Heat Treating Oven

[Ed Tipton]

I have the opportunity to purchase an older (1900 era) industrial heat treating oven for the very attractive price of $100.00. It was made by Stewart (Stewart Warner), and it is approximately three feet square and about 2 feet top to bottom. The oven is mounted onto a very sturdy cast iron table which appears to be original. The heat chamber is approximately 12"x18" x 24", it is gas fired, and I estimate the weight to be somewhere around six hundred pounds. There are no orifices on the unit, and I am told it can be operated on either natural gas or propane. The overall condition of this oven is excellent, and the size would allow the simultaneous treating of several knives at once. It is well insulated and I am told that once it is at temp, it retains the heat for quite a while.

Here is my question/problem. I have relatively tight quarters, and this unit has a large footprint (I am presently using a small toaster oven for heat treating). Also, I am not sure of how to regulate the heat using propane. The design is to have flames which heat the chamber through two "windows" on each side of the unit, thus preventing the steel from coming into direct contact with the flames. The windows are quite large and could possibly accomodate two heating elements, which I think would be easier to regulate the heat with. Since I work exclusively with 10xx and 5160 steels, I have no need for great temperature during tempering (500 degrees max).

Converting the oven to electric seems to me to be feasible, but I was wondering if anyone out there has tried such a thing and I would welcome their comments, especially on the type of elements and the temp controls (110 volt).

[cdent]

For what you describe, I'd consider working with the toaster oven. Maybe wrap it with an insulating blanket and put a chunk of fire brick or thick tile on the rack to even out the temperature swings.

Maybe consider playing with the big oven if you need to run the heat up to 1500*. Wear a mask, if it's that old, everything on the inside is probably asbestos. Not a bad thing, but may make a difference if you start modifying it.

There's a good tutorial on Don Fogg's forum about a homemade electric heat treat furnace, but it may be easier to rig it up for propane and use some of the tutorials that are floating around for pid controllers and solenoid gas valves.

Good luck with the project, Craig