Geometrical tolerances are indicated by stating the following details in compartments in a rectangular frame.
(a) the characteristic symbol, for single or related features;
(b) the tolerance value
(i) preceded by 0 if the zone is circular or cylindrical,
(ii) preceded by S0 if the zone is spherical;
(c) Letter or letters identifying the datum or datum systems.
Fig. 20.3 shows examples.
Third compartment: datum identification letter(s)
Second compartment: total tolerance value in the unit used for linear dimensions
Indications qualifying the feature within the tolerance zone should be written near the tolerance frame and may be connected by a leader line.
If it is necessary to specify more than one tolerance characteristic for a feature, the tolerance specification should be given in tolerance frames positioned one under the other as shown.
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