Bandsaw issue.

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Bandsaw issue.

Postby Simon Magennis » Thu Apr 04, 2019 10:47 am

I have a small bandsaw and am having a new problem with it. I have next to no experience with bandsaws.

The problem is most likely self-inflicted. It was not used for a good few months and I readjusted the blade tension (if is a simple model with no tension indicators of any kind) during which process the blade came off the wheels so effectively it is like replacing a blade.

Now trying to cut using the guide I find it is cutting a curve instead of a straight line. (curving in towards the guide). Before this it cut straight lines just fine with the guide. Most likely explanation is that something is seriously a miss with the tension/set-up. Any ideas what I might have done wrong?

Thanks.
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Re: Bandsaw issue.

Postby Bob Gramann » Thu Apr 04, 2019 11:01 am

A dull blade will cause all kinds of directional cutting issues. The smaller bandsaws (those with three wheels instead of two) are particularly prone to issues because the blade has to be thinner to bend over the three small wheels. Replace the blade and see if things improve.
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Re: Bandsaw issue.

Postby Bryan Bear » Thu Apr 04, 2019 11:20 am

I'll also add that all small bandsaws have some degree of drift angle and it changes from blade to blade. Even taking the blade off and setting it up slightly differently can change the drift angle. If you fence doesn't match the drift angle the blade may end up pulling into the fence or pushing out.

Definitely get a fresh blade but also read up a bit about setting the tracking on the wheels, positioning the guides and evaluating drift.

Tell us more about the saw. Is it a 3 wheel? A small 10 or 12 inch benchtop? A 14 inch delta clone?
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Re: Bandsaw issue.

Postby Peter Wilcox » Thu Apr 04, 2019 12:22 pm

When you say it curves toward the guide, do you mean it cuts toward the fence, or that the vertical cut is curved?

I don't know if this will help with your small saw.

https://www.highlandwoodworking.com/lib ... 20Wood.pdf
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Re: Bandsaw issue.

Postby Simon Magennis » Thu Apr 04, 2019 2:43 pm

Thanks guys. The blade is almost new. I doubt if I have run it more than 30 mins in total.

The curve is horizontal - as if I was trying to cut a curve such as the waist of a guitar. Somehow the blade starts to point inwards to the guide at the beginning of t he cut and as I finish it up it points back out producing a curve. When I freehand I can get a reasonable good cut by following a pencil line. The problem is when using the guide and trying to get a straight line. It worked fine previously.
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Re: Bandsaw issue.

Postby Bob Gramann » Thu Apr 04, 2019 3:12 pm

Make sure the blade is centered on the tires when the saw runs. It doesn’t matter how much you’ve cut previously if you hit something hard and dulled the blade. Find a bandsaw setup guide and make sure all of the steps have been performed. Google “bandsaw drift” and see if anything applies to your case.

I happened on to a 3 wheel bandsaw once. I olayed with it for a while and then gave it away. It was just too hard to get good results with it.
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Re: Bandsaw issue.

Postby David King » Thu Apr 04, 2019 5:05 pm

The bandsaw blade may have been damaged when it came off the wheels at speed. I.e. all the teeth on one side hit hard metal while bouncing around in the wheel covers. It also sounds like the tensioning system may not be up to holding tension over the longer term or that the wheels are falling out of alignment under continuous tension.
You need a new blade and you might consider de-tensioning it between uses.
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Re: Bandsaw issue.

Postby Peter Wilcox » Thu Apr 04, 2019 5:41 pm

While you're waiting for a new blade:
If your guide (by which I presume you mean fence) is adjustable as to horizontal angle, you can try to adjust it parallel to the cut your saw wants to make (the drift as mentioned above), to see if that solves the problem. On a piece of wood about a foot long with a straight edge, draw a pencil line parallel to the edge about an inch away. Cut along the line (with no guide/fence) about halfway and stop the saw. Don't move the wood, and draw a pencil line along the straight edge on the table. Take the wood away, and move your fence to the line. If it's not at the same angle as the line, adjust it until it is. Your saw should then make a straight cut with the fence.
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Re: Bandsaw issue.

Postby Bryan Bear » Thu Apr 04, 2019 7:42 pm

Remember that wou will
Likely need to adjust the fence for drift angle every time you change the blade or setup particularly on smaller less precise machines. I have a little 10” craftsman bench top 2 wheel saw that is way better than it should be for it’s size but the drift angle starts to change as the blades near the end of their usable life so it is never a set it and forget it situation.
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Re: Bandsaw issue.

Postby Simon Magennis » Fri Apr 05, 2019 6:31 am

I think I have it figured out. :-)

When I installed the new blade I cur a few things free hand and all was ok. I didn't use the fence/guide. This time I wanted some straight cuts so I used the fence. Thew blade is a bit smaller than the old blade so what I didn't do when I put the new blade in was change the position of the tracking bearings, the result is that the blade was not in the correct position and was able to wander more. I move the bearings a couple of mm and now, one quick cut, it seems to be tracking correctly. Maybe not perfect, but the banana effect is gone. I will review the installation guide to make sure I have covered all the options.

Thanks Guys.


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Re: Bandsaw issue.

Postby Brian Evans » Fri Apr 05, 2019 6:44 am

When resawing basically you use a guide for the verticalness of your cut and free-hand the straightness of the cut. I use a tall guide set beside the blade, with it's base at 45 degrees to the direction of cut. That keeps the wood vertical, keeps the distance from the blade constant, and lets me guide the work along a line free-hand. A wider blade helps to slow down the inevitable wander, and a very coarse blade (3 - 6 tpi) with deep teeth gives the sawdust somewhere to go. But you never use a fence to try to guide the work straight through the blade except maybe on quite thin material. At least I don't, but then I don't even have a fence for my bandsaw... :)
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Re: Bandsaw issue.

Postby Peter Wilcox » Fri Apr 05, 2019 10:38 am

Each to his own. For me, resawing is a no brainer when the saw is set up right with a sharp blade. It's just a matter of holding the wood against the fence and pushing it through. Glad you fixed your problem Simon.
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Re: Bandsaw issue.

Postby Steve Sawyer » Wed Apr 10, 2019 9:35 pm

Peter Wilcox wrote:Each to his own. For me, resawing is a no brainer when the saw is set up right with a sharp blade. It's just a matter of holding the wood against the fence and pushing it through. Glad you fixed your problem Simon.


This. Absolutely this. Been having an ongoing debate on this with others in my woodworking club. Some people make the band saw out to be some exotic piece of machinery that requires all kinds of special setup. There are guys that have made entire careers writing books, teaching clinics and writing articles for woodworking magazines. Checking that the wheels are co-planar, adjusting for "drift" etc.

Balderdash.

Attended a band saw class with Michael Fortune a few months ago, and he went on a 20-minute rant about this (and I had to work mightily not to say "See!!! I done tol' you guys and tol' you..." :lol: )

Tracking is most often the cause for "drift" when cutting against a fence. If the blade is perfectly square to the table (by adjusting the table) and parallel to the fence (by adjusting the tracking) they work absolutely beautiful provided I don't let the blade get dull.

Band saws are flat-out my most beloved, very favoritest stationary power tool in the whole universe! :D

PS - I have to admit though that I hated the ball-bearing guides that came with my saw. Just the dumbest most fiddly things ever. I designed a replacement and had my machinist son fabricate it for me. This is SO much easier to set up than those stinkin' ball-bearing guides!!

New BS Upper Guide.JPG
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Re: Bandsaw issue.

Postby David King » Sun Apr 14, 2019 1:14 am

Are the new side guides 660 bronze or something? I use lignum endgrain blocks on my stock Delta 14" and they have been fantastic. I give them a light touchup on a sanding block as they begin to wear.
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Re: Bandsaw issue.

Postby Brian Evans » Mon Apr 15, 2019 8:18 am

I use the roller bearing guides, so far perfect. Take seconds to adjust when I change blades. Aside from sharp blades, I find letting the saw do the work the way it wants to works for me. Be nice to have some more power - I resawed some 6" cherry the other day, slow and the saw kept trying to stall. Maple resaws easier for me.
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Re: Bandsaw issue.

Postby Steve Sawyer » Mon Apr 22, 2019 11:59 am

David King wrote:Are the new side guides 660 bronze or something? I use lignum endgrain blocks on my stock Delta 14" and they have been fantastic. I give them a light touchup on a sanding block as they begin to wear.

Sorry, David - been a little heads-down lately and just saw this.

The "rub blocks" are just plain hardware-store brass. I suggested bronze or oilite or something more exotic, but my son said that just plain ol' brass works really well as a wear surface under the extremely minimal forces involved here (his area of specialty is maintenance of injection-molds). I have some lignum vitae that I was going to use for this, but they were going to be a bit fiddly to make (1/2" wide x 1/16" thick pieces with a tiny #6-sized screw slot), so it was easier to just have my son use a mill to make 'em out of some brass stock I handed to him. Lignum is also an ideal material for this application, being incredibly hard and "self lubricating".

The problem I had with the ball bearings is that a) the should NOT be in contact with the blade when running freely, i.e. when not actually cutting, and b) tightening the screw that locks them into place always shifts them slightly from the position I want for them, so it's an almost endless cycle of adjust, tighten, check, loosen, adjust, tighten, check, loosen, adjust, tighten... I even sprung for a set of "premium" ball-bearing guides from Carter ($$) thinking that the cheap asian saw I'm running might have cheaped out on the guides, but the Carter was only slightly better than the originals. Anything that uses rubbing blocks - steel, "cool blocks", ceramic, lignum - which can actually be touching the blade when adjusted properly are SO much easier and faster. I used to hesitate to change blades because it was such a PITA to re-adjust the guides, but you really can't make tight curves with a 1/2" blade, and the 1/4" blade is much to fine-toothed for resawing or cutting anything thicker than 3/4"-1".
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