Make a large heat treating oven 650Deg celcius for 2hrs?

[apples]

I am looking into making my own lathe and mill. It would be made from plate steel that I can weld into shape.

Once welding is finished it needs to be stress relieved which can be done by heating it to a dull red which is apparently
somewhere around 650 degree's Celsius.

Now I'm thinking that this might be possible to do in the backyard instead of paying hundreds of dollars sending it to a proper
heat treating mob. It might still cost the same amount to set up, but at least then I will have the equipment to make a smaller
forge, right.

Two main issues I can think of are.

1. The size of it and keeping the heat evenly spread across the part.
2. Keeping the temperature at a constant 650 deg. C for 2 hrs.

The size of the oven/forge will need to hold a part that is any where up to say 1500mm long (about 60", or 5ft) and then about
600mm wide (24" or 2ft) and lets say 3-4ft high. These are rough figures to give an idea on the size of the oven I would need
to make.

Having said all this I would also need to run it for about 2hrs, I wonder how many gas burners I'd need to get an even heat and
how many bottles of BBQ size gas bottles it would burn up? 9kg ones ( 20lbs)

The other cheaper fuel option would be oil or diesel powered as opposed to gas.

Any ideas or thoughts on this? Of should I maybe just find a heat treating mob and get them to do it?

Peter
Australia

[Glenn]

5 x 2 x 4 feet is about 40 cubic feet of space.

[pkrankow]

Check your plans again. I am sure your lathe bed is bolted to your headstock and tail stock, and the legs can be made separate to bolt on. This means the whole shooting match can fit inside a hot water tank or a couple drums end to end.

Now temperature control is a different story.

Atlas lathes were aged for a year as a means of stress relief before final machining, but they are a cast bed.

Phil

[BIGGUNDOCTOR]

Metal lathe, or wood lathe? Unless you are doing this purely as and I can do this project, I would say look for used equipment. You can buy a good used industrial lathe for less than you can build one for. How are you going to grind the ways, keep the warpage controlled, inert atmosphere to prevent scaling.........? BBQ tanks, better get a truckload of them. If you have to make it, look for a ceramics shop with a big kiln that will do up to cone 10 (2,350 IIRC).

Then again you may not even have to stress relieve the frame, use as is. Stuffing it in an oven may just create worse problems for you.

[forgemaster]

Not only do you have to hold it for 2 hours, but you have to get it up to 650 first then hold it. Plan on lots of caravan bottles. The problem with oil is 650 deg is too cold to allow the flame to burn properly so it is going to keep running very badly if at all. We can with difficulty get our oil furnace to run down to 780 deg but only after it has been running all day and already has a bank of heat to keep the flame ignited, having said that at 780 it runs very smoky and it is very hard on the eyes, (stings the eyes). To compare, we have a electric heat treat furnace with internal dims of 650mm x 1330mm x 400mm high it has a rated electricity load of 22Kw but it can run up to 1100 deg C. Energy used is still energy used, be it gas elect or oil.

Phil