Tinker,
No, the small hole gages are either ball end or half ball end and the appropriate size should bridge the groove. They are limited to 1/2" holes. You are thinking about the much larger "T" shaped ones that go to well over 3". Note I said "decent" measurement, I concede it may be a fraction of a thou. off.
Mike
Hi Mike
I was speaking of small hole gages, not telescoping gages.
I've been working with measuring tools and machining equipment since 1973
I see what you are illustrating with the small hole gages suggestion - and I acknowledge your work-around, but I maintain that a small hole gage mesurement represents a distance across two points. Also note that an engineer or technician can employ a small hole gage outside it's range in order to reach features that are crowded by other features.
In the context of a 500 bpe bore, a telescoping gage could be too bulky, but a small hole gage from the smaller end of the range may be used to read the dimension between a land and a groove in some odd-groove barrels depending on groove width and the width of the measuring surfaces of the gage employed.
I have used small hole gages, telescoping gages, pin gages, and numerous other tools to evaluate the dimensions of bore features.
At times things can end up being a little complicated, and interesting work-arounds like your example can be very useful.
There are also numerous ways to accurately measure the casting shown above,
