I am looking at a company-written standard for cast parts. The castings are blanks for driveshaft yokes, similar to what is pictured below. The standard defines general tolerances for the dimensions on the part, and it classifies them into two categories:
- Outside dimensions and center-to-center distances
- Inside dimensions (core dimensions) 1
There is some confusion between us and our supplier as to what constitutes an inside dimension. Obviously, anything that requires a core (such as pilot holes for the yoke ear holes seen below) will be an inside dimension.
However, when our internal inspection requirements were laid out, things such as the distance from inside edge to inside edge of the ears were determined to be inside dimensions, while the outside edge measurement on the ears is an outside dimensions.
First, is this terminology common to castings (or even forgings) in general? I have looked at ISO standards regarding general tolerances, but they make no reference to it. If it is common, are inside dimensions strictly related to features requiring cores? Should other dimensions be considered "inside"?
For reference, the tolerances for outside dimensions are asymmetrical, with the high end being larger than the low end (e.g. +1.0/-0.5), and the inside tolerances are symmetrical to the same absolute value as the low end of the outside dimensions (e.g. +/- 0.5 to match the first example).
1. This is verbatim how it is listed in the standard.