#Datum reference frame how to

How To Select Datum Feature In The Order of Precedenceĭatum features are selected to meet design requirements. Datum A is the primary datum, datum B is the secondary datum, and datum C is the tertiary datum because this is the order in which they appear in the feature control frame.

Thus eliminating all six degrees of freedom.ĭatums are specified in order of precedence as they appear from left to right in the feature control frame they need not be in alphabetical order. Finally, the part is slid along the first two planes of the datum reference frame until the third datum feature contacts the third plane of the datum reference frame with a minimum of one point of contact. The secondary datum feature is pushed up against a second plane of the datum reference frame with a minimum of two points of contact. In order to properly place an imperfect, rectangular part in a datum reference frame, the primary datum feature sits flat on one of the planes of the datum reference frame with a minimum of three points of contact that are not in a straight line. The datum reference frame is not absolutely perfect, but it is made sufficiently accurate with respect to the part to consider it to be perfect. A part is oriented and immobilized relative to the three mutually perpendicular planes of the datum reference frame in a selected order of precedence. It can also rotate around the X-axis, the Y-axis, and the Z-axis. A part can move back and forth in the X direction, in and out in the Y direction, and up and down in the Z direction.

Datum reference frame