Free GD&T Calculator [ + Much More ]
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
Characteristic
GD&T Symbol
Notes
Form
Controls form (shape) of size and non-size features.
Datum reference is not allowed
Controls form (shape) of size features only.
Datum reference is not allowed
Orientation
No relation between features
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.
Location
Locates center points, axes and median planes for size features. Can also control orientation. See also True Position.
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.
Runout
Controls surface coaxiality
Can also control form and orientation of surfaces
Location of derived median points.
Locates derived median points of a feature
Not common, consider position, runout, or profile instead
Feature Control Frames: 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
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
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