PDA

View Full Version : Bandsaw question



Timbuck
04-29-2016, 11:51 AM
I have an occasional problem on my bandsaw....When sawing thin slices off a billet at about 7 inch, every thing is going great ..then
all of a sudden the saw blade starts to vibrate and gives off a resonant howl and the finish of the cut is rough:( ...I suspected it could be the wheel bearings or the tension of the blade could be wrong I've fiddled about with it but the problem is still there...it dosn't do it on shorter hight timber..any thoughts on the problem are welcome.

Michael N.
04-29-2016, 12:01 PM
You should be able to check the bearings, see if there is any play. A 7" cut would require a pretty low TPI. If the blade can't clear the waste it can lead to a poor cut, clogging the tooth gullets.

Timbuck
04-29-2016, 12:36 PM
You should be able to check the bearings, see if there is any play. A 7" cut would require a pretty low TPI. If the blade can't clear the waste it can lead to a poor cut, clogging the tooth gullets.
Hi Michael it's a special blade I'm using at the moment 3 TPI with a small tooth in between the main teeth..it's supposed to be specially designed for cutting veneers...I sliced off about six slices at about 3.5mm with a really good finish.. Then the resonance started up I changed the blade for another new one, but the problem was still there so it looks like some thing in the machine is amiss ..Ill strip it down tomorrow and give it a good service and see if that fixes it.

oudin
04-29-2016, 06:45 PM
A perfectly set up bandsaw is capable of doing this. Although it never hurts to strip it down and tune everything up, in my experience if that dosn't fix it the problem is caused by blade tooth set and as you observed only occurs when cutting a particular thickness. If the tooth set is too regular a wave pattern can propagate in the wood and once it does it causes the runaway vibration you are observing and is unlikely to stop until you stop feeding the work into the blade. Although the irregular-sized-tooth blade you describe is less susceptible to this problem, it may be that the tooth set is something like Right-Left-Rake-Right-Left-Rake, etc. A more irregular set pattern will be less likely to succumb to harmonic vibration. I'm sorry if this reads pedantic. I have struggled to figure this out as well and have more or less arrived at the conclusion for myself that it's a blade issue and can't really be fixed, only replaced. I hope you figure it out and if you do please let me know how you do it!

chuck in ny
04-29-2016, 06:59 PM
if the saw cuts lesser height wood well it's probably set up correctly. i do resaw work with 1.3 tpi although my blades do not leave a smooth finish. try things at half your usual feed rate. if they improve, you can figure the gullets were getting clogged. i just got in 2 tpi blades and figure to take it slower with them and see if finish can be improved. guys talk up the carbide blades but it's too easy to stay with steel tips as you can touch them up on the machine with a dremel and a fiber wheel.

Michael N.
04-29-2016, 09:38 PM
Hi Michael it's a special blade I'm using at the moment 3 TPI with a small tooth in between the main teeth..it's supposed to be specially designed for cutting veneers...I sliced off about six slices at about 3.5mm with a really good finish.. Then the resonance started up I changed the blade for another new one, but the problem was still there so it looks like some thing in the machine is amiss ..Ill strip it down tomorrow and give it a good service and see if that fixes it.

You must have the Tuff Saws vari cut blade? If so I have that blade too and it works extremely well. I'm not cutting to that kind of depth though. Most I do is a mere 4". I think that blade has a minimum set. You could try phoning the guy at Tuff Saws (forget his name, Ian?) but he's pretty helpful at things like this. Another type of blade might solve the problem, at the expense of a slightly rougher cut.
Here's what I got when I tried to cut 6" Maple. It was quite a few years ago, so probably wasn't a Tuff Saws blade. It's a clear sign that the blade can't remove the waste fast enough. That and the fact that my bandsaw is of the very cheap variety, probably not being able to tension the blade properly. At 4" and under it works extremely well. Given that I buy my wood as sawn veneers, I don't really need big resaw capacity.

http://i56.photobucket.com/albums/g193/mignal/Veneer503x671.jpg (http://s56.photobucket.com/user/mignal/media/Veneer503x671.jpg.html)

Timbuck
04-29-2016, 10:40 PM
Yes you are right Michael ..it is from Tuff Saws ....it's the "Super Tuff Fastcut" My bandsaw has two speeds i think i'll give it a try at the slower speed and let you know if it works.
Now I think about it it's just like what we call "tool chatter" when machining a fine finish on metal in the lathe....Here is a bandsaw artical on it
http://link.springer.com/chapter/10.1007%2F978-3-642-28768-8_63#page-1 it identifies the problem but dosn't help much...I'll do more research ;)

Timbuck
04-29-2016, 11:13 PM
Found out some more stuff..I like the "Flutter" idea i'll try that, But! don't think the oil and kerosine lubrication spray is a good idea on soundboards :(
http://www.suffolkmachinery.com/six-rules-of-sawing.html

Kekani
04-29-2016, 11:53 PM
If it always happens in the same place, check for drift, if any. Something may be grabbing the backside of the blade, of course that something is wood.

And check for square, of course.

I used to have this when I had my 3" Stellite on my Hitachi - right at 3" in, flutter would occur. Doesn't happen anymore with my 1" blade conversion, and a Lenox Woodmaster CT.

Since I re-setup my saw per Carter's (gullet on the center of the top wheel), saw cuts like a champ!

Michael N.
04-30-2016, 02:00 AM
Actually I've never thought to lubricate a bandsaw blade. Must try it. Candle wax might be good, applied before each cut. If it's good enough for handsaws and plane soles.

FarmerBill
04-30-2016, 04:07 AM
Could the blade be getting too hot in the thicker cut and going slack. I have been using the Wood slicer and it works well. They have a setup sheet that was a help to me.
http://www.highlandwoodworking.com/library/Slicing%20Wood.pdf

Timbuck
04-30-2016, 05:46 AM
Just realised that I can't test the bandsaw out now co's i've already resawn all the mahogany that I had in stock...Maybe some sympathetic wood supplier on the Big Island could send me a spare Koa billet he dosn't need, to experiment on ???.. 24" x 7" x 4" would be ok Sir .:rolleyes: (Ken you are a cheeky sod, nice try tho)

Timbuck
04-30-2016, 09:43 AM
Good old Matthias ...He explains in detail whats happening but still no cure https://www.youtube.com/watch?v=DfW0W-dilfg ... I'll get on the phone on monday and have a chat with Tuff Saws and see what they recommend.

chuck in ny
04-30-2016, 11:59 AM
If it always happens in the same place, check for drift, if any. Something may be grabbing the backside of the blade, of course that something is wood.

And check for square, of course.

I used to have this when I had my 3" Stellite on my Hitachi - right at 3" in, flutter would occur. Doesn't happen anymore with my 1" blade conversion, and a Lenox Woodmaster CT.

Since I re-setup my saw per Carter's (gullet on the center of the top wheel), saw cuts like a champ!


a good thing is not taking yourself and your knowledge too seriously. i had read enough about bandsaws and talked to enough guys, and then happened on the carter youtube video and got my mental clock cleaned. i had been using wide blades where they could be moved back some but not exactly centered, these are 1.25", and ordered some .75" so they would be easy to center. you can resaw with half inch and up blades no problem. haven't put them on yet. the guy really knows bandsaw operation.

Kekani
04-30-2016, 06:39 PM
a good thing is not taking yourself and your knowledge too seriously. i had read enough about bandsaws and talked to enough guys, and then happened on the carter youtube video and got my mental clock cleaned. i had been using wide blades where they could be moved back some but not exactly centered, these are 1.25", and ordered some .75" so they would be easy to center. you can resaw with half inch and up blades no problem. haven't put them on yet. the guy really knows bandsaw operation.

Not sure how to take this Chuck; I might be missing something in the internet context.

Yeah, I take my tools seriously, after all those with the most, wins!;)

I'm very fortunate to have a resaw. Big $$$, but lots of fun.

Posted this before, and sharing again.

https://youtu.be/HEPCP1IxRBw

Timbuck
05-01-2016, 09:31 AM
To day i stripped down the bandsaw..cleaned and greased the bearings cleaned the tyres..fitted a new blade and reset the guides so they were almost touching the blade set the blade so that the teeth were just forward of the tyre center line...Found some offcuts tested a cut on some 4" thick mahogany and it sliced off a 1/8" perfectly, then I had a go at some more mahogany this time 8 1/4" high about the max the saw will allow.. the first cut at 1/8" again, was a little noisy but the finish was quite good, The second slice was a lot quieter and the finish was spot on (good enough to glue without sanding)..So it's all down to getting the right set up and having a decent bandsaw and the right blade. https://www.youtube.com/watch?v=zvAbF57noRA

https://www.youtube.com/watch?v=AheG4XnOwJA

Timbuck
05-02-2016, 10:58 AM
This Guy is worth watching...Remember you should not ever get drift on a bandsaw, never..if you do it's set up wrong ;)
https://www.youtube.com/watch?v=wGbZqWac0jU

Michael N.
05-02-2016, 12:10 PM
I've seen that video before. It's interesting what he says about co planar. I spent a good hour or so trying to get my bandsaw co-planar. Pretty much everyone said that it's good for performance.
i wouldn't like to argue with that guy though! The tip about the gullets being in the centre of the wheel is a good one.