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Category: GD&T Symbol Rules and Examples

Articles related to GD&T symbol rules and walk-through examples of GD&T Symbols and their uses

Multiple Identical Features

by Crystal Bemis on January 4, 2024.

The #X designator is used to prevent redundant dimensions when a print has multiple identical features or a pattern. The number placed in front of the X represents the number of repetitive features that the dimension applies to.

Rule #1 and Derived Median Line Straightness

by Crystal Bemis on May 30, 2023.

"Why doesn’t Rule #1 apply to the straightness of a Derived Median Line?" In this article, we look at both surface straightness and straightness of a feature of size to understand why Derived Median Line Straightness overrules Rule #1 of GD&T.

Slope

by Crystal Bemis on February 15, 2023.

The slope modifying symbol is placed with a value to indicate that this value is controlled as a slope, or a “flat taper.” The value listed with the symbol is the ratio of the height change to length change.

Conical Taper

by Crystal Bemis on February 6, 2023.

The conical taper symbol is placed with a dimension value to indicate that the value is controlled as a standard taper. The value listed with the symbol is the ratio of the diameter change to length change.

Arc Length

by Crystal Bemis on January 5, 2023.

The Arc Length symbol, also known as the Arc Modifying symbol, is placed above a value to indicate that the arc’s length is being dimensioned on a curved outline. 

Parting Line

by Crystal Bemis on January 5, 2023.

A parting line is the location where separate parts of a mold or die come together. If the parting line is not dimensioned on the drawing, the location of the parting line is up to the manufacturer’s discretion.

Dimension Origin

by Crystal Bemis on December 14, 2022.

The dimension origin symbol is used to indicate where a dimension must be measured from. This symbol is used in place of a dimensional arrow leader to indicate the origin for measurement.

Depth

by Crystal Bemis on December 1, 2022.

The depth symbol is used to indicate a measurement from the bottom of a feature to the outer surface of a part.

Spherical Diameter

by Crystal Bemis on October 10, 2022.

The Spherical Diameter symbol is used to indicate that the Diameter is of a spherical, rather than circular, feature.

Diameter

by Crystal Bemis on October 4, 2022.

The diameter symbol is used to indicate that the size of a circular feature is being dimensioned using the diameter of that feature.

Controlled Radius

by Crystal Bemis on October 4, 2022.

The Controlled Radius symbol is a variation of the Radius, and is used when the surface of the contour is required to be a "fair" curve.

Spherical Radius

by Crystal Bemis on September 29, 2022.

The Spherical Radius is used to indicate that the Radius is of a spherical, rather than circular, feature.

Square

by Crystal Bemis on September 29, 2022.

The Square symbol is used to indicate a square feature on a drawing.

Radius

by Crystal Bemis on September 28, 2022.

The Radius symbol is used when a circular feature is dimensioned using the radius length.

Countersink

by Crystal Bemis on September 7, 2022.

A countersink consists of a conical hole that is coaxial to a cylindrical hole, where the angle of the cone is determined by the fastener to be used. The purpose of a countersink is to allow a fastener, typically a flathead screw, to sit slightly below the surface of the part.

Spotface

by Crystal Bemis on September 7, 2022.

A spotface is a very shallow flat-bottomed cylindrical hole that is larger than and coaxial to another cylindrical hole. Its purpose is to provide a flat mounting surface for mating parts, such as washers or pan head screws.

Counterbore

by Crystal Bemis on August 9, 2022.

The counterbore symbol is used on a drawing to indicate that a counterbore hole feature is required. A counterbore is a flat-bottomed cylindrical hole that is larger than and coaxial to another cylindrical hole.

Tangent Plane

by Jason Richter on July 8, 2022.

The Tangent Plane Symbol is used in conjunction with GD&T surface controls to indicate that a specific control is applied to a theoretical tangent plane simulated by the high points of irregular tangible surface rather than the actual elements of the surface themselves.