GD&T Geometric Symbols & Notation

Question 1

What does the symbol ⌀ represent in GD&T?

Accepted Answer

Diameter of a circle.

Answer

In Geometric Dimensioning and Tolerancing (GD&T), the symbol ⌀ is universally recognized as the diameter symbol. It is used to indicate that a dimension refers to the diameter of a circular feature, such as a hole, shaft, or boss. This ensures clarity and precision in engineering drawings, distinguishing it from a radius or other linear dimensions.

Question 2

What does the symbol x signify in GD&T?

Accepted Answer

Multiplication factor for tolerances.

Answer

In GD&T, the 'x' symbol, often appearing before a dimension (e.g., 2x ⌀10), indicates a multiplication factor. It specifies that a feature or pattern is repeated a certain number of times. For example, '2x ⌀10' means there are two holes, each with a diameter of 10 units, and the tolerance applies to both.

Question 3

Which symbol is used to indicate flatness in GD&T?

Accepted Answer

⎯⎯.

Answer

The symbol ⎯⎯ (two parallel lines) is the standard GD&T symbol for flatness. This geometric characteristic tolerance specifies how much a surface is permitted to deviate from a perfect plane. It ensures that all points on the designated surface lie within two parallel planes, thereby controlling the overall evenness of the feature.

Question 4

What is the purpose of the perpendicularity symbol in GD&T?

Accepted Answer

Ensures a feature is square to a reference surface.

Answer

The perpendicularity symbol (⊥) in GD&T is a form tolerance that controls the orientation of a feature relative to a datum (a reference feature). It specifies that a surface, axis, or center plane must be at a 90-degree angle to a designated datum feature. This ensures that components align correctly during assembly and function as intended.

Question 5

What does the angularity symbol control in GD&T?

Accepted Answer

Angle between a feature and the reference plane.

Answer

The angularity symbol (∠) in GD&T is an orientation tolerance that controls the angle of a feature relative to a datum plane or axis. It specifies the allowable deviation from a true angle, typically a non-90-degree angle, between the feature and the specified reference. This ensures that angled surfaces or features are correctly oriented for proper assembly and function.

(GD&T) Geometric Dimensioning and Tolerancing Certification Practice Test

(GD&T) Geometric Dimensioning and Tolerancing Certification Practice Test

GD&T Geometric Symbols & Notation