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.

View attachment 4580104 View attachment 4580105

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

 

[ultrarunner]

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! ;-)

Only a problem if a warranty claim is made.

I’ve seen plenty denied because manufacturers instructions disregarded…

 

[DGF]

The shear bolt on my 6' rotary cutter is really stuck. Cut the bolt head off and tried driving it out from both sides. The bolt will only move about 3/8" in before it won't go any further.

It isn't rusted in place. I'm guessing it is partially sheared?

At this point, I'm guessing my only option is to drill it out. It's a 1/2 inch regular bolt.

How do I drill it out without boring out the PTO collar and the PTO shaft by mistake? I would think I would first need to drill a pilot hole, but I would probably get it off center.


View attachment 4567249View attachment 4567250

Hi,

I had a somewhat similar experience a while back and had decent luck doing this - Soaked the metal with penetraiting fluid over a period of a week and warmed the metal with a hair dryer before applications. In my case it was a broken bolt but had an uneven surface on the face as does yours. I used a larger drill bit to clean up the face to give it a clean cone and then using the cone as the new center used a bit about 1/3 the diameter of the bolt and drilled through. It takes some time and you have to be carefull not to break the bit so keep adding cutting oil and go easy. Once through step up the bit another size or two and do it again. The bigger hole allowed me to get an easy-out into the bolt and work it until it loosened up. Kept tapping it with a hammer and appling penetraiting fluid and warming it along the way. If you can get your pin to turn it should knock it out. I am assuming this is a straight pin without a step in the shank but even with that just start on the smaller end if you know which one it is. Good luck with it.

 

[Little Red Tractor]

I'm wondering if you had tried to back the bolt out before you ground the head off. If not, you could try (if you have the capability) welding a nut on the end of bolt and backing it out. If the other end of the bolt is close enough, you could try the same thing there.

The continuing struggle with shear bolts is why I purchased a clutch, put a grade 5 bolt in place of the shear bolt and haven't looked back.

 

[D&D]

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.

Thanks for the description

 

[LouNY]

Afternoon all;
I'm going to get on a soap box for a bit.
It has become a common reference to call a bolt securing a PTO yoke to an implement shaft a SHEAR bolt.
I'm old school that never used to be called a shear bolt it was a connecting bolt.
The design of shear bolts was normally a single shear on the untreaded portion of a bolt in a flange. There used to be commonly available charts as to the ft. pounds of torque of the common sizes and grades of bolts used as shear bolts. This value is highly dependent on the distance the shear bolt location is from the centerline of the rotating shaft. I was having a hard time trying to locate one of those charts or the information in an easy to read and display manner. I did fine the information on the BONDIOLI & PAVESI web site and catalogs.

They offer many shear bolt PTO yokes that can pass from 650 Nm to 9000 Nm or 480 ft. pound to 6638 ft lbs. of torque being transmitted before being sheared.

On this page the R1 distance is the distance from the shaft center line to the shear bolt center line.

Then this page lists the sizes of the shear bolts for each different PTO yoke to achieve the desired torque transmission

Lots of information on shear bolt PTO flange yokes.
Most people will not care, but it is a peeve of mine when a product is not being used in the proper manner (as far as farm equipment goes).

SO NO A CONNECTING BOLT HOLDING A PTO YOKE ON AN IMPLEMENT IS NOT A SHEAR BOLT,
I don't give a damn what it has been bastardized to from the cheaper equipment manufacturers.

End of rant, all have a good day.

 

[ptsg]

Afternoon all;
I'm going to get on a soap box for a bit.
It has become a common reference to call a bolt securing a PTO yoke to an implement shaft a SHEAR bolt.
I'm old school that never used to be called a shear bolt it was a connecting bolt.
The design of shear bolts was normally a single shear on the untreaded portion of a bolt in a flange. There used to be commonly available charts as to the ft. pounds of torque of the common sizes and grades of bolts used as shear bolts. This value is highly dependent on the distance the shear bolt location is from the centerline of the rotating shaft. I was having a hard time trying to locate one of those charts or the information in an easy to read and display manner. I did fine the information on the BONDIOLI & PAVESI web site and catalogs.

They offer many shear bolt PTO yokes that can pass from 650 Nm to 9000 Nm or 480 ft. pound to 6638 ft lbs. of torque being transmitted before being sheared.

View attachment 4582807


On this page the R1 distance is the distance from the shaft center line to the shear bolt center line.
View attachment 4582827


Then this page lists the sizes of the shear bolts for each different PTO yoke to achieve the desired torque transmission
View attachment 4582828

Lots of information on shear bolt PTO flange yokes.
Most people will not care, but it is a peeve of mine when a product is not being used in the proper manner (as far as farm equipment goes).

SO NO A CONNECTING BOLT HOLDING A PTO YOKE ON AN IMPLEMENT IS NOT A SHEAR BOLT,
I don't give a damn what it has been bastardized to from the cheaper equipment manufacturers.

End of rant, all have a good day.

But what US manufacturers do is using gearbox with a smooth input shaft, for some weird reason and then use a through bolt as shear bolt. A circlip is what prevents the PTO shaft from coming out of the input shaft of the gearbox after the bolt is sheared.

Once the bolt inevitably shears, then the operator has to fight the sheared section in the input shaft, a terrible design. A standard 6 spline input shaft and these shear bolt yokes would solve many issues and reduce downtime by a lot.

If you're saying that that is not a shear bolt, then they offer no driveline protection at all? Which would be even worse.

 

[LouNY]

But what US manufacturers do is using gearbox with a smooth input shaft, for some weird reason and then use a through bolt as shear bolt. A circlip is what prevents the PTO shaft from coming out of the input shaft of the gearbox after the bolt is sheared.

Once the bolt inevitably shears, then the operator has to fight the sheared section in the input shaft, a terrible design. A standard 6 spline input shaft and these shear bolt yokes would solve many issues and reduce downtime by a lot.

If you're saying that that is not a shear bolt, then they offer no driveline protection at all? Which would be even worse.

A shear pin yoke is available in the shaft size being used which is what the manufactures should be using.
Besides which what is the double shear of a 1/2" bolt? compared to what the shear factor should be to protect a gear box.

So a half inch grade 5 bolt has a single shear of 6300 to 8100 ft. lbs. double that for being in double shear.
In my mind that is not protecting a gear box.
In my opinion the reason that these half inch bolts finally break is all the shock loads accumulated over the life of the bolt, the shock starting and stopping then the impacts while being used.

As far as I'm concerned anyone that doesn't use a properly maintained slip clutch or a properly sized shear flange is just asking for excessive wear and damage.

 

[Gregster613]

Afternoon all;
I'm going to get on a soap box for a bit.
It has become a common reference to call a bolt securing a PTO yoke to an implement shaft a SHEAR bolt.
I'm old school that never used to be called a shear bolt it was a connecting bolt.
The design of shear bolts was normally a single shear on the untreaded portion of a bolt in a flange. There used to be commonly available charts as to the ft. pounds of torque of the common sizes and grades of bolts used as shear bolts. This value is highly dependent on the distance the shear bolt location is from the centerline of the rotating shaft. I was having a hard time trying to locate one of those charts or the information in an easy to read and display manner. I did fine the information on the BONDIOLI & PAVESI web site and catalogs.

They offer many shear bolt PTO yokes that can pass from 650 Nm to 9000 Nm or 480 ft. pound to 6638 ft lbs. of torque being transmitted before being sheared.

View attachment 4582807


On this page the R1 distance is the distance from the shaft center line to the shear bolt center line.
View attachment 4582827


Then this page lists the sizes of the shear bolts for each different PTO yoke to achieve the desired torque transmission
View attachment 4582828

Lots of information on shear bolt PTO flange yokes.
Most people will not care, but it is a peeve of mine when a product is not being used in the proper manner (as far as farm equipment goes).

SO NO A CONNECTING BOLT HOLDING A PTO YOKE ON AN IMPLEMENT IS NOT A SHEAR BOLT,
I don't give a damn what it has been bastardized to from the cheaper equipment manufacturers.

End of rant, all have a good day.

I've got a shaft like that on my woodmax woodchipper but nowhere in the manual does it specify which end attaches to the tractor pto. Both ends fit either end? I "assume" the sheer bolt end attaches to the implement pto stub? Have had zero problems but would really like to know for sure where it's supposed to attach. Thanks.

 

[LouNY]

Some where there is a standard on that. I have seen it and it was related to the shielding and so called personal safety. The more common is on the implement end as that is usually more open and easier to work with.

 

[RayIN]

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.

FWIW, I use gr 2 bolts, but decided to try a gr 5 after reading here. The gr 5 bolt broke on both sides, but one end of the bolt was long enough it cut a groove in the cast iron PTO end. I promptly went back to gr 2 @ $1.55 ea. including Nylok nut.