Form and Orientation Tolerances Flashcards

Which GD&T symbol is used to control the straightness of a surface element (line element) on a cylindrical part?

Answer: Straightness (⏤)

Straightness controls individual line elements on a surface or the derived median line of a feature of size.

A flatness tolerance zone is defined as the space between two:

Answer: Parallel planes

Flatness tolerance zone consists of two parallel planes within which the entire surface must lie.

When angularity is applied to a surface, what is the shape of the tolerance zone?

Answer: Two parallel planes at the specified angle to the datum

Angularity applied to a surface creates a tolerance zone of two parallel planes oriented at the specified angle relative to the datum.

Cylindricity differs from circularity in that cylindricity controls:

Answer: Both the roundness and straightness of the entire surface simultaneously

Cylindricity simultaneously controls circularity, straightness, and taper of the entire cylindrical surface in a single tolerance.

Which statement about form tolerances and datums is correct?

Answer: Form tolerances never reference datums

Form tolerances (flatness, straightness, circularity, cylindricity) by definition control the shape of an individual feature and never require datum references.

A perpendicularity callout on a pin's axis controls the orientation of the pin's derived median line relative to:

Answer: A referenced datum plane or axis

Perpendicularity applied to an axis controls how closely the feature's derived median line is 90° to the referenced datum.

Under ASME Y14.5, the circularity (roundness) tolerance value must be:

Answer: Less than or equal to the size tolerance

Per Rule #1 (Envelope Principle), the circularity tolerance cannot exceed the size tolerance because the feature must remain within its size limits.