Shear bolt on rotary cutter breaks at one end only

[porchdog 352]

I hit a log and the shear bolt broke at one end only and the head broke off and fell to the deck. I was able to keep mowing because the other part of the bolt stayed in the drive shaft joint. The bolt eventually dropped out and the mower stopped turning. My question is, why did the bolt break in one place only and not at two places? TIA

 

[ruffdog]

Was the shear bolt too tight? I normally use a locking nut so the bolt has no tension on it.

https://www.tractorbynet.com/forums/attachments/118878-shear-pin-torque.html

 

[RalphVa]

I've an RC2048 Frontier with shear bolt. The bolts that JD keep wanting to sell me fit through the collar of the PTO shaft but are tight in the hole in the shaft to the RC gear housing. It came with a smaller bolt, and that is what I continue to use. Since the smaller bolt is a tad loose in the hole, it'll easily come out. Sounds like that is a good thing. No way was I gonna use a hammer to drive the bigger bolts that JD thought it needed in through the shaft.

I use one of those nyloc locking nuts, too.

Ralph

 

[chim]

Probably not the case, but what if the holes in the male and female parts aren't quite in alignment, or one of the holes is a tad larger?

 

[Texasmark]

Was the shear bolt too tight? I normally use a locking nut so the bolt has no tension on it.

https://www.tractorbynet.com/forums/attachments/118878-shear-pin-torque.html

Me too. Has proven itself many times over. Also I use Grade 2 bolts. They survive several whacks before breaking due to their ductility rather than snap like 5-8 grades.

 

[Texasmark]

Was the shear bolt too tight? I normally use a locking nut so the bolt has no tension on it.

https://www.tractorbynet.com/forums/attachments/118878-shear-pin-torque.html

Me too. Has proven itself many times over. Also I use Grade 2 bolts. They survive several whacks before breaking due to their ductility rather than snap like 5-8 grades.

In answering the why, apparently your yoke is worn and one side connected before the other and you must be running a higher grade bolt as I mentioned above.