On Sun, 15 Apr 2012 09:23:28 +0000 (UTC), David Lesher
wrote:


So I broke off a M3 tap in a block of 0.5" aluminum.

Its tip is barely emerging on the far side, and broken below
flush on the feed side.

If you got lots o' time, nitric acid will disolve the tap and not hurt
the AL

Karl