GD&T Datum Reference Frames 2

Question 1

In a datum reference frame, what is the maximum number of degrees of freedom that can be constrained?

Accepted Answer

6

Answer

A complete datum reference frame constrains all 6 degrees of freedom: 3 translational and 3 rotational.

Question 2

Which datum feature simulator contact rule applies when establishing a primary datum plane from a flat surface?

Accepted Answer

True contact with at least 3 points

Answer

A primary datum plane is established by physical contact with at least 3 high points on the part surface.

Question 3

A datum reference frame established by [A|B|C] uses datum A as primary. How many degrees of freedom does datum A constrain?

Accepted Answer

3

Answer

A primary planar datum constrains 3 degrees of freedom: 1 translation and 2 rotations perpendicular to the datum plane.

Question 4

What is a 'basic dimension' in relation to a datum reference frame?

Accepted Answer

A theoretically exact dimension used to locate a datum or feature

Answer

Basic dimensions are theoretically exact values enclosed in a box, used to define the true position of features relative to a datum reference frame.

Question 5

When a cylindrical feature is used as a secondary datum after a planar primary datum, how many additional degrees of freedom does it constrain?

Accepted Answer

2

Answer

A secondary datum cylinder constrains 2 translational degrees of freedom (the two directions perpendicular to the cylinder's axis).

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