As anyone made a long tempering oven?

[Aerindel]

Usually, I temper things in my kitchen oven.

However, I'm working on a crossbow prod now, and need to temper something both hotter...600º, and longer, than will fit in my oven.

Thinking it shouldn't be that hard to rig up an electric oven with a 600º capacity and say, 4' long or so....but wondering if anyone has just done it so I don't have to invent it first.

 

[Magus]

I made a quenching vat out of stainless tubing for BIG knives. My "oven" was a rosebud.
will this help?

 

[Magus]

 

[SoulSeeker]

I would say take 1-2 gas oven elements end to end and make one. Want it longer? Go 3. It may go through more propane but will get the job done.

 

[Magus]

The last big blade I tempered was over wood coals in a pit using a leaf blower.

 

[Aerindel]

I would say take 1-2 gas oven elements end to end and make one. Want it longer? Go 3. It may go through more propane but will get the job done.

I don't know how I would control gas burners well enough for tempering.

 

[SoulSeeker]

I don't know how I would control gas burners well enough for tempering.

There used to be available from Trader Joe's a high pressure regulator for propane to 60lbs. If you angle the burners and make a 1 to 3 manifold out of brass fittings you can control all 3 with the 1 regulator and 1 flow valve. I have a setup for my backyard foundry.

 

[Aerindel]

There used to be available from Trader Joe's a high pressure regulator for propane to 60lbs. If you angle the burners and make a 1 to 3 manifold out of brass fittings you can control all 3 with the 1 regulator and 1 flow valve. I have a setup for my backyard foundry.

Regulating the propane isn't the problem, its that I would need a thermostat for gas control, I'm sure they exist but no idea how to source or use one. This oven needs to be accurate within about 20º between 400º and 700º. I don' think I could manually set a regulator to maintain that temp. Even on the lowest possible setting I think the burners would have to turn off and on, so I would also need pilot lights for re-ignition.

I think electric is just going to be a lot easier for this.

My plan is to cut off the top a old hot water heater, insulate the inside, regular fiberglass should be fine for such low temps, place a electric range burner in the bottom, with a 240v thermostat set up 'somewhere' inside the tank.

With a relatively low volume, and basically no thermal mass outside of the part to be tempered, it shouldn't take that much of a burner to heat the space to the desired temp, then its just a matter of letting the part heat soak long enough to be sure its up to temp, and then turning the the thing off.

 

[Peanut]

Electric ovens are made to cycle on and off... GE says theirs have a temp cycle of plus or minus 30 degrees..

You'll find it much easier controlling gas heat for a stable temp than electric.

Check tool & die shops or machine shops. All their tempering ovens are gas. You might be able to hire them to do it for you. No idea what it might cost, doesn't hurt to ask though.

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https://products.geappliances.com/appliance/gea-support-search-content?contentId=18068

Understanding Expected Oven Temperature Fluctuation
The Oven temperature fluctuation varies by model and each individual Oven can be different.

The temperature range can vary by + 30 degrees and – 30 degrees Fahrenheit as the oven cycles on and off for a total temperature fluctuation of 60 degrees.

This fluctuation is common for our Ovens. Some may fluctuate a little more, some a little less.

The temperature swing can vary by how and where you are measuring the temperature in the Oven.

The temperature swing can also be influenced by the room temperature or number of door openings.

 

[Canon29]

Haven't done such- my metal projects never exceeded the capacity of the ol oven. Im usually tempering @450.

A crossbow prod at 600 eh? And one that's closer to 4 feet long? Makin a monster eh?

Plan sounds pretty good. How long does the piece need to temper before cutting off the heat and air cooling? You might be able to get away with regulating it manually if you can control the heat, might be worth experimenting with ila little before buying a thermostat.

 

[Tirediron]

If I was doing this, I would use a couple of pieces of steel pipe, with screened wood ash for insulation. that way there is some thermal mass for temperature stability. maybe even a stand off third pipe inside and use indirect heating. I concept looks good in my head, don't know if it can out clear