Subject: Machining Invar

From: [email-masked] (James Kirkpatrick)
Date: 19 Nov 93 11:33:21 MST

Anybody have tips for machining Invar?  This is an alloy of
Nickel and Steel, with a very low coefficient of thermal
expansion.  It is reputed to be difficult to machine, perhaps
on a par with stainless steel.

One suggestion given to me was that Carbon Tetrachloride was
a good cutting fluid, but carbon tet isn't such a nice thing
to breathe or heat!  Mainly I'm concerned with low-speed operations
such as drilling and threading (with hand taps and dies), though
I might need to do a small amount of turning/facing.

The item in hand is a 42-inch rod of 5/16-inch diameter, for
use as a precision clock pendulum.  Among other things I need
to thread the end for a rating nut, and want a fairly fine thread.
I'm thinking about 5/16-32 or perhaps even 5/16-40.  Or, I
suppose the end could be turned to a smaller diameter, and
use a different diameter thread/nut.  Suggestions?

Jim Kirkpatrick
[email-masked]