Bandsaw oddity: Could my blade be damaged?

[Frederick Skelly]

Hi folks,
My little bandsaw - a 12" JET with an aftermarket tension spring - was acting strangely and I'm trying to understand what I was seeing. I say "was" because the problem resolved when I swapped to another blade. Here goes.....

I was running a 14 tpi, 1/8" Timberwolf blade making a slighly curved cut, when I got the dreaded "spoing! bang!" noise. Thought I'd pushed the little saw too hard and broke the blade. Oddly, I hadn't. It had come off "somehow". The blade had a couple kinks so I tried to smooth those out, put it back on and went back to work. The cut felt a bit different but still seemed to work well enough. So I've been using it on and off for a month since.

Tonight I kept getting excessive blade drift cutting straight lines in 3/4" mahogany, using my fence. I could not get a straight cut. I varied the tension up and down - it would still drift off the line by 1/16 - 1/8". Then I started adjusting the tracking. Here's where it got wierd. The blade would center on the top wheel (per JET's manual) but it would be at the very front edge of the bottom wheel. No amount of upper wheel adjustment would bring the blade more than 1/8" back from the front edge of the bottom wheel.

Now I got out a straight edge and confirmed that when the blade was centered on the top wheel, the bottom wheel and top wheel were coplanar. Then I moved all guides, etc way out of the way to make sure there wasn't any interference or problems that way. Finally, I noticed that the blade would get close to the center of the bottom wheel if I did not tension it. Huh? At this point I gave up and swapped to another blade - a 1/4". Everything cleared up. The blade tracks straight and true.

I put the 1/8" blade on top of my tablesaw and checked it for distortion - none. That blade is totally coplanar - it's back side touches the tablesaw top at every point along its circumference. There is still a slight kink at one point, but even there the back of the blade is coplanar.

What do you make of this? Is the blade damaged in some way I can't see - twisted or something - that's making it ride the bottom wheel wrong? Curiouser and curiouser.

Thanks for your help!
Fred

[John McClanahan]

You may have damaged some of the teeth on one side of the "set" making them dull. Every time this part of the blade cuts, the blade tries to drift.


John

[Frederick Skelly]

Thanks John. I hadn't thought of that.

[Erik Loza]

Just my opinion, for what it's worth. "If" you damage a BS blade, even minorly, I would toss it and get a fresh one. I've never kinked one myself but talked to lots of folks who have over the years, and it seems like they never cut the same once that happens. Yeah, maybe keep it for general purpose use if the size is suitable but as John popinted out, there can be damage to the teeth that you and I probably can't see with our eyes. Just my thoughts.

Erik

[Frederick Skelly]

Yeah, I think you're right Erik. I think I've been pushing my luck using it and the performance just hasn't been the same. I'm throwing that one out. Thanks!
Fred

[Shawn Pixley]

If switching to a new blade solved the problem, then I would say the other blade was damaged. Use the new blade.

[Frederick Skelly]

Yup. I'm thinking the same way Shawn. Thanks,

[Curt Harms]

If you cut 'dodgy' wood such as reclaimed with possible metal it's nice to have a blade you don't care too much about.

[John TenEyck]

On most well adjusted BS's when the blade is centered on the top wheel it will be closer to the front of the bottom wheel. Just the mechanics of how the blade reacts to the tilt of the top wheel and tension of the spring. Nothing abnormal there.

FWIW, a 14 tpi blade is a poor choice for cutting 3/4" thick stock. Something with 4 to 6 tpi would be a much better choice.

John

[Frederick Skelly]

Thanks Curt.
Thanks John. The blade I swapped to is riding forward as you explained, but not right up against the front edge of the wheel like the 14 tpi was. I was wondering if I had that right, so thanks for the advice - sounds like I do. The "new" blade is about 4 tpi and when I used it last night it worked beautifully. Lesson learned there too. Again, thank you!
Fred

[Randy Bonella]

Timber wolf every once in a while has a problem with their brazing alignment. Usually with the larger 1/2" to 3/4" blades. It results in a distinctive vibration and movement in the blade on the wheel. I haven't seen one come off the saw but it is possible I suppose. IF the blade was cutting ok prior and didn't have the vibration I'd guess it got damaged somehow as what others have stated.