CNC GD&T Symbol Interpretation 3

Question 1

What is the difference between circular runout and total runout?

Accepted Answer

Circular runout is measured at individual cross-sections; total runout accumulates error along the entire surface

Answer

Circular runout checks each individual circular cross-section separately, while total runout sweeps the full surface and captures cumulative form and location errors.

Question 2

A part drawing shows the concentricity symbol ◎ with a tolerance of 0.004 A. What is being controlled?

Accepted Answer

The median points of a feature must fall within a cylindrical zone coaxial to datum A

Answer

Concentricity controls the median points (derived median line) of a diametric feature to lie within a cylindrical tolerance zone coaxial with the datum axis.

Question 3

On a feature control frame, what does placing a datum reference in the third compartment (tertiary datum) accomplish?

Accepted Answer

It constrains the remaining rotational degree of freedom not fixed by primary and secondary datums

Answer

The tertiary datum eliminates the last remaining degree of freedom (usually rotation about an axis), fully constraining the part for measurement.

Question 4

What does the free state symbol (F in a circle) indicate when applied to a GD&T callout?

Accepted Answer

The tolerance applies to the part in its unrestrained, free condition without fixturing

Answer

The free state modifier means the tolerance applies while the part is in its natural unrestrained condition, which is critical for flexible or non-rigid parts.

Question 5

A GD&T callout shows angularity of 0.003 A on an angled surface. What does the tolerance zone look like?

Accepted Answer

Two parallel planes 0.003 apart, inclined at the basic angle relative to datum A

Answer

The angularity tolerance zone is two parallel planes separated by the tolerance value, oriented at the basic angle specified on the drawing relative to the datum.

(CNC) Computer Numerical Control Machinist Technical Practice Test

(CNC) Computer Numerical Control Machinist Technical Practice Test

CNC GD&T Symbol Interpretation 3