Geometric Dimensioning and Tolerances: Symbols (ASTM Y14.5-2009)
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Angularity – The condition of a surface, centerplane or axis being exactly at a specified angle |
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Circularity – A condition where all points of a surface of revolution, at any section perpendicular to a common axis, are equidistant from that axis. |
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Concentricity – The condition where the median points of all diametrically opposed elements of a cylinder (or a surface of revolution) are congruent with the axis of a datum feature. |
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Cylindricity – A condition of a surface of revolution in which all points of the surface are equidistant from a common axis. |
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Flatness – The condition of a surface having all of its elements in one plane.
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Parallelism – The condition that results when a surface, axis or centerplane is exactly parallel to a datum. |
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Perpendicularity – The condition that results when a surface, axis, or centerplane is exactly 90° to a datum. |
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Position – The zone within which the axis or center plane of a feature is permitted to vary from true (theoretically exact) position. |
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Profile of a Line Control – A geometric tolerance that limits the amount of error for line elements relative to their true profile. |
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Profile of a Surface Control – A geometric tolerance that limits the amount of error a surface can have relative to its true profile. |
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Circular Runout – A composite control that affects the form, orientation, and location of circular elements of a part feature relative to a datum axis. |
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Straightness (Axis or Centerplane) – The condition where an axis is a straight line (or, in the case of a centerplane, each line element is a straight line). |
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Symmetry – The condition where the median points of all opposed elements of two or more feature surfaces are congruent with the axis or centerplane of a datum feature. |
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Total Runout – A composite control affecting the form, orientation, and location of all surface elements of a diameter (or surface) relative to a datum axis. |
Geometric Dimensionsing and Tolerances: Modifiers (ASTM Y14.5-2009)
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All-Around Symbol – A circle placed on the bend of the leader line of a profile control. |
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Basic Dimension – A numerical value used to describe the theoretically exact size, true profile, orientation, or location of a feature or datum target. |
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Between Symbol – A double ended arrow that indicates the tolerance zone extends to include multiple surfaces. |
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Controlled Radius – A radius with no flats or reversals allowed. The symbol for a controlled radius is “CR.” |
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Datum Feature – A part feature that contacts a datum. |
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Datum Target – A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes. |
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Feature Control Frame – A rectangular box that is divided into compartments within which the geometric characteristic symbol, tolerance value, modifiers, and datum references are placed. |
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Least Material Condition – The condition in which a feature of size contains the least amount of material everywhere within the stated limits of size. |
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Maximum Material Condition – The condition in which a feature of size contains the maximum amount of material everywhere within the stated limits of size. |
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Projected Tolerance Zone – A tolerance zone that is projected above the part surface. |
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Radius – A straight line extending from the center of an arc or circle to its surface. |
Reference Specification for Geometric Dimensioning and Tolerances:
ASTM Y14.5-2009
