Exam 40: The Datum Reference Frame

A surface plate can be used as a primary datum for a part with a flat surface.

When a part is touching primary and secondary datum planes and comes in contact with a tertiary plane, it theoretically touches the tertiary plane in ____.

When checking the accuracy of a flat surface against a datum surface, there will theoretically be more than three points on the flat surface touching the datum surface (gage).

Another name for a three-plane datum system is __________________________________________________.

When a chain line is used to designate a datum, its length must be dimensioned.

If a part is brought into contact with a secondary plane while lying on a primary plane, it will theoretically touch a minimum of ____ points.

A datum feature is a feature of a part which is used to establish the location of a datum.

When only a part of a surface is to be designated as a datum, a ____ line drawn parallel to the surface is used to indicate the portion of the surface acting as the datum.

Geometric tolerances, such as straightness and flatness, refer to unrelated lines and surfaces and generally relate to datums.

The datum feature symbol is ____.

A point, axis, or plane from which dimensions are measured, or to which geometric tolerances are referenced, is a ____________________

Datums are exact geometric points, axes, or ____________________, each based on one or more datum features of the part.

The three types of datums are primary, secondary, and ____________________.