Pin and Bushing Material for Loader Bucket
I will be rebushing my front loader bucket in the near future. The cost of off the shelf bushings and pins is too steep for me to justify when I can manufacture them myself.
For the pins, I have a bar of forged and heat treated 4140. I assume the bushings should be the wear item, and made of a softer material. For material, should I used a softer steel? Anyone have experience with a project like this or have input on a bushing material choice? Is my material choice for pins somewhat correct? I have access to an assortment of material, so what would be ideal?
For clearance, I figured I’d go with around .005 diametrically.
Thank you for any input or guidance.
Usually it’s the other way around. The bushings are hard as a coffin nail and the pins are soft. I would figure the bushings are 8630 or something like that and carburized. The pins would be 1045 or something like that.
No actual experience with this exact situation, but in working with pilger mills. Make the most easily changed item the wearable and change frequently.
Hardened steel on hardened steel is a good bearing. Soft steel is never a good bearing unless you run it on bronze or aluminum.
I’d make the pins and bushings out of C4140 prehardened. I’d advise that you buy the factory bushings if available, they are very hardened and will last better in the dirt. Then your 4140 pins will last decently at moderate hardness. I’d go for .010″ diametral clearance, tighter than that is risking a seizing issue, even a rusting-seizing issue if the thing sits for a year in the weather, in unworn condition.
If you have the lathe skills, forego making a shiny smooth pin. Leave it with feed scallops at about a .010″ feed. This rougher surface will hold the initial greasing far longer than a baby ass smooth finish will.
I remember the late Mark McGrath telling me before he died that he at one time was sub contracted to make bucket pins for JCB and they were ordinary low carbon mild steel EN1 or EN3 as was
What size and type of machine are we talking here? ..and what are the original pins and bushes made of ? i.e does the welded in bush have a liner bush for the pin to run on.
Ditch Witch has used Garmax self lubricating bushings on their equipment for years. My dad has a couple of their 4 wheel drive 4 wheel steer backhoe loaders, about 20 yrs old, and the joints on them are still as tight as you’d expect the joints on a typical one year old backhoe to be. The ability of Garmax to survive shock loading is what sets it apart from other self lubricating bushings, and the typical earthmovers have most of their bushed joints beat out long before they’re worn out.
The machine is a case 450B with a 4 in 1 bucket. Its a 16k lbs machine. The bushings are not welded, they are a liners.
I suppose having both the bushing and pin be hard would not be an issue. I just assumed one would be the wear item. I figured it wouldn’t be the pins as they are seeing a heavy shear force where the bushings are seeing compression.
I replaced the bucket hinge pins and bushings in my Cat track loader a few years ago. The pins were very hard, and the hardness was pretty deep, deeper than the wear. 4140 HT should be OK for part time use. Forget what the bushings were like, not super hard but not soft either.
While you have it apart, make some steel shim washers to take up the wear space between the arm and the bucket, they will help keep the dirt out of the joint. One washer per arm is OK, 4140HT if you have it, anything else if you don’t. Cat sells bucket shims but I wanted one thick washer instead of several thin shims
When I worked heavy equipment the pins were the replacement items, I never replaced a bushing in 8 years. The only problem I had was if I didn’t grease it enough and the grease port plugged up. I would go with .005″ clearance and put a good grease spiral groove in the bushings. Use enough grease and you will be fine. I would think the harder the better for both items.
When I started carrying TGP for pins, our customers were confused. It’s a replaceable item, and for the most part, our customers were a bunch of farmers or small time construction gigs. The guys that need the machine up as much as possible, just call CAT to do the repair.
I’ve done many of these. The holes get egged out and movement is such that greasing becomes a waste of time. The mechanic would ask me to make them “donuts” of 4140 at least as long as the original boss material is thick, and the OD larger enough that welding wouldn’t get the ID too hot if the welder took his time. I was using LaSalle’s Acraloy TGP for pin stock, and boring the center of those donuts to press fit hardened steel bushings in.
These off the shelf repair hardened and ground bushings are about 1/4″ wall and have a shallow radiused groove both inside and out with 1/4″ holes between so that if they do spin the grease will still find a route to the interface between the pin and the bores of the hard bushings.
In practice they would carefully air arc the egg shaped hole out bigger and rounder and with weld prep 45. Then they would line them up with the pins, tack weld the donuts in hard bushings and all and start welding them in, weld a couple inches, move to the next and weld that, take a break or whatever but never let the repair bushing get color.
As for how long they lasted I don’t know, I stopped working for lumber mills long ago. But I just did what I was told.
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