Cutting and Welding new backhoe pin

[2manyrocks]

So I managed to break a 1" diameter by 6.25" backhoe pin on my Terramite. I'm not sure that I'm going to be able to find a replacement part and wondered if I could weld a new polished and hardened rod to the arm that holds the pin in place.

McMaster Carr has 1"x12" 4140P rods that are hardened to rockwell c40, I think it was.

Is it possible to cut this kind of rod down to the length I need with a 4x6 bandsaw or a cutting disk in a grinder or is this just a machine shop job?

If it is possible for me to cut this rod, is standard flux core mig welding going to work or is there some special rod I should be using in my stick welder?

 

[BukitCase]

Found this

How To Weld 4140 Steel

Let’s keep it simple. 4140 steel can be welded without problems as long as you follow some simple guidelines. This also applies to AISI 4140 and 4340. We will not be discussing the metallurgical properties of 4140 or trying to explain what happens to its microstructure when it cools too...

weldinganswers.com

A quick read tells me NOT to even try with flux core, your stick welder and some 7018 should do. I would read the above CAREFULLY, kind of depends on how much of the characteristics of this material you need to maintain.

Oh - bandsaw, no way - thin cutoff disk on side grinder will work... Steve

 

[Terra Joe]

Are you sure that the pin is hardened? I don’t know that the 1”pins are hardened on the T5’s.

There is a gentleman in WV selling Terramite parts on Facebook Marketplace. Looks to me like he may have bought a bunch of stock when Terramite had their auction. He lists various complete pins. Might be cheaper to see if he would ship you one in a flat rate box.

 

[4570Man]

I doubt the previous pin was hard. Take a file or hacksaw and see if if does anything against the old pin.

 

[the old grind]

Use 'stress proof' steel bar to make pins as many do and plan to attach a TM-style locating tab mechanically because while it's 'free-machining' steel and easy to work with it doesn't weld for crap because of the alloy.

Surface finish/hardness, size, and dimension are ideal and being softer than pin holes the pins take the wear. It's cheap & easy to drill or groove for greasing if you want, but TM's OEM zerk fittings are enough for me.

For our Terramites it's also easy enough to make them longer and cross drill (easy peasy) for bolts to hold the pins in place vs the std banjo-thingie on the end.

If your local supplier doesn't carry it (most do) find it here:

Speedy Metals Information for Stressproof® Cold Roll Bars

Speedy Metals Material Library, get Information, Analysis, Mechanical Properties, Applications, Machineability and Weldability, Heat Treating, Tolerances, Speedy Metals items. Goto www.speedymetals.com to purchase.

www.speedymetals.com

 

[LD1]

C40 isnt really that hard. IT can be cut with a bandsaw or drilled with HSS drillbits. And a file will cut into it so file testing the old pin isnt gonna be an accurate way to determine if its "hard" or not. A file will only skate on stuff north of 55-58rc And over 60-62 or so and carbide dont even like cutting it, need to go to CBN at that point.

But regarding the welding....just what is being welded to the pin? I assume just some kind of washer or something to retain one side of the pin? And it has a cotter pin or something on the other side?

Its possible to not have to weld at all and just use a cotter on both sides. Do you have any pictures? What was the nature of the break? Mild steel (or pins that arent hardened) usually dont break.....they simply bend. Unless it was seized in a bore and twisted in two.

 

[2manyrocks]

Here's the pin.

 

[LD1]

Lots of good material choices. But 4140p wouldn't scare me at all for that pin

 

[2manyrocks]

What material should I use to attempt this repair? I assume that I should be using polished material because that's what was on the machine. But I don't actually know if the original pin was hardened.

 

[the old grind]

Yes, go for a hardened pin, not what's commonly used. Ask people who 'would' not those who have. Don't seek info anywhere but here. Next year you can ask how to re-bush the pin holes.

Guess you didn't check out stress proof or find out how common it is for this use and why. It's surface is hard and finished like DOM tubing but you didn't hear it from me. GL