GD&T Symbols Reference Table

Here’s a detailed GD&T Symbols (Geometric Dimensioning and Tolerancing) Table in English, based on ASME Y14.5-2018 and ISO 1101 standards:

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GD&T Symbols

GD&T Symbols Reference Table
Symbol	Name	Category	Description
⏀	Straightness	Form	Controls deviation of a linear feature (e.g., axis or edge).
◯	Circularity (Roundness)	Form	Controls roundness of a circular cross-section.
⌭	Cylindricity	Form	Controls the shape of a cylindrical surface (combines roundness + straightness).
⌓	Flatness	Form	Controls the flatness of a planar surface.
↗	Profile of a Line	Profile	Controls the deviation of an arbitrary curve.
⌖	Profile of a Surface	Profile	Controls the deviation of an arbitrary 3D surface.
⫱	Angularity	Orientation	Controls the angular deviation of a feature relative to a datum.
⊥	Perpendicularity	Orientation	Controls 90° deviation from a datum plane/axis.
∥	Parallelism	Orientation	Controls parallelism between a feature and a datum.
◎	Position (True Position)	Location	Controls the deviation of a feature (e.g., hole) from its true position.
⊕	Concentricity	Location	Controls the coaxiality of two cylindrical features (deprecated; use Position).
⌯	Symmetry	Location	Controls symmetry about a central plane (deprecated; use Position).
⇔	Circular Runout	Runout	Controls radial/axial wobble in a single cross-section of a rotating part.
⌖	Total Runout	Runout	Controls combined radial + axial wobble across an entire rotating surface.

Additional Modifiers & Symbols
Symbol	Name	Description
⌴	Datum Feature	Identifies a datum reference (e.g., A, B, C).
(Ⓜ)	MMC (Maximum Material Condition)	Allows bonus tolerance as material decreases.
(⒍)	LMC (Least Material Condition)	Ensures minimum wall thickness by adding tolerance at LMC.
(⒔)	RFS (Regardless of Feature Size)	Tolerance applies independent of feature size (default condition).
↗︎	Tangent Plane	Specifies control of a tangent plane (used with Profile).

Key Notes

Form Tolerances (e.g., Flatness, Straightness) do not require datums.
Orientation/Location Tolerances (e.g., Perpendicularity, Position) must reference datums.
Runout Tolerances are used for rotating components to ensure functional fit.

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