"Nick Müller" wrote in message
...
Ed Huntress wrote:

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?

No, I'm not that sure. But I know, that there do exist special steels
that do not change their sizes (or _very_ little) if hardened. They are
used for stamp and die making. Roechling has them (among others). And I
_think_ they are called invar, but have no source at hand to verify
that.

OK, I did a quick Google. Invar is not cast.

This will be a big surprise to the precision machine tool builders,
especially Moore, who used Invar castings for over 30 years. g

It's probably one of those metals that you cast or not, depending on what
you need. I've never read about its mechanical properties so it may not
matter. The zero-temperature-expansion coefficient is its reason for
existing. It is a b*tch to machine, however.

--
Ed Huntress


But also I didn't find that
property of not changing it's size when hardened. But still it doesn't
change it's size over a big temerature range. It's mostly used for
gauges.

Anyone has a name at hand?


Nick
--
Motor Modelle // Engine Models
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