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GD&T Tips and Symbols

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GD&T Symbols and Definitions

GD&T Symbol - All Around Symbol

All Around Symbol

Indicates that a tolerance applies to surfaces all around the part.

GD&T Symbol - All Over Specification

All Over Specification

In addition to a general profile of a surface tolerance there is the option of specifying that the tolerance applies all over on the field of the drawing. It is important to realize that this specification, whether in a general note or on the field of the drawing, applies UNLESS OTHERWISE SPECIFIED.

GD&T Symbol - All Around This Side of Party Line

All Around This Side of Parting Line

To apply a requirement to all features all around one side of a parting line, the graphical symbol for all around this side of parting line is indicated on the leader line.

GD&T Symbol - All Over This Side of Parting Line

All Over This Side of Parting Line

To apply a requirement to all features all over one side of a parting line, the graphical symbol for all over this side of parting line is indicated on the leader line.

GD&T Symbol - Angularity

Angularity

Is the condition of a surface, axis, or centerplane, which is at a specified angle from a datum plane or axis.

GD&T Symbol - Arc Length

Arc Length

Indicating that a dimension is an arc length measured on a curved outline. The symbol is placed above the dimension.

GD&T Symbol - Basic Dimension

Basic Dimension

Used to describe the exact size, profile, orientation or location of a feature. A basic dimension is always associated with a feature control frame or datum target. (Theoretically exact dimension in ISO)

GD&T Symbol - Between

Between

To indicate that a profile tolerance applies to several contiguous features, letters may designate where the profile tolerance begins and ends. These letters are referenced using the between symbol (since 1994) or the word between on drawings made to earlier versions of the Standard.

GD&T Symbol - Circularity

Circularity

Describes the condition on a surface of revolution (cylinder, cone, sphere) where all points of the surface intersected by any plane.

GD&T Symbol - Concentricity

Concentricity

Describes a condition in which two or more features , in any combination, have a common axis. No longer available in the 2018 standard.

GD&T Symbol - Conical Taper

Conical Taper

Is used to indicate taper for conical tapers. This symbol is always shown with the vertical leg to the left.

GD&T Symbol - Continuous Feature

Continuous Feature

The note CONTINUOUS FEATURE or the continuous feature symbol is used to identify a group of two or more features of size where there is a requirement that they be treated geometrically as a single feature of size. Although the definition only mentions features of size, there is an example of CF being applied to a pair of planar features.

GD&T Symbol - Controlled Radius

Controlled Radius

Creates a tolerance zone defined by two arcs (the minimum and maximum radii) that are tangent to the adjacent surfaces. Where a controlled radius is specified, the part contour within the crescent-shaped tolerance zone must be a fair curve without flats or reversals. Additionally, radii taken at all points on the part contour shall neither be smaller than the specified minimum limit nor larger than the maximum limit.

GD&T Symbol - Counterbore / Spotface

Counterbore / Spotface

Is used to indicate a counterbore or a spotface. The symbol precedes the dimension of the counterbore or spotface, with no space.

GD&T Symbol - Countersink

Countersink

Is used to indicate a countersink. The symbol precedes the dimensions of the countersink with no space.

GD&T Symbol - Cylindricity

Cylindricity

Describes a condition of a surface of revolution in which all points of a surface are equidistant from a common axis.

GD&T Symbol - Datum Feature

Datum Feature

Is the actual component feature used to establish a datum.

GD&T Symbol - Datum Target

Datum Target

Is a specified point, line, or area on a part that is used to establish the Datum Reference Plane for manufacturing and inspection operations.

GD&T Symbol - Datum Target

Datum Target Alternate

Is a specified point, line, or area on a part that is used to establish the Datum Reference Plane for manufacturing and inspection operations.

GD&T Symbol - Datum Translation Symbol

Datum Translation Symbol

This symbol indicates that a datum feature simulator is not fixed at its basic location and shall be free to translate.

GD&T Symbol - Depth / Deep

Depth / Deep

Is used to indicate that a dimension applies to the depth of a feature. This symbol precedes the depth value with no space in between.

GD&T Symbol - Diameter

Diameter

Indicates a circular feature when used on the field of a drawing or indicates that the tolerance is diametrical when used in a feature control frame.

GD&T Symbol - Dimension Origin

Dimension Origin

Signifies that the dimension originates from the plane established by the shorter surface and dimensional limits apply to the other surface.

GD&T Symbol - Dynamic Profile Tolerance Zone Modifier.png

Dynamic Profile Tolerance Zone Modifier

New in 2018 and is used with profile tolerancing. The function of the dynamic profile is to allow form to be controlled independent of size.

GD&T Symbol - Feature Control Frame

Feature Control Frame

Is a rectangular box containing the geometric characteristics symbol, and the form, runout or location tolerance. If necessary, datum references and modifiers applicable to the feature or the datums are also contained in the box.

GD&T Symbol - Flatness

Flatness

Is the condition of a surface having all elements in one plane.

GD&T Symbol - Free State Variations

Free State Variations

Is a term used to describe distortion of a part after removal of forces applied during manufacture.

GD&T Symbol - From-To

From-To

New in 2018 for the direction in which a tolerance or other requirement applies.

GD&T Symbol - Independency Symbol

Independency Symbol

The Independency symbol is applied to the size dimension in order to invoke the principle of independency to regular features of size and override Rule #1.

GD&T Symbol - Least Material Condition (LMC)

Least Material Condition (LMC)

Implies that condition of a part feature of size wherein it contains the least (minimum) amount of material, examples, largest hole size and smallest shaft size. It is opposite to maximum material condition.

GD&T Symbol - Maximum Material Condition (MMC)

Maximum Material Condition (MMC)

Is that condition of a part feature wherein it contains the maximum amount of material within the stated limits of size. That is: minimum hole size and maximum shaft size.

GD&T Symbol - Movable Datum Targets

Movable Datum Targets

The movable datum target symbol may be used to indicate movement of the datum target datum feature simulator.

GD&T Symbol - Number of Places

Number of Places

The X is used along with a value to indicate the number of times a dimension or feature is repeated on the drawing.

GD&T Symbol - Parallelism

Parallelism

Is the condition of a surface, line, or axis, which is equidistant at all points from a datum plane or axis.

GD&T Symbol - Parting Lines

Parting Lines

Are depicted on casting, forging, and molded part drawings as a phantom line extending beyond the part in applicable views, with the parting line symbol added.

GD&T Symbol - Perpendicularity

Perpendicularity

Is the condition of a surface, axis, or line, which is 90 deg. From a datum plane or a datum axis.

GD&T Symbol - Position

Position

Defines a zone within which the axis or center plane of a feature is permitted to vary from true (theoretically exact) position.

GD&T Symbol - Profile of a Line

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.

GD&T Symbol - Profile of a Surface

Profile of a Surface

Is the condition permitting a uniform amount of profile variation, ether unilaterally or bilaterally, on a surface.

GD&T Symbol - Projected Tolerance Zone

Projected Tolerance Zone

Applies to a hole in which a pin, stud, screw, etc., is to be inserted. It controls the perpendicularity of the hole to the extent of the projection from the hole and as it relates to the mating part clearance. The projected tolerance zone extends above the surface of the part to the functional length of the pin, stud, and screw relative to its assembly with the mating part.

GD&T Symbol - Radius

Radius

Creates a zone defined by two arcs (the minimum and maximum radii). The part surface must lie within this zone.

GD&T Symbol - Reference Dimension

Reference Dimension

A dimension usually without tolerance, used for information purposes only. It does not govern production or inspection operations. (Auxiliary dimension in ISO)

GD&T Symbol - Regardless Of Feature Size (RFS)

Regardless Of Feature Size (RFS)

The condition where the tolerance of form, runout or location must be met irrespective of where the feature lies within its size tolerance.

GD&T Symbol - Runout

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.

GD&T Symbol - Slope

Slope

Is used to indicate slope for flat tapers. This symbol is always shown with the vertical leg to the left.

GD&T Symbol - Spherical Diameter

Spherical Diameter

Shall precede the tolerance value where the specified tolerance value represents spherical zone. Also, a positional tolerance may be used to control the location of a spherical feature relative to other features of a part. The symbol for spherical diameter precedes the size dimension of the feature and the positional tolerance value, to indicate a spherical tolerance zone.

GD&T Symbol - Spherical Radius

Spherical Radius

Precedes the value of a dimension or tolerance.

GD&T Symbol - Spotface

Spotface

Counterbore and spotface previously used the same symbol. A spotface now looks like the counterbore symbol with the addition of the letters SF.

GD&T Symbol - Square

Square

Is used to indicate that a single dimension applies to a square shape. The symbol precedes the dimension with no space between.

GD&T Symbol - Statistical Tolerance

Statistical Tolerance

Is the assigning of tolerances to related components of an assembly on the basis of sound statistics (such as the assembly tolerance is equal to the square root of the sum of the squares of the individual tolerances). By applying statistical tolerancing, tolerances of individual components may be increased or clearances between mating parts may be reduced. The increased tolerance or improved fit may reduce manufacturing cost or improve the product's performance, but shall only be employed where the appropriate statistical process control will be used. Therefore, consideration should be given to specifying the required Cp and /or Cpk or other process performance indices.

GD&T Symbol - Straightness

Straightness

A condition where an element of a surface or an axis is a straight line.

GD&T Symbol - Symmetry

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.

GD&T Symbol - Tangent Plane

Tangent Plane

Indicating a tangent plane is shown. The symbol is placed in the feature control frame following the stated tolerance.

GD&T Symbol - Target Point

Target Point

Indicates where the datum target point is dimensionally located on the direct view of the surface.

GD&T Symbol - Total Runout

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.

GD&T Symbol - Unilateral and Unequally Disposed Profile Tolerance

Unilateral and Unequally Disposed Profile Tolerance

To indicate that a profile of a surface tolerance is not symmetrical about the true profile, this symbol is used. The first value in the feature control frame is the total width of the profile tolerance. The value following the symbol is the amount of the tolerance that is in the direction that would allow additional material to be added to the true profile.

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