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GD&T Symbols Reference Chart
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:
Control Type
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Characteristic | GD&T Symbol | Notes |
Form | Flatness | ![]() |
Controls form (shape) of size and non-size features. Datum reference is not allowed |
Straightness | ![]() |
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Circularity (Roundness) | ![]() |
Controls form (shape) of size features only. Datum reference is not allowed |
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Cylindricity | ![]() |
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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 | ![]() |
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Angularity | ![]() |
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Location
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Position | ![]() |
Locates center points, axes and median planes for size features. Can also control orientation. See also True Position. |
Profile of a Surface | ![]() |
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. |
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Profile of a Line | ![]() |
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Runout | Total Runout | ![]() |
Controls surface coaxiality Can also control form and orientation of surfaces |
Circular Runout | ![]() |
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Location of derived median points. | Concentricity | ![]() |
Locates derived median points of a feature Not common, consider position, runout, or profile instead |
Symmetry | ![]() |
Feature Control Frames: Modifiers
Symbol
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Modifier
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Notes
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Free State
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Only applies if part is otherwise restrained. |
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Least Material Condition (LMC)
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Useful to maintain minimum wall thickness |
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Provides bonus tolerance only for a feature of size | |
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Projected Tolerance Zone
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Useful on threaded holes for long studs |
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Regardless of Feature Size (RFS)
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Not part of the 1994 standard |
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Tangent Plane
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Useful for interfaces where form is not required |
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Unilateral
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Appears in the 2009 version and refers to unequal profile distribution |
A 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