Constantly breaking shear bolts on my cutter....help?

[aczlan]

I'm wondering why there is a shear bolt at that end anyway. Isn't that the end that attaches to the tractor? If there is a shear bolt at the other end (which it is on the one I have) then is there a real need to have two? If not, would it not be possible to just bolt it together at this end? No shear bolt. Just rely on the one at the mower end?

Our tiller (60" Kubota tiller) has a 6 spline PTO shaft on the tiller end and a very similar shear bolt setup on the tiller end.

Aaron Z

 

[Guidshir]

I'm wondering why there is a shear bolt at that end anyway. Isn't that the end that attaches to the tractor? If there is a shear bolt at the other end (which it is on the one I have) then is there a real need to have two? If not, would it not be possible to just bolt it together at this end? No shear bolt. Just rely on the one at the mower end?

The tractor end does not have a shear bolt. This is the end that is on the mower, but I suppose it would be turned around. You're right that two would be a waste.

 

[Gary Fowler]

I have never seen a shear bolt hub that separated when the bolt sheared. That looks extremely dangerous to have the PTO shaft flinging about. I would fix it so it stays together or get a different set up altogether.

As for the bolt shearing, drill out the hole so you can put in a larger bolt-at least 1/16" larger in diameter than the existing one. Keep increasing size till you can start the mower without shearing the bolt. I had to do that on B.I.L.s mower, one size up solved the problem.

 

[BKBoiss]

I have a Titan flail with hardly any hours on it and after the factory shear bolt on the driveline that came with it broke, they break every time now within a couple minutes of starting. So it doesn't shear on PTO engage, it shears in regular grass. Today I tried a grade 5 and it still broke quickly.

What I am trying to figure out is why it looks like there is groove for bearings. Makes no sense but the main part of the shaft is not a tight fit at all.

That setup has definitely failed. It is supposed to have a bearing so when the shear bolt breaks the PTO shaft just spins on that bearing. If it comes apart like that it is really dangerous and can easily damage your equipment or you.

 

[3gunr]

Look at georgia equipment, They have new shafts with slip clutch for reasonable prices. I got one for my old 6 ft yanmar tiller and it works great.

 

[LouNY]

The few shear bolt PTOs that I have used have all had some type of retainer, one very similar to yours had several loose ball bearings and grease that where held in by a short screw. That allowed the shaft to spin free when the shear bolt let go.
Without the retaining balls I expect that yours is flexing in service which loosens the shear bolt which will then easily break.

 

[WranglerX]

It looks like there is/was a setscrew on the far side (see the little hole through the groove on the bottom of the shaft side) so that it doesn't separate when the shear pin breaks.
The groove is probably for grease to go around the joint.
I have a similar joint on a tiller and it has a large circlip to keep the two sides together when the shear pin breaks.

Aaron Z

Set screw (if there) is probable access for inserting ball bearings... IF both pieces are "mated" and internal races are full of balls it should contain shaft side with PTO side but allowing PTO to spin free if mow deck (or other PTO implements) is bound up and shear bolt has done its job...

Dale

 

[Guidshir]

Look at georgia equipment, They have new shafts with slip clutch for reasonable prices. I got one for my old 6 ft yanmar tiller and it works great.

Thanks, I ordered one from GA Equipment. Hate to spend that money so soon, but maybe I can rehab this one and use it as a backup.

 

[Guidshir]

GA Equipment with slip clutch came in.

 

[SplitHoof]

Don’t you just love the smell of a new pto shaft!!