Where it is not clear that a hole goes through an object, the abbreviation
THRU follows the dimension. A blind hole is a hole that does not pass
completely through the object. The depth dimension of a blind hole is the
depth of the full diameter from the surface of the part. Where a blind hole is
also counterbored or counterdrilled, the depth dimension applies from the
Figure 3-30 shows how to correctly dimension round holes.
Figure 3-30.Dimensioning rounded holes.
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