Get under sized taps and work up. The undersized ones are standard when
you buy them - and don't bite as much out of the hole.

Martin

On 4/13/2015 12:30 PM, Don Foreman wrote:
On Sun, 05 Apr 2015 07:47:14 -0500, Ignoramus10114
wrote:

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?

6-32 is an abomination. If you are ever going to break a tap, it'll
probably be a 6-32. The 32-pitch thread is too coarse for the skinny
diameter. The standard should have been 6-40.

If you insist on tapping aluminum, use plenty of lube. A lube that
works really well in aluminum is ... Goo Gone! Orange Goop works
quite well also. Both have high content of d-limonene. Use HSS taps
rather than the sharper and cheaper but much more brittle carbon
steel taps found at hardware stores.