Bandsaw Blade Guide theory!

[Terry - Somerset]

I have also found that failing to set the rear guide close to the blade is a quick way to ruin a blade.

As the blade moves back between the side guides the teeth get mullered and remove the kerf/set. With no kerf the blade struggles to cut - slow and burns the wood.

 

[Hornbeam]

But this is totally predictable. It's how the blade naturally tracks on the tire and the harder you feed, the more it moves. To avoid oversteer on a narrowboat, you return the rudder to centre before you complete the turn. You can easily back off the feed pressure on your bandsaw before you reach the line to allow for this ?

If cutting tennons, I would be using a medium width fine blade set up with a stop block behind the blade to set the tennon length. If the blade is set up correctly with a good blade there is minimal movement so the rear guide can be set tight to the back of the blade (just catching)
I do have a couple of questions.
How do people track their blade. I set it so the teeth just overhang the tyre
Do narrower blades move more. Logic says they should as they are less stiff and can take less tensioning, I always use the widest blade I can get away with and I dont do many tight curves/circles/bowl blanks
I am generally nowhere near the capacity of my machine so I suspect less blade movement. My general principle is buy the machine which has more capacity than you think you will need and then add some rather than trying to strain an underpowered under engineered machine

 

[deema]

I have also found that failing to set the rear guide close to the blade is a quick way to ruin a blade.

As the blade moves back between the side guides the teeth get mullered and remove the kerf/set. With no kerf the blade struggles to cut - slow and burns the wood.

If the blade is moving back something is wrong with the setup, the blade guides are only there to stop bad things happening when something isn’t right. A bandsaw doesn’t need blade guides when everything is setup correctly.

 

[deema]

@Hornbeam it depends on the type of tyres you have. Crowned tyres need the gullet of the teeth just in-front of the top of the crown. Flat topped tyres need the teeth overhanging the front of the wheel. Semi crowned tyres run wide blades with the teeth overhanging the front of the wheel and for narrow blades where this isn’t practical, the gullet of the teeth just in front of the crown.

 

[Sideways]

As the blade moves back between the side guides the teeth get mullered and remove the kerf/set. With no kerf the blade struggles to cut - slow and burns the wood.

This means tha the side guides were wrongly set. Totally agree that they should never touch the teeth or they cause damage exactly as you describe. If the rear guide is set a little back (just a mm or two), then the side guides must be set back the same amount.

 

[Sideways]

If cutting tennons, I would be using a medium width fine blade set up...

When you feed the end of your stock into the blade to cut the cheeks of your tenons, what is the max thickness of timber you are trying to rip with a fine tooth blade ? You could be making jewellery boxes where this would sound reasonable or doors where it wouldn't.

 

[sometimewoodworker]

@deema I thought that everything you said was so obviously the correct way to set the guides. I just followed the instructions in my bandsaw manual. The only point with setting a guide touching the blade is if the weld hasn’t been ground to exactly the same width as the blade they will catch & many users may not have the skill or equipment to correct tat problem.

positioning of the blade on the wheel if the tyre is flat is also the way my manual reads & I’ve been doing that for 50 years.

The one point you haven’t covered is blade drift. With a crowned wheel you can adjust the position on the wheel to run the cut parallel to the mitre slot and set your rip fence parallel to the mitre slot. But with a flat wheel that method does not work so you have to adjust the angle of the rip fence to be at 90 degrees to the cut, this will probably not be parallel to the mitre slot. It is the reason for rip fences on flat tyre bandsaws to have adjustment available.

 

[Ttrees]

For those folk who adjust their fence instead of the table,
would you go back to using that method after using a machine that has a rail for crosscutting?

 

[Hornbeam]

@Hornbeam it depends on the type of tyres you have. Crowned tyres need the gullet of the teeth just in-front of the top of the crown. Flat topped tyres need the teeth overhanging the front of the wheel. Semi crowned tyres run wide blades with the teeth overhanging the front of the wheel and for narrow blades where this isn’t practical, the gullet of the teeth just in front of the crown.

My tyres are flat topped so yes where blade width allows I would set with the teeth just overhanging the edge

 

[Hornbeam]

When you feed the end of your stock into the blade to cut the cheeks of your tenons, what is the max thickness of timber you are trying to rip with a fine tooth blade ? You could be making jewellery boxes where this would sound reasonable or doors where it wouldn't.

By fine I am talking relative to what I would use for a standard cut. but agree that if i was cutting 1/2 inch material I would be using a finer blade than say 3 inch material. What I am looking to achieve is a joint surface straight off the saw and as I am cutting joints I would probable be using a slower feed speed

 

[sometimewoodworker]

For those folk who adjust their fence instead of the table,
would you go back to using that method after using a machine that has a rail for crosscutting?

I adjust my rip fence to my blade blade drift.
I do not understand your question.

 

[Ttrees]

@sometimewoodworker Only saying it's just as quick to adjust the table.
I can't see why one wouldnt want to line up the mitre gauge slot.
I think having table aligned makes for a better chance of a good result when milling logs, when the timber disagrees.
Could even fit up a system like this which looks interesting.
mines just a bit of ply with two cleats

 

[RobinBHM]

That’s an interesting experience, what problems do you encounter. I have to admit, I use the same blade for both and as long as I haven’t distorted a thin blade (usually overheating it) by cutting too tight a radius and forcing it (no, nobody ever does that….right!) I’ve not noticed any issues with it cutting straight.

I think cutting curved work tends to wear the blade more one side than the other, either sharpness or set, then when cutting straight it won’t cut cut parallel to the fence

 

[RobinBHM]

I have to say, with a well set up bandsaw and a decent sharp blade, it can be used for high precision work. I’ve done rips on the bandsaw that are consistently within about 0.3mm throughout the length.

I use a bandsaw mostly for ripping timber, almost never for curved work.

 

[Sporky McGuffin]

If the blade twists too much it will break, which is exciting

Really good set of posts - thank you.

I would like to applaud the above in particular as a marvellous bit of writing.

 

[sometimewoodworker]

@sometimewoodworker Only saying it's just as quick to adjust the table.
I can't see why one wouldnt want to line up the mitre gauge slot.

@Ttrees it may be true that for some bandsaws that adjusting the table is as quick as adjusting the fence. That is far from the case with mine. I don’t know if the 4 table bolts are in holes large enough to allow for adjustment, I do know that they are steel bolts almost certainly going into an aluminium casting, whereas there are 2 adjustment socket screws Accessible from the top for the rip fence. This makes adjustment of the rip fence a simple job as everything is done from the top.
In my usage I seldom use the mitre slot and it has never been a problem or even a slight difficulty that the angle set on it may be slightly different from the cut.

So in short the adjustment from the top of the rip fence is quick and easy, adjusting the table is neither.

You may have a need for the mitre slot to be parallel to the cut, your table may be quick to adjust.

If I ever find any benefit to taking the time to adjust the table I will remember your suggestion.

 

[Ttrees]

I'm only half joking really, as it might be more practical for other machines.
Only made a bracket not so long ago for table alignment, so will be interested to see how i get on once I get that fettled, as my tires are dressed properly, new dual milled beam for wheel alignment, seems a lot more sure than just a shot in the dark with most other methods I've seen, i.e laser which is not on the wheels, not seen proof that it works yet.

So I suppose I might be talking junk, and no one ever needs look at their table again,
if they can line up everything without needing to touch it.
One could do this a few ways with a laser, the one method I've watched I'm not convinced its as easy as that, but possibly a start?

I reckon the beam would be more accurate so far, but I suppose its all in the air if the tires aren't proved to be accurate first (plus other niggles)

Why does this matter?
It darn well does on some machines as misalignment causes motor bearing damage,
is less than an moment on some machines.

So without knowing everything about ones machine, condition+tires+ wheel alignment,
I see no one has a real excuse for sticking to their guns in regards to this drift discussion, if those things are omitted.....

If being as much of a stickler as myself and wanting the machine to run as good as it possibly can, and for as long as possible.


That's coming from someone who's got experience with 2 lemons, brand new and old, but even if my most recent machine was perfect, still made all the mistakes already with it, and wrote a juicy plonking thread with all there to see the why's.

A better read if done backwards, before reading the normal way after, just to see the tact where I was going astray.

All the best
Tom

 

[sometimewoodworker]

So I suppose I might be talking junk, and no one ever needs look at their table again,
if they can line up everything without needing to touch it.

it is only a small minority, those with flat tires on the bandsaw, where it is even a thing. I highly doubt that you are talking junk, just that your saw and cutting needs are not universal. for your saw and cutting needs it’s probably a good plan. While for me, my saw, and cutting needs alignment of the rip fence is quick, easy and gets my saw ready.


If you have crowned tyres then it’s a completely different setup and neither the table nor rip fence needs adjustment as it can all be done by tracking the blade on the wheels.

FWIW I am considering adding a crown to my tires when I fit the new ones I recently got, the jury is still out on that idea.

 

[Ttrees]

@sometimewoodworker
Regardless of what might suit ones work, I was just picking up that one should probably
have a very good idea of the machine, including disassembly of the table to use the beam.
Once one does that more than twice, I reckon they might likely choose to fix their "error"
as that is what it will seem like more so than if one were to adjust the fence instead.

The part where I may be talking junk is something like ....
If you haven't taken the table off, how do you know the machine is set up as good as it can be?....

Not saying there's not an easy way around this which hasn't been demonstrated,
but I have yet to see it.
This is relevant if one has a large hub in which the belt rides in,
Misalignment here, one could say a cattywompus effect is an understatement, so
my take on things is its possibly easy to end up with the same effect as the other S45
on ...."the place we can't mention here, 2"
in which it seems the hub is going to get machined for larger bearings!,
but even if that were not the case, seems easy to do the same with the motor too,
or just to knacker them enough to make them real scratchy.

Hopefully I'll get a wee part made within the next day or two and get to test out my
newly fettled machine....should I not find other issues, and get things done to my liking.
Pity I don't have any good narrow gauge blades to compare with my Axi ones,
what a difference in table adjustment I needed to make,
fair enough everything was all up in the air and serious work needing doing to the machine, so I can't say it that adjustment would be any different now.

That's a big question in my opinion, using differing blades of the same width,
and that's only to start with!.

It may change ones opinion whether that table or fence adjustment would be preferred.
Not that I think I'll be changing my ways,
I could just be here to sell you a bandsaw buddy!

All the best
Tom

 

[Ttrees]

I've since made some changes to that alignment method,
dressed the face of the wheels until the scribing beam couldn't pick up an error,
in regards to alignment, turns out a 0.5mm discrepancy of the wheels, depending on where the
beam were placed on the wheel, could mean anything up to 4mm on a 24" machine.
Most enlightening!

Little bit of explanation into this technique.
Suitable blade used, and tracked as such in order not to scuff the timber

PEN, not a pencil

The suggestion of where the blade may be going...if one doesn't have an accurate alignment groove for the tires, and is bonding new rubber (pre crowned), flush with the edge,
for it may not be trustworthy at all.
I'd certainly tram on new pre crowned rubber tires if there was no groove.

Couldn't get my 0.5mm Shinwa rule between the tram on the lower bandwheel.

Dressed the faces of both wheels to within around 0.2mm, as that was about the point where the pen on the beam wouldn't pick up the error, on these 24" wheels.
Mark where you can hear it, use a finer file when getting close,

Make the custom file handle, thick enough so it's dead centre, and cannot be turned upside down.
Arrows are no good, as cast iron drawfiling will get things messy.

And you'll just have to pretend I have a machine with a foot mounted motor
to align the motor with the datum line.
On my machine that's the upper wheel, but that could differ dependent on some saws.

Bearing to clear the shaft

Motor aligned on two axis