Turns out that 6-32 screws fit the fets nicely so that’s what I tapped the heatsinks with, instead of 4-40. The cnc code did fine. I had to add a step that chamfered the top of each hole so that the tap would start easier. The nicest part of using the mill is for power tapping. It makes perfect threads and the mill does the work. The 6-32 tap is the smallest I’ve every power tapped with. It’s a cheap tap too, but it worked just fine!

Here they are just finished. Image shot with my G1 cellphone.