On Thursday, January 7, 2021 at 2:28:02 PM UTC, RobH wrote:
On 07/01/2021 13:22, misterroy wrote:
Can plug tap sometimes mean second and sometimes bottoming?

Here is RS's plug taps selection, some of them look like they get close to the bottom, others less so.
https://uk.rs-online.com/web/c/hand-...ons=4294885797

The names seem to vary from website to website.

Is there a definitive answer?

ta

when I was serving my engineering apprentceship many moons ago, I was
told that taps are named as First, Second, and Plug taps

A plug tap does not have any tapering of the threads, while the first
tap has quite a bit, and the 2nd tap has about half as much.

I hope that helps
You live and learn. I never knew that. I recently bought one of those combined drill bit and taps and was surprised it worked quite well in 6mm aluminium amd some softwood.