I might add that the original shear bolt had a triangle stamped on the head. In metric terms that must have been equal to a grade 2. It's the first one I've ever seen. Last winter I caught a rock and stalled the tractor, the bolt did not shear off ! The assembly was rusted tight. I cleaned it up and lubed everthing. The bottom line is ; make sure those parts are free to move or the shear bolt is useless. Same for a slip clutch. If the clutch packs are rusted or frozen they can't work.That's why you don't see slip clutches on snowblowers.