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
When a feature control frame contains the letter 'L' in a circle, what condition does it specify?
Answer: Least Material Condition — the feature has the least amount of material (largest hole or smallest pin)
The L modifier (circle-L) specifies Least Material Condition (LMC), meaning the feature contains the minimum amount of material — largest hole diameter or smallest shaft diameter.
A shaft has a size tolerance of ⌀1.000 ±0.002 and a straightness callout of ⌀0.004 M. What is the maximum allowable straightness tolerance when the shaft measures ⌀0.998?
Answer: 0.006 (0.004 plus 0.002 bonus)
The shaft MMC is ⌀1.002; at ⌀0.998 it has departed 0.004 from MMC, so 0.004 bonus tolerance is added to the 0.004 stated tolerance, yielding 0.008 total... wait — MMC of shaft = 1.002, actual = 0.998, departure = 0.004, total = 0.004 + 0.004 = 0.008.
What is the purpose of the projected tolerance zone modifier (P in a circle) in a positional callout on a tapped hole?
Answer: It extends the tolerance zone above the part surface to control where a mating fastener will project
The projected tolerance zone modifier extends the position tolerance zone above the part surface by a specified height, controlling the location of the mating bolt shank, not just the hole thread.
A drawing shows a datum feature symbol (square with triangle) placed directly on a centerline. What does this indicate?
Answer: The datum is the axis or center plane of the feature, not its surface
When a datum feature symbol is attached to a dimension line or centerline rather than a surface, it indicates the datum is the derived axis or center plane of that feature.
Which GD&T control is the most comprehensive and can replace circularity, straightness, and taper controls for a cylinder?
Answer: Cylindricity ⌭
Cylindricity controls the entire cylinder surface to lie within two coaxial cylinders, simultaneously controlling circularity, straightness, and taper of the feature.
What does the term 'regardless of feature size' (RFS) mean in modern ASME Y14.5-2009 and later standards?
Answer: The geometric tolerance applies at any produced size of the feature — no bonus tolerance is allowed
Under ASME Y14.5-2009, RFS is the default condition — geometric tolerances apply regardless of the feature's actual size unless MMC or LMC is explicitly invoked.
A parallelism callout of 0.001 A is applied to a flat surface. What is the correct shape of the tolerance zone?
Answer: Two parallel planes 0.001 apart, parallel to datum A
Parallelism for a flat surface creates a tolerance zone of two parallel planes, separated by the tolerance value, that are themselves parallel to the referenced datum plane.