By chance are you using Grizzly's blades? I ask as when I first got my Grizzly G1019 bandsaw I couldn't cut 4" of pine without problems. Switching to a different manufactures blade made a world of difference.
I recommend Suffolk "Timberwolf", Highland Hardware's "Woodslicer" or Olsen "All-Pro" blades.
Hi Doug,
When you say "3-4 TPI" do you mean that it's a variable pitch blade? Or, are you not sure of the pitch? You want to make sure that the pitch is coarse enough that you don't clog the gullets before the teeth get all the way through the wood. Clogged gullets will produce chatter (blade vibrations) and require more cutting force to maintain the same feed rate. Does the vibration go away when you reduce the feed rate? This could be the (a) problem. By the way, variable pitch blades are great for helping to reduce vibration and chatter.
The blade guides should not become loose and move. Make sure that they are properly adjusted and tight. The goal is to keep the blade from flexing (side to side or front to back) during the cut. If they won't stay tight, get yourself some Loctite or consider upgrading to better guides.
It sounds like you are hitting a resonant frequency and causing the blade (and likely the whole frame) to vibrate quite a bit. Changing the tension will move the resonant frequency of the blade. The higher the tension, the higher the resonant frequency. This notion that you should tension the blade to match a particular musical note is folklore (promulgated by a particularly famous but technically inept author). The proper tension is going to vary depending on a number of factors including the mass of the frame, the size of the blade, the cutting speed, the feed rate, position of the blade guides, etc. It might be one note for a particular machine/blade/speed/feed rate and a completely different note for another combination. You don't need perfect pitch (or an electronic tuner) to adjust your blade tension. Adjust the tension so that you obtain a straight, square cut with minimal vibration and chatter (i.e. you'll need to develop some skill here).
When the blade guide is properly adjusted, moving it up and down will also change the resonant frequency (just like fingering a different fret on a guitar). Changing the blade speed will make it much more difficult to hit a resonant frequency. And, as I mentioned above, the feed rate can have a great effect on vibration and chatter.
Even knowing all of this may not help you solve the problem. Some time ago I was re-sawing some 6" thick bubinga. The same saw, with the same blade, and the same tension sliced through a similar piece of black limba like a hot knife through butter. But, it was nothing less than hell on Earth getting through the bubinga. I just had to grit my teeth, put on the hearing protection, and fight for every inch of progress. The process was painful but the results were worth it.
Ed Bennett snipped-for-privacy@ts-aligner.com
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