GD&T Symbols Reference Guide - CNCCookbook

Last modified: March 15, 2024

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This is your convenient guide for Geometric Dimensioning and Tolerancing (GD&T) symbols.  Click on any link below to lean more about each GD&T symbol or concept. You can also download a PDF version of this information by clicking the button:

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Control Type

Characteristic

GD&T Symbol

Notes

Form

Flatness

An oblong metal rectangle with slight size variation.

Controls form (shape) of size and non-size features.

Datum reference is not allowed

Straightness

Simple blue line on white background.

Circularity (Roundness)

Blue circle outline on white background.

Controls form (shape) of size features only.

Datum reference is not allowed

Cylindricity

Blue line drawing of a circle with diagonal measuring line.

Orientation

No relation between features

Perpendicularity

Blue line with two perpendicular extensions.

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

Two diagonal lines perfectly aligned.

Angularity

Two intersecting lines forming a corner with a longer top line.

Location

Position

Blue target symbol with intersecting horizontal lines.

Locates center points, axes and median planes for size features. Can also control orientation.  See also True Position.

Profile of a Surface

Half dome metal surface with rounded edges and smooth finish against a white background.

Locates surfaces by describing a tolerance zone around the surface or line.

Can also be used to control size, form, and orientation based on datum reference.

Profile of a Line

Simple blue line graph with single curved line, varying y-axis values and visible x-axis is not marked.

Runout

Total Runout

Blue arrow pointing upwards, set against a light grey background with a subtle blue gradient effect.

Controls surface coaxiality

Can also control form and orientation of surfaces

Circular Runout

A blue arrow with tip on the left, pointing to the right.

Location of derived median points.

Concentricity

Blue concentric circle icon.

Locates derived median points of a feature

Not common, consider position, runout, or profile instead

Symmetry

Horizontal Equal Sign Symbol

Feature Control Frames: Modifiers

Symbol

Modifier

Notes

Black "F" within a white circle on a light grey background.

Free State

Only applies if part is otherwise restrained.

Black circle containing lowercase "L", thin white border.

Least Material Condition (LMC)

Useful to maintain minimum wall thickness

Circular icon with bold M.

Maximum Material Condition (MMC)

Provides bonus tolerance only for a feature of size

Black P in a circular symbol.

Projected Tolerance Zone

Useful on threaded holes for long studs

Black and white logo featuring bold sans-serif letter G within incomplete circular border.

Regardless of Feature Size (RFS)

Not part of the 1994 standard

Capital T letter in a black and white circle.

Tangent Plane

Useful for interfaces where form is not required

White circle with black border containing off-center small white rectangle with two narrow vertical lines.

Unilateral

Appears in the 2009 version and refers to unequal profile distribution

Feature Control Frame describes the conditions and tolerances of a geometric control on a part’s feature.

Notes:

"RFS" means regardless of feature size.  It simply means that whatever GD&T callout you make, it is controlled independently of the size dimension of the part.  RFS is the default condition of all geometric tolerances (by rule #2 of GD&T) and requires no callout.

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

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