Originally Posted by
Charlton Wang
I'm embarrassed to report back here but...
I cranked the tension to basically as high as it would go and the bandsaw didn't buckle. This seems to have improved things rather dramatically though I haven't had a chance to do any rigorous testing. I guess that whole "deflection of 1/4" at 6" down from 9:00 of the wheel" doesn't always work. My bandsaw has no blade width markers on the gauge so it's pretty much just a guessing game. I somehow missed the post from Andrew Joiner where he suggested cranking the tension up...
Thanks for the help/advice everyone.
Charlton
No reason to be embarrassed it is comon among hobbyists to under-tension blades, especially carbide blades. Further, many of the shortcuts to tensioning blades are based on small Delta 14" saws and their clones along with carbon steel blades, it is a shortcut since we should actually be using a strain gauage and setting it correctly (or as close as a particular saw will get, and optimally never using a blade a particular saw can't tension properly). Yes strain gauges can be expensive but most everyone has some small clamps and a set of caplipers. Google homemade bandsaw tension gauge and enter the world of Young's modulus and the linear elastic properties of steel.
Bandsaws should NOT come with width indications on the tension scale, it is useless, and steers one wrong more often than right. It should only be used to record and re-tension a specific type/size of blade not to determine the correct tension. Consider two 1/2" blades, one a carbon blade and one a carbide blade. The carbide blade may have a significantly larger cross section as well and needing nearly twice the actual tension so the difference on the bandsaw tension scale for those two blades may be vastly different when they are tensioned correctly. Now with time you can develop a touch that gets you very close BUT you can't read about that touch on a forum, in a book or even watch a video and get it right, you have to physically push on a accurately tensioned blade many times to develop this feel. If you don;t run a bandsaw everyday they make (or you can make) strain gauges.
People have all sorts of issues with bandsaws and like anything else you have to eliminate one variable at a time, especially with bi-metal and carbide blades tension is usually a good place to start but until one is able to get a good approximation of the actual tension on the blade it is just a crap shoot.
This issue has become more of a problem in the last decade or so since smaller lighter bandsaws are being built with serious resaw height, significant power boosts and carbide blades are being made with more flexible and thinner backers so that they can run on these saws. Add to this tensionning methods left over from long before these changes are still being repeated, yeah they worked for someone for 50 years but it is a new game now.
Of all the laws Brandolini's may be the most universally true.
Deep thought for the day:
Your bandsaw weighs more when you leave the spring compressed instead of relieving the tension.
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