On Sun, 8 Nov 2009 08:42:26 -0000, "N_Cook" wrote:

As used in thermal switches. Instead of in form of a bimetal strip and
continuous curving with temperature, these are 0.5 inch diameter and make a
definite flip from concave to convex at a specific temperature. About 1mm of
abrupt movement gives a very positive transition for the switch contacts.

Like this?
http://www.google.com/patents/about?id=VQ4XAAAAEBAJ&dq=5903210
or this?
http://www.google.com/patents/about?id=BygyAAAAEBAJ&dq=3852697

Would it be possible to change the characteristic temperature by grinding
back a spot/ring/radii? on one face? which face? or would it just destroy
the action/activation force?

I don't think so (but I'm guessing). Grinding might change the
deflection or force but probably not the transition temperature. Below
some force level, it simply will not transition. My guess(tm) is that
the transition temperature is controlled by the curvature which is
rather difficult to modify.

Note that some discs are "manual reset" or "single operation" and act
as thermal fuses.

Search Google for "bimetallic snap disk".
http://www.cpi-nj.com/snap.htm
http://www.thermodisc.com
(etc...)
I tried to find the vendor of the actual discs, which might include
design information, but couldn't find anything useful.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558