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GD&T Symbols Definition List
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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 |
|
| 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
|
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 |  |
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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
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Symbol
|
Modifier
|
Notes
|
 |
Free State
|
Only applies if part is otherwise restrained. |
 |
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
|
Useful on threaded holes for long studs |
 |
Regardless of Feature Size (RFS)
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Not part of the 1994 standard |
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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
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