"Ed Huntress" wrote in message
...
"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

I've machined Invar 36 with no difficulties. It's not like titanium, for
example.
What is a bitch is the price. I had bid on the tool in question, but had
the good sense to bid with the Invar provided by the buyer, which they did.
I needed only a small piece, about four square inches, material thickness of
1/2". I was quoted $1,000 for a piece 12" square, and couldn't buy it any
smaller. Buyer be ware!

Harold