Copper is the nastiest stuff I have ever machined. Being a good heat
conductor, soft, sticky, etc, it's just aweful. I made a number of
custom cable swages for 1/8" aircraft cable, and it was a nightmare.
8 feet of 1/4" dia copper round bar got turned into 2" long pieces,
faced both ends, and drilled through with a #29 drill. Some got stuck
in collet blocks, clampled a wierd angles, and fishmouthed in
preparation for brazing, while others got threaded #10-24. In the
process I snapped 4 #29 drill bits and had my lathe drill chuck (this
is a large toolroom lathe with a lever collet closer) pulled bodily
out of the tailstock by the stickyness of the copper. It also
transmitted heat very effectively, to the point where the heat of the
drilling operation (this is with extensive mist coolant, no flood
available) heated the collet to the point where it expanded and did
not grip the part firmly.
The project turned out well, but it was one of my least favorite
machining experieces.