Annealing brass

[Brad Y]

Josh- just done a baby formula can too! Used a 70rpm motor but have a PWM voltage controller and capacitor on the motor. Should be working later on the weekend!

[shooter mcreid]

Would love to see some pics brad, my control system consists of a series variable resistor, the motor doesn't draw much so no problems with heating.

[Brad Y]

I was a bit optimistic with the motor size I got so a trip to the local jaycar set me right. Pulse width modulation controllers are supposed to be the go but the guys also said a capacitor on the back will prevent damage to the brushes when really turning down the voltage. With a 70rpm motor I have the voltage down to 1.2V to get the motor working down where it will need to be. With a 120 amp hour deep cycle battery this thing will be able to anneal every day for a bloody long time before it needs recharching! Will also be running Map gas on my torch to get the cases heated quicker which might let me run the motor a bit quicker. Next motor I get will be a 35RPM model. Still got a few things to get it all set up properly. Find that Ive just put it all together to get it working and then going back to individual parts of the unit to get them finished off better.

[scott/r]

Do you guys rapid cool your brass or just let it cool by it self?

[shooter mcreid]

Hey Scott,
I had done a little reasearch before I started and everything I read indicated that rapid cooling was not necessary for any reason. Rapidly cooling brass has vertically no effect on its grain structure which is very different from quenching steel. The other reason I could imagine people wanting to do it is to keep heat away from the head of the case. The structure of brass will start to change around 430f if memory serves so by using 400f tempilaq I was able to determine exactly how far down the case the changes where starting. I'm not sure how clear it was in the clip but the 400f tempilaq only made it about 10 to 15mm past the 700f tempilaq (didn't get near the head). Using a fan to cool won't hurt but using water could cause issues.

I found this article to be the most interesting read:
http://www.6mmbr.com/annealing.html