Googling the machining of copper and checking out a few machinist forums...from what I can tell most machinists hate it, it's like machining a hot glue stick...it's grabby, it rips more than it cuts, it clogs end mills in seconds...ever try and cut a chunk of copper tube with a hacksaw?
It was actually kind of validating reading that...as some of you know, I make my own center pins for the Atomics so I can hybrid them for a direct connection...I tried making one out of copper rod (instead of brass), long story short, 5 drill bits, 5 pieces of copper rod, 5 failures...anything deeper than a 1/2" center hole and it would just grab the bit and snap.