> On Jan 26, 2020, at 8:01 AM, John Ruth  wrote:
> 
> Please get out your magnifying glass, and tell us if it’s really GL1 rather
than G11.
> 
> The HSG11 might be intended to be read “HS GL1” where the HS indicates High
Speed [Steel] and the G number is an indicator of Pitch Height on a Ground
Thread tap.  L1 means the Pitch Height is Lower than the standard.
> 
> There are GH taps with the Pitch Height Higher than standard and GL taps with
the Pitch Height Lower than standard.
> 
> Explained, with a diagram, here:
> http://tapmatic.com/tapping_questions_class_of_threads_h_limits.ydev

OK, I think it actually reads HS  G11. That suggests High Speed and G11 means??
Best guess is it is .0055 oversize. I had only said that there are several
manuf. included. These are the only two that are marked P&W — Pratt and Whitney.
Perhaps they had a need for unique taps.

Starting w/ your link above I have spent too much time wandering in the thread
nomenclature wilderness this morning. Found no definitive answer.

> Every time you buy a package of nuts from one maker and a package of bolts
from another, and they fit, you are standing on the shoulders of giants.

And every one of them seems to have developed a chart w/ idiosyncratic
terminology.
> 
> John Ruth,
> Who says, “Of threads, and threading systems, there is no end!”

Amen.