Main GD&T Symbols in the Y14.5 Standard
Angularity
Is the condition of a surface, axis, or centerplane, which is at a specified angle from a datum plane or axis.
Circularity
Describes the condition on a surface of revolution (cylinder, cone, sphere) where all points of the surface intersected by any plane.
Cylindricity
Describes a condition of a surface of revolution in which all points of a surface are equidistant from a common axis.
Flatness
Is the condition of a surface having all elements in one plane.
Parallelism
Is the condition of a surface, line, or axis, which is equidistant at all points from a datum plane or axis.
Perpendicularity
Is the condition of a surface, axis, or line, which is 90 deg. From a datum plane or a datum axis.
Position
Defines a zone within which the axis or center plane of a feature is permitted to vary from true (theoretically exact) position.
Profile of a Line
Is the condition permitting a uniform amount of profile variation, ether unilaterally or bilaterally, along a line element of a feature.
Profile of a Surface
Is the condition permitting a uniform amount of profile variation, ether unilaterally or bilaterally, on a surface.
Runout
Is the composite deviation from the desired form of a part surface of revolution through on full rotation (360 deg) of the part on a datum axis.
Total Runout
The simultaneous composite control of all elements of a surface at all circular and profile measuring positions as the part is rotated through 360.
Straightness
A condition where an element of a surface or an axis is a straight line.
GD&T Symbols Removed in Y14.5-2018
Concentricity
Describes a condition in which two or more features , in any combination, have a common axis. No longer available in the 2018 standard.
Symmetry
Is a condition in which a feature (or features) is symmetrically disposed about the center plane of a datum feature. No longer available in the 2018 standard.