Jam nut help shear bolt?

[MHarryE]

Are you sure grade 2 are recommended? None of my machines with shear bolts use grade 2. Two explain further. Grade 2 are a more ductile material that often deforms when it shears making the broken stubs more difficult to get out. Also, they are not made to the same quality standard as a grade 5 so shear torque is less predictable. Grade 5 is harder, more brittle, and is less likely to smear while shearing, and torque is more predictable. Depending on the design, tight shear bolts are less likely to shear so double nutting is good practice. The forage chopper I use for my nephew always gets double nutted or i get early unplugged failures. My New Holland baler has its own special shear bolt for main drive and knotter. They come with lock nuts.

 

[RSR]

I'll second the use of a jam nut, or nyloc nut. On my snowblower I noticed bolts (grade 2) breaking for no apparent reason. I think it was because the nut would loosen up, and there was quite a bit of shock during normal operation due to the bolt wiggling around when the nut would loosen up. I put nyloc nuts on now, and make sure they are tight enough that there is no play. I still break them, but now it only happens when I hit something.

The other comment is be sure to engage your PTO with idle at a minimum, and then bring up the RPM's. I actually broke a shear bolt simply by engaging the PTO when the RPM's were at full PTO speed when I wasn't paying attention.