PTO shear pin advice.

   / PTO shear pin advice. #21  
My experience is quite different than the rest I guess....

I continually sheared the bolts on my snowblower for about a year. I changed to the hardened bolts about 10 years ago and have had no problems (other than shearing those bolts under hard conditions) since then. No instructions with the blower so I dont know if I am doing right or wrong.

One interesting note, I guess, is that I took the drive chain to the shop to have a link removed ( the chain was loose) and I was told that since the chain had stretched that there was something wrong with the unit, no chain should stretch to require removal of a link. Well I come from the motorcycle age when everything was driven by chain ( no driveshaft) and you always had an adjustment to tighten the chain and you also had a splicing link to alow the removal of chain links.

Anyway I am not sure that my use of the hardened bolts is correct, but I know regular bolts would not work in my case.
 
   / PTO shear pin advice. #22  
On industrial chains you can also do a half link. Sounds like they are trying to sell chain.
 
   / PTO shear pin advice. #23  
BrianC, I noticed a long time ago that my Bush Hog tiller manual, in telling about maintenance on the chain drive, says "If chain has one link or more of slack, have an authorized Bush Hog dealer resize the chain." So I guess that may not be too unusual; however, in over 6 years of hard use, I've not had to do that.

Bird
 
   / PTO shear pin advice. #24  
<font color=blue>I continually sheared the bolts on my snowblower for about a year.</font color=blue>
I had this problem with a Lucknow rear snowblower. The shear pin was located on the front u-joint of the PTO shaft. I consisted of 2 lobes intergrated into the casting of the u-joint that were bolted together with a 1/4" bolt. The hole through these lobes had been drilled as far away from the center of the shaft as possible- even at the point where the casting started to round off.There was too much leverage out there- I redrilled the same sized hole closer to the center of the PTO shaft, about a 1/2", and that solved the problem. Changing that shear bolt up under the PTO guard of the tractor, in the dark at 10-20 degrees F was my definition of a royal pain in the @ss

RCH
 
   / PTO shear pin advice. #25  
The grade 2 bolt issue is a real can of worms. There are various material specifications that could be sold as a grade 2 bolt but are not. The problem is there is no head marking requirement for a grade 2 bolt. The head is plain and may not even have a manufacturers symbol on it. The grade marking designations came from the automotive industry with Specification J429. The J429 grade 2 has a tensile strength of 74,000 psi for bolts between 1/4 and 3/4 in diameter and 60,000 psi for bolts between 3/4 and 1 1/2 diameter. An J429 grade 1 also has no head marking but it only has a tensile strength of 60,000 psi and the diameters run from 1/4 to 1 1/2. Then there is the ASTM A307 specification that alot of people try to pass off as a grade 2 bolt but comes in grades of A and B, it only has a minimum specified tensile strength of 60,000 psi. The long and short of it, you as a purchaser have no way to really identify what is being sold to you. This is why when you go to the hardware store and buy an unmarked bolt, some of them can be almost as strong as a grade 5 depending on how the bolt was manufactured. I have noticed that in the last few years the ASTM A307 designation has started showing up on the head of the bolt. I would not buy the A307 and try to use it as a grade 2. There are no proof load requirements for an A307 bolt and this is why you can have a real soft bolt that does not shear readily but just stretches.
Sorry for the long post but it something as an OEM manufacturer that we face everyday and sometimes have to take a bolt sample to the lab just to see if we received what we ordered. Good luck.

Randy
 
   / PTO shear pin advice. #26  
I used a grade 5 bolt in my snow blower in place of the grade 2 and the next time I picked up a rock I blew out the drive chain. I've been using grade 2 bolts ever since. I view a clutch as a self-repairing, adjustable grade sheer bolt. That's why I'm getting one.
 
   / PTO shear pin advice.
  • Thread Starter
#27  
Randy,

I think that you have explained why the JD guys suggested that I use a Grade 5. He stated that the Grade 2 didn't shear but bent or stretched.

I'm going out early tomorrow to drop of the youngest daughter to get certifiied as a baby sitter (yep, nice to do that now...) and hit the Home Depot and another JD dealer. Lost a pin for my FEL latch and need to pick one up.

Let's see how much more I can add to this saga. /w3tcompact/icons/smile.gif

Terry
 
   / PTO shear pin advice. #28  
Terry,

I use a #2 1/2"X3 1/2" shear bolt on my Land Pride 60" rotary cutter and they shear just fine. No bending, no stretching, just "zing" and I'm reaching into my spares.

The cutter came from the manufacturer without instruction on this point, (they presume all were ordered with a slip clutch - an option I was unalert to and which my dealer did not mention). But dealer and previous posts on this board led to me use #2's, and as I suggest above, they do a fine job protecting the gear assembly etc.

Since I have gotten better at using the cutter, and since I've gotten the very tall stuff cut so I can see where I am going, I hardly ever break a bolt, so the idea of retrofitting a slip clutch seems less necessary...esp if it involves cutting the PTO shaft to accomdate. Though if I had slip clutch, I might not need the New Holland toolbox where I keep spares and some wrenches. Could store a thermos of coffee or something.

Good luck,

Chas
 
   / PTO shear pin advice. #29  
Shear Bolt Strength
Shear Bolt Strength Chart

18-48044-JFM3BW5205SigFile.JPG

"You are what you eat, drink, think, say and do..."
 
 
 
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