the safety switch it acts exactly like pushing the stop button and the power to the motor is cut.

The safety switch is an Italian one, available from a few sources if a spare is needed.





This image shows there are actually two switches inside for versatility, a NO and a NC.






We use only the contacts that are Closed when the actuator is inserted.





The safety switch is bolted to the chassis just above the on off switches and is connected into the circuit inside the on off box.


----------



## Sideways (27 Jan 2022)

Jester129 said:


> @TRITON, that comes when he asks me what colour I want it, as he's kindly giving it to me, aren't you Deema (please!) ?


Is it just me ? I really like those big Otto Martin panel saws with the graffiti paintjobs.....
No, not volunteering. If I tried it would look like a 3yr old did it !


----------



## Jitter (27 Jan 2022)

deema said:


> Not a hugely productive day today. The new owner asked for a mains cable 5m long…….and as is typical we had just 4m left……not a big deal, we had anticipated supplying a cable of circa 3m, so hadn’t ordered a new real. Rather than relying on the unreliable post we popped to the local electrical distributor to pick up some additional cable. We selected a particular type of cable for this saw, Sideways will explain the rational as he is in charge of the rewiring of the machine. We always replace all the cables in a machine, with age they become brittle and for us it’s a false economy for the new owner if it isn’t rewired throughout.


My apologies Deema. I should have had the cable distance measured out well before now. In all honesty, I should have realised you needed the length size when you asked how I was needing to connect the machine to the transwave and did not expect you would be actually wiring it up ready to use. When I bought the Wadkin, it arrived without a cable or plug, I paid my sparky friend to wire it all up once the machine was in place, he supplied the parts after seeing it in place. 4 metres may well have been enough length to get me started, I added a metre because it may be in future that I will pull the machine away from the wall to maximise flexibility of use when cutting. You have obviously bought quite a bit now for the saw and for reasons that will benefit me greatly and really appreciate it. Please do let me know if I can help with the funds at all, I did expect to have to pay my sparky to wire it up after arrival so happy to help with the cost of at least that.

The S45 is looking great. You guys are making it look like new. If I ever meet another with an S45, I will be pointing them to this thread, it’s like Haynes manual step through guide with a personal touch and better pictures!


----------



## TRITON (28 Jan 2022)

deema said:


> I’m so sorry, you were pipped to the post by another member of this forum. It is detained to fly north when we have it finished.


Up North ?.
Well thats ideal. A nice bright colour will show up in the snow and mean it will never get lost


----------



## deema (2 Feb 2022)

Sideways and I have made a bit more progress, the wiring is all done and electrically tested, Sideways will I’m sure detail what was involved. 
The table insert is made, and the new owner will also receive an brand new SCM official insert, which I believe are plastic. The one we have made is aluminium. I’m biased, but I like a metal insert.






The fence has been cleaned up and fitted, it’s perfectly square to the table which is great.





The belt that came off the saw, which I believe was original was an A37, which we replaced with like for like. However, an A37 was far too tight and didn’t facilitate any tightening. So, we have ordered and now replaced it with an A38. I’d be curious to know what belts are on other peoples S45.


----------



## Jitter (2 Feb 2022)

The insert plate looks perfect. Great to know the fence is accurate too.


----------



## deema (2 Feb 2022)

We have started to setup the saw, first off is the vertical alignment of the blade. Before doing any adjustment we ensure that none of the bkade guides are anywhere near the blade, otherwise they affect the blade alignment. The bottom wheel is held by 4 bolts that adjust its alignment, these are used to both set the blade vertically square with the table and also to track the blade to cut parallel to the fence.





The bolts at 12 and 6 O Clock adjust the vertical alignment. The top wheel is used to track the blade correctly on the wheels, so, by nodding the bottom wheel either up or down tips the blade either forward or backward. As an aside, o should say that the hub of the two wheels need to be coplaner, or as close as possible or the adjustment doesn’t work. 

The bolts at 3 and 9 o’clock are used to track the blade to the fence. So, if the blade is cutting away from the fence you tilt the lower wheel to correct this. You unscrew say half a turn one of the bolts and tighten the other. Now, the shaft that these bolts act on is round, so, you have to slacken one of the other pair of bolts. I.e. adjusting the bolts at 3 and 9 needs the bolt at 12 slackening. If you don’t, the adjustment won’t move the shaft as expected. Equally if you move the shaft two far, it affects the setting of the other pair of bolts. I.e. adjusting the alignment to the fence can also affect the vertical alignment. It’s a bit fiddly, and can either take a while or you can be lucky.

So after a bit of messing about, this is the vertical adjustment dialled in.


----------



## deema (2 Feb 2022)

Alignment of the blade to the fence is next. 





This piece of ply is cut with the fence, you can see how far out the alignment was to begin with. The lower wheel needed to be tilted away from the fence. To do this we slackened the bolt at 3 and tightened the bolt at 9 o’clock.

This isn’t complete, I thought we had 3 or 4 good blades that came with the saw…….but when we examined them we found that two are for foam cutting, we used one of these for the verification plate alignment, and the third which is a wood blade was badly damaged. So, a new blade is required before we can complete the setup…..darn! Tufsaws will be getting an order.


----------



## Sideways (2 Feb 2022)

Interesting about the belts. When you overhaul an old imperial machine and fit a modern motor made to IEC / metric standards, one or both pulleys may need changing and belts usually do because the new motor has different dimensions. It is quite tricky judging the correct belt length from measurements even when you understand how belts are sized.
In this case, the motor is already IEC and in good condition. No need to change. The starting point was to fit a new belt the same size as the one taken off. Even the most straightforward swap can be tricksy.
Here you can see the range of adjustment available in the (original and unchanged) motor mounts for tensioning the belt. There's about 1 inch vertical movement in the slots of the four bolts. So the belt needs to be pretty close. With the A38 belt, the mounts are about the middle of the slot, rather than being over tight at the downward limit of the holes with an A37.





The motor is held by the four 4 bolts through a flange. The bolts are loosened, and the motor dropped to fit the belt. The lower band wheel is removed for a belt change as the belt is too small to be stretched over the wheel while it's in position. Once the belt is sitting in the grooves of the motor pulley and lower wheel, the wheel is refitted to it's spindle and the motor lifted by a jacking bolt until the belt is comfortably tight. About 1/2" sideways movement when you push firmly but not hard on the belt midway between pulleys is about right.


----------



## deema (2 Feb 2022)

Finally for today from me, I’d really appreciate some help from anyone with a SCM bandsaw. We are concerned that the spring which creates the tension on the blade could have been over compressed at some stage in its working life. If it has it will be shorter than it should be having taken a permanent set. I would be extremely grateful if anyone with this bandsaw could measure the length of the tensioning spring.

To Measure it, if you could be so kind to simply unscrew the tensioning handle until it comes out. The spring and washer just lift out. What we would really like to know is how long it is, measured as accurately as possible. It simply screws back in, no fitting or fiddling around to out it back in.

A big thank you in advance.

The spring in the saw is
Outside diameter 20.5mm
Inside diameter 11.4mm
Wire diameter 4.6mm
No. Of coils 9.5
Length. 61.7mm. We think it should be possibly 6mm longer. This is the dimension we would appreciate verifying.


----------



## Sideways (2 Feb 2022)

Interesting about the foam cutting blade in Deema's photo above. It's scalloped like a bread knife and has no set at all. I'd not seen one of those before.


----------



## deema (2 Feb 2022)

The table has a stop, which can be adjusted to ensure that the table always returns to be perpendicular to the blade. We reset it correctly. It’s just a bolt, however the nut inside the saw isn’t captive and it’s quite difficult to reach to both slacken and then tighten. Again adjustments are done without the blade guides anywhere near the blade.


----------



## Sideways (2 Feb 2022)

The promised word on the wiring. The saw is all good now. 3 phase 16A red plug. HO7 rubber flex to a compact enclosure on the back of the saw where the contactor and overload relay are housed. Motor is wired "star" for a 380-400-415 Volt supply.
Start stop buttons and the safety switch for the doors all wired up and proven.

As well as functional tests, we do a couple of safety tests using an installation test meter. These devices include the ability to measure low resistances so the first tests ensure that we have a reliable connection from the ground pin of the plug to several points on the chassis of the machine. Zero the meter first to eliminate the resistance in the test leads, then a reading of 0 is what we want.




Motor housing





Table




Etc

The second set of safety tests makes sure the insulation of the wiring and motor are in good condition by applying a 1000V test Voltage and measuring any leakage resistance. The reading here is "Resistance greater than 1000M Ohms". This is what my tester says when it can't see any leakage so it's the right result and is repeated for all phases and with the contactor manually held in so that the motor windings are included in the test.




he other


----------



## Ttrees (3 Feb 2022)

Never heard anyone suggest the bottom wheel adjustment on flat tyres relates to tracking or "drift" !
surely that is done via the trunnion bolts.
Have heard it suggested before regarding crowned tires, but I'd take that with a pinch of salt also, as most folk don't seem very concerned about dressing tires.

In my book the bottom wheel setting is done without a table, as I also had that very same belt issue which I was to find out was an expensive lesson.
Misalignment of wheels + belt too small = damaged motor bearings when ran for only a second.

That said it all as far as I'm concerned, the top wheel rules over anything and hopefully the pulley will match.
Everything else is adjustable, even if it isn't .


Must check my belt now, to see what size it is, seems/pot shot guess they are made in inch increments from what you say.

I thought my spring looked compressed, but found a factory bit of footage showed the same.
Haven't seen much on these machines to suggest anything, and have went to the far corners of the interweb looking 
At various machines and whatnot.

I could tell ya Eric Loza on the creek would be one fella I'd chance asking. (He doesn't work for MM no longer)

Tom


----------



## deema (3 Feb 2022)

@Ttrees, firstly an admission; Sideways checked the tyres yesterday and reported them to have a slight crown. So, my error, I’d believed that this saw had flat tyres. 
The top wheel mechanism normally is designed to have a lot of slop, so you can without a blade move it wiggle it around a vertical axis. It will therefore follow the lower wheel. With a new sharp blade, properly set teeth and tensioned, you can adjust the tracking using the lower wheel adjuster bolts. There are lots of things that affect the drift of cut, from position of the blade in the wheel, how stress relieved the blade is, set of the teeth, tension etc etc. however, logically, if you look at the construction of a bandsaw, there are no reference machined surfaces for the wheel mounts, so, it has to have adjustment to get everything working together properly.


----------



## FlatlandsF7a (3 Feb 2022)

deema said:


> Sideways and I have made a bit more progress, the wiring is all done and electrically tested, Sideways will I’m sure detail what was involved.
> The table insert is made, and the new owner will also receive an brand new SCM official insert, which I believe are plastic. The one we have made is aluminium. I’m biased, but I like a metal insert.
> View attachment 128476
> 
> ...



Just to note that the belt on my S45 is an A38, but it also looks newer than the saw, so I suspect it was replaced at some point in the life of the saw, probably with the exact same experience as you.

On the spring size, mine was compressed fully for a long time, and it came in at almost exactly 60mm long, but I don't have the number of coils to hand I'm afraid.

Thanks again for this whole thread @Sideways and @deema, it is already really useful, and will definitely be in the future if anything goes wrong with my S45.

Finally, my machine doesn't have the rack and pinion rise and fall for the blade guard, and the travel isn't square to the table or parallel to the blade. Is it possible to retro-fit something like is on your version, as it looks much easier to use, and would save altering the guides every time the cut of height is adjusted?


----------



## deema (3 Feb 2022)

@FlatlandsF7a thank you so much for the measurement, I think you have a different generation of saw to the one we are working on if it doesn’t have a rack. I wasn’t aware they did a variant without a rack. Do you have a picture / serial number of the machine and I will see if I have a parts list for it.

There are two reasons we think it’s taken a set, firstly the saw is rated for standard blades between 6 and 20mm, and the spring when not compressed at all is just a smidge above the line indicating correct tension in a 6mm blade. Secondly, I think the clear acrylic pot has crazed due to the adjuster handle having been screwed down so far it’s actually compressed the pot. A sign they couldn’t get the tension high enough. (Although some blade materials, ie M42 need a higher tension, so a saw that takes a 20mm standard blade may not be able to fully tension a 20mm tougher material blade.) We are going to make a spacer to stop this ever happening again and also replace the threaded bar on the adjuster to make it longer to a accommodate the spacer. 


If anyone else with a S45 could also measure their spring that would be really brilliant. If all three are the same / similar, we know it’s good.


----------



## Ttrees (3 Feb 2022)

deema said:


> @Ttrees, firstly an admission; Sideways checked the tyres yesterday and reported them to have a slight crown. So, my error, I’d believed that this saw had flat tyres.
> The top wheel mechanism normally is designed to have a lot of slop, so you can without a blade move it wiggle it around a vertical axis. It will therefore follow the lower wheel. With a new sharp blade, properly set teeth and tensioned, you can adjust the tracking using the lower wheel adjuster bolts. There are lots of things that affect the drift of cut, from position of the blade in the wheel, how stress relieved the blade is, set of the teeth, tension etc etc. however, logically, if you look at the construction of a bandsaw, there are no reference machined surfaces for the wheel mounts, so, it has to have adjustment to get everything working together properly.


I noticed this with a far eastern 20" machine, but my acm seems pretty rigid, when locked at the back.
(Bar a issue with the spacer) which is very subtle.
Someone before me attempted to skew the wheel to suit the post, but obviously that didn't work.

Not the first time I've heard of some Italian machines with differing profiled rubber.
I'll try finding that link mentioning differing profiles on various italian machines, i.e. True flat, slightly crowned, more pronounced crowned.

Not sure if that "drift" /call it what you want, thinking, would suggest to keep adjusting the bottom wheel of not.
I've learned my lesson about setup, and if I wanted that profile on my wheels, and things were going aray, I'd just dress the tires rather than risking my motor bearings, and duffing the set on my blades.

That's my 2cents on the matter.
Might not be as apparent with a wheel which has a smaller hub, in which the belt rides, compared to my machine which it's quite large hub compared to most.

Can edit my post to add link about tires.





A Question for Flat Tired Bandsaw Owners - Page 2


Hi! When I bought my 20" Davis and Wells bandsaw it had flat tires, but the previous owner was tracking the blade in the center of the wheels, which did not work well to say the least. So I crowned the tires and the blade tracking suddenly became good, with the blade tracking on...



sawmillcreek.org




All the best

Tom


----------



## deema (3 Feb 2022)

@Ttrees, I understand the concern and agree. The amount of movement you need to make in the wheel is very very small. The motor, wheel and table are when fitted initially all ‘aligned’ the tweaks are only very small and don’t affect the belt alignment. We check it and if it’s out too much would just shim the motor mounts. Probably the most important thing is not to over tighten the belt.
Belts come in 1/2” increments. I bought at A37.5 as well as an A38.


----------



## deema (3 Feb 2022)

@Ttress, thanks for the link to the other site, a very interesting read. The S45 manual states that the blades should be run with the teeth off the front edge……which is normal for a flat tyred machine. Sideways observation, and also a comment on the link is that they have ‘slightly’ crowned wheels. I can see a logic for this. I like flat wheel, I think they provide better tracking as the blade in not ‘balanced’ on top of the crown which can create variances in tracking. Flat wheels seem to track far more consistently, and are normally found on high end saws / saws of larger capacity. However, the S45 can take a 6mm blade, and tracking that width to run with the teeth overhanging the edge of the wheel would be a challenge. Folk on the link have said they would run small blades on flat tyres in the middle. So it seems that by having a slight crown you have the best of both worlds. Running the smaller blades in the middle of the wheel with a slight crown will leave space for the set teeth to sit without chewing up the wheel. Larger blades can run with the teeth overhanging the edge of the wheel.


I wish I knew how to thank threads rather than just add a like?


----------



## deema (3 Feb 2022)

SCM have been very kind to provide me with the dimensions of the spring. I don’t know what standard tolerances springs are made to, but ours is a little shorter (3.3mm or circa 5%) than the drawing. There is no bump stop in the design, so the spring can be compressed by the mechanism until the coils touch each other. So, either this is a poor design, or springs of this type can be completely compressed, I don’t know, are there any experts in springs?
We are having a bit of a think about the tensioner design, we already have one feature we are going to improve over the original design, but also wondering about other improvements. A replacement spring from SCM is part number 0332661250E and costs £38 plus vat. (Minimum order value £70 excluding VAT.)


----------



## FlatlandsF7a (3 Feb 2022)

deema said:


> SCM have been very kind to provide me with the dimensions of the spring. I don’t know what standard tolerances springs are made to, but ours is a little shorter (3.3mm or circa 5%) than the drawing. There is no bump stop in the design, so the spring can be compressed by the mechanism until the coils touch each other. So, either this is a poor design, or springs of this type can be completely compressed, I don’t know, are there any experts in springs?
> We are having a bit of a think about the tensioner design, we already have one feature we are going to improve over the original design, but also wondering about other improvements. A replacement spring from SCM is part number 0332661250E and costs £38 plus vat. (Minimum order value £70 excluding VAT.)
> View attachment 128522


I happen to have recently replaced my spring due to fears over it being over-compressed in the past (I made a thread on this site somewhere).

I ended up purchasing mine from Berger Tools which had a huge range and really good prices. I ended up buying 3, unsure of which would work best, and to reach the minimum order, and it all came to c.£15 including delivery. So excellent value.

I ordered the following:


G25-064G Yellow Die Spring ISO10243, Extra Heavy Load1£2.51G25-051G Yellow Die Spring ISO10243, Extra Heavy Load1£2.30G32-064G Yellow Die Spring ISO10243, Extra Heavy Load1£3.34

But found that the G25-064 was the best replacement and the G32 didn't actually fit through the aperture in the saw case (I didn't think to measure that!).

Very interested on opinions on how (in)appropriate these might be. The G25-064 seems to be tensioning everything well, certainly better than the original that came with the saw.


----------



## Ttrees (3 Feb 2022)

@deema 
I agree with your comment on the flat tires, concerning them providing better tracking....
if you mean whilst "dynamic testing" (Kelly Mehler has mentioned _that term _aptly named term on a tablesaw video, I think it's good way of putting it)

So if you are referring to tracking whilst the machine is cutting, then most folks running larger Italian machines with flat tires agree, especially the folks using euro guides, and not ceramic ones, 
Statements like the machine cutting as fast as one can feed the material through it, 
without the blade walking back and rubbing against the thrust guides, leads me to think so.

After dressing my real rubber vulcanized tires, it seems to have even more grip on the blade than before, although yet to be 100% on that. (Too many variables for science)

I have asked about the grip differences regarding actual rubber, and the composite rubbery compound which is on replaceable tires, but haven't found much talk about it, 
not to mention adding urethane tires to the equation, a bit odd!

I've not come across anyone who actually tracks a narrow band off, or close to the set being off the wheels.
There is a lot of talk about tires/tyres on the web, but not many folks actually dress the tires, which is odd, as I'm guessing not everyone who has flat tires or near flat tires 
uses a resaw blade only.

Plenty of evidence out there, suggesting that this makes sense to me.
A tell tale sign is folks running only narrow blades on these machines,
because the front of the tires, acting much the same as a pronounced camber 
is too worn for the wider blade to track well.

I've looked into this as I have more unanswered questions about flat tires, to do with the possible importance of the edge of the rubber.
(a non concern regarding even a tiny camber)

To cut to the chase, I reckon along with most, agree its worth evening the wear out as much as possible,
say if ones tires were somewhat old and a bit soft, but still OK, are likely more prone to wear.
Not having experienced that from the one narrow very very fine blade I have, 
which hasn't had much use,
but can see what a 3/4" blade does to a dressed tire, so this occurrence likely exists to some extent, and good practice to keep an eye on things periodically,
as I'm guessing all tires aren't created equal.
Even the two vulcanized tires on my machine differs in hardness, so checking wear on both suggests to me to be good practice.

The Centauro/minimax being the machines which are talked about on the American forums, as not too many in the UK seem to be seeking to do the best resawing possible, and regard the bandsaw as more of a jack of all trades tool.

I reckon there would be a lot more than vague(ish) talk about tires if Centauro didn't have that quick change system which Sam Blasco demonstrates on the MInimax MM16.

Perhaps we would have a better answer whether wear occurs with small blades and various rubber compounds and such.
Not very interesting to the folks who can swap them out in a few minutes.
Some interesting comments I've read before, about NOT putting this type of "rubber" in very hot water beforehand!


Sorry for mucking up your thread with my ramblings.
Thanks for taking the time to show why these machines are a cut above the rest.

Cheers 
Tom


----------



## Sideways (3 Feb 2022)

Thanks for the link to Berger. They have a great range of stuff.
Springs are proving interesting to investigate. we'll figure this out and write it up, but the starting point is :
We need a spring with a 10mm or greater bore to fit the adjusting screw that goes down the middle.
Unless we modify something, we need a spring with a 20mm or less outside diameter because the spring drops into a tube.
We have a target length of 65mm but can use a longer spring if that's better. Longer may inded be better in some regards but any change from 65mm would be at the expense of the tension scale on the new perspex collar we've just ordered which is calibrated against a 65mm spring (ho hum).
Sources of advice say that it's better not to compress a spring to the point where the coils bottom out (all turns touching) as this does reduce the life of the spring (at least when you are putting it through thousands of cycles of compression and release. 
But fully compressing a spring is a way to limit the amount of tension that can be applied and so it acts as a designed in limit to prevent overstressing the frame. A new spring is far cheaper than a new frame. I can see why SCM may have designed this as they did.

Figures in the range of 15,000 to 20,00 to 25,000 pounds per square inch are given by vendors as recommended tensions for carbon steel blades. Higher for bimetal and special steels. We're asking some questions to confirm these, then we'll convert them to a tension for the heaviest blade that the S45 can safely run, and that in turn into the max tension needed from the spring. That will be interesting.

Once we know what force we require from the spring, we can start looking through the options that fit.


----------



## Ttrees (3 Feb 2022)

Sorry to keep butting in, but as a self professed bandsaw fanatic, I can't resist, as it makes for very interesting reading!
"Just" incase you guys haven't seen this thread before.



Upgrading the blade tension spring on the Hammer N4400 Bandsaw | Swedish Woodworking


----------



## FlatlandsF7a (3 Feb 2022)

Sideways said:


> Thanks for the link to Berger. They have a great range of stuff.
> Springs are proving interesting to investigate. we'll figure this out and write it up, but the starting point is :
> We need a spring with a 10mm or greater bore to fit the adjusting screw that goes down the middle.
> Unless we modify something, we need a spring with a 20mm or less outside diameter because the spring drops into a tube.
> ...


Ah yes, your outside diameter is limited to 20mm because of the indicator gauge cup. My saw doesn't have one of those, so the spring sits 'through' the frame, and the bore of that hole is 30mm (if memory serves) allowing me to use the 25mm spring.


----------



## Sideways (3 Feb 2022)

Ttrees said:


> Sorry to keep butting in, but as a self professed bandsaw fanatic, I can't resist, as it makes for very interesting reading!
> "Just" incase you guys haven't seen this thread before.
> 
> 
> ...


It's a good article. As it happens, yes, I had read and bookmarked it some time ago. Thanks for the reminder  
Tuffsaws continue to earn their good reputation and are being extremely helpful with data about their carbon and M42 steel blades. Once we've have all the numbers we need, we'll add the calculations and conclusions here


----------



## FlatlandsF7a (4 Feb 2022)

deema said:


> @FlatlandsF7a thank you so much for the measurement, I think you have a different generation of saw to the one we are working on if it doesn’t have a rack. I wasn’t aware they did a variant without a rack. Do you have a picture / serial number of the machine and I will see if I have a parts list for it.
> 
> There are two reasons we think it’s taken a set, firstly the saw is rated for standard blades between 6 and 20mm, and the spring when not compressed at all is just a smidge above the line indicating correct tension in a 6mm blade. Secondly, I think the clear acrylic pot has crazed due to the adjuster handle having been screwed down so far it’s actually compressed the pot. A sign they couldn’t get the tension high enough. (Although some blade materials, ie M42 need a higher tension, so a saw that takes a 20mm standard blade may not be able to fully tension a 20mm tougher material blade.) We are going to make a spacer to stop this ever happening again and also replace the threaded bar on the adjuster to make it longer to a accommodate the spacer.
> 
> ...



Was just in the shed and snapped these pictures of the blade guard assembly. Pretty difficult to get clear pictures, but perhaps it will be enough. I forgot to look for a serial number on the machine, but will edit this post when I get one!


----------



## Fergie 307 (4 Feb 2022)

Sideways said:


> Interesting about the belts. When you overhaul an old imperial machine and fit a modern motor made to IEC / metric standards, one or both pulleys may need changing and belts usually do because the new motor has different dimensions. It is quite tricky judging the correct belt length from measurements even when you understand how belts are sized.
> In this case, the motor is already IEC and in good condition. No need to change. The starting point was to fit a new belt the same size as the one taken off. Even the most straightforward swap can be tricksy.
> Here you can see the range of adjustment available in the (original and unchanged) motor mounts for tensioning the belt. There's about 1 inch vertical movement in the slots of the four bolts. So the belt needs to be pretty close. With the A38 belt, the mounts are about the middle of the slot, rather than being over tight at the downward limit of the holes with an A37.
> 
> ...


Looking great. From earlier pictures looks like you have a solid v belt. Might be worth considering a notched type, they grip better so you can get away with less tension. Bit late I know as you already have the new one, but for similar projects well worth a try.


----------



## deema (4 Feb 2022)

Sideways and I have spent some time reading up about springs and doing the calculations. Now, neither of us would claim to now know a lot about springs, but we know a lot more than we did!
So, I’m summary, compression springs should not be compressed so that the coils touch each other, in fact they typically should not be compressed more than 25% of their relaxed state. Each spring has a slightly maximum compression limit, which is stated in the specification. Good design would incorporate some form of bump stops to or event the spring being over compressed.

Ian at Tuffsaws has been extremely helpful and provided us with a lot of data on blades, we are eternally grateful to him for his help and assistance. I run Tuffsaws blades in my own bandsaw, and have always been extremely pleased with the blades and delighted by their customer service. We always recommend them to the new owners of any bandsaw we sell or service. In reality, the saw is only as good as the blade you put into it.


----------



## Sideways (4 Feb 2022)

Fergie 307 said:


> Looking great. From earlier pictures looks like you have a solid v belt. Might be worth considering a notched type, they grip better so you can get away with less tension. Bit late I know as you already have the new one, but for similar projects well worth a try.


Spot on with your advice there.
There is a future thread in the pipeline when I finish my Fobco 7-Eight drill.
There's a notched belt hanging on that waiting to be fitted 
I think of notched belts as especially useful if you need the belt to go around a small diameter pulley, but they work as an upgrade to most machines.


----------



## deema (5 Feb 2022)

Sideways and I have backward engineered the tensioning arrangement for the saw, it’s the first time we have done this, so although we believe our maths and assumptions are correct if anyone knows better / spots an error in our thinking please pitch in.

First off, we wanted to get a good idea of what the spring constant should be for the existing spring. We could measure it, but we know the spring has gone beyond its yield point, as it’s shorter than it should be. Therefore, any constant we measure may not be correct as the elastic slope may be different as well as shifted due to none elastic stretch. I will highlight that neither of us are mechanical engineers, we are both electronic engineers, I have spent most of my working like running mechanical engineering company’s for my sins. So, a long winded way of saying that I think I know enough to be dangerous with mechanical stuff

To help with the explanation, there are two important points when stretching a material, the first is the point at which a material won’t return to its original length after being stretched. This is called the yield point. Below this, the material is elastic, it will stretch and not take a set. Beyond the yield point the material stretches and will permanently remain stretched. However, it hasn’t broken. This area is none elastic and none linear, if you keep stretching the material it will eventually break, the peak force it can withstand before it breaks is the ultimate tensile strength of the material, which is higher than the force needed to break it.





The spring must be designed to operate in its elastic region, so, it’s compression is proportional to the force it generates. As way of explanation, if it takes 100kg to compress the spring 1mm it will take 200kg to compress it 2mm and so on up to the yield point. We used this to work out the spring constant. A springs equation is Force = spring constant x change in springs length.

We measured separation f the graduations on the clear plastic cut, which indicated how compressed the spring should be for each width of blade. The results were






We know the spring should be 65mm long, so by measuring how long the spring would be at each graduation we could work out the amount by which it was compressed. As a check, we calculated the linear spacing to verify our measurements were accurate. It isn’t easy to measure as the lines in the cup are fairly think. We found that our measurements were very good and had good correlation to the theoretical values.

We now had the amount by which the sping was compressed. One part of the equation.


----------



## deema (5 Feb 2022)

We needed to know what force the spring needed to exert on each blade width to work out the contact by rearranging the equation. Tuffsaws came to the rescue, and Ian provided us with support, help and data to work out the next bit. A big thank you to Ian. 
We decided to look at the thinnest blade and widest blade the saw can take, which covers the range of tensions the spring has to work over. The SCM S45 specification is that it takes anything between 6mm and 20mm wide blades. We also wanted to cover the range of materials Tuffsaws provide for blades. From standard carbon steel blades to the more expensive but far longer lasting M42 which is what I use on my own bandsaw. 

Tuffsaws web site can be found at 









Tuff Saws


Tuff Saws - bandsaw blades, bandsaw, bandsaw machines, woodworking blades, m42 blades, professional bandsaw blades, ecommerce, shop, online. Call us today on 01443 819261.




www.tuffsaws.co.uk





I hope Ian doesn’t mind a quick snap shot from his web site of the M42 blade characteristics. I’m sure with the benefits they bring that the new owner who cuts a lot of oak will be using these blades and we want to ensure the saw can tension them up.





Ian’s blades need different tensions depending on the material they are made out of. This is something that should be considered when tensioning a blade on a bandsaw, the markings will be ‘a rough’ guide as the manufacturer will have assumed a particular blade material and also tooth design. So, for Tuffsaws blades:






We have stated the data in both PSI and N/mm2, it’s the same just different units of measurement, and you will come across both when looking at saw data. The pressures are defined by how much pressure is being exerted over a square inch (PSI) and over a square MM (N/mm2). The same pressure is required for every blade of that material. So, a 6mm wide blade and a 20mm wide blade need the same pressure to tension them. However, they are different sizes, so initially it would seem from the data that you just need one pressure for each blade material irrespective of the blade width. This is where the area comes into consideration. To work out the force needed to apply the same pressure in the different blade widths we need to know the cross sectional area of the different blade widths. A 6mm bkade will have a smaller cross sectional area than a 20mm blade.


----------



## deema (5 Feb 2022)

Bandsaw blades can be bought in numerous teeth per inch configurations, each designed for specific cutting jobs. We are only interested in wood cutting and not metals for this saw. The blades thickness varies and increases as the width of the blade increases. Ian’s blades use typical thicknesses that are found within the industry. The 6mm blade is the thinnest and the 20mm blade is the thickest material. We also need to consider how much material is taken out of the blade to create the teeth. This effectively reduces the cross sectional area. Again, Ian helped with tooth depth data and I measured a couple of blades. So for the two extremes of blade the cross sectional area is





If you multiply the PSI or N/mm2 constant of each material size by the cross section of each blade you end up with the force required to tension the blade. I used the N/mm2 so the tension is expressed in Newtons. 

The bandsaw is a continuous loop, so the sling is pulling against a loop, or effectively two blades, so the actual force the spring needs to exert is twice that which is calculated for a single blade. In other words is the about calculation times 2. You therefore end up with: (I used N/mm2 so the result is in Newtons. If you want it in KG divide by 9.81, or 10 for a rough estimate)


----------



## deema (5 Feb 2022)

We can now work out what the spring constant is likely to be using the tensioning scale on the machine as we have all the data we need. Rearranging the equation, Spring Constant (K) = Force (F) / extension. So for the 6mm and 20mm in Carbon steel we get 
K = 835 / 5 = 167. (6mm)
K = 2400/ 11.7 = 205. (20mm)

K is not the same due to the tooth geometry, and is gives a range of what K can be. This is why the exact marks on the bandsaw tension gauge are just an indicator. 

Looking at M42 the constant K needs to be to 
K = 1236/ 5. = 247. (6mm)
K = 4900/ 11.7. = 419. (20mm)

So we can see that the M42 needs a much larger force to tension it and to use the scale of this saw for the material would give a terrible tension. Usually Ian would recommend a narrower blade when selecting a M42 due to the likely hood that the saws not capable of fully tensioning it. 

We come back to the yield point, which now becomes relevant. Springs of this power must not be compressed beyond a certain limit, certainly not so the coils touch each other. Of the spring is over compressed it won’t have the same spring constant and probably be shorter. So, a good design would incorporate some mechanical means of limiting the travel. This saw doesn’t have one, and I. Fact I have yet to see a bandsaw with a bump stop for the spring. We will for this saw hopefully incorporate one to more ent the sling being overly compressed. 

The M42 needs the spring to exert 4900 N of force to properly tension the blade. To out it roughly into KG which is easier to think about, it’s 490 KG or about 1/2 tonne. That’s a lot of pressure in the spring, and also the saw frame must be able to withstand it without exceeding its elastic limit. The frame will flex, but after the tension has been released should return to its normal position. If it flexed too much the geometry of the wheels will be interrupted and the saw not cut well, the frame will become part of the spring. This is why it’s important to loom for a bandsaw that has a very strong frame. Well designed and thick walled components. Cheap bandsaws use thinner materials and flex too much / can’t properly tension up the blades they are supposed to take. Sideways and I may comment about this again……hope your not getting too bored!


----------



## deema (5 Feb 2022)

Springs to have a long life and also to not go beyond their yield point should be compressed in their working range as little as possible. Typically springs should not be compressed more than 25% of their length. It’s far better to be around 15% of the length. For a user, it would also be nice to have a scale which is as long as possible to make reading / adjusting easier. The scale on the SCM is very small, especially as you can see the forces that are being applied. However, if we use the typical spring design guides we can work out what the ideal length of spring should be for the scale.

The total compression of the spring on the scale is 11.7mm, so the ideal spring length would be no shorter than 78mm at 15% compression. For the spring used the actual percentage is 11.7/65. X 100 or 18%. So not a bad design. 

Most badsaws are designed for use with carbon steel blades, so the spring constant will be some where around 200.,I’ve actually asked SCM technical what it is, and what the maximum compression is so that we could design the bump stop properly if we don’t change the design.

What we can say with a high degree of confidence is that the existing spring cannot fully tension a 20mm M42 blade (which is why Ian at Tuffsaws if ordering a M42 blade will advise a blade narrower than your saws capacity).

Sideways and I have been playing around with improvements to the design of the tensioning system for this saw. We would like to use longer springs to reduce the fatigue, a bigger scale, and one that can accommodate a 20mm M42 blade. We also want to reduce the friction in the mechanism to make it easier to adjust. We will on Monday be ordering the parts needed, and will document how successful we are.


----------



## Sideways (5 Feb 2022)

And cheers FlatlandsF7a - the spring tables at Berger tools have been really useful to understand what forces and spring rates are achievable with a readily available range of springs.


----------



## Andrewy (8 Feb 2022)

Hello, interested to read this. I have a 2019 sc45 n. I found the thread while looking for information on setup of the lower wheel (a 1" blade sits with the gullet at the edge of the top wheel, but overhanging the bottom by 3/8) will check planarity etc. 

My tension spring is 63mm.


----------



## Sideways (8 Feb 2022)

Hi Andrew. How do you find the 25mm blade runs ?
I ask because the older version we are working on is only specified for blades between 6 and 20mm max. At 25mm I'd expect you to have problems tensioning it fully.
Do you have a manual for your s45n ?


----------



## Andrewy (8 Feb 2022)

Hi, it seems to run pretty well. I had some tracking problems when I first got/tried the saw.. using the blade which came with it. I did the usual recommended thing and bought some blades from tuffsaws. Using the 1" blade I was able to resaw some 280mm (apologies for going metric) sycamore, much easier/better than I had dared to hope. Currently running well in that sense. Sticky lower guide bearing, stiff depth of cut adjustment and the lower wheel blade overhang are my only concerns. I was able to get a pdf manual from the service/parts outlet in uk.


----------



## mindthatwhatouch (8 Feb 2022)

Hi,
What a great thread, looking forward to the blade tensioning update as never been happy with mine. Not wishing to hijack your thread but would appreciate your thoughts on the below. (If you want me to move it to a new thread, just say so)

Single phase machine. I got it running (came with electrical motor issues) believe it or not cleaned it up a bit and may have changed the wheel bearings, honestly can't remember. With the view to using it and improving it when I get round to it. 

Main issues are Bottom guides. 
approx 50mm to the underside of the table. options on changing the cool blocks type set up. (yes, those bits of wood are the same ones that it came with about 4 years ago)













Woeful dust extraction.
previous owner has cut a hole near the top of the lower cabinet, this is boxed in internally with a slot for the blade but I still get a lot of dust falling to the lower outlet at the base of the saw and this gets dragged to the top cabinet.


----------



## FlatlandsF7a (8 Feb 2022)

mindthatwhatouch said:


> Hi,
> What a great thread, looking forward to the blade tensioning update as never been happy with mine. Not wishing to hijack your thread but would appreciate your thoughts on the below. (If you want me to move it to a new thread, just say so)
> 
> Single phase machine. I got it running (came with electrical motor issues) believe it or not cleaned it up a bit and may have changed the wheel bearings, honestly can't remember. With the view to using it and improving it when I get round to it.
> ...


This looks a lot like (a slightly more hard-lived version of) mine, although mine has a manufacturer included dust extraction port at that point. I am also curious about installing different guides under the table, as mine has the same very small clearance.


----------



## deema (9 Feb 2022)

I wouldn’t replace those guides, with the right material they will be excellent, they were originally designed to be used with lignum, a good source is old bowling balls, or these days you can get ceramic inserts that may also fit, having the guides just under the table with minimum clearance is actually better than having them inside the cabinet. I will post some photos of how the lower guide is located on this saw shortly. Ive posted a thread on bandsaw blade guides you might find useful here:








Bandsaw Blade Guide theory!


My good friend and ‘partner in crime’ Sideways started a thread about the tear down and overhaul of a SCM S45 bandsaw which is presently ongoing, and has led us both down rabbit holes of learning. It’s been a fantastic project that has challenged a number of our preconceived perspectives. If you...




www.ukworkshop.co.uk


----------



## baldkev (11 Feb 2022)

Good job as always 
@deema on my mobile, if i press and hold over the like button, a few different emojis and a thank you sign appear.....

Interestingly my new ( to me ) startrite has a tension guage but im still guessing what is 'right'. Although i havent used it much yet, mostly put back together


----------



## deema (19 Feb 2022)

Sideways and I are now considering all aspects of the design we have come up with. One area that needs consideration is the capacity of the two wheel bearings. We needed to verify that the proposed worst case loads created by a M42 20mm blade can actually be accommodated by the bearings that are used. This is one reason we always use high quality bearings such as SKF, FAG etc and never in rotating load bearing applications cheap generic bearings. 

The Bandsaw is designed to use two 6202 bearings in each wheel mounted on an axle. This will set the limit on what loads we can reach by the springs tensioning the blade without damaging the bearings.

Bearings have many design factors specified in their data sheets, two of which are important for our application. The static and dynamic load capacity of the bearings. 






The dynamic capacity is when the bearing is turning, and is virtually always a much higher value than that for the static or not turning. The reason is that when turning, the loads that the race see are lower due to there being a rotating element, this reduces the effective racial load on the race: the faster a bearing turns the higher load it can withstand. To understand this better look up force diagrams.

The bearing can handle just over 8KN of dynamic load but only 3.75KN of static load. This is one of the major reasons that you should release the tension on the blade when the bandsaw is not being used.


----------



## Andrewy (19 Feb 2022)

deema said:


> Sideways and I are now considering all aspects of the design we have come up with. One area that needs consideration is the capacity of the two wheel bearings. We needed to verify that the proposed worst case loads created by a M42 20mm blade can actually be accommodated by the bearings that are used. This is one reason we always use high quality bearings such as SKF, FAG etc and never in rotating load bearing applications cheap generic bearings.
> 
> The Bandsaw is designed to use two 6202 bearings in each wheel mounted on an axle. This will set the limit on what loads we can reach by the springs tensioning the blade without damaging the bearings.
> 
> ...


----------



## Andrewy (19 Feb 2022)

Sorry.. is off topic, but the morticer in your signature pic looks very like the old one I have in the workshop .


----------



## deema (19 Feb 2022)

As we have two bearings to ensure they have a good life expectancy we checked the actual load that they can achieve and find an estimate for their life expectancy. I use the SKF bearing calculator tool that can be found on SKFs web site. We used SKF bearings to replace the wheel bearings.

First this is the data that is used to calculate the parameters





The results are:


----------



## deema (19 Feb 2022)

The bearings are limited by their static load capacity, so the maximum load that can safely be applied and left on the machine is 4KN. The L10 numbers represent, basically that 90% of all bearings will survive for at least this length of time. It’s the number usually used for determine the suitability of the bearings / application. For anyone interested further the SKF web site gives a good explanation. 





SKF







www.skf.com





This is a worst case scenario, with the bandsaw loaded to to its maximum tension, and running continuously. It would be expected to survive at least 181 days running 8 hours a day continuously. This type of bandsaw wouldn’t be expected to spend its entire life doing this type of operation, if this was required a larger bandsaw would be appropriate.

Typically this saw will generally be using a smaller blade, typically around 12mm or 1/2”. To tension a M42 12mm blade requires a lower tension. So plugging that data in to see what the elected life is:









The L10 is now 4750hrs or around 2.6 years of being run 8hrs a day (assuming 220 working days in a year). Again, if the saw was to be run continuously in what would be a production environment it wouldn’t be the right choice, a saw with larger bearings would be a better choice. However, in either scenario, for a typical professional small joiners / cabinet makers shop, this saw will probably last over 20+ years without any issues from the bearings. (That’s using it 1 hour every day with different blades)


----------



## deema (19 Feb 2022)

I always find this exercise interesting, it highlights the level of value engineering that has been applied to a machine. For instance, it wouldn’t have cost that much more to have moved to a slightly larger bearing for the wheels which would have increased the load capacity of the bearings and provided a longer life expectancy. But it all costs, and typically every £1 of extra material costs the end customer £8 by the time it’s gone through the distribution chain, so saving material cost it’s important to hit a marketing price point.

The fatigue life of a bearing, where it starts to skid and tear up the race is finite, so, when refurbishing a machine we always change every single bearing with high quality bearings that have been tested and verified to have a know life expectancy. It resets the clock, and in comparison to the new owner both frustrated that a refurbished machine has broken down and the cost of getting the bearings out and replacing them, we believe it’s a very small investment. 

For us, there are three important things concerning the bearings to look for when buying a machine.
1. High quality branded bearings are used throughout. If buying refurbished check what’s been used.
2. All bearings have been been replaced, including the motor bearings.
3. Look for machines with the biggest bearings possible. The bigger they are the longer they will last.


----------



## deema (19 Feb 2022)

The exercise has highlighted to us that the machine can safely be run with a 20mm carbon steel blade and left under tension for period of not being used. It can also safely be used with 16mm M42 blades without any concerns. However, the bearings aren’t really suitable for tensioning up a 20mm M42 blade due to the static load capacity. If left under tension and not in use the bearings will quickly fail. This is something that may change what we had planned to do. The spring arrangement we had devised can create a tension that is easily capable of tensioning up a 20mm M42 blade and not fatigue the springs, however the bearings are not really suitable for this.


----------



## deema (19 Feb 2022)

I often hear / see comments where people have cranked up the tension on a bandsaw to the point where the springs are touching and advocate that their saw can therefore take a much larger blade than is specified. Those who do this in all likelihood have not considered and done the engineering exercise to see if the springs will fatigue / fail due to being compressed by more than 25% of their relaxed length and that the static capacity of the bearings probably is sufficient for the loads, if not they are shortening their saws life considerably.

Ian at Tuffsaws usually advocates using a M42 blade at least one size lower than the stated capacity of the bandsaw, this exercise has demonstrated that Ian’s wisdom should be followed. I would go further, if it’s not at least a commercial grade of bandsaw, which the SCM saws are, then only use M42 blades that are around half the capacity of the saw. Never try to use blades larger than that specified by the manufacturer, and again, for none commercial grade saws use as a maximum carbon steel blades one size down from the maximum size in the specification to have a saw with a good life expectancy.


----------



## deema (19 Feb 2022)

@Andrewy it’s one of the few pictures I have of my great grandfather using an ancient Morticer in the family business. My grandfather and father were all apprenticed either master joiners or cabinet makers. I think it goes back further generations…..but no photos of that!


----------



## Sideways (19 Feb 2022)

As a point of reassurance while exploring spring options and blade tension, we kept an eye on the flex of the bandsaw frame by simply measuring how much the open mouth of the frame is pulled together by a blade under tension.





The good news is that the S45 lives up to it's reputation for a strong frame. 
With a 3/4" carbon steel blade fully tensioned, there is just 0.5mm of movement across an aperture of over 250mm.




Nothing to be concerned about and well within the elastic limit of steel. The deflection returns to zero when the tension is released as the physics say it should.


----------



## Jitter (19 Feb 2022)

Allot of useful advice there. It makes me feel much more confident about the S45’s capabilities and of course the upgraded bearings lifespan within the correct limitations is great to know also. I guess there must be many chippies who are tempted to push their machines to the limits or over without realising the potential damage to the machine doing so. Possibly may not even realise that a number of issues will gradually arise and cause problems and cost money along the way. Thanks for all the interesting and important information.


----------



## deema (20 Feb 2022)

To finalise what we are going to do with the spring(s) we needed to ascertain how much of the spring force was actually translated into tension on the blade itself. There is a lot of friction in a bandsaw tensioning system, all of which requires force to overcome. The SCM like many others has a carriage upon which the wheel upper wheel is located that is attached via a pin to the carriage holder through a pair of slots that allow the carriage to move up and down and tension the blade. The tracking is achieved simply by the end of a threaded rod pushing against the carriage with the pin acting as a pivot. None of these have ‘slippy’ surfaces and when under pressure caused by the blade being under tension generate a lot of friction. It’s for this reason, the losses through friction that most bandsaw blade tension gauges are next to useless. 

Sideways sourced a suitable spring to do tests with, this was a spring that had a sufficient spring tension and compressible length to determine how much force was being input into the system. A Lenox Blade tension gauge was used to measure directly the tension that the blade was seeing.

At this point I have to say a huge thank you to Ian at Tuffsaws. I contact Ian to ask technical questions for this project, and he very kindly offered to lend me his Lenox Blade Gauge for the testing. 

The photo shows the parts of the tension system.


----------



## deema (20 Feb 2022)

The spring with a known spring constant was mounted in the normal place and replaced the original spring, it didn’t fit in the sling holder which we temporarily removed.

The Tension meter reads directly the tension on the blade by converting the amount the blade stretches, elongates when under tension. It also allowed us to verify that the blade was operating in its elastic region.

















We slowly cranked up the tension checking the compression of the spring and the tension we were able to achieve on the blade. We also checked the amount of ‘nod’ or elastic deformation generated in the frame of the saw by placing a clock from the table to close to where the blade comes out of the top wheel. 

There was a significant loss of force from that created by the spring to that generated on the blade. This will be accommodated within the revamping of the tensioning system.


----------



## deema (20 Feb 2022)

For anyone serious about using a bandsaw a blade tension gauge is a vital tool to have and use. We used the gauge to check my Felder bandsaw, and that was actually applying significantly higher tension than the tension indicator on the saw suggested. So, the question is, how does the gauge work in case anyone wants to make one. A Lenox is eye watering expensive! In case you want one they are around £420!

There are a few uTube videos on building one, here is one for reference……I make no comment on woodworking practices shown!



Any material will elongate when under tension, the amount of elongation for a given force is related by the Young’s modulus. The standard equation is rearranged and what we are measuring written in:

Force / area = Youngs Modulus * change in blade length / initial blade length

Force / area is the units of PSI which the gauge reads directly, or by a conversion N/mm2

The gauge grips the blade at two points, one end of the gauge is fixed, and the other is a seesaw that creates a pivot magnifying the elongation of the blade by 3. Ie 1:3. The two points when the blade is slack are exactly 100mm apart. So, by direct measurement, 0.1mm of blade elongation was measured by the clock as 0.3mm to be 30K PSI or 206.84Nm2

If you plug those numbers into the equation you find that the gauge is calibrated to use a Youngs Modulus of 206.84! (Give or take a smidge due to measurement error)

Most HSS has a Youngs Modulus of 207 and including M42 fits within a band of c190 to 220, which although fairly broad only represents a maximum range of potential error of circa +/- 7%, which is more than accurate enough for setting blade tension. The bandsaw indicator would have been circa 60% out with the frictional losses!


----------



## deema (22 Feb 2022)

Last bit of ‘boring stuff’ before we get back to doing stuff. Sideways today made a good analogy. A Range Rover Sport (not that either of us have one) weights with a single driver and all fluids around 2000Kg. Each wheel therefore sees around 500KG or c4900N which is exactly the tension required for a 20mm M42 blade. 

So Wheel bearings typically have a life of c100,000 miles or, c 161000KM. 
A Range Rover Sport tyre has a circumference of 2.54M 
So, the wheel rotates 63,385,826 times in the bearings expected total life.

The bandsaw rotates at 750RPM, so the bearings will have done the same amount of work as the car wheel bearings in 1408hrs. A little less than the L10 (which is roughly work they need to do for there to be a 10% chance they will have failed) for this bandsaws wheel bearings! 

However, the car wheel bearings are significantly larger, they are around 90mm OD and have a width of 51mm. Where as the 6202 used in the bandsaw are only 35mm OD and only 11mm wide.

The bearings in a bandsaw are doing a lot of work!


----------



## Andrewy (23 Feb 2022)

deema said:


> @Andrewy it’s one of the few pictures I have of my great grandfather using an ancient Morticer in the family business. My grandfather and father were all apprenticed either master joiners or cabinet makers. I think it goes back further generations…..but no photos of that!


I haven't used it in a long time.. there was a similar one in a local industrial heritage museum therefore I wondered just how old it was. No makers name on the castings.


----------



## Sideways (23 Feb 2022)

Teaser post 
The S45 has now been modified with a new spring tensioning mechanism.
This uses three springs in parallel, moved inside the upper wheel tension / tracking assembly so the look is very little changed.




Initial tests look great. It easily goes up to the 20,000 psi needed to start properly tensioning a 20mm m42 blade with ample headroom to spare.





Hard stops are included at 25% compression so that the springs can never be over compressed and this is equivalent to 6,600N force on the wheel hub / 3,300N N blade tension so there will be no question of being able to achive proper blade tension upto the max specification of the saw.

If you look back at Deema's posts on page you you'll see that we need 4,900N at the wheel hub to tension a 20mm M42 blade to 25,000 psi, the top end of its recommended range. We have 20% in hand to cover losses due to friction in the mechanism and any weakening of the springs over time, though this shouldn't be an issue if they can't be over compressed.

The springs are 89mm long with a rate of 110N/mm compression. That means 330N at the wheel hub and 165N tension in the blade for every 1mm on the tension gauge which will be subtly remodelled but stays on top like the original.
The feel of the adjuster with the new springs is nice 

A couple more sessions in the workshop and this will be all done


----------



## FlatlandsF7a (23 Feb 2022)

Sideways said:


> Teaser post
> The S45 has now been modified with a new spring tensioning mechanism.
> This uses three springs in parallel, moved inside the upper wheel tension / tracking assembly so the look is very little changed.
> View attachment 130087
> ...


Teaser indeed!

I am eager to hear and see how your new mechanism works (unless you're waiting to submit a patent first!).


----------



## deema (23 Feb 2022)

We just ran out of time, there is a thrust bearing on order that we need to finalise the assembly of the system. That’s due any day now. Sideways will write up with photos what has been done.


----------



## Sideways (23 Feb 2022)

FlatlandsF7a said:


> Teaser indeed!
> 
> I am eager to hear and see how your new mechanism works (unless you're waiting to submit a patent first!).


It does involve surgery !
The old internal brackets need to be cut and ground out. New ones milled tapped and welded in place. Not a job for the faint hearted 
But some of the methods are just like you would apply with a wood saw, just using an angle grinder and cutting discs....


----------



## Sideways (27 Feb 2022)

We had three objectives for our redesign of the S45's tension mechanism.
1. To achieve the tension recommended for the widest (20mm) blade that the saw is specified for when using M42 blades, nor just carbon steel.
2. To be robust, easy to use and to add in stops to prevent over compression of the springs and the damage that results from this.
3. To keep as close as we could to the original look and feel of the saw.

It's time to let you all decide if we succeeded 

As a reminder, here is the two part pressed steel assembly that carries the upper wheel, tilts it for tracking and allows 30 to 40mm of vertical movement. In this image, the two parts have been opened like a book so that you can see the inside. Here the narrower fixed part is on the Left, the moving front part on the R.





Here's the modified assembly for the upper wheel laid out like an exploded diagram:





We have left to right:
The original tension knob
A new alloy disc with a groove cut and black filled for reading the tension
A new clear tube on which the tension scale will be applied
The original steel base of the tension scale
A new 10mm threaded rod and nuts
A new ball bearing thrust race to reduce friction when tightening and slackening the tension (boxed)
A new floating plate with guides for the outer pair of springs
A brass sleeve for the centre spring
Three new springs. These are part G25-089 from Berger tools. 25mm OD, 12mm ID, 89mm long and the G represents a specific family of heavy duty springs made from rectangular section wire something like 4×5mm cross section. These springs are conveniently colour coded. There are a few families of less strong springs and just one heavier grade but the yellow ones were a nice fit for the job. They cost less than £5 apiece. 
Modified original backplate.

Here are the new springs installed in the back plate (this time on the right), and the modified front plate (left).




On the L, the welded bracket was originally higher up. It has been cut out, ground back and a new bracket milled, tapped and welded in place lower down.

On the R, three springs sit on a new welded in shelf.
A floating bridge piece rests on top of them.
Both of these plates have an oversize hole in the centre for the tension rod to pass through.
A brass sleeve protects the middle spring from the threads.
Guide rods keep the two outer springs in position. These springs are 89mm long so to limit compression of the springs to 25% max, the guide rods project 89-22=67mm.

Two nuts are locked together to form a fixed stop on the tension rod. When the springs are compressed, the bridge piece pushes upwards, force passes through the thrust bearing onto the stop and pushes the rod upwards. When all is assembled, it's this upward force on the rod that pulls on the upper wheel and tensions the blade.







To assemble the bracket, the upper wheel is first refitted to the front part of the bracket, this is then placed over the back part and the tension rod screwed into the lifting tab to take it's weight.
A cross pin fits through two slots that allow about 40mm of vertical adjustment
This is secured with washers and circlips at each end.

At this point the upper wheel assembly can be bolted into the saw.

To finish off, the components for the tension indicator are threaded and screwed onto the tension rod.





The black line provides a definite index mark for reading the scale. Previously there was just a thick washer and no information about whether you should take the top, middle or bottom edge of the washer as the "pointer". SCM told us that we should use the bottom edge of the washer to read the tension and avaoid over compressing the original single spring, but that isn't explained in the instructions ...

As we have changed the springs, the old scale isn't relevant anymore. I'll draw up a new one based on the combined spring rate and this will be printed on clear film and applied around the clear cup.
By keeping to a 10mm tension rod, the original knob screws neatly on top 

A comment on the finish. Obviously grinding and welding on the metalwork affects the plating applied to these parts in manufacture. We can't practically replicate that but we do want to protect the metal afterwards. The brackets here have been degreased, given two coats of high zinc content cold galvanising spray and sealed with silver aluminium.


----------



## Sideways (27 Feb 2022)

Deema's rather pleased with his work here. Very neat  
The index ring screws on the tension rod, is secured with a grubscrew and a brass plug to avoid damage to the thread. It is sized such that the stem of the tension knob sits neatly within the clear tube and doesn't go to far down as you tighten up.


----------



## Sideways (27 Feb 2022)

In case you DO want to try this at home, here are the important dimensions.
This assembly is actually more complex than it looks because
1. The assembly allows tilt of the bandsaw wheel.
2. The tension rod is not parallel with the brackets because of this and it's angle changes depending both on the amount the springs are compressed and the tracking.

These mean that the threaded hole in the front bracket can't be drilled on centre, and the clearance holes in the rear bracket need to be oversize.















Just a note here that the bright zinc plated thread above turns out not to be good enough for the task. As the thread is turned under load to adjust tension, the zinc plate isn't robust enough and gets rubbed off the threads. Our local engineers merchant helped out with some better quality, self colour (aka black) threaded rod. This meets the same specification as steel nuts and bolts stamped with the 8.8 tensile strength code. 
In later posts, if you look at the tension knob, you'll notice the thread has changed to black.


----------



## Sideways (27 Feb 2022)

This is the Dunlop thrust bearing we added. It makes it far easier to turn the tension knob. Essential given that the saw can now properly tension a 20mm M42 blade.
A ball bearing type is better than needle rollers for this application.






Note the static load rating is 14kN. Our triple spring design maxes out at 22mm compression x 110N/mm x 3 springs = 7,260N so the bearing is more than up to the job.

Similarly, as we are re engineering the mechanism, we need to check that we are safe staying with M10 for the threaded tension rod. Preferable so that we can reuse the top knob and other parts.
One way to judge this is using the recommended tightening torque





For am M10 thread in standard 8.8 grade steel. Max torque tightening up a nut or bolt is 57Nm.
I have no idea what a Newton feels like but close enough the weight of a 1Kg bag of sugar = 10Newtons and I can picture that.
So 5.7Kg (force) at 1 metre is about 28Kg at the end of a 200mm long spanner. 25Kg is a very heavy bag when you have to heave it onto the scales at airline check in ! Hand tightening a 100mm diameter knob on top of a bandsaw, this is equivalent to over 50Kg of force. I would judge this sufficient for any reasonable expected use.

For a final check, the yield strength of 8.8 grade threaded fasteners in the 10mm range is given as 640 MPa
10mm rod: assume a worst case 2mm deep thread, giving a minimum cross sectional area of Pi x 6mm^2 / 4 = 2.8 x 10^-5 square metres
x 640 × 10^6 Pa (1 Pa = 1 Newton / square metre)
= 17,920 N More than double the maximum force that the springs can produce


----------



## Sideways (27 Feb 2022)

Does it work ?
Thanks to the loan of Ian's tension gauge, we can see the modifications pay off in a real, usable blade tension .
Here is a new, premium carbon blade bought for the saw tensioned to just under 19,000 psi with plenty of headroom left in the springs


----------



## deema (27 Feb 2022)

The thrust bearing chosen has a static and dynamic load bearing capacity of at least double the force that will be exerted by the springs. The number of rotations it will do tightening and slackening the springs means that it should have a life of multiple generations of users.

The threaded rod was replaced with one that is grade 8.8, again to ensure that the thread loading is well within its capacity. If too lower grade of threaded rod is used there is a danger that the threads will strip / gaul up and destroy themselves. Grade 8.8 has a proof strength of 580KN more than adequate!


----------



## Sideways (27 Feb 2022)

We decided that the top needed to be tidied up rather than just reusing original parts:





Two tuffsaws premium carbon blades were fitted, tensioned and tracked.
17,000 psi is a a good high tension for carbon blades. On our scale, these two blades (12mm and 20mm) reached tension at 8mm and 15mm.





12mm blade





20mm blade


----------



## Sideways (27 Feb 2022)

Then functional tests:

Blade guides were pulled completely away from the blade


----------



## Sideways (27 Feb 2022)

Wide open under power is NOT the way to do it !




Your browser is not able to display this video.


----------



## Sideways (27 Feb 2022)

What the tension sounds like




Your browser is not able to display this video.


----------



## Ttrees (27 Feb 2022)

@Sideways thanks for making the video of the ping test.

It sounds like the blade is hitting off a guide or something, certainly not as musical as I was hoping for, can you clarify?
i.e is there a point in which the blade stops ringing out and makes it sound as such?

Cheers

Tom


----------



## Jitter (27 Feb 2022)

This setup looks awesome guys! I’d presume (knowing nothing about engineering) that the incredible tension on the 10mm threaded bar would stop any movement/slip on the thread with vibrations while the saw is running now that the upgraded thrust bearing is making it easier to dial? Other than this, I can’t see any possibility why it would not work really well.


----------



## deema (28 Feb 2022)

The test cuts were done with the blade guides fully retracted. From end to end the blade cut straight to within 0.1mm when measured at either end. Not only does this highlight its setup correctly but also that the blade guides do not when the saw is correctly set play any part in the cutting, they are only there to stop problems due to either poor setup, bad practice or a dull blade. This is not to say that you don’t need to set your blade guides, you should they are an important safety feature.

@Jitter There Is still sufficient friction in the system to ensure that the threaded rod won’t walk out.


----------



## Sideways (28 Feb 2022)

Ttrees said:


> @Sideways thanks for making the video of the ping test.
> 
> It sounds like the blade is hitting off a guide or something, certainly not as musical as I was hoping for, can you clarify?
> i.e is there a point in which the blade stops ringing out and makes it sound as such?
> ...


Hi Tom, yes the blade was definitely hitting something when plucked, hence the harsh metallic vibration you noticed. I'm not sure exactly what, part of the guide mechanism I think.

Before we were fortunate enough to get the proper blade tension gauge, we talked about ways to measure tension and it's not easy.
If you have new springs, properly specified and well made, it is easy to calculate tension because you know the newtons/mm compression, can measure the spring length and the blade cross section.
Friction losses can introduce a sizeable error though.

Another cheap method is use of mobile phone apps for tuning instruments, bandsaws etc. These all rely on the idea of a plucked string, known length and detect the frequency to calculate back to tension. Deema bought one and we couldn't really make it work. The fundamental frequency for this saw at proper tension seems to be around 180 Hz. That's pretty low. Compared to many musical instruments it's a slack string and you have to pluck very gently, not with your fingernails, to get a clean note that low. The phone struggles to hear it.

Of course the audio method depends on the length of the "string" so all else apart, smaller bandsaws will make a higher note than bigger ones when both are correctly set to the same tension.

The lenox tension gauge has been very useful to us in this project. The concept is very simple. It just measures stretch in the blade directly and assumes a fixed average value for stress / strain to display the meaasured stretch as tension in PSI. We'll be making our own version of this to use with the workshop dial indicators


----------



## FlatlandsF7a (28 Feb 2022)

Really fantastic work guys. 

I'd love to do this to my saw, but I don't think I've the skills to pull it off! Ingenious design, and lovely to see it come together so well. Congrats on a great build, and thanks for showing us your working step by step, this is an invaluable thread to any S45 owner!


----------



## Sideways (12 Mar 2022)

Just popping this on the end. Proper test cut with a good new tuffsaws blade, tensioned and tracked.




Your browser is not able to display this video.



































































55mm oak.

That worked


----------



## Ollie78 (13 Mar 2022)

Good job, never had a bandsaw cut as sweetly as that.

Ollie


----------



## squib (16 Apr 2022)

What a superb thread and a huge thank you for spending the time and effort to share this.
I have only just read it, which is a shame as I have exactly this model, except mine is 240v, and could have helped with measurements and I also have a manual etc .
Mine had been caned cutting up waste in a uPVC factory and I had to have the bottom wheel sleeved for new bearing. Actually twice as the first engineering guys made it worse!
Also I used urethane blue tyres which seem ok but the tracking is a bit tricky on some blades, having said that I don't use the Bandsaw that often and tend to use a different blade for different jobs which means I maybe don't spend enough time on setup.
I look forward to hearing about your tension meter.....I have a spare dial guage...


----------

