I was first going to lathe a larger round piece but then used my band saw to cut this "square" out of a "2x4" piece of T6-6061 aluminum. To quicken the process I cut the corners off.

For the mount, I drilled a hole to accept a 6/32 tap. I used the tap as the arbor. Worked great.

I could not figure out how I was going to bore out such a large hole with precision. Then it hit me, use an endmill as the boring tool! Awesome!

I cannot believe how easy it was to bore this out! The endmill made butter out of the aluminum! Here are the chips after just one pass cutting 1mm deep (2 total) since it's on the radius. Use oil.

I than switched to the cutoff blade and started making the fins. This part took sometime as the chips didn't clear as quickly. (NOTE: In the 2nd version the fins were cut first and the hole bored after. Much better way).

Here is the completed heat sink. It came out dead on but I wanted it to be a little tight for a good fit. I had to cut a larger slot using the bandsaw and then pinch it together in the vise. Nice, but heavy

Here you can see the cut. After pinching, it fits really tight!

Weight: Heavy! 13.1 grams See the new heatsink made after killing this one?