GD&T Symbols and Rules 5

Question 1

Which of the following best describes the 'unilateral' profile tolerance symbol introduced in ASME Y14.5-2009?

Accepted Answer

A 'U' in a circle with a value indicating how much of the zone shifts outside the true profile

Answer

The unequal (unilateral) profile modifier uses a circled 'U' followed by the amount of the zone that falls outside the true profile, shifting the bilateral default.

Question 2

What is the key difference between concentricity and coaxiality in modern GD&T practice (ASME Y14.5-2018)?

Accepted Answer

Concentricity controls derived median points; coaxiality controls the axis using MMC/LMC modifiers

Answer

Concentricity is an RFS control of derived median points (difficult to measure), while coaxiality uses the axis and allows MMC/LMC for easier functional gaging.

Question 3

A straightness tolerance applied to the surface of a cylinder (not its axis) creates a tolerance zone that is:

Accepted Answer

Two parallel lines on the surface in the direction of measurement

Answer

Surface straightness controls each line element of the cylinder surface within two parallel planes (lines in 2D), independent for each longitudinal line element.

Question 4

Which GD&T symbol is used to indicate that a dimension is for reference only and does not govern production or inspection?

Accepted Answer

Parentheses around the dimension value

Answer

Reference dimensions are enclosed in parentheses to indicate they are informational only and are not to be used for manufacturing or inspection purposes.

Question 5

The 'statistical tolerance' symbol (ST) in a feature control frame indicates that the tolerance:

Accepted Answer

Is valid only when statistical process controls are in use during manufacturing

Answer

The ST symbol means the tolerance is valid only if the manufacturing process is controlled using statistical methods (SPC), allowing slightly larger individual tolerances.

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

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

GD&T Symbols and Rules 5