"Nick Müller" wrote in message
...

Generally, steel will always change it's size when hardened. This is due
to the fact that the carbon-atom changes it's position in the crystal.
But there are special steels that will not react that much when
hardened. I think they are called "invar". But I can't give you any
numbers because they are hard to obtain and also we (Krauts) have an
other nomenclature.

Invar, IIRC, is a special cast-iron alloy that has a near-zero coefficient
of thermal expansion. Moore Special Tool used it for the heads of their jig
grinders.

I wasn't aware that it had special hardening properties. Are you sure you
aren't thinking of its freedom from thermal expansion, in use?

--
Ed Huntress