kiln ideas for annealing jackets....

[sideironjohn]

Hey all. I guess most swagers just do the propane torch operation to anneal the jackets when bonding. But really, the temp and times are very uncontrolled, aren't they? Maybe well within the range of "good" but I was thinking, how to easily make a kiln for annealing copper?....
It's just one more way to tighten the tolerances batch-to-batch.
One idea is to just use the oven. The recrystalization temp for copper is around 250-270 deg F, if held for an hour, to grow the grain you could go all the way to 400 deg for say 30m, then turn it all off and let it slow cool overnight.
Of course, the main downside is that you have a giant oven on full blast for an hour and a half, so unless you're doing three cookie sheets at a time [Fun Fact of the Day: how many bullets fit on a cookie sheet? About 3300 .308" cals or 2400 .358" cals!] then you're wasting a lot of energy.
How to make a job-specific kiln?
However big you make it, that will be your batch size. 6"x5" is enough to do a 200-pc batch of .358" jackets, so we're not talking big.
My thought is to scavenge from a throw-away oven the elements, thermostat and associated wiring and build them into a brick oven of a size appropriate to your operation. Problem is, the elements are as big as a kitchen oven, so maybe water heater elements would work better? Even those are kinda big for this. Maybe build it 3" deep by 26" long, and have the elements laying along the bottom and top. Build it out of brick (what are they? about 4" wide?), bottom base, row of bricks all around (leaving the front ones un-cemented), maybe a grill on top for strength, with a row of bricks across for the lid... you'd need a grill above the bottom element to support the jacket tray... what else?
The other FAR SIMPLER thought I had was to use a toaster oven. Anyone know if these can withstand 400 deg? I'm sure you'd have to override the controls to get it to stay on that long - not a difficult thing, so long as it doesn't mean burning the house down!

Who else has ideas? Anyone?
(Feel free to vote "not a real issue!")

[Rick Teal]

I thought we needed about 1200 degrees to anneal copper. :?:

If it can be done at lower temperatures, I just missed out on a heat treat oven that may have done the job.  It had about a 550 degree maximum.

Although it would be nice to be able to get 800 degrees out of one, and then you could core bond in it as well.

[sideironjohn]

Well, the info I'm getting (net research) is that it all depends on the time it's in there. When we think about it we likely picture a propane torch for a short amount of time.
But at one hour, pure copper will recrystallize at something just over 250d. Nobody's holding a propane torch for an hour though. With 5% zinc it jumps to 600d, so I guess we need to know the real composition of the jackets. Brass is about 800d, but again there's all sorts of alloys so we need to know the typs of brass (e.g., using spent cases for jackets).
Growing the grain, which makes it more ductile happens at temps above that,  but until an expert of metallurgy comes along, it loks to me like that measn about 400d for copper.
I'll keep loking into it. Good reading.
Those little home ceramic kilns that run on 110v should do the job, if my numbers are right. Further research needed....

[talon]

I think you will find that the most expensive component in your home-made aneling oven will be the temperature sensor ( thermometer). Also, a good read in this area is Corbin Company's " Tech Bulletin #3, Chapter 8: Heat Treating Bullet Jackets." I anneal quite a few jackets of almost all calibers and thicknesses ( mostly c220): While I've one of those small Corbin furnaces, I've found that the little hand held propane torch does a great job. You have to do the job in low light to see the color the jacket takes on when it's received the proper heat. Yes, I know that this only approximates perfection, but it does the job quite well.

[sideironjohn]

Also noting that brass anneals at 950-1025*F. That's hot. Copper melts at about 1085*F.
This makes me wonder how people that use cases for jackets ever anneal properly.
Also, who knows the Rockwell or BHN range of annealed copper and brass?
This stuff isn't easy to find!

[talon]

The Rockwell Hardness numbers for various grades of temper of the most common bullet jacket materials is found in the Corbin booklet article  cited above. That article is a reprint  from  "The American Rifleman", Feb 1983. The term " copper jacket" usually refers to jackets made of 'gilding metal',  and its melting temp is somewhat different than pure copper. However, those of us who make jackets from copper water pipe (tube), know that this is almost pure copper and does have to be anneled a little differently. The real problem with achieving a perfect anneal for us hobbyists is that more often than not you don't know the exact alloy you have in your hand, and unless you are really fortunate your temperature gage is not all that accurate. Like most theory, using it is hard to put into practice unless you have the financial backing and excellent quality control of your supplies.

[sideironjohn]

I can dig it, Talon. I will check out the Corbin publication.
Thanks.

[Cat Whisperer]

The classic method for annealing gas checks (right much similar to jackets) is to take  3 to 5" section of black iron pipe threaded on both ends and two black iron pipe caps.  (Black iron side steps any issues with zinc fumes; is used for gas pipe & commonly available too.)

Some will drill a very small hole for a vent into one of the ends.

Most folks toss in something combustable (to consume the oxygen to lessen it's effects) inside.

Then heat the rig.  This started out with the originator putting it into the wood fire and retreaving it from the ashes.  

Since there's lots of iron it heats slowly and cools slowly.  Measure temperature any way you wish - dull red iron, temp stick, pyrometer, etc.