On Tue, 10 Nov 2009 13:06:53 +0000, Chris Wilson
wrote:

I seem to remember being taught in school that metric countersunk Allen
srews had a 90 degree countersink angle, and Unified had an 82 degree
angle. Is that right, and does it matter if I just use a 90 degree
countersinking bit for both, as here in the UK no one seems to stock 82
degree bits for ferrous material? Thanks.

Correct.

I guess in non critical applications you could get away with an 90 D
c'sink on a unified flat head.

Thank You,
Randy

Remove 333 from email address to reply.