Re: Blade tracking problem
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Yep that iterative approach (loosen adjust re-tighten) is necessary, and yes the spring-bending of the frame can be used to set the tension - but there is the same old problem - you have to know what full tension IS before its any use.
Having a blade that you know tracks properly is a sort of given when adjusting tracking, like knowing how to adjust to full tension. Couple things to try: 1. Blades not welded square don't track truely?and would cause the problem you?describe. Probably something everyone should do first, when trying to solve tracking problems, is try a new blade. If it cures the problem you're ahead of the game, if not, you know it's?not the blade and you've?got a?good spare. 2. If the blade was cracked it would track away from the rim. You can test this out by cutting a piece of steel at full (8lb) bow weight - if the blade is cracked the head will bob up and down as the crack passes over the rear support rollers. Not well known, but the blades crack just by running them enough around the standard bandwheels - even without?guides twisting it, a blade will only last from?20-50hrs. Possibly yours is cracked???? I'll keep thinking - jv
John,
Following your suggestions, I loosened/removed the blade and zeroed the upper wheel, laying a straight edge across it to monitor the tilt as I adjusted the tracking mechanism.? Then I re-tensioned and adjusted until the blade was just above the rim flange.? The blade still was misaligned enough to scrape the guard.? I noticed that tightening the mechanism's center bolt also affected the tracking so I used an interative approach -- adjust the bottom screw, tighten the center screw, check the tracking, loosen it and re-adjust the bottom one, and so on.
FYI, I became curious about how much the frame itself is bending on that axis.? I didn't expect much, but what the heck.? I again used my laser pointer, attaching it to the top of the frame and aimed it down.? There is a lip near the bottom where I could place a machinist ruler to check the deflection.? From no-tension to fully tensioned, the beam deflection was pretty small -- something on the order of .02 inch, .5mm.? ?I just realized that this could be a way to set the blade tension.....with some characterization, anyway.
I also loosened up the blade guides and found that worsened the tracking problem.? Moving the bottom blade guide down also exacerbated the tracking problem.
Other than fooling around with the tracking mechanism and blade guides, I haven't modified the band saw.
The blade isn't the newest in the world, although it is NOT the one that came with the saw -- not long after getting the saw I got a bimetal blade for it.? If the problem is (somehow) related to the blade, would there be any other symptoms to look for?
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John Vreede