The Beginner’s Guide to GD&T Symbols Quick Ref – CNCCookbook

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GD&T Tutorial Home          GD&T Symbols

CNCCookbook Beginner’s Guide to GD&T: Symbols

Geometric Dimensioning and Tolerancing (GD&T) Symbol Quick Reference

 

Control Type

 

Characteristic 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

Circular Runout
Location of derived median points. Concentricity Locates derived median points of a feature

Not common, consider position, runout, or profile instead

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

GD&T Table of Contents

 

The Beginner’s Guide to GD&T Symbols Quick Ref – CNCCookbook
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