Chapter 3 Datums 109 Example 3-37. Using movable datum target symbols with datum target points. Movable Datum Target Symbols and Datum Target Spheres The movable datum target symbol can be used with a spherical diameter specified for the datum target size, and a circular phantom line is used to represent the spherical datum feature simulator as shown in Example 3-38. The spherical datum feature simulators are used to establish the datum axis in this example. The conical shaped ends on the part allow the spherical datum feature simulators to restrict the movement of the part and define the datum axis. In this example, the spherical datum targets move horizontally normal to the axis to contact the actual surface of the part, with datum A specified at RMB in the feature control frame. datum target symbol C1 until contact is made. This example shows how to define the direction of the movement. When the datum feature simulator is required to move and when the movement is not normal to the true profile, the movable datum target symbol is used and the movement direction is defined. If the 45° basic angle is not given, the datum target can move “normal” to the surface or radial toward the center of the round feature.