how to drill out stuck PTO shear bolt?

[GrandpaSmurf825]

Don't use an air hammer on it. If you swell it in the shaft then you will have to drill it out. It's truly not an issue unless it quits driving the input shaft. Then it's easy to deal with.

Here is something some might disagree with however it's something some manufacturers promote. If the correct shear bolt comes with a self locking nut. When you install it don't tighten it tight. The reason being is a tight bolt will shear easier than a bolt that is "relaxed". I first learned this many years ago on a John Deere 14T baler. The flywheel on the side that keeps the plunger running smoothly that cuts off the hay on the incoming side and compresses it in the chamber used a little 1/4" bolt to drive it. If you put it in and tightened it up tight it would shear again in probably 15 minutes. If you left it loose so you could wiggle it you probably only replaced it every 2 or 3 years. Fast forward to my years as a heavy equipment mechanic. Cylinders on work heads that cycled up and down thousands of times a day rapidly with 1" bolts that secured them. If you ran them loose they would have to be changed because of getting "crankshalved" about once a year. If they were ran tight they would break without warning. That was a mess you wanted to avoid. Broken fittings and oil all over.

Farmer I help. Replaced some flighting in a truck auger. (Auger we load the semi out of the bin with) The bolts that drive the flighting off the gear box have special rubber washer kits to prevent being able to tighten them tight. Because they had failures of the shear bolts related to the bolts being tight. I guess they learned the same thing my father did 60 years ago. Just a lesson I learned that has stayed with me. Tension on a shear bolt makes it more shear easily and that's not always a good thing.

Sorry for writing a book here.

 

[jmc]

Say, the yoke wall thickness is 3/8", then you would only need to drill 3/8" deep from each end with an undersize drill to severely weaken the two shear zones. It might even finish shearing the bolt when you engage the PTO.

 

[RayIN]

The gearbox shaft on my KK is hardened, a drill bit will not touch it. Test yours with a file, if the file doesn't cut, neither will a drill bit.
That said, I agree with continuing to run the bolt until it completely breaks, it will make things much easier.

 

[2manyrocks]

Tried mowing for 3 hours, but the bolt stayed put.

Since it was a nice day here, I opted to drill with a heavy duty slow speed drill. Started with 1/2" bit and then decided to go slightly smaller. Since the bolt would slide back and forth in the shaft, I tried knocking it out with the air hammer, but mostly used the air hammer to slide it from one side to the other while drilling one side and then the other. Finally got the whole bolt shaft shortened enough that the air hammer was able to knock it out.

Looks like the bolt didn't really shear, but was bent enough to wedge itself in place.

Now I'm wondering if I ought to buy a slip clutch. Never had this issue with 5' cutter on a smaller tractor, but this 6' cutter powered by 52hp Kubota seems harder on the shear bolt.

 

[not2old]

To me, that looks like if it had sheared completely, the centre straight section would have come out easily.

 

[skipmarcy]

I always use a 7/16" grade 2 bolt with a self-locking nut on my old Howse 6' cutter. 9 out of 10 times the remainder of the bolt and the nut would fall right down onto the deck of the cutter and I could re-use the nut. Have broken dozens & dozens over the years.

 

[repete]

Tried mowing for 3 hours, but the bolt stayed put.

Since it was a nice day here, I opted to drill with a heavy duty slow speed drill. Started with 1/2" bit and then decided to go slightly smaller. Since the bolt would slide back and forth in the shaft, I tried knocking it out with the air hammer, but mostly used the air hammer to slide it from one side to the other while drilling one side and then the other. Finally got the whole bolt shaft shortened enough that the air hammer was able to knock it out.

Looks like the bolt didn't really shear, but was bent enough to wedge itself in place.

Now I'm wondering if I ought to buy a slip clutch. Never had this issue with 5' cutter on a smaller tractor, but this 6' cutter powered by 52hp Kubota seems harder on the shear bolt.

View attachment 4579505

If you add a clutch you would be well served to also have a shear bolt. I have seen a LOT of clutches so frozen up with rust that they no longer function.

 

[CalG]

I always use a 7/16" grade 2 bolt with a self-locking nut on my old Howse 6' cutter. 9 out of 10 times the remainder of the bolt and the nut would fall right down onto the deck of the cutter and I could re-use the nut. Have broken dozens & dozens over the years.

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.

 

[ptsg]

If you add a clutch you would be well served to also have a shear bolt. I have seen a LOT of clutches so frozen up with rust that they no longer function.

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.

 

[DarkBlack]

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