[joesgarage11]

I'm working on a GPU waterblock for my ATI 9600 Pro and had some trouble milling slots in it. It's 3/16"(4.8mm) thick copper bar cut to 1-3/4"(44.5mm) square not including the mounting tabs. In the picture, it's not cut to final size.

I cut 1/8"(3.2mm) x 1/8" deep with a two-flute end mill on a very large vertical mill at about 3000 rpm. I figured a high speed would avoid snapping the end mill as I had to hand feed the cut. The cuts sounded and felt good while doing them and I kept them lubricated with a generous application of cutting oil from a flux brush.

When I tried to clean the block, all the slots were full of copper shavings that feel like they're welded to the sides of the slots and welded to each other. The clear slots are the ones I went back and milled in the opposite direction, but the 1/16"(1.6mm) material left between the slots just bent over.

What did I do wrong?