Is going through sheer bolts bad for an implement?

[Domush]

I snapped my first PTO shaft sheer bolt the other day using my 5' Howse (consumer grade) rotary cutter. I was a little freaked out when it happened, as I didn't even know it had one.

The episode brought up the question:

Is it bad for the implement to break a sheer bolt or are the sheer bolts weak enough to prevent any damage?

 

[s219]

Shoot, my old man used to buy shear pins in bulk! (this was for a large snow blower implement that was used on a gravel driveway). They should be designed/sized to break well before any damage could occur. The times I remember them breaking, it seemed obvious to me that the break was quick and easy.

 

[Mud Mechanik]

I have sheared the one on my howse bush hog many times with no ill effects, I always replace it with a 1/2 X 3 1/2 grade 3 bolt to ensure that it snaps before something else does.

 

[RoyJackson]

First broken shear bolt...in how many hours of usage?

If you break one on occasion, no big deal...happens to most of us. If you're snapping them frequently, that's cause for determining why...too soft a bolt? Operating the equipment beyond it's capabilities (in your case, hitting stumps too big for the cutter to handle)?

The intent of the shear bolt is to minimize damage to the tractor and implement. Sounds like your shearbolt did exactly what is was designed to do.

 

[Gary Fowler]

Some of the new hydrostatic drive tractors have electric PTO engage and no clutch to enable feathering in the rotary cutter. My Brother In Law has a NH tractor that is that way and if he has the tractor much above idle when he engages the PTO, it shears the shear bolt on his Fred Cain bush hog. I have also seen it shear when just clipping along on low grass with out hitting anything. Perhaps it was weakened from engaging it. If it were mine, I would drill the hole and put in a slightly larger bolt as I think that the 3/8" is way too small for that mower. I just sold my old Howse BH and I have cut 4" trees and never sheared a bolt. I think it had a 1/2" bolt in it. THe bolts are for protecting the equipment, but they shouldnt shear when engaging the drive at 1000 RPM.
If you hit something like a stump or junk iron etc, it should shear to protect the tractor and or BH gear box, but if it is constantly shearing find the cause and correct it or get a harder bolt or fit a slightly larger one.

 

[greg_g]

Yup, the occasional shear bolt is part of the cost of ownership. But there is no such thing as a universal shear bolt. Check your owner manual for exact bolt specifications. You don't want one that too soft, too hard, too tight, too loose, too skinny, too short, too long, or with the wrong head. Using just any old bolt that kinda fits, is no substitute for the correct shear bolt.Lock washers are bad too; just use the spec shear bolt and a self-locking nut tightened only to the point where the bolt won't rattle.

//greg//

 

[Domush]

I have also seen it shear when just clipping along on low grass with out hitting anything. Perhaps it was weakened from engaging it.

Oh, make no mistake, I earned this bolt snapping . I was using 4wd to back the cutter over a pile of 2"branches, and my creeper and first gear don't work, so I can't exactly go slow in reverse.

This cutter has a 1/2 inch bolt already, and given I had already gone crazy cutting up other areas I'm not to surprised it finally gave in.

Thanks for setting my mind at ease, everyone. I hope I don't need to buy them in bulk, but I did buy three more, cause I have about three more acres of these piles to back over at high speed :laughing:

Sent from my SCH-I500 using TractorByNet

 

[Domush]

Lock washers are bad too; just use the spec shear bolt and a self-locking nut tightened only to the point where the bolt won't rattle.

//greg//

Oh, thanks for that. The guy at the tractor store gave me lock washers! I'll swap it out for the old lock nut.

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