Question (WOODWEB Member) :
How many times should you sharpen the blades before fatigue may break the blade? Which blades appear to hold up the best?
(Sawing and Drying Forum)
From contributor S:
I get up to 20 sharpening out of quite a few, they are down to 1" wide by then and don't cut too good any more. Lots of them break sooner than that but you should get at least five to seven sharpenings. I run the flange on the guide wheels 1/4" behind the blade, some manufactures recommend only 1/8" which causes the blade to bend around the guide wheels causing early failure. I run a TK mill but go by Cook’s recommendations.
Blade tracking: Assume the blade is running in idle, with the middle of the body on the top of the crown. ("Middle" is 50% from the bottom of the gullet to the back). The blade tension is now equally spread in the steel in the back and in the front gullet bottoms. (The tension is about 10 % of the force as would break a new blade, it prolongs the blade about 1mm/meter). If you now start to cut the blade it moves back 1/8" and will be pushed by the guide roller flanges. More of the stress from blade tension will now be distributed to the steel in the gullets bottom. It is not good from a stress/fatigue point. It is good because the blade will cut straighter. If you let the blade run so far as 1/4" behind the idle position, you will, in my opinion, shorten the blade life. It makes it much harder for the blade.