De-hardening

Start from scratch, use your lathe to make a new spacer. The bearing is not hard because of heat treatment rather it is hard because of the elements found in it. Annealing/normalizing won't make it soft.

Silvio Kapaa wrote:

hardening

Red heat is somewhere around 900 to 1200F depending on what you define as "red heat" typical anneal temp is up around 1450F - 1500F, starts taking on a fairly orange glow at that point. Then, depending on what the actual alloy is, you may be cooling it too fast.

You pretty much need to encase it > Hey everybody,

Not sure what part of the world your from but here in the UK the most common material for bearings is EN 31 which will quite happily air harden in small section sizes if heated too much. Try heating to a very dull red and then covering in dry sand. The trick is to cool it down as slowly as possible.

Hope this helps more than it hinders.

If he has access to lime I think that is what some people use. Just put some in a bucket and after you get it the temp you want just poke it deeply into that lime and leave it a good while. I knew a fellow who had several small hardened tools that needed softening and I *think* he left them in there about half a day or more. Don't know if they needed that much time or not.

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Napole> Not sure what part of the world your from but here in the UK the most common

Silvio

I don't think it will ever be that easy to fully soften a ball-bearing race. I think the stuff is made from 1%C about 1.6%Cr, is it not? The stuff is a mass of hard carbides in a bit of matrix metal which gives it some metallic toughness. I would have thought a very very slow cool from red hot would soften it. You would need to bury it in sand - and the sand would have to start off at red-hot too, in an insulated container, to give the necessary slow cooling rate, especially in the higher temperatures down to "only just red hot".

may be easier to find any other source of a piece of steel for a spacer.

RS.

Very difficult. You'll need to cool it down _very_ slowly to aneal it, so slowly that it's more a question of reducing the heating during cooling in a forge, rather than just turning the heat off altogether. You'll need something like a firebrick box forge to work in, sufficiently well insulated that it remains visibly glowing for at least 1/4 hour. Even cooling it in "a bucket of sand" isn;t enough IMHO (woodash or grey charcoal is better, because it's less dense and a better insulator)

Chisels and files are easy. But the high-speed steels or extra-tough steels used for bearing races are a real problem to soften in a home workshop. OTOH, hardening them is pretty easy.

This is what a "tool post grinder" is for. In a pinch, you can rig an electric die-grinder to a boring-bar with hose clamps, but dont expect a great cut or any precision that way.

Thanks for all the input. Dave