Shear is directly proportional to the area. a 5/16" bolt would be
1.55 times more shear strength. Drilling it out to a clean hole
would also eliminate some unknown amount of bending that is going
on.

The grade 5 and grade 8 bolts would have more shear strength than
the usual soft steel but they would be much harder than the shaft
and tube so you would mangle them before the bolt sheared, NOT
what you want.

Terry King wrote:

Buy snowblower shear bolts appropriate for your make/model machine. Any good
H/W store or small engine service place should have them,


I've used the hardware-store shear bolts; they actually shear a little
easier; they have small grooves in them.

They have definitely sheared; usually a central part is in the center
shaft and must be pushed out.

I HAVE jammed a couple of rocks; I WANT the pin to shear then! But I've
had the regular 1/4" bolts shear biting into a semi-frozen drift or
embankment.

Anyone have an idea what the ratio of shear torque would be for a 5/16"
mild steel bolt VS the 1/4" ones?? Is it proportional to area? Or some
other factor??

I'm realizing that the 'worn hole' thing may be significant; I think I
only sheared one the first season.. 5 years ago. I've moved a lot of
snow since then!!