[Gooserider]

A week or two ago, I bought a big hunk of copper bar from my local surplus metals dealer ($2.80 / lb) This bar was 3/4" x 2.25" x ~2', (20mm x 58mm x ~600mm) and I cut a couple peices off it about 3.125" (78mm) long to use in making waterblocks for my dual Athlon mobo. I was quite suprised to find both peices and the remainder of the bar have a 'cup' across the 2.25" dimension. One surface is slightly concave, the other convex by what looks like the same amount. Good news is they appear flat in the other dimension.

I don't have an exact dimension on the degree of the cup, but if I hold a straight edge accross it, it looks like about .010 to .030 gap in the center.

Is this normal, or did I get stuck with a bad hunk of copper?

Is it flattenable? If so, what is the best time and method to do so?

I could attempt to fly cut and / or lap the surface flat now, or wait until after the block is milled, or even milled and assembled and do whatever flattening is needed then.

Tool resources available include a Smithy (TM) combination lathe / mill setup, which is not all that great. However my machinist skills are worse, this is my first real precise machining project, up until now I've just hacked at things by eye.

My plan was to mill my water passages into the 3/4" block, leaving about 3/16 (4mm) thickness on the bottom, with about a 50/50 ratio between water passages and 'interference pins' (each about 1/8" wide) over the core area. The top would be 1/4" thick, and contain the barbs. It will use a clip on mount, not a bolt through. The top will be attached by soldering it to the bottom.

Is there any reason to change this?

If I were working in wood, I would probably cut the design into the hollow side of the cup, put everything together, and flatten it as the last step. Is this a good plan for working in copper? I am somewhat afraid that if I flatten it now, I'll get more distortion later, and need to flatten it again then.

I know there are several machinists that read this forum, I really feel a need for advice if you can give it.

Thanks,

Gooserider