Bi metal (thermostat metal) question

Edmund Scientific sold both last I knew, though I doubt they actually manufacture them.

T.I. (Klixon) makes it.

I think another supplier of material is Chace. It's been a long time since I made bimetal snap discs at Sylvania in Standish, Maine. We made millions of these a year for circuit breakers and temperature sensors.

I made some by hand by using a dome shaped tool, pressing the disc against a urethane backing block. By choosing the radius of the tool and carefully using the same force and stroke length each time, I could make discs of the desired click and reset temperature.

If you are trying to get a specific snap temperature, its important to choose a bimetal thickness, material, diameter and deformation. Another variable is heat treating temperature and time. If you are looking for longevity (lots of cycles), you need to stone the edges so you don't have any stress risers to cause cracking. There are some pretty extreme forces created when the disc snaps through.

It's been over 35 years since I've worked with bimetal material, so take my recommendations with a grain of salt.

Earle Rich Mont Vernon, NH

--The guy who made the disks for Edmund took the secret of their manufacture to the grave, at least according to the person I talked to at the company. But there must be tooling knocking around somewhere; one wonders what happened to it. --My million dollar idea was to make big disks, maybe 4" dia with a gentle radius of curvature to get the delta-T down to a narrower band, then coat one side with something piezoelectric. Paint the other side black, set it in sunlight under an LCD shutter and see if there's surplus current generated after driving the shutter in an on/off/on cycle. Never did the test because of problems getting the materials. Sigh. Forget patenting it; must have occurred to lots of people over the years, but I got an ovation when I presented the idea at a conference half a dozen years back, heh.

Texas Instruments, Klixon division ...lew...