Bandsaw woes?

[MIGNAL]

Bandsaws again
I've had a cheapo Perform Bandsaw for some 5 years and despite it's obvious limitations it has served me well. Having said that it never has had a great deal of use and the maximum depth of cut had been 4 inch (rarely) but more usually 2 inch or less. Until now. I tried resawing some highly figured Maple at this bandsaws maximum ie. 6 1/4 inch. Below is the result:

Not bad for a cheap bandsaw and the cut is dead on 4 mm top to bottom but there are some fairly deep diagonal gashes/striations. The horizontal piece shows it best but they are just as bad on the vertical piece of Maple. Is this due to the figure? the 3 TPI dure-edge blade? Have I exceeded the capability of this particular bandsaw? The bandsaw has been set to run co-planar and the guides are oiled hardwood dowels virtually touching the blade.

 

[orangetlh]

looks like your trying to feed it into the blade a bit too quickly and the blade is trying to catch up on itself... if you know what i mean. try a bit less pressure while your feeding

 

[Chris Knight]

You are sawing a pretty hard wood and from the looks of it you have not been able to tension the blade enough - so it bows slightly as you feed the wood to the blade. You don't say how wide a blade you were using but on a small saw I wouldn't expect to be able to sufficiently tension a blade wider than half an inch.

You can try to reduce the feed rate. The tooth configuration should preferably be a hook blade. 3 tpi is about right for your saw size and the feed rate you are likely to find optimal.

 

[MIGNAL]

Yes, it was a 3 TPI 1/2 inch, hook tooth. Too fast a feed rate is possible (probably very likely, knowing me), in actual fact it seemed to go through in stops and starts as though it was hitting a whole row or series of knots. I just assumed it was having trouble with the different grain structure of figured Maple.

 

[mailee]

Not sure if this is the reason but on mine when I try to cut deeply it tends to build up dust in the blade teeth and does just as you describe. Maybe a skip tooth blade might be the answer. IMHO. :wink:

 

[MIGNAL]

Hold it. I just assumed it was a hook tooth, I think I should go and check. Interesting that you should say that the blade might be clogging with saw waste, the bandsaw does not have a brush and it might be worth rigging something up.

 

[DaveL]

MIGNAL,

The brush in some bandsaws is normally to keep the tyre on the lower wheel clear of saw dust, not to clean the blade.

The build up of dust, which I have had happen to me, is the gullet of the tooth not being able to move all of the dust produced by cutting the depth of board that is being resawn. Normal solution is a lower tooth count or different tooth configuration, but if you have no option but to use the blade you have then try a slower feed rate.

 

[David C]

I am familiar with those marks which seem to represent a form of vibration (harmonic??) which can be set up during sawing.

Mine are generally less pronounced and not always present.

Deeper cuts in closer grained timbers do suffer. I have made ten inch deeping cuts on my Robinson, which is a much larger machine.

Just hoping some expert sawyer can help to solve this one?

I suspect inadequate tension as 3TPI should be plenty coarse enough for your depth of cut.

best wishes,
David

 

[Scrit]

Deeper cuts in closer grained timbers do suffer. I have made ten inch deeping cuts on my Robinson, which is a much larger machine.

Just hoping some expert sawyer can help to solve this one?

I suspect inadequate tension as 3TPI should be plenty coarse enough for your depth of cut.

If you have a Robinson, David, can it take a 1-1/4in blade? If it's a TD/E, TD/T, EY/E, EY/T or YD/T then it should be able to tension a thicker blade such as a Lenox Trimaster III TCT 2 to 3tpi vari-pitch hook form on a 1-1/4in body. The variable pitch reduces the harmonics dramatically, although a power feeder, such as the Comatic AF/19 resaw feeder will also help provide a much better quality veneer by making the ridges more even

I've been able to produce 0.8mm veneers on an Agazanni Cosma 700 bandsaw with the earlier AF/18 resaw feeder in this way for a number of years.

The downsides are that the TCT blades will cost you circa £120 to £150 for your saw whilst the power feeder is around £1200 or so from Conway Saw in West Bromwich. This model really won't go on anything smaller than a 24in/600mm machine, although smaller ones are available

For smaller saws the best thing I've found is to go for a hook tooth rather than skip tooth as the larger gullets handle waste better and to try and keep the tension as high as possible. I suspect that the OP's Perform BS cannot really tension the 1/2in blade adequately.

Scrit

 

[MIGNAL]

What does baffle me is how near the cut is to 4 mm. I have a long reach dial caliper accurate to within 1/10 th of a mm and it measures 4 mm (+ or - 3/10 th's) irrespective of where I measure it, edge, middle, ends. That seems pretty accurate for such a cheap bandsaw at it's absolute maximum capacity. Low tension on the blade and I wouldn't expect to get that kind of accuracy. I'll try some more cuts and see if a slower feed improves things.

 

[David C]

Mignal,

+ or - 0.3mm is quite good though I get disapointed if the error is more than + or - 0.1mm.

Scrit,

Thank you so much, I could certainly run a 1 1/4" blade, though I would have to do some major work on my homemade Lignum guides.

Currently using 5/8" meat and fish, because of the fine kerf and small set. The small set leaves a surface quite good enough for gluing, and I often use polyurethane glue for bandsawn veneers now as I worry less about the posibility of small voids!

I will look into the details of that vari pitch blade, kerf width and resharpenability. I think I would not be able to justify the cost of the power feeder, though I am aware of how much these improve most machines from my commercial friends with larger machinery.

I have also wondered if the 40? year old tension spring on the Robinson needs replacing, as it might be a little tired by now?

Robinson Cadet, Mc. no 30, Type EY-E, size 24" wheels. Would you have any idea how old this wonderful machine is please? It is much my favorite machine in the workshop.

best wishes,
David

 

[ivan]

No expert sawyer here, but plenty of washboard experience! No bowing, looks like so called 'harmonic vibration' when blade teeth vibrate twisting side to side in the cut, inside the wood like this:

top guide
(
)
(
)
table

You can hear it begin (if you push too hard) and feel the extra resistance as kerf increases somewhat.

Cause? probably not enough tension/a springy bandsaw frame
Cures?
1/ Narrower blade (can tension more rigidly)
2/ Hook tooth blade (feeds with less pressure)
3/ Variable pitch blade. For occasional use a 'Woodslicer' from Highland Hardware is cheaper than a new bandsaw.(3-4pitch hook available in 1/2", see their website)
4/ Small tension adjustments - to move away from resonance (may help, but likely not a full cure)

edit PS:
Highland's blade is unusually thin so lighter saws can tension it, and they have a useful article on resawing, too.

 

[Stu in Tokyo]

Mingal, you have gotten a lot of good advice here.

Like Ivan has said, it sounds more like a tension problem to me, how old is the saw and or the spring?

A new better spring is not much money. Sometimes the spring that comes with the saws are not the "Best" out there. Of course, if your frame cannot withstand the extra tension, then a better spring is not going to help.

I use a dedicated resaw bandsaw for doing my resawing, but, I have used the Phoenix for a few cuts, just for fun....

I used a 3/8" 3 TPI blade I got from Lee Valley........

These blades (previously identified as the Timber Wolf® brand) have a five-tooth pattern with minimal set (every fifth tooth is a straight raker), a 6-1/2° rake angle, and a hook angle that results in an incredibly fast-cutting, thin-kerf blade with fast chip removal and, most important, a smooth finish that requires little sanding.

I use the 105" blade, which costs $20.50 US from LV.

I have the 1/2" blade and it even does a nicer job!

Cheers!

EDIT:
Sorry I forgot to add the Health and Safety bit...

WARNING DON'T TRY TO DO THIS AT HOME, MY BANDSAW AND MY TECHNIQUES FOR CUTTING WOOD MAY BE COMPLETELY IDIOTIC AND NOT A GOOD IDEA TO ATTEMPT, DO NOT EMULATE ANYTHING I DO OR SHOW IN MY POSTS, AS YOU COULD GET SERIOUSLY INJURED. :wink:

 

[woodbloke]

David C wrote -

homemade Lignum guides.

Just a snippet...glad someone else apart from me uses lignum blade guides, I also use the thin 14 thou blades from Axminster which you must order by 'fone, they are the same blades as in the catalogue but made from thinner gauge steel. The ones quoted in the 'book of words' are made from stuff which is far to thick for my Euro260 - Rob

 

[MIGNAL]

Just an update. I've had the chance to check some of the potential causes of the rough cut. The blade is not a hook tooth, it's a skip tooth 3 TPI 1/2 inch (not the fault of Dure-edge). The bearing on the top wheel has a slight 'ticking' noise when spun, I think it affects the balance because the wheel has a tendency to stop between 9 & 12 'O' clock. I can't detect any 'play' in the bearing and I'm quite sure this ticking noise was there from new but I've always known that the bearings in this machine were far from good. That's partly why a few years ago I replaced the roller blade guides for Bubinga dowels. That really was an upgrade.
I also have my doubts on the bottom wheel being balanced. That's proving difficult to check because the pulley belt gets in the way. It doesn't 'tick' but it does seem to reverse direction at the end of the spin, again it could be the poor bearings. The drilled blind holes are present so at least they had a go at balancing the wheels.
The main frame post seems reasonably substantial for this size of machine but it obviously doesn't compare to larger and more expensive machines. I wouldn't call it 'weak' though. Of more concern (I believe) is this section:

There seems quite a lot of flex in the frame section where the cut out is for the blade guard. I'm not sue how much that affects things? Obviously short of getting a Stu style welder out there's not a lot I can do about that, and the machine isn't worth it. With a hook style blade and better main bearings things just might improve.

 

[David C]

Thank you everyone, lots of good information indeed.

Stu,

Would I be right in thinking that the cylinder and also a cone are demonstrated in bandsaw Video/dvd or book by one of the American experts? Either Patrick Spielman or ######? (I forget......)

Best wishes,
David

(NB both techniques certainly break current Euro health and safety regulations.)

 

[Stu in Tokyo]

Thank you everyone, lots of good information indeed.

Stu,

Would I be right in thinking that the cylinder and also a cone are demonstrated in bandsaw Video/dvd or book by one of the American experts? Either Patrick Spielman or ######? (I forget......)

Best wishes,
David

(NB both techniques certainly break current Euro health and safety regulations.)

Nope, well, not to my knowledge. A buddy in the US who has two really high buck bandsaws, a 16" and a 24" (with a power feeder on the 24" for cutting veneer) told me that with a 1/4" blade on there, I should be able to take a tall piece of wood and cut a1" dowel out of it, IF the saw is preforming how it should be. He says both of his saws will to it to the max cut depth without a bit of drama. Now I'm not saying he said to use as small a piece of wood as I did, but this was a test of a very talented very experienced wood worker who makes a TON of custom interior stuff, and has for years, he can still count to ten on his fingers too. I will refrain from telling you his name, in fear of him being called bad names :lol:

Cheers!

 

[David C]

Stu,

Its always good to hear where people saw things.

I know I have seen cylinder and cone cutting in a well known USA bandsaw tune up or use video, just can't remember precisely where.....

best wishes,
David

 

[ivan]

Most top guides will move a bit if pushed, unless you have a real industrial machine. Fine Woodworking tested some blades on a 14" wheel bandsaw and used a 7lb pressure to feed the stuff in; I guess you'd feed more gently than this on a saw you knew was light, when aiming for a fine cut. The flexible saw frame problem that affests blade vibration, relates to the ability of the saw to hold it's wheels in place as you crank up the blade tension. A rigid frame allows high tensions, and will be fitted with a strong spring. You need more tension for deeper cuts, unfortunately. (15,000psi ideal) See here for cheap way to measure;
https://www.ukworkshop.co.uk/forums/view ... sion+gauge
However, tension is measured in psi (pounds/sq inch in the X section of the blade) so the same load set by the tension screw on a thinner or narrower blade, will result in higher psi. FW writers have sometimes suggsted 1/4" blades for deep cuts, but probably not for veneer cuttting - wouldn't steering be more difficult? narrow blade lead etc? Hence the interest in thinner than normal blades for lighter saws. We used to have a lightweight 16" bandsaw, same problem exactly with standard 1/2" 3tpi blade, cured with one of those Woodslicers. The thinner Axminster blades Woodbloke mentions would be easier to try.

I think it was Mark Duginske who did a video (and a book too) Ax probably sell both.

 

[David C]

Thanks Ivan,

That was the chap.

David