Hotter ‘n a scalded dog ….

Another of my ongoing projects — this one now pretty much complete. Following a presentation at the Furniture Society Conference back in June, 2012, I got interested in ‘metal clay’ as a medium for hand forming or casting custom bronze parts for cabinets or tools. Here’s a link to some info on bronze metal clay. To use this stuff you need to be able to fire it at around 1500°F, which coincidentally happens to also be the Curie point for 0-1 tool steel. So I set out on a search for a kiln or furnace capable of such temps. I was about to try building my own (insulated fire brick, Kanthal wire and other components are readily available), but happened upon this unit being sold locally via CraigsList. Professionally made by Applied Test Systems, it is a hell-for-stout stainless steel box with the requisite insulation and three 115v heating elements. Designed as a lab furnace for who-knows-what, I got the thing for reasonably cheap, but of course found out later that two of the elements were burned out (I think the previous owner had connected it to 220v wiring). I called ATS and had them send the two new elements (raising the cost of my new treasure considerably, but not ridiculously). With those in place you could just plug the thing in and let ‘er heat up to the max, but for firing the metal clay and especially for precisely heat treating tool steel you need a ‘process controller’, or PID, a thermocouple (temp sensor) and solid state relay. These I got from eBay, and with a few other local parts wired up a control box. Test firings proved easy and accurate, so the furnace is now ready for activity. I have to get some kiln ‘stilts’, or make some supports for the work pieces out of Kanthal or nichrome wire, plus I also need some good tongs and thick leather gloves (1500°F is pretty danged hot!). I’ll report on my experiments in the future.

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