GD&T Symbol Interpretation Flashcards
7 cards from real CNC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 GD&T Symbol Interpretation flashcards as text
What is the difference between circular runout and total runout?
Answer: Circular runout is measured at individual cross-sections; total runout accumulates error along the entire surface
Circular runout checks each individual circular cross-section separately, while total runout sweeps the full surface and captures cumulative form and location errors.
A part drawing shows the concentricity symbol ◎ with a tolerance of 0.004 A. What is being controlled?
Answer: The median points of a feature must fall within a cylindrical zone coaxial to datum A
Concentricity controls the median points (derived median line) of a diametric feature to lie within a cylindrical tolerance zone coaxial with the datum axis.
On a feature control frame, what does placing a datum reference in the third compartment (tertiary datum) accomplish?
Answer: It constrains the remaining rotational degree of freedom not fixed by primary and secondary datums
The tertiary datum eliminates the last remaining degree of freedom (usually rotation about an axis), fully constraining the part for measurement.
What does the free state symbol (F in a circle) indicate when applied to a GD&T callout?
Answer: The tolerance applies to the part in its unrestrained, free condition without fixturing
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.
A GD&T callout shows angularity of 0.003 A on an angled surface. What does the tolerance zone look like?
Answer: Two parallel planes 0.003 apart, inclined at the basic angle relative to datum A
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.
Which of the following is NOT a valid GD&T form tolerance (applies without a datum)?
Answer: Parallelism
Parallelism is an orientation control that always requires a datum reference; form tolerances like flatness, cylindricity, and straightness stand alone.
What does the term 'basic dimension' mean in GD&T?
Answer: A theoretically exact dimension used to define the true location, orientation, or profile of a feature
A basic dimension (shown in a rectangle/box) is a theoretically exact value used to establish the true geometry of a feature; the actual tolerance is specified in the feature control frame.