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What material to use to make a pin for a hydraulic excavator

rickseeman

Cast Iron
Joined
Oct 7, 2014
My friend wants me to make him a pin for his excavator. This is a medium size machine, around 50,000 lbs. This pin goes through the hydraulic cylinder that connects to and moves the "stick". The pin is 3.140" in diameter and 10-7/8" long. I don't have any way of finding out the original material. I think of pins as needing to be hard. I was thinking maybe O1? And then have it heat treated. I don't know how the heat treating will effect the size. Thank you for your help.

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Hi rickseeman:
Here's a snip from a quick Google search.
Take it for what it cost you...this is not an official engineering recommendation.

Also I don't know if these pins are commonly case hardened or nitrided...one would think yes, but who knows???
Maybe they'd rather wear out the pins regularly than wear out the bushings in the boom.
I would be very surprised if they were through hardened.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 

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I was suprised when he tore it down. I figured it would have a hard pin and a bronze bushing. I figured they would want the wear to go to the bushing and the pin to be reused. But the steel? bushing in the end of the cylinder was perfect and all the wear was on the pin. The wear was so bad you can see it in the photo.
 
What Marcus said, I have made many out of 4140/or 4340 depending on what i have on the shelf. Usually i heat treat treat them to 38-42 rc adds some wear resistance and a-lot of strength. Could probably just use commercial pre- hard 4140/4142 as that is a good go to material for projects like this.
Scott


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They all wear out. Bushings and pins. Your friend's machine may have had the bushings replaced already. That is a very common repair. In such an environment (dirt prevalent) there is a natural abrasive present all the time. Soil. Tends to wear things out no matter how hard they are. The machines with automatic grease lubricators fare the best, but even they wear.

I'd either go with a hardened pin, hard chrome plated or the aforementioned 4140 and flame hardening for the best wear characteristics.
 
The pins I typically see are induction hardened, when you can see the end of the pin it is natural colored near the center with a band colored from heating at the outside edge. If asked to make a pin I usually HT a piece of 4140 to about 45-50 Rc. Stay away from chrome plated as the chrome peels and grinds up in the grease.

Ed.
 
I second the 4140 PH. I have made dozens of them and they hold up fine. It's a lot easier to make a new pin then fix a wallowed out hole. I just finished making a set for a Ditch Witch backhoe. There was some kind of black plastic bushing driven into the bore that held up pretty well. I don't know what it is but it must be some pretty tough stuff. The pin was worn but the bushing was fine.
 
Most bigger machines use steel bushings.
Have you looked for aftermarket pins? Often you can buy them cheaper than making one, and it will be harder than 4140HT.
 
Like crossthread, back in the day such pins were a bread and butter job for me, and for booms and dippers EN24 T was spec'd ** which I think is your hardened and tempered 4340.

** For bucket pins and the like that were often in mud and water - EN8 .mainly cos it was cheaper and 24T lasted little or no longer.
 
According to wiki, EN24 is equal to 4340.

From my quick read on wiki and other sites it seems that EN classification is disappearing in favour of some different Euro listing? True? Thankfully my local still use SAE numbers that I know....

L7
 
A typical source of material is junk hydraulic cylinder rams from other construction equipment. They are usually induction hardened chrome plated. That being a 80mm rod it may be a tough find unless they already ruined a cylinder. Don't use a ram from farm equipment even if you find one large enough, they aren't tough enough.

The world is full of aftermarket parts manufacturers for popular construction equipment. If someone makes an aftermarket pin that will fit that machine, the cost will probably be less than the heat treatment cost alone of your custom made replacement. It doesn't even have to be for that machine, just the necessary diameter and at least minimum length.
 
The pins I typically see are induction hardened, when you can see the end of the pin it is natural colored near the center with a band colored from heating at the outside edge. If asked to make a pin I usually HT a piece of 4140 to about 45-50 Rc. Stay away from chrome plated as the chrome peels and grinds up in the grease.

Ed.

Thin chrome will do that. Thick chrome won't. Gotta do it right or if won't last. Being that it's going to wear out either way though, I'd probably second/third - whatever it is up to now - the 4140 recommendation.
 
AS mud says ...buy commercial pins and bushes,its cheaper......a local crowd here called "K-Set" make all this stuff ,option of 1040 or 4140 ,induction hardened to file hard .........this is essential with earthmoving ,as anything softer than RC 60 just gouges and seizes in operation....I ve spent 60 years fixing this kind of stuff,and the best of the best is Caterpillar,and their pins and bushes are glass hard surface.
 
4140 seems to be getting the most votes. I see a 4140 that is already heat treated. That would save a big step for me. It's only 25 on the C scale though. I assume my tooling would cut that. I wonder if that is hard enough for this pin application?
 
The 4140 PH is not hard enough and will chew up ....I suspect you pictured example is probably PH....Ive seen lots of pins made from PH ,and done some myself ....its good for ocassional use ,and as get you going again replacement.
 
4140 seems to be getting the most votes. I see a 4140 that is already heat treated. That would save a big step for me. It's only 25 on the C scale though. I assume my tooling would cut that. I wonder if that is hard enough for this pin application?

Typical 4140PH is 28-32Rc and usually down closer to the 28 end.
You can buy 4140 PH that is 33-37Rc, but it is harder to find.
http://bicosteel.com/wp-content/pdfs/4140PH.pdf
 
Last time I had this problem I used 4130PH and it outlasted the machine. Wore out the bushing with little noticeable wear. For the bushing I would use hard bronze or leaded steel.
 








 
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