"Ignoramus10114" wrote in
message ...
I have an aluminum heatsink that I need to tap , I wanted to know if
I
should use 6-32 or some less coarse thread like 8-32 would be
better?

I've never had a breakage problem with good-quality 6-32 taps in
aluminum, if that's your worry. If possible I use two flute spiral
point (gun) taps in through holes and kerosine etc for the lubricant,
and I don't start the tap without some sort of squareness guide,
either the mill or a hand-held fixture like this:
http://www.spaco.org/Blacksmithing/TapDrillBlock.htm

Some people prefer cubical ones.

-jsw