ASME GDTP Technologist flashcards
ASME GDTP Technologist · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Rule #1 envelope principle
- Unless otherwise specified, the limits of size of a feature of size define a boundary of perfect form at MMC, and the surface may not violate that envelope.
- Basic dimension
- A theoretically exact dimension shown in a rectangle without a tolerance; it establishes the true profile or true position used with geometric tolerances.
- Feature control frame
- A rectangular frame containing the geometric characteristic symbol, the tolerance value with optional modifiers, and datum references, read left to right.
- Rule #2 RFS default
- Regardless of feature size is the default condition; the MMC or LMC modifier must be explicitly shown after the tolerance value to change it.
- Datum reference frame
- Three mutually perpendicular planes, or an axis or point, established from datum features in order of precedence; tolerances citing datums are measured from it.
- Primary datum plane
- The plane established by contact of the datum feature simulator with the datum feature at a minimum of three points; it constrains three degrees of freedom.
- Datum feature simulator
- The true geometric counterpart of a datum feature: the surface of inspection equipment such as a surface plate, mandrel, or chuck used to establish the datum.
- Datum shift at MMB
- When a datum feature of size is referenced at MMB, the simulator is fixed at its virtual condition, and size variation lets the part translate, adding shift tolerance.
- Flatness
- A form tolerance whose zone is two parallel planes; the entire surface must lie between them, and no datum reference is permitted.
- Circularity (roundness)
- A form tolerance whose zone is two concentric circles in a cross-section with radial separation equal to the tolerance; it controls roundness independent of size and is always RFS.
- Cylindricity
- A form tolerance whose zone is two coaxial cylinders with radial separation equal to the tolerance; it simultaneously controls circularity, straightness, and taper and is always RFS.
- Axis straightness at MMC
- Straightness applied to the axis of a feature of size giving a cylindrical zone; when at MMC the derived median line may exceed the limits of size.
- Perpendicularity
- An orientation tolerance establishing a 90-degree basic angle to a datum; the zone is two parallel planes or a cylinder oriented perpendicular to the datum.
- Angularity
- An orientation tolerance at a basic angle other than 90 degrees; it requires a basic angle dimension and a datum, and the zone is oriented at that angle.
- Parallelism
- An orientation tolerance requiring a feature to be equidistant from a datum; the zone is two parallel planes or a cylinder parallel to the datum plane or axis.
- Orientation tolerance scope
- Orientation controls limit tilt only, not location; the tolerance zone remains free to translate unless it is combined with a locating control.
- Bonus tolerance
- Extra tolerance equal to the amount a feature's actual mating size departs from MMC, available only when the MMC modifier follows the tolerance value.
- Position tolerance
- A location control that positions features of size relative to datums using a cylindrical or parallel-plane zone centered on true position derived from basic dimensions.
- Concentricity
- A location control applied to the median points of diametrically opposed elements of a feature of size relative to a datum axis; zone is two coaxial cylinders; always RFS.
- Symmetry
- A location control applied to the median points of opposed elements relative to a datum center plane; the zone is two parallel planes; the control is always RFS.
- Profile of a surface
- A profile tolerance whose zone is two parallel surfaces or a boundary offset from the true profile; default bilateral; it can control size, form, orientation, and location.
- Profile of a line
- A profile tolerance whose zone is two parallel lines in each cross-section, controlling individual line elements of the surface; it is always RFS.
- Unilateral profile tolerance
- A profile zone placed entirely on one side of the true profile, indicated by a phantom line at the true profile and the U modifier with the offset value.
- All-around symbol
- A small circle on the leader of a profile feature control frame indicating the tolerance applies to all surfaces around the part in that view.
- Circular runout
- A runout control whose zone is two concentric circles at each cross-section, with radial separation equal to the tolerance, evaluated independently on each element during full rotation.
- Total runout
- A runout control whose zone is two coaxial cylinders or parallel planes, with separation equal to the tolerance, evaluated over the entire surface during rotation and axial traverse.
- Runout datum requirement
- Runout always requires a datum axis established from a datum feature of size, and the tolerance value is never modified by MMC or LMC.
- Face runout
- Runout applied to a flat face; it controls perpendicularity of that face to the datum axis and is verified with an axial indicator during rotation.
- Virtual condition
- The boundary generated by the collective effects of a feature's MMC size and its geometric tolerance at MMC; it is the worst-case mating envelope.
- Resultant condition
- The worst-case boundary opposite virtual condition; for an external feature it equals LMC size plus geometric tolerance, and for an internal feature LMC minus tolerance.
- Composite position tolerance
- A single feature control frame with two or more segments; the upper segment locates the pattern to datums and lower segments control feature-to-feature location and orientation.
- Two single-segment controls
- Separate stacked feature control frames with independent segments; each is verified independently and may reference different datums and tolerance values.