30 GD&T: Application and Interpretation
Copyright Goodheart-Willcox Co., Inc.
The position tolerance symbol is composed
of two lines crossing at the center of a circle. See
Figure 2-16. It is symbolic of the center lines used
on a drawing to indicate the desired location for a
hole. Another type of location tolerance is concen-
tricity. The concentricity symbol is indicated by
two concentric circles.
A third type of location tolerance is symme-
try. Symmetry may be indicated by either of two
types of symbols, depending on the type of con-
trol desired. A position symbol may be used when
specifying the symmetrical location of features of
size at maximum material condition (MMC). A
symmetry symbol that consists of three horizontal
lines may be used for other symmetry tolerances.
The symmetry symbol containing three lines was
not included in the 1982 standard.
Modifi ers are often applied to tolerance speci-
fi cations. The proportions shown for modifi ers in
Figure 2-16 apply to material and boundary con-
dition modifi ers, the independency symbol, free
state symbol, projected tolerance zone symbol,
tangent plane symbol, and the unequally disposed
tolerance zone symbol.
A double-ended arrow is used in place of the
word between. It is used for tolerance specifi cations
that extend between labeled points, edges, or other
features.
A tolerance calculated by statistical methods
may be identifi ed with a special symbol. The sta-
tistical tolerance symbol is an elongated hexagon
containing the letters ST.
The continuous feature (CF) symbol is an
elongated hexagon containing the letters CF. This
Symmetry
Concentricity Position
Total runout Circular runout
Angularity
Parallelism Perpendicularity
Surface profile Line profile
Cylindricity Flatness Circularity Straightness
Miscellaneous
Profile
Runout
Orientation
Form
Location
Between
Statistical tolerance Modifier Translation
Continuous feature
Goodheart-Willcox Publisher
Figure 2-16. Tolerance symbols are shown grouped by tolerance categories.