Estimating Blade Sharpness by Temperature

Blades heat up more as they get dull, but other factors can also have this effect. March 31, 2008

I have been thinking about ways I could improve on my saw blade sharpness status. I don't think I get the most out of my blades because I am guessing when to change a blade out. Some blades get left on too long, others are taken off too early. I recall reading about measuring the sawdust temperature to determine if the blade is sharp. I know folks watch the blade cut and look for change in accuracy to determine if the blade is sharp. Isn't there a way to measure sharpness as the saw is running?

Forum Responses
From Professor Gene Wengert, forum technical advisor:
There are two issues with blades. The first is the sharpness of the teeth. As a tooth dulls, it takes more power. So if you had an ammeter on the saw's motor, you could estimate the increased power required as the saw dulls. Unfortunately, the thickness of the piece and the hardness of the wood also change the power. So, this is not practical until the saw gets extremely dull, which is way too late to know that it is dull. So, experience and length of time since the last sharpening are the usual manner of estimating dullness. A duller saw means more heating, so the temperature of the saw near the teeth or the temperature of the sawdust would estimate dullness, but again, the depth of cut and the density of the wood also affect the heat, as well as saw tension.

The second issue is the tension in the saw. Saw tension helps a blade run straight. Lack of adequate tension means wobble or wandering. Tension is put into the saw by "hammering" it, in the old days. Today, hammering is often done by rolling the saw. Tension is very important in wide band saws and large diameter circular saws. It is possible to measure the lack of tension by measuring the saw variation or wobble. This is often done with band saws in large, modern, commercial operations.