In article ,
J. Clarke wrote:
On 6/25/2010 8:43 PM, dpb wrote:
J. Clarke wrote:
Got the bright idea of using a 1/2" copper pipe union as a bushing and
then realized that I don't have a drill bit the right size. Looks like
it's a tight 11/16, an 18mm, or a slightly loose 23/32. Anybody know
offhand which one is right?

Will depend on whether it's M or L. Can't just is mic it???

And that tells me that it's a tight 11/16, pretty close to right on
18mm, or a slightly loose 23/32. The question is which one makes a hole
that it actually fits. The nominal diameter of the bit and the diameter
of the hole are not the same.

Plumbing stuff is specced by inside diameter.

O.D. is whatever the manufacturer feels like.