are the Rules?
The rules of geometric dimensioning
and tolerancing have changed over the years. In addition, the
meaning of such symbols as runout, total runout, concentricity
and symmetry have changed. You cannot go by the drawing
date since many companies may delay adoption of a new
revision for several years. Unfortunately, the drawing doesn't
always state the revision to use when translating the symbols
into plain English. Often you can determine which Standard was
used by observing differences in the callouts. Your choices of
Y14.5 standard revisions are 1966, 1973, 1982 and 1994. Here
are a few things to look for when determining which revision
of the Standard to use.