196 GD&T: Application and Interpretation
Copyright Goodheart-Willcox Co., Inc.
established and the movable datum target symbol
is shown, the target defaults to move along a path
that is normal to the surface and passes through
the fi xed point. If a different direction of move-
ment is desired, the direction must be specifi ed.
The tool used to locate the given part, assum-
ing datum A is primary and datum B is secondary,
is shown in the given fi gure. The fl at plate simu-
lates datum A. The two vertical dowel pins serve
to pick up datum targets B3 and B4. The two pins
are in a slider that is free to move and pick up the
two vertical target lines B3 and B4 while pushing
the part against datum targets B1 and B2.
The V-block surfaces have horizontal edges
to simulate datum targets B1 and B2 because line
contact is required and the edges are fi xed in loca-
tion. Targets B1 and B2 could also be simulated
with cylindrical surfaces.
Drawings containing equalizing datums
were in past practices allowed to show a datum
feature symbol on the center plane. This was an
exception to the general requirements for applica-
tion of the datum feature symbol. The datum fea-
ture symbol is no longer placed on a centerline or
center plane regardless of whether or not equaliz-
ing datum targets are used. The targets adequately
Notation permitted when
using equalizing datum
This line indicates line contact
by the V-type equalizer
Dowels (simulators) contact
targets B3 and B4
Edge makes contact
at targets B1 and B2
targets
Goodheart-Willcox Publisher
Figure 6-56. Equalizing datum targets are used to locate a center plane or axis.