Est. 1998 — 27 years of woodworking knowledge
Saw mill circle mill blades
Bill Tindall, E.Tn.
There was some discussion of teeth on these saws. This picture may explain the insert teeth used. A replicable tooth is held in place with a locking ring. The teeth conceivably could come out upon hitting something.
Re: Saw mill circle mill blades
Pete in Holland MI
https://www.youtube.com/watch?v=2FHYLFEUDHM
Here's how the teeth on an inserted blade are inserted. We use one at our tractor show. Never had an issue with them falling out. They are very secure.
Inserted blades were a big step ahead of a non-inserted blade. Normal abrasion & the occasional nail/rock destroys the teeth on a blade. With either style, some careful filing will bring the blade back into performance, but if too bad, the inserted blade can be brought back into operation in an hour. A non-inserted blade takes a lot of time and talent to even get close to the factory set-up.
Inserts are either made of tough steel, hard steel, or carbide tipped. Obviously the hard & carbide will last longer, but impact with a nail or rock will most likely destroy a more expensive tip with no opportunity to repair in the field. It's a trade off on productivity & cost.
Most of us woodworkers only deal with nice pristine wood from the store. Sawmills deal with grit in the bark, barb wire & nails, and in my case, a ceramic insulator one time.
Pete
I've hit ceramic insulator also,
Keith Newton
It was high up in a Post Oak from a back yard. I figured it was part of someone's short-wave radio antenna, and at the time thought to myself, I'll bet nobody else had hit one. Of course if you read any sawmill forums you will find it pretty common.
Back to the holes in the tin roof. I suspect the blade hit something large like a 20 - 30d nail, which would dull some teeth causing the blade to wobble, then snag the short part from the plank sending a projectile large enough to penetrate the metal.