Thread ring gages. What's the difference between LO and NO GO? Any?

[Technical Ted]

I picked up a bunch of thread gages in a purchase I made. Some of the ring gages are marked "LO". I'm only familiar with "GO" and "NO GO" gages, never seen "LO". I see by doing some searching, some gages available are "HI and LO".

What's the difference? From the marked pitch diameters it appears that LO on a ring gages = NO GO.

What's up?

Thanks,
Ted

 

[sfriedberg]

I wasn't familiar with that abbreviation, but Google reveals that LO can be used for external NO GO, while HI can be used for internal NO GO. See the discussion here.

 

[Technical Ted]

Thanks, I saw that as well when doing some searching. I was interested in the history or reasoning for the two methods, as in, is the LO an older method? I've got a few gages that have the LO and others that have the NG and was looking for some background information if anyone had any.

Thanks,
Ted