Nice project you got going, the first problem I see with your copper cutting is that your using HSS!
carbide is almost a must for much copper cutting, secondly, you should get ahold of some good coolant, and thirdly, whats your spindle speed at? for a 3/8" carbide it could be up 5000+ the faster you spin it the easier it is and the more heat gets transfered to the chips.
The only hss end mills I have are ones given to me, I learned after my first set of hss end mills.
Power supply cooling, I have wanted to do that for the longest time! Maybe this summer Ill hop on it
Jon