On Sat, 17 Feb 2001, Jim Foreman wrote:
> Now as to the corresponding drill size, that becomes a bit more
> difficult. You need to drill a hole the size of the bottom of the threads.
> Such information is readily available in machinist's handbooks for SAE but
> I've never seen it for metric. That certainly doesn't mean it's not
> available.
All three of my metric taps came with this information on the packaging and it is also stamped onto the tap itself.
alex