Gudgeon pin steel

I am building a simplex loco, the drawing says i need 3% ni case hardening steel for the gudgeon pin in the crosshead, where can i get this from, or can i use bms and case harden this or can i use silver steel.

Thanks IAN

Sounds like EN36, M-Machine do a limited range of sizes.

J

Hi Ian,

EN 36 seems a bit over the top to me. I can't recall what material I used when I built a Simplex many years ago but I would have thought that any mild steel that can be heat treated would be up to the job. Failing that you could use EN24 which has good wear properties.

Bob

On my 2-8-0 Nigel Gresley the drawings states silver steel or case hardened steel for the pin, I'll probably opt for silver steel and harden and temper the pin.

Bob

you can't make mild steel harder by heat treating it. You can case harden it, but not the leaded stuff. If it has threads on it you'd be better casing before cutting the threads, then hardening (case just increases the carbon content, let it cool very slowly). Other way is to copper plate the thread, then it won't case. If using silver steel, temper it well down, you don't want it snapping. I'd be surprised if mild steel wasn't good enough without hardening. It's very easy to replace if it eventually wears.

A2 tool steel makes for gudgeon pins, and can be flame air hardened and then tempered.

Neil

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Surely case hardening is heat treating ??

hi ian,

i think the spec for simplex gudgeon pins is overkill, and certainly not what martin evans would have done himself or what most miniature loco builders would do.

ordinary free turning BMS if a good finish is quite ok with bronze small end conn rod bearings. these bearings wear quite badly if lots of heavy use as heavily loaded compared to size, plus usually receive insufficient oil, as difficult to apply.

my own personal practice with the few walschaerts locos ive built is to case harden the gudeon pin after making with a nut on the thread. i use hard drawn phos bronze for the small end bearing (dont use gunmetal). ali bronze is a good alternative for the bearing material. make sure you add an oiling point in the top of the drop link and through the crosshead to the bearing.

cheers,

julian

Case hardening changes the chemical composition of the surface of the steel, you then harden it by heat treating (ie dropping it in water from red hot). It's all a matter of definition