Question: Where can I buy a small electric heat treat furnace capable of 600F? All I need is something that will handle a flat spring that is 1/2" x 1/8" x 4". I am working with C1080 plain carbon steel, so time is not a factor--only the 600F tempering temperature. Going above 700F is of no interest, and adds no furnace value to me. I heat to a cherry red with a torch, and so the heat treat furnace is not used for quenching. Your suggestions will be greatly appreciated.

All I can think of is to check EBAY.

I would suggest that you make your own electric furnace. You can check out Andy Gasciogne's thread at the Tool Time section. All electric furnaces I've seen go upto around 2000F, if you really want one that only reaches 600F you'll have to get one custom made or do it yourself.

I assume you want this for cost savings as opposed to getting a furnace capable of austenitizing temps. I just remember ceramic kilns like Olympic and Paragon have small kilns that I believe were designed for jewelers. These might be the thing for you as I believe some were only $150. Of course if you were to just make it yourself that $150 could already get you an electric furnace (one w/o a digital control that is, that would be +$130) capable of hardening and tempering blades.

All I have to say is toaster oven. Go to a second hand store, dump, yard sale, salvation army where ever and buy one for a couple bucks and then line with k-wool and they become very efficent and will hold large peices. then just get a oven temp gauge in the cooking section of wal mart and they go to 600 degrees and you are set for less than $20 bucks mine works like a champ. Wyane goddard does it as do many more of us.