Gd & t definitions

COMMON TERMS AND DEFINITIONS



Basic Dimension
A numerical value used to describe the theoretically exact size, profile, orientation, or location of a feature or datum target. It is the basisfrom which permissible variations are established by tolerances on other dimensions, in notes, or in feature control frames.


Datum
A theoretically exact point, axis, or plane derived from thetrue geometric counterpart of a specified datum feature. A datum is the origin from which the location or geometric characteristics of features of a part are established.


Datum Target
Aspecific line, or area on a part used to establish a datum.


Maximum Material Condition (MMC)
The condition in which a feature of size contains the maximum amount of material within the stated limitsof size-for example, minimum hole diameter, maximum shaft diameter.


Least Material Condition (LMC)
The condition in which a feature of size contains the least amount of material within thestated limits of size-for example, maximum hole diameter, minimum shaft diameter.


Regardless of Feature Size (RFS):
The term used to indicate that a geometric tolerance or datum reference appliesat any increment of size of the feature within its size tolerance.
Full Indicator Movement
The total movement of an indicator when appropriately applied to a surface to measure its variations(formerly called total indicator reading-TIR).
Virtual Condition
The boundary generated by the collective effects of the specified MMC limit of size of a feature and any applicable geometric tolerances.Feature Control Frame
The feature control frame consists of: A) type of control (geometric characteristic), B) tolerance zone, C) tolerance zone modifiers (i.e., MMC or RFS), D) datum referencesif applicable and any datum reference modifiers.
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PROFILE TOLERANCES



Profile of a Line
A uniform two dimensional zone limited by two...