Backhoe Bushing Boondoggle - Advice needed!

[3RRL]

john,

</font><font color="blue" class="small">( I'll be making my own pins from 4140.)</font>

That's a pretty good choice of material. Consider that they will be about 300 Brinnel (about 26-30Rc) hardness. You may want to case and carburize them 1/32 to 1/16" deep for a hard surface. They'll end up super strong. You can use them in the pre-hard stage as bought, but they will wear a lot faster.

If you're going to heat treat them, you can also use any low carbon steel (either HRS or CRS) and case and carburize them too and still get super hard, strong pins out of it. The case and carburize heat treat for any of the 3 steels will be the same process so you can save a little on the material and turning cost. If it was me, I'd also OD grind after heat treat to guarantee size and concentricity...but maybe you won't need to do that depending how good your bushing job turns out and the running clearance between the pins and bushings?

I'm sure 5030 would love to turn some mild steel for you. /forums/images/graemlins/grin.gif

 

[5030]

Rob:

Like I need the work. I'm playing around with anodizing at the moment. Vegetable dye makes nice colors. Besides, I'm trying to get my Triumph and sidecar back together for warm weather.

One thing for sure is that you can start with the cheapest steel and with a good heat treat technician, turn it into a silk purse. Just ask General Motors. /forums/images/graemlins/grin.gif

I'm thinking about buying a radius draw tube bender and one of the manufacturers who's bender I am looking at has a distributor in Chicago that also sells line boring equipment complete with that Miluakee drill and nice insert tooling. It's only money. /forums/images/graemlins/grin.gif

 

[john_bud]

Rob, Daryl,

I was planning on heat treating the pins after any drilling or welding that is needed. I am NOT a heat treat technician, but I can turn a silk purse into a sows ear! Uh, well where was I going with that?

Oh yeah, Heat Treat! Right. My method is just to torch heat the pins until red hot and quench. Have been using water and snow in a metal bucket. Then temper at 450F for about an hour in an old toaster oven in the shop. I don't have any way to turn or machine other than going to a machine shop and the $ just aren't there for that right now. Do you have any hits tips or tricks to help the process?


Ugly Pictures

Before

Under the barnicle

In the crack - Slag --yuck /forums/images/graemlins/frown.gif

My welds

Pivot / boom lift cyl --note repairs and pin trap welded by a washer


Thanks!
jb

 

[Egon]

John:

Looks like you have some serious rebuild here. Have you considered just ctting off some of the ugly parts and frabricating new. It may be easier in the long run.

On Heat Treating:

Have you considered a propane tiger torch and some high temp bricks pilled up to make a little kiln. Would allow for better heating and even post quenching temperature control.

Please note I do not weld.

Egon /forums/images/graemlins/grin.gif

 

[5030]

Egon & John:

Egon: Nice barbecue. /forums/images/graemlins/grin.gif Bet that would do some Ball Park Franks real fast. /forums/images/graemlins/grin.gif

John: I don't heat treat any parts other than the AGD indicator extensions I sell on E-Bay when I'm bored. That's is oil hardening drill rod and I harden the spherical tips only. Once in a while I anneal copper sealing washers because I'm too cheap to buy new ones too.

I use AST in Perrysburg, Ohio for all heat treating. The problem with hardening most any alloy is that it has to be done in a controlled atmosphere furnace and then normalized to remove the internal stresses that are created in the first process. Normally, most heat treaters do small quantities, you just have to wait until they are running a compatable alloy run and they will incorporate your parts in that run. It should be quite reasonable to outsource it. By the way, those pictures are ugly and so are the welds. Looks like a 6013 goober job with the old Lincoln buzz box to me. I'd be rightfully ashamed of that job. Hope whomever you got the backhoe from gave it to you real cheap and I hope it's not a poster here.

The reason I mentioned GM before was that AST does the rocker arms for GM and GM buys the absolute cheapest steel they can get and then AST turns it into a "silk purse". /forums/images/graemlins/grin.gif

It's actually more cost effective to obtain and machine a cheap, mild steel and then heat treat it to the specification you desire. You can internally alter most characteristics of steel to suit your needs with a competent heat treater.

 

[jmc]

John,

Have you considered using an unhardened pin since it is easy to replace and may be less likely to wear the bushings?

John

 

[john_bud]

JMC,

One of the bucket pins was unhardened. To get it out, I had to grind one end down so it would fit out of the bushing and hammer the living snit out of it to get it out the other side. It has about 1/4" of banana bend and a couple of 1/4" grooves worn in it. The pin next to it was hard and it only has 1/16" wear and no bending. Oh, both sets of bushings were worn. My biggest fear is not future wear, but bending the pins and not being able to get them out.

I think the biggest factor is the use of $.98 of grease every 10-20 hours of use. Yup, the prior owner must have saved a hundred bucks or more! What a thrifty individual. (Or was that shifty? --> oops! sorry for the mis-spelling! How did that "f" get in there?)

jb

 

[3RRL]

John,
I had to give myself a little refresher class on heat treat by reading my Machinery's Handbook. These are very general, basic steps and vary on the kind of carbon steel you use, but in general should work for what you're doing.

In regards to heat treat of carbon steels, I think you've got the right idea by heating to cherry red or orange around 1335° to 1355°F. The purpose is to get the alternating bands of ferrite and cementite (known as pearlite) to merge into each other forming what is known as austentite. Tool steels need higher temps to get this done....not in your case.

A little about quenching baths... The purpose of the quenching bath is to remove heat faster than the critical cooling rate so the metal keeps it's merged characteristics and won't revert back to it's original characteristics. When a piece of steel is cooled at this rate or faster, a new structure is formed which is called martensite with very high hardness, but also brittle.

Then quenching in water or a salt solution or oil is Ok. There are several others too. To minimize cracking and distortion without sacrificing depth of hardness penetration it is desireable to select a quenching media that cools rapidly at higher temperatures and more slowly at the lower temperatures (below 750°F). Oil quenches in general meet this requirement because it cools at a slower rate than water....I've used motor oil (used and black) and the steel comes out nice and black too like it's been parkerized. Heat the oil quench to between 90° to 130°F for the quench....You can use water but but I've had bad luck with the steel remaining too brittle (too hard) and cracking.

Then drawing (tempering) between 300° to 750°F for at least 1 hour to reduce the brittleness and remove the internal strains of the hardened steel. When the steel is first quenched, it is mostly martensite. On reheating to the draw temperature and holding for 1 to 2 hours a structure known as troosite is formed. It is slightly softer and tougher than the brittle super hard martensite. Heat treaters know all this stuff and EXACTLY the right heating and drawing temperatures for the kind of steel used.

So yeah...you're on the right track. It should work fine for you.
Hope this helps,