Shearing too many bolts on cutter

[dpmonk]

I am a new owner, LS XR3037 shuttle shifter. Just bought 12 acres of overgrown land with tons of junk hidden in the weeds. My problem is shearing bolts on the cutter. I have sheared most of them engaging the pto. Sheared them at the recommended 1200 rpms, sheared them at 1000 rpms. Being a rookie we finally figured the pto is in manual mode. Should I be operating in auto? Any suggestions appreciated.

 

[Gary Fowler]

My BIL's Fred Cain bush hog was the same way, couldn't get it started without shearing the pins when the engine is above idle. Sometimes the bolt would shear (or maybe it was finish shearing) when just mowing along in light grass. Finally went to a harder bolt and it helped. I suggested that he drill out the holes to accept the next larger bolt but he manages with grade 8 bolts rather than grade 5.
I had a Howse bush hog that I cut 4" trees down with and never sheared a pin in the 3 years that I had it.

 

[stuckmotor]

I was shearing bolts like crazy too. I finally realized that my bolts were one size too small to completely fill the hole. An easy and obvious fix.

 

[SPYDERLK]

I am a new owner, LS XR3037 shuttle shifter. Just bought 12 acres of overgrown land with tons of junk hidden in the weeds. My problem is shearing bolts on the cutter. I have sheared most of them engaging the pto. Sheared them at the recommended 1200 rpms, sheared them at 1000 rpms. Being a rookie we finally figured the pto is in manual mode. Should I be operating in auto? Any suggestions appreciated.

Like Gary said ... , but I would avoid Gr8 as they are hard enuf to cause cummulative damage to the shear joint. Use a grade 5. --- 1st/easiest - Be sure the bolt is long enuf so that no threads are in or real close to the shear zone. ?Maybe that was part of the problem? ... 2nd] the shearing from quick startup - Is there and adjustment? Check with dealer. ... 3rd] Fit your bushog gearbox with a slip clutch. Some modification but sure to fix it completely.

 

[LD1]

Get a slip clutch

 

[dpmonk]

ok, this is a stupid question probably. But is there any difference between a grade 2 or 5 bolt from the tractor store and from Home Depot? I guess my question is are these bolts made specifically to shear or are they just plain old bolts?

 

[SPYDERLK]

Plain old, unless they are grooved at the shear points. Sometimes the special/grooved bolt is employed. It is more sparing of the shear points but weaker and lots more expensive. Tractor Supply has bolts in bulk. Much cheaper than Home Depot and Lowes

If you have been using Gr2 it may explain the nuisance shearing.

 

[AaronS]

ok, this is a stupid question probably. But is there any difference between a grade 2 or 5 bolt from the tractor store and from Home Depot? I guess my question is are these bolts made specifically to shear or are they just plain old bolts?

No difference. Grade 2 aren't made specifically for shearing, they're just softer metal.

 

[vwnotrunning]

I had always "heard" shear bolts should be grade 2. Sheared many grade 2 bolts until I actually checked and my BH was rated to utilize grade 5. No more nuisance shearing!

 

[phiferpharm]

I'm not sure if I'm reading this incorrectly, but you are NOT engaging the PTO at 1000/1200 rpm initially? Use a grade 5 bolt and bring it up to operating speed slowly.