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
In a GD&T feature control frame, what information is always contained in the first compartment (leftmost box)?
Answer: The geometric characteristic symbol (e.g., flatness, position, perpendicularity)
The first compartment of a feature control frame always contains the geometric characteristic symbol that identifies which type of control is being specified.
A CNC machinist sees a symmetry callout of 0.005 A on a part. What does this control?
Answer: The median points of the feature must lie within two parallel planes 0.005 apart, centered on datum A's center plane
Symmetry requires all median points of a feature (derived center plane) to lie within two parallel planes equally disposed about the datum's center plane.
When interpreting a composite position feature control frame with two rows, what does the lower segment's datum reference control?
Answer: The orientation and location of the pattern within itself (feature-to-feature relationship), not the pattern's location relative to datums
In a composite positional callout, the lower segment's datum references control only the orientation of the pattern (and internal feature-to-feature location), not the pattern's location to those datums.
A drawing shows a circularity (roundness) tolerance of 0.002 on a turned diameter. How is this checked?
Answer: At each cross-sectional slice, all points of the circle must lie between two concentric circles 0.002 apart
Circularity (roundness) is checked at individual cross-sections perpendicular to the axis; each circular slice must lie within an annular zone of two concentric circles separated by the tolerance value.
What is 'virtual condition' for an external feature (shaft) at MMC?
Answer: MMC size plus the applicable geometric tolerance — the worst-case boundary the feature can occupy
Virtual condition for an external feature is the MMC size plus the geometric tolerance, representing the worst-case outer boundary that must clear mating parts.
A position tolerance of ⌀0.014 M A B C is shown for a pattern of holes. The holes are at MMC (smallest size). Which statement is true?
Answer: Only the stated 0.014 tolerance applies; bonus tolerance is zero because the holes are at MMC
At MMC (minimum hole size, maximum material), there is no bonus tolerance — bonus only accumulates as the hole grows larger (departs from MMC toward LMC).
On a CNC part drawing, a true position callout uses a basic dimension of 2.500 for hole location. During inspection the hole center measures 2.503 from the datum. The position tolerance is ⌀0.010. Is the part in tolerance?
Answer: Yes — the 0.003 deviation falls within the ⌀0.010 cylindrical zone (radius 0.005)
A ⌀0.010 position zone has a radius of 0.005; the 0.003 deviation in one direction is within this radius, so the hole center lies inside the cylindrical tolerance zone.