Craneman - I'm not a metalurgist. Maybe you, or someone else can help me understand something a bit better. You said that some links are hardened almost down to the ribs. Can you tell me how can you tell how far into a piece of metal the "hardening" penetrates? Is there a simple way to test an undercarriage component (link, roller, idler) to see (a) how hard the surface actually is; (b) how deep that hardening goes? Sorry if these are dumb questions. Is hardening the same as "hard-facing". My primitive understanding is that hardening is something you do by heating and cooling metal in the proper way, and hard-facing is something you do by welding on special hard rod materials. This is all building back to my original questions about re-building rails and rollers... once one has built up a link (for example) should one then do something to harden that link, or add some hard-facing rod to the surface? Thanks.

Back up a post.........we both hit at the same time:D
Your assumptions are basically correct. Yes, there may be some hardening at a greater depth but anything with .250 - .300 in. wear is considered 100% worn, at least with the small to medium sized tractors.

The 100% wear point would have to do with the pin bosses hitting the roller flanges as well as the depth of hardening.

Jshoots,

I expect the depth of hardening could be measured with a rockwell tester as the rail wore down, or if one link was to be tested, as layers were milled off to expose the next test point. It might also be possible to just saw or mill into on and determine when the cut sped up.

the rails are heat treated as you say, and the depth of said heat treating is what is in question. When there's no paint, the color of the steel can show something about the depth of the heat treating.

Some of the filler metals that can be welded onto rail surfaces will "work harden" significantly under impact with the rollers and idlers. this is convenient because the surface has a chance to get peened down smooth as the work hardening is occurring,,,Unlike the application of hard facing rod where it's hard from the get-go and would accelerate the wear of the roller and idler surfaces due to the very hard, slightly rough surface left by the welding. A compromise would be to find a material that wasn't quite so hard that could wear or be ground smooth before it wore the idler and rollers too much.

Craneman had it right with the Nicromang. .I remembered it as Cromang:confused: . .oops, old age kicking in there. Thanks for the correction. . .hmm, now where DID I shove that walker to this time?