KEY TERMS
The minimum amount of clearance, or the maximum amount of interference, between two mating parts.
Allowance
Geometric dimensioning and tolerancing
GD&T
GD&T specifications used to control the location of workpiece features related to other workpiece features.
Location tolerances
A theoretical, ideal dimension shown on a print or an engineering drawing.
Basic size
A rectangular box with sections for a geometric tolerancing symbol, the amount of the tolerance, and the reference to a specific datum (if required), which is used to show how to control the size and/or shape of a particular feature of a part.
Feature control frame
GD&T specifications used to control the location of workpiece features related to other workpiece features.
Location tolerances
The relationship of tightness or looseness between the sizes of two mating parts.
Class of fit
A situation in which a feature of size contains the most workpiece material within its tolerance.
Maximum material condition (MMC)
GD&T specifications that relate one part feature to another part feature or features through use of datums.
Orientation tolerances
In GD&T, a plane from which dimensions are referenced, shown on a drawing as a capital letter inside a square with a line extending to the part feature.
Datum
A part feature that is either cylindrical or contains two opposing parallel surfaces.
Feature of size
GD&T specifications requiring a workpiece surface to be a particular shape within a certain tolerance zone.
Profile tolerances
GD&T position condition requiring that the specified position tolerance zone must be maintained no matter the size of the feature.
Regardless of feature size, or RFS
A situation in which a feature of size contains the least material within its tolerance.
Least material condition (LMC)
Tolerances used to check for runout of diameters related to a center axis, another diameter, or perpendicular surface.
Runout tolerances