[304065]

Craig,

I see what you mean, if the hole is elliptical, the not-go gauge might contact the narrow sides of the bushing and trick you into thinking the bore is in spec, when in fact the other end is too big.

I suppose a bore gage could be used with the appropriate small head and it could be rotated inside the bushing to give you a picture of the dimensions and the ovality.

Using the bore gage with a micrometer on the stand is not easy for the beginner. Some do it with predictable regularity-- I would prefer something like an intrimik or mitutoyo holtest ($,$$$) for the exact size-- bue even those can't tell you if it's oval.