Band Saw Misbehaving

[algale]

My Shopsmith band saw is acting weird.

I needed to resaw some 3 x 5 inch sappele. I mounted my 5/8 blade, tensioned it up to the recommended 1/2, set my Kreg fence (which i had previously adjusted to this blade) and started up. The work pulled away from the fence and the cut was bowed. Stock ruined.

I stripped everything down, checked and recalibrated the tension gauge, checked and adjusted the autorack bearing, checked readjusted the upper back up bearing, checked and adjusted cool blocks. Checked wheel cant. All good.

Remounted the blade. It is riding properly in the autotrack bearing groove. It is riding against the lower back up bearing. There is the recommended 1/64 space between the back of the blade and the upper back up bearing. All good. All is as it should be.

Except one thing: the blade is at an angle where it goes through the table insert. The front of the blade (teeth) point left and the rear of the blade points to the right! The angle is such that there's not enough play in the trunnion brackets to allow the table to be set up with the miter slot parallel to the blade.

I remember another user had this problem with this blade and I don't think we ever got him straightened out (literally or figuratively).

Called Shopsmith and described my problem. Checked the blade weld and back of blade. All good. They suggested first increasing upper wheel cant (no effect) and then reducing upper wheel cant. Reducing the upper wheel cant has reduced the angle of the blade to where I can adjust the table so the miter slot is parallel to the table.

Readjusted the Kreg fence for drift and tried to resaw some scrap. Same problems. Work is pulled away from fence after the cut and the blade is bowing. And cuts using the miter gauge are drifting too.

I will try mounting the blade in my recently acquired older vintage Shopsmith band saw and see if it is a problem on that band saw too. I will also try mounting some smaller blade in both saws and see what gives.

At the moment I am at a loss and very frustrated.

[Gene Howe]

Glad I'm not the only one.
I never found a fix with the 5/8 blade.
3/8 seems to be ok.

[beeg]

Is it a SHARP blade? Increase the tension.

[algale]

The blade is sharp.

Gene, if you would be so kind, please fill me in on the issues you had with this 5/8 Shopsmith blade.

My plan is to set up my other band saw and see if if it makes a difference. Small issue there is that the right side table bolts (from operator's perspective) are coming up through the miter slot. Suspect I need to add a washer or two).

[dusty]

This sorta highlights the problems and solution that I have.

[rpd]

This video by Matthias Wandel explains why the blade can bow and drift when re-sawing.
The physics of bandsaw resawing

[algale]

Playing a hunch here: can someone tell me what the factory specified lower back up bearing is?

Here's my hunch: The lower back up bearing is not adjustable front to rear. But if the wrong sized bearing was used there, one with too large a diameter, I believe it would cause the very issue I am seeing.

I've never changed the bearings but who knows if the PO did or if someone at the factory grabbed the wrong bearing....

[wa2crk]

How are the tires on that bandsaw? If the upper tire is worn toward the front the wider blade, that is thinner at the front, It may appear that the blade is twisting when it actually trying to make contact with a worn tire.
Just a thought.
Bill V

[algale]

How are the tires on that bandsaw? If the upper tire is worn toward the front the wider blade, that is thinner at the front, It may appear that the blade is twisting when it actually trying to make contact with a worn tire.
Just a thought.
Bill V

Tires are orange silicone from Shopsmith and reasonably new.

[Gene Howe]

Algale,
5" wide walnut board. The blade bowed in the cut really bad, as if it were not tightened enough. I use a pointed fence 1/16th or so ahead of the blade. I tightened it a bit more and got the same result. Gave up.