how to drill out stuck PTO shear bolt?

[repete]

For implements that don't get used all the time and therefore have an higher risk of the clutch discs getting rusted together, I would rather recommend the shear bolt, but the style in the picture below.

Super easy to use and you can replace it in less than 1 minute with two simple wrenches.

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I like this style as well.
Even if the implement with a clutch is used frequently, it MUST on occasions be allowed to slip to keep clean. I like to use my rotary in heavy heavy stuff every once in a while just to confirm it slips. If you take some paint and draw a line across the clutch you can see if it slips. You can also use one of the point and shoot thermometers to look for heat if it is slipping. If you see heat under a light load it needs some adjusting.

 

[LouNY]

For implements that don't get used all the time and therefore have an higher risk of the clutch discs getting rusted together, I would rather recommend the shear bolt, but the style in the picture below.

Super easy to use and you can replace it in less than 1 minute with two simple wrenches.

View attachment 4580104 View attachment 4580105

That is shear pin yoke, many different ones are available. with different sized bolts and differing lengths from the shaft center to the shear bolt location. this provides for many different torque ratings for the shear force.

The straight thru or conical tapered bolts through a hub and shaft are not proper shear bolts they are attaching bolts being improperly used.

 

[LouNY]

Some of my PTO shaft components specify grade 8 bolts for shear points.
Seems counterintuitive, since light duty homeowner equipment usually specify soft grade 2.
The grade 8’s do work, they shear clean, with a bang

Correct, they shear with a clean snap and no deformation.

 

[joecdeere]

We always backed the tension off the slip clutches in the fall on equipment that was done for the year. In the spring as things were first used we lit up the clutch real good allowing the rust and corrosion to be worn off before readjusting the tension for normal use.

 

[not2old]

I've heard it said,......

Use a grade five bolt, they shear off more cleanly and don't result in the distorted bound up mess as this example shows.

But who really knows, that could be a grade 5 bolt, and the shaft and collar holes may be all wallowed out.

One of the implements I bought came with specific instructions to use a grade two bolt.

 

[CalG]

One of the implements I bought came with specific instructions to use a grade two bolt.

I could care less what the manufacturer instructs for most things.

I take pride in common sense and successful outcomes.

Your experience may be different! ;-)

 

[D&D]

For implements that don't get used all the time and therefore have an higher risk of the clutch discs getting rusted together, I would rather recommend the shear bolt, but the style in the picture below.

Super easy to use and you can replace it in less than 1 minute with two simple wrenches.

View attachment 4580104 View attachment 4580105

I’ve never seen one of that type. How do the two halves interlock other than the shear bolt?

 

[ptsg]

I’ve never seen one of that type. How do the two halves interlock other than the shear bolt?

So one of the halves is technically a shaft, while the other has the bore when the shaft slides into. Both parts get a rounded groove machined.

Then the half with the bore, has an hole machined on the side, this hole is used to insert various bearing balls that will lock both halves together.

Finally, the hole is plugged using a grease fitting as these parts need to be greased since those spins when the bolt is sheared.

Hopefully my explanation made sense. I can make a quick 3D model if needed.

EDIT: Here is a repair manual for one of these. You can see how it's put together.

 

[toot77]

Grade 2 bolt tensile strength 60,000 psi
Grade 5 bolt tensile strength 105,000-120,000 psi
Grade 8 bolt tensile strength 150,000 psi

My Bush Hog specifies a 1/2" grade 2 bolt which is intended to protect the gear box, which is considerably more expensive that a 1/2" bolt. I believe that a 1/2" grade 2 bolt is pretty common for lighter rotary cutters. I will continue to use what is specified in manual as opposed to using a bolt that is two to two and a half times stronger than what is specified. I assume this would also affect shock loads that are transmitted through the pto shaft back into the tractor's pto drive line.

Shear bolts are cheap, I do not understand risking the damage that can be caused by using a stronger bolt. If people are getting away with it, I am happy for you, but I am not going to risk it.

Other than for a shear bolt, I do like to use grade 8 bolts where ever I can. You can beat them in with a hammer and still spin the nut on with your fingers. Whereas with a grade 2, you can mess the threads up by dropping it and then you fight to get the nut on.

 

[TORQUIN]

The shear bolt on my Howse cutter is 0.5". I used grade 2 bolts in it for a while, but they sheared regularly in moderate grass. I went through 3 of them before I ended up putting a grade 5 in it and now I think I have a happy medium. It no longer shears when doing moderate cutting.

Chris