I have to drill a hole for the waste pipe from a kitchen sink.
As I understand it, the section of pipe to go thru the wall will be 40mm
diameter. But I find that most cored drill sets have 38mm and then 52mm,
etc.
I would have thought that a 40mm drill would be a more common
requirement of core drill users especially people who buy sets of core
drills.

I must be wrong..

Arthur