Shear Pin/Bolt hardness

[runwoolf]

I need a shear pin/bolt for my bush hog..what hardness should I use, I get different opinions when I ask dealer/hardware/friends/etc.

 

[J Hamilton]

I've always been told to use a grade #5 because it's hard enough not to snap easily but soft enough to break in the event of a sudden impact.

 

[Janicholson]

If the brand is still in business, call and ask. If not, I would use grade 2 bolts from a single source. If they fail in light loads, or repeatedly (assumes sharp blades, and reasonable use of the tool) then go with single source of grade 5. I would not use grade 8. Bolts from hardware stores need to meet strength standards, but can be very inconsistent from different sources. Especially imported bolts. Using shear bolts designed for the tool is far better. broken gear boxes are not a good return on the poor choice of a shear bolt. Jim

 

[Swittig]

I use grade 5 bolts for shear bolts on my brush hog, the reason is grade 2 bolts will smear and 5 will snap off cleanly so replacement is easier.

 

[Russ from MN]

I think King Kutter specified grade 2, but after shearing 100 of them I put a slip clutch on it, but, you have to know how to run a slip clutch or you may have an expensive problem!

 

[Texasmark1]

Over the years I have used bolts that fit the diameter of the holes. On length, I buy them longer than needed and use lock nuts leaving space between the head and nut and the yoke casting....proven to last longer than torque tight. Usage has been with Grade 2 and 5 for mowers and I prefer 2. Reason is that the 2 will take several hard whacks before yielding whereas the 5 will snap. Additionally, the 2 smears when it shears making it easier to line up the yoke and shaft to find the hole in the shaft allowing the remains to be punched out.