Andy Wade wrote:
John Woodison wrote:

http://www.cjseymour.plus.com/mechdata.htm


I think he was talking about masonry drills, not the old number-sizes of
morse twist drills, to which that table refers.

For masonry drills the following is about right:

No. Dia./mm
--- ---
8 4.5
10 5.5
12 6.5
14 7.0
16 8.0

Thank you both for taking the trouble to answer. Perhaps you can see
why I am confused, how can a No 14 drill in one case be 4.6mm and in the
other 7.0mm.