Geometric Symbols & Notation Flashcards

The GD&T symbol for 'Angularity' controls which characteristic?

Answer: The orientation of a surface at a specified angle to a datum

Angularity is an orientation control that constrains a surface or axis to a specified angle (other than 0° or 90°) relative to a datum.

What is the purpose of a 'projected tolerance zone' modifier (circled P) in GD&T?

Answer: Extends the tolerance zone beyond the part surface to control mating part fit

A projected tolerance zone extends the positional tolerance zone above the hole to control the orientation of a fastener as it protrudes into a mating part.

Which feature control frame compartment always contains the geometric characteristic symbol?

Answer: The first (leftmost) compartment

Per ASME Y14.5, the first compartment of a feature control frame always contains the geometric characteristic symbol.

What does 'BASIC' written below a dimension value indicate in a GD&T drawing?

Answer: The dimension is theoretically exact and has no tolerance of its own

A basic dimension (shown in a box or labeled BASIC) is a theoretically exact value; its allowable variation is defined by the feature control frame tolerance.

The GD&T symbol for 'Circular Runout' differs from 'Total Runout' in that:

Answer: Circular runout is checked at individual cross-sections, while total runout accumulates across the entire surface

Circular runout measures the variation at each individual circular cross-section independently, while total runout measures the combined variation over the entire surface.

A 'datum target' symbol consists of:

Answer: A circle divided by a horizontal line with the target number below and area size above

Datum target symbols are circles split horizontally: the lower half contains the target identification (e.g., A1) and the upper half optionally contains the target area size.

In GD&T, the 'Tangent Plane' modifier (circled T) means:

Answer: The tolerance applies to a plane tangent to the high points of the surface

The tangent plane modifier specifies that the tolerance zone is evaluated using a plane contacting the high points of the surface rather than the entire surface.