Standard
STD 101-0001
Volvo Group
Version
4
Page
25
4.6.1.2 Identification of datums
Figures 21 and 22 demonstrate symbol attachment methods for identifying datums on a model. The datum
indicator should be attached to the surface representing the datum feature. Single extension lines of model feature
outlines should not be used for the attachment of datum indicators. Particular requirements and the preferred
attachment methods for datum indicators are as follows:
a) Identification of planar surface (integral feature)
The datum indicator shall be attached directly to the surface (see datum A in figure 21 a) or to a reference
line using a leader line terminated with a dot to the surface (see datum D in figure 21 a).
b) Identification of the centre point of a spherical feature (derived feature)
The datum indicator shall be attached to the reference line for the dimension (see datum F in figure 21a).
or to the tolerance indicator as shown in figure 21b.
c) Identification of an axis on a cylindrical feature (derived feature)
The datum indicator shall be attached to a reference line and using a leader line terminated with a dot to
the surface (see datum B in figure 21a).
NOTE: It is also possible to attach the datum indicator as an extension of the dimension line as shown for
two opposed parallel planes in figure 21a, but this often becomes impractical for diameters in 3-D.
d) Identification of the median plane of two opposed parallel planes (a width) (derived feature)
The datum indicator shall be attached as an extension of the dimension line as shown in figure 21a or to
the tolerance frame as shown in figure 21b.
a) Direct attachment
Figure 21 – Datum indicator attachments
