Method of indicating geometrical tolerances on drawings

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.

Left-hand compartment:

Third compartment: datum identification letter(s)

Second compartment: total tolerance value in the unit used for linear dimensions


0 0.03


Indications qualifying the feature within the tolerance zone should be written near the tolerance frame and may be connected by a leader line.

Not convex

Fig. 20.10

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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