That's why I gave the woodgears.ca link in the first post. He has an excellent write up.
In short it's a gage for tensioning a band saw blade. It's based on the elasticity of the steel and the use of Young's Modulus to predict the amount of stretch associated with a given tension. The usual implementation is to attach a gage to one point on the blade and a measurement point at a known distance to the previous point. As the tension is applied the blade will stretch a fixed distance for the length of the blade between the two points. You then use Young's Modulus to convert the measured stretch to tension in PSI. This device amplifies the responce by placing a hinge 1" away from the blade and taking the measurement 3.625" on the other side, increasing the response by a factor of 3.625
... So ...
for each .001" on the dial there will be a stretch of .00027582".
- divide that by the 4" of blade captured between the clips and you get:
.00027582/4 = .00006896551724
- multiply that by Young's modulus for steel - 29,000,000 and you get
.00006896551724*29,000,000 = 2000 ... 2,000 psi for every .001" division on the gage.
If not otherwise specified, a rule of thumb spec for band saw blade tension is 15,000 psi so you would tension the blade till the gage showed an offset of between .007" and .008". Low tension blades like Timberwolf call for a lower spec of between 6000 and 8000 psi (I think) so a gage reading of between .003" and .004" would be needed.
Hope that helps.
"I was always afraid of dying. Always. It was my fear that made me learn everything I could about my airplane and my emergency equipment, and kept me flying respectful of my machine and always alert in the cockpit. " - Chuck Yeager
Last edited by GulfcoastGuy; 04-12-2013 at 02:27 PM.