New to Me: Posthole Digger... PTO Shaft Questions.

[Iplayfarmer]

How is the 1-1/8 shaft joined to the drive collar ... shear bolt?, ... clamp and key? ... ?
larry

Shear bolt

 

[SPYDERLK]

Shear bolt

Id say bushing it will compromise shear bolt function badly. The shear area is no longer distinct and tight. The bolt will bend and smear rather than shear clean. Im thinking its not a good alternative.
larry

 

[KWentling]

Id say bushing it will compromise shear bolt function badly. The shear area is no longer distinct and tight. The bolt will bend and smear rather than shear clean. Im thinking its not a good alternative.
larry

As long as the bushing has a good fit I don't think there will be a problem. Might want to tack weld the bushing to the yoke so there is only the one shear point. I looked at McMaster Carr and MSC and didn't find a suitable bushing. You might have to go to a machine shop and have one made. 30 minute job. Another alternative would be to replace that yoke with one with a 1 1/8" bore. Once again Baum would probably have that or the shop that gave you the price to make a new shaft could get one for you.

If it were me, I'd bush it but I'm a machinist and all I'd be out is a little time. Has anyone sheared a pin on a post hole digger? I've drilled a few hundred holes in the past 45 years or so and I don't think we ever did. Not many rocks around to hit though.

Kim

 

[SPYDERLK]

Yes, Iv sheared mine several times. Rocks and roots ... The problem with a bushing in a shear pin joint is the soft action of the anulus presented by the bushing. Normally the collar and shaft are hard enuf to shear Gr5 bolts cleanly without damage to either component. A bushing is probably not going to be this hard, is fairly thin, and even if welded at accessible points will still present relative flexibility in the shear zone. The shear will work, but will not be at the same value -- and more importantly will damage the shear area more than the 2pc setup would have. It willwork to get you up and running. It may work forever, or close enuf, in your circumstances. I would do it, for myself, but with awareness of the mechanical difference.
larry

 

[Iplayfarmer]

...The shear will work, but will not be at the same value -- and more importantly will damage the shear area more than the 2pc setup would have. It willwork to get you up and running. It may work forever, or close enuf, in your circumstances. I would do it, for myself, but with awareness of the mechanical difference.
larry

I think that's where I'm at. If I had a brand new implement and a 30 HP tractor I may be more concerned. As it is, I paid less than $200 for the digger, and my tractor has only 15 hp at the PTO. I may stall out the engine before a bolt shears anyway.

 

[KWentling]

The problem with a bushing in a shear pin joint is the soft action of the anulus presented by the bushing. Normally the collar and shaft are hard enuf to shear Gr5 bolts cleanly without damage to either component. A bushing is probably not going to be this hard, is fairly thin, and even if welded at accessible points will still present relative flexibility in the shear zone. The shear will work, but will not be at the same value -- and more importantly will damage the shear area more than the 2pc setup would have.

So if the bushing were brass or Nylon or something I'd buy that. Any steel bushing that could be welded to a yoke is probably going to be similar in hardness to the yoke. If I were making it would be out of 4140 or better because that is 90% of the material we stock at the shop, so likely harder than the yoke. If he has a bushing made I would recommend having it made with an interference fit of .001", freeze it and install it. Tack weld it and drill the shear bolt holes. He'll want a close slip fit ( not more than a couple thousands loose) to the digger's shaft. In a perfect world he would have parent bore yoke. If done right this will be danged close.

Kim

 

[SPYDERLK]

The problem with a bushing in a shear pin joint is the soft action of the annulus presented by the bushing. Normally the collar and shaft are hard enuf to shear Gr5 bolts cleanly without damage to either component. A bushing is probably not going to be this hard, is fairly thin, and even if welded at accessible points will still present relative flexibility in the shear zone. The shear will work, but will not be at the same value -- and more importantly will damage the shear area more than the 2pc setup would have.

So if the bushing were brass or Nylon or something I'd buy that. Any steel bushing that could be welded to a yoke is probably going to be similar in hardness to the yoke. If I were making it would be out of 4140 or better because that is 90% of the material we stock at the shop, so likely harder than the yoke. If he has a bushing made I would recommend having it made with an interference fit of .001", freeze it and install it. Tack weld it and drill the shear bolt holes. He'll want a close slip fit ( not more than a couple thousands loose) to the digger's shaft. In a perfect world he would have parent bore yoke. If done right this will be danged close.
Kim

:thumbsup: Thats what Id do if I was going for the best under the bushed circumstance. Not the same, but as near as feasible.
larry

 

[whitedogone]

I'd take the cross apart on the digger end and see if you can fit that 1 1/8 end to the cross on a new standard shaft assy. The cheapest Quality shafts I've found are at Northern tool.

pto from Northern Tool + Equipment

They are braber equipment shafts. You can get the BE model # off Northern tools site of a shaft that will be long enough and have the right end for your tractor and call BE to see if your digger end you have will mate up with one of there shafts at northern tool. BE's # is 604-850-7770. Be sure to have all your cross dimensions ready when you call.

 

[Iplayfarmer]

I ordered the shaft from Value Barn. I'm already impressed with their customer service. somehow I ordered it twice. I sent an e-mail asking them to correct it. I didn't expect a response until Monday, but I got a reply e-mail today (a real reply, not some canned automated "we'll get to you" form letter) saying that the problem is fixed.

 

[Iplayfarmer]

I figured I'd post an update. I got the shaft from Value Barn. It took two trys as the first time I only got half of it. They were good to get a replacement tag out to me quickly, and the replacement arrived this past week.

I got a bushing from McMaster Carr. I still have to drill the bushing for the shear bolt. I hope to try it out soon. I have a lot of post holes to dig.

Any advice on running a post hole digger? This will be my first time.