Frederick Skelly
12-30-2015, 10:36 PM
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
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