GD&T Datum Systems & Reference Frames 5

Question 1

What is a 'datum reference frame' (DRF) as defined in GD&T?

Accepted Answer

Three mutually perpendicular planes that define the origin for dimensional measurements

Answer

A datum reference frame consists of three mutually perpendicular planes forming a 3D coordinate system from which the location and orientation of features are measured.

Question 2

In the context of GD&T datum systems, what is 'true geometric counterpart'?

Accepted Answer

The theoretically perfect form of the datum feature used to establish the datum

Answer

The true geometric counterpart (or datum feature simulator) is the theoretically perfect boundary or surface used to establish a simulated datum from the actual imperfect part feature.

Question 3

Which datum modifier requires the datum feature simulator to expand or contract to make maximum contact with the datum feature?

Accepted Answer

RFS (Regardless of Feature Size)

Answer

Under RFS (regardless of feature size), the datum feature simulator adjusts to make maximum contact with the actual datum feature surface, with no datum shift allowed.

Question 4

A secondary datum axis established from an internal cylinder is defined by:

Accepted Answer

The largest inscribed cylinder axis

Answer

An internal cylindrical datum feature at RFS is simulated by the largest inscribed cylinder (maximum inscribed cylinder) that fits within the bore, defining the datum axis.

Question 5

When datum targets are used to establish a primary datum plane, the minimum number of target points required is:

Accepted Answer

Three

Answer

A minimum of three datum target points are needed to define a primary datum plane, just as three points define a unique plane in space.

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

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

GD&T Datum Systems & Reference Frames 5