Lengthening BH bucket pin

[afish]

I need to build a thumb for a L39. In order to pin on the thumb I will need a longer pin for the bucket and since it already has the quick coupler and Kubota dosnt offer a thumb I doubt they offer a longer pin unless the b26 has the same size pin for the bucket but I'm usually not that lucky. I think I will need to lengthen the stock pin or make a new one. What kind of steel is suitable for this if I wanted to make one from scratch? Also I was thinking of cutting the stock pin in half and adding a piece of mild steel in the middle. Since most of the shearing stress is at the ends where the bucket pivots do you think this would work without causing any problems? I have metal fab experience but we never get into hardened material so this aspect of it is newer to me.

 

[RickB]

I need to build a thumb for a L39. In order to pin on the thumb I will need a longer pin for the bucket and since it already has the quick coupler and Kubota dosnt offer a thumb I doubt they offer a longer pin unless the b26 has the same size pin for the bucket but I'm usually not that lucky. I think I will need to lengthen the stock pin or make a new one. What kind of steel is suitable for this if I wanted to make one from scratch? Also I was thinking of cutting the stock pin in half and adding a piece of mild steel in the middle. Since most of the shearing stress is at the ends where the bucket pivots do you think this would work without causing any problems? I have metal fab experience but we never get into hardened material so this aspect of it is newer to me.

Start from scratch and make a complete new pin. I think you are giving them a lot of credit worrying about hardened pins. Chances of it being anything more than cold rolled round stock are slim at best. Hit it with a center punch and see how hard the original pin really is.

 

[BlacknTan]

If I were to make it out of CRS (mild steel), I would have it case hardened.

Saving that, I'd scrounge up as piece of 4130, 4140, 4340 or the like.. Machine it and use as is...

 

[3RRL]

If I were to make it out of CRS (mild steel), I would have it case hardened.

Saving that, I'd scrounge up as piece of 4130, 4140, 4340 or the like.. Machine it and use as is...

My experience is that case hardened CRS or HRS will warp quite a bit and needs to be centerless ground to be true if the pin is to be of any length. Plus it might swell during heat treat a bit. The suggestion of 4130, 4140 or the like is excellent...maybe even P-20?

 

[BlacknTan]

Unfortunately, in my experience, 40+ years as a Tool & Die Maker in the shops of one of the National Laboratories, a round pin will warp little from the case hardening process, even if done with Kasenite as a DIY person would do as opposed to a professional salt bath.
Case hardening is a very thin surface treatment. While it can be performed to greater depths, that would negate the desired result of having a glass hard surface with a soft, tough core.. Centerless grinding would remove the glass hard surface to a great degree.
If a pin such as this needed to be centerless ground, another alloy should be chosen that would allow hardening through..
I agree that in thin sections, the case hardening process can produce warpage, but that's not what we're talking about here..

In a tractor part, which does not require a precision fit in the true sense of the term, a case hardened pin as finished would be more than acceptable, and I would guess tougher than the part as provided by the manufacturer, but I'm only guessing here.

Were the tractor in question mine, I'd grab a piece of good chromemoly and call it a day..

 

[3RRL]

Bill,
I wouldn't say "Unfortunately", in fact I would say you have been extremely fortunate.
I have not had that kind of luck with any heat treat during my career...rounds, squares, all kinds of shapes and heat treat for my plastic injection and die cast molds. In my shop, it's always ground to the number after heat treat and nothing goes out with even a "little warpage". Having suffered some unfortunate heat treat results, I couldn't afford the risk.
But you're right, that is a different story and we're talking tractor parts here.

I agree that for a tractor part a little warpage or size change would work, as long as he could get the pin through.
I also agree his best bet is to use some readily available pre-hard material and just turn it to size.

 

[BlacknTan]

Of course, you're right Rob.

Coming from our backgrounds, it's easy to overlook the fact that what we might consider flat, round or true, is far different from what the average person considers it to be.. not better or worse, as I don't mean to insult anyone here, jusy different.. It has taken a looong time to recognize that not everyone views the world as precisely as a Machinist does.. or needs to.

Of course materials move in heat treating.. It's unavoidable.. it's just the degree.. In many die shops, we heat treated small parts ourselves. It's not the optimum, as there was more grinding later, but we always accounted for that.. For "money" parts, we always used professional heat treatment, and there was a difference. Less movement=less grinding, and it's important with a steel like D-2 that loads up a wheel..

I agree, nothing goes out unless it's right.. Thankfully, many things do not require our style of precision! (I'd like to put a smilie here, but for some reason, they're not available)

 

[KML]

First off, I am by no means an expert in metal! FWIW, here's the direction I took,

When I wanted to make 1" dia. pins I went a couple of cubicles down to our mechanical engineers and asked what they would use for tractor implement pins and 3 for 3 agreed that in a home shop environment W1 water hardening "drill rod" was the best choice.

They said it's cheap and readily available, has a high enough carbon content to be used without heat treat and still provide wear and strength suitable for this purpose. It was said that a 1" pin was grossly oversized for the forces generated and that that was a good thing as it allows for the use of more readily available materials. They did say that a surface heat treat would increase the wear resistance but wasn't needed as you actually want the pin to wear! If you use a super hard pin all of the wear will occur on the machine and what would be harder and more expensive to replace, the pin or a loader arm or back hoe boom?

The W1 pins I made haven't been in service very long but I have to say they show no wear or distortion and at $25 for 3' at the local fastenal I can't complain. Another plus is it's available in many diameters with relatively close tolerances and a surface finish that can be used as is.

 

[sandman2234]

I have a 55 gallon drum that was headed for the scrap yard, on the last day of my friends ownership of the shop. I just happened by there, and decided to load it up on the truck, since I had my Ford with the jib crane on it. I later suggested taking it to the scrapyard, and the old owner was amazed that I even managed to pick it up.(or got it before the new owner arrived) He told me to keep it, use the scrap in it when I needed something. One of the things in the barrel was some shaft that is already chromed. I don't know what the technical name for it is, but it might be worth looking into. It is something we made shafts for the a can company plant here locally and also used it in repairs on a pallet manufacturing companies machines. It could be bought in sizes pretty close to whatever we needed.
Another thought would be TG&P round stock. Should fit right into the bushings without machining if you order the right size. Won't have the anti wear surface of the chrome stuff, but with plenty of grease, it should be ok, and not need machining.
David from jax

 

[chickenman]

would a class 8 bolt do?