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GD&T Symbols Definition List

Control Type	Characteristic	GD&T Symbol	Notes
Form	Flatness		Controls form (shape) of size and non-size features. Datum reference is not allowed
	Straightness
	Circularity (Roundness)		Controls form (shape) of size features only. Datum reference is not allowed
	Cylindricity
Orientation No relation between features	Perpendicularity		Controls orientation (tilt) of surfaces, axes, or median planes for size and non-size features. Datum reference required. Optional: Angularity symbol may be used for all orientation controls.
	Parallelism
	Angularity
Location	Position		Locates center points, axes and median planes for size features. Can also control orientation.
	Profile of a Surface		Locates surfaces. Can also be used to control size, form, and orientation basaed on datum reference.
	Profile of a Line
Runout	Total Runout		Controls surface coaxiality Can also control form and orientation of surfaces
Runout	Circular Runout
Location of derived median points.	Concentricity		Locates derived median points of a feature Not common, consider position, runout, or profile instead
Location of derived median points.	Symmetry

Feature Control Frame Modifiers

Symbol	Modifier	Notes
	Free State	Only applies if part is otherwise restrained.
	Least Material Condition (LMC)	Useful to maintain minimum wall thickness
	Maximum Material Condition (MMC)	Provides bonus tolerance only for a feature of size
	Projected Tolerance Zone	Useful on threaded holes for long studs
	Regardless of Feature Size (RFS)	Not part of the 1994 standard
	Tangent Plane	Useful for interfaces where form is not required
	Unilateral	Appears in the 2009 version and refers to unequal profile distribution

These GD&T symbols are provided as a reference for CNCCookbook’s free GD&T Tutorial. To learn what they mean, clicks the links, read on or check the Table of Contents for more information.

GD&T Tutorial Home GD&T Symbols