lower link pin steel type?

[charlz]

Not sure if this is the best place to ask but here goes:

I may need to replace my 'lower link pin' with a longer version. This is the pin that goes through the back of the tractor and then the lower 3pt lift arms are placed on. Will just cold rolled round work or is there some other steel type I should be looking for? I'm thinking cold rolled for its tighter tolerances as I want a good fit where it goes through the mounts on the tractor. My only real concern is bending over long term use. I would be adding a total of about 4-5 inches to the stock pin (few inches more on each side).

Background: my b7100 has a BH and there are mounting plates that mount to the rear end. Over time the installation and removal of these plates has caused bolt holes to be stripped. I have all the stuff to heli-coil the holes. In looking at the way the plates mount they are no or not much lower than the loader subframe under the tractor. I am inclined to fix the holes, bolt on the plates and never take them off.

Today I have to install/remove the plates, take off one rear tire to get the link pin reinstalled/removed (no holes in the bh mounting plates) etc. etc. All this takes about a hour to switch from 3pt to hoe and another hour to switch back. Leaving the plates on and the link pin in place would save me a lot of time and effort.

Sorry for being so long winded.

Thanks,

Charles

 

[RobJ]

I think they are just cold steel, keep in mine the longer they are the more the leverage on the attach points.

Rob

 

[Corm]

Ditto what Rob said...

corm

 

[Renze]

Cant you weld some brackets to the loader frame, at the desired spacing ?

I know these Kubotas as my neighbor had one, but i dont think the pins will hold up long, the way you described, as you're going from a situation where the pins are shear loaded only, to a situation where they are bend loaded too.

 

[Huskerplowboy]

Most hitch pins are made of better than average steel and heat treated to improve both strength and wear resistance.

I'm most familiar with big ag tractors, 100 hp and up, but they also have larger pins in addition to being good steel with heat treat. (The lower link to quick coupler pins on 275 hp (PTO) row-crop tractors is about 1.5" diameter and made from something like 4140 or another steel along those lines, then heat treated.

Since a do-it-yourself project usually rules out heat treat, I'd look for 1040 or 4140 grade cold rolled bar, which will inherently have better hardness and strength than typical cold rolled barstock... What diameter are the pins? One possibility could be to find an off-the shelf drawbar pin in that size and cut off the head/handle or modify it to fit your needs... Some of those are just cold rolled something, but some are heat treated, might be worth a look...

 

[Huskerplowboy]

McMaster-Carr has a decent description of different steels: Typicall cold rolled is around a 1018 grade, not bad, but not great...

http://www.mcmaster.com/param/dsc/dsc.aspx?dsc=Metals

 

[charlz]

Thanks for the input guys. Here are a couple pics that help show what I am talking about. I heli-coiled the bad holes, drilled holes for the link pin in the brackets and mounted them with the old link pin inserted.





Turns out it only moves each side out 1 and 3/16 inches. Since the brackets are made to take the rear hoe weight/flex I think I would be ok if they would take some load if the link pin flexes. I think that takes care of what Renze noted.

As for the diameter of the pin it is 7/8 inch and it would need to be about 17 and 1/2 inches long. Probably rules out any off-the-shelf pins.

Since the 3pt is rated at like 1200 lbs would 4140 or the like be overkill?

Thanks!

Charles

 

[3RRL]

I don't think 4140 would be overkill.
If it was me, I would want it hardened, but pre-hard like 4140 or 4130 would probably do. What I don't like is that the pin is one length going through your tractor and those plates. If it bent you would have a heck of a time getting it off for replacement.

 

[Huskerplowboy]

Did a little more digging... Most places I found online sell 4140, 4130, etc in an annealed or normalized state, basically about as soft as they can be. One option that should be readily available is "Stressproof" rod, which is an 1144 and comes with some heat treatment. A lot of places stock stressproof for use as shafting because it's strong but reasonably machinable. I'd look for either stressproof or some type of pre-hardened 4140, 4130, or 4340.

Online Metal Store | Small Quantity Metal Orders | Metal Cutting, Sales & Shipping | Buy Steel, Aluminum, Copper, Brass, Stainless | Metal Product Guides at OnlineMetals.com

...has stressproof. They also have a guide that shows some of the properties of the steels they have. For example, they list a yield strength of 100,000 psi for stressproof, but list a yield strength of just 52,200 psi for annealed 4130... Looks like the normalized 4340 would be good stuff too...

 

[sandman2234]

A friend has a B6000 and somebody removed his 3pt hitch arms and put a bolt on Tiller on it. We used the bolt holes in the bottom of the gearbox, plus a couple of the same ones your using, to mount a new plate under the rear, and we just used 3pt hitch pins to mount the arms on. We welded them to the plate I made to go under the bottom of the gearbox.
I made 3 extra plates while I had the thing setup to make, althought the owner swore he would never any of them. He has one left now, and I think he has it commited for another project. Those pins aren't made of anything special, and work just fine.
David from jax