GD&T Datum Systems & Reference Frames 2

Question 1

In the three-plane datum reference frame, which datum plane constrains the most degrees of freedom?

Accepted Answer

Primary datum plane

Answer

The primary datum plane contacts the part at a minimum of three points and constrains three degrees of freedom (one translation and two rotations).

Question 2

A datum feature simulator for a flat primary datum must be:

Accepted Answer

Nominally perfect in form

Answer

Datum feature simulators are nominally perfect counterparts of the datum feature, used to establish the datum from which measurements are taken.

Question 3

When a cylindrical feature is used as a primary datum, it constrains how many degrees of freedom?

Accepted Answer

Four

Answer

A cylindrical primary datum constrains four degrees of freedom: two translations perpendicular to its axis and two rotations perpendicular to its axis.

Question 4

What does the order of datum references (primary, secondary, tertiary) in a feature control frame determine?

Accepted Answer

The sequence of part setup and degree-of-freedom constraint

Answer

The order of datum references establishes the hierarchy of constraint, dictating the sequence in which the part is brought into contact with datum simulators.

Question 5

A datum reference frame is established by a minimum of:

Accepted Answer

Three datum features

Answer

A complete datum reference frame typically requires three mutually perpendicular datum planes established from at least three datum features to fully constrain six degrees of freedom.

(GD&T) Geometric Dimensioning and Tolerancing Certification Practice Test

(GD&T) Geometric Dimensioning and Tolerancing Certification Practice Test

GD&T Datum Systems & Reference Frames 2