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GD&T Symbols Definition List
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. |
Profile of a Surface | ![]() |
Locates surfaces.
Can also be used to control size, form, and orientation basaed 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 Frame 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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Maximum Material Condition (MMC)
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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 |
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