GD & T Definitions

Class Vocabulary
Term Definition
angularity
A three-dimensional orientation tolerance that describes the allowable variability in the angular relationship between a surface and a datum.
ASME Y14.5M-1994
The Dimensioning and Tolerancing standard.
circular runout
A two-dimensional runout tolerance that describes the distance between the surface and axis of a circular feature.
circularity
A two-dimensional form tolerance that describes the allowable variability in the shape and appearance of a circle in a section view.
coaxial
Sharing the same axis.
concentricity
A three-dimensional locational tolerance that describes the location of opposing points in cylindrical features with respect to a datum reference.
cylindricity
A three-dimensional form tolerance that describes the allowable variability in the shape and appearance of a cylinder.
datum
A specified point, line, or plane that acts as a point of reference for a feature.
datum reference frame
The combination of points, lines, and planes that define three dimensions for a part.
feature control frame
The box that contains the geometric tolerancing requirement information for one condition of the part.
flatness
A three-dimensional form tolerance that describes the allowable variability in the shape and appearance of a surface that lies in a plane.
form tolerance
A group of geometric characteristics that describes the shape of the feature.
geometric characteristic
The mathematical specification applied to a feature.
geometric dimensioning and tolerancing
A three-dimensional tolerancing system that describes a feature and its relationships in mathematical language.
least material condition
The circumstance of the feature with the least material during which the geometric tolerance applies.
limit tolerancing
A two-dimensional tolerancing system that describes a feature in absolute maximum and minimum dimensions.
location tolerance
A group of geometric characteristics that describes the placement of features on the part.
material condition modifier
The circumstance of the feature during which the geometric tolerance applies.
maximum material condition
The circumstance of the feature with the most material during which the geometric tolerance applies.
orientation tolerance
A group of geometric characteristics that describes the angular relationship between features.
parallelism
A three-dimensional orientation tolerance that describes the equal distance between pairs of points, lines, or planes.
perpendicularity
A three-dimensional orientation tolerance that describes the allowable variability in the 90 degree angular relationship between a surface and a datum.
position
A three-dimensional location tolerance that describes the exact location with respect to a datum reference.
profile of a line
A two-dimensional profile tolerance that describes the allowable variability in the contour of the edge seen in the section view.
profile of a surface
A three-dimensional profile tolerance that describes the allowable variability in the contour of a surface.
profile tolerance
A group of geometric characteristics that describes the appearance from the two-dimensional section view.
regardless of feature size
The circumstance of the feature with any amount of material, for any size, during which the geometric tolerance applies.
runout tolerance
A group of geometric characteristics that describes surfaces around an axis.
straightness
A two-dimensional form tolerance that describes allowable variability in the shape and appearance of a line in a section view.
symmetry
A three-dimensional locational tolerance that describes the location of opposing points with respect to a datum reference.
tolerance
The acceptable variation from a specified dimension.
tolerance zone
The space created by the cushion of tolerance.
total runout
A three-dimensional runout tolerance that describes the distance between a surface and axis.