GD&T - Geometric Dimensioning and Tolerancing Profile Tolerancing Applications Questions and Answers

Question 1

A designer needs to control the form of a complex, curved surface on a casting, but its location and orientation relative to other features are not critical. Which of the following GD&T callouts is most appropriate?

Accepted Answer

Profile of a surface with no datum references.

Answer

When profile of a surface is used without any datum references, it controls only the form of the surface. The tolerance zone is established relative to the true profile, but it is free to translate and rotate. This application is ideal for controlling the shape of a feature independently of its location or orientation.

Question 2

On an engineering drawing, two separated, non-continuous surfaces must be treated as a single plane. Which is the best GD&T application to control this coplanarity requirement?

Accepted Answer

Specifying a profile of a surface tolerance across both features.

Answer

Profile of a surface is the preferred method for controlling coplanarity. By applying a single profile tolerance to both surfaces (often indicated with a leader to a phantom line connecting them and a note like '2X'), it establishes a single tolerance zone that both surfaces must lie within, ensuring they are treated as one continuous plane.

Question 3

An engineer has specified both a profile of a line and a profile of a surface tolerance on the same airfoil feature. What is the typical relationship between these two controls?

Accepted Answer

The profile of a line tolerance is typically tighter than the profile of a surface tolerance.

Answer

When used together, the profile of a line tolerance provides a tighter control on individual cross-sectional elements of the surface, while the profile of a surface tolerance provides a looser overall control for the entire feature. This ensures critical cross-sections maintain a precise shape, while allowing for more variation across the full length of the surface.

Question 4

A part has a complex contour defined by basic dimensions. A composite profile tolerance is applied. What is the primary function of the lower segment in the feature control frame?

Accepted Answer

To refine the orientation and/or form of the profile within the larger tolerance zone defined by the upper segment.

Answer

In a composite profile tolerance, the upper segment locates the profile tolerance zone relative to the specified datums. The lower segment establishes a smaller tolerance zone that refines the form and/or orientation of the profile. This smaller zone is free to float within the larger location zone but must maintain its orientation to the datums repeated in the lower frame.

Question 5

Which of the following is the key difference between Profile of a Line and Profile of a Surface?

Accepted Answer

Profile of a Line is a 2D tolerance controlling individual cross-sections, while Profile of a Surface is a 3D tolerance controlling the entire surface.

Answer

The fundamental distinction is dimensionality. Profile of a line defines a two-dimensional tolerance zone that controls the form of a line element at any cross-section of a feature. Profile of a surface defines a three-dimensional tolerance zone that controls the form, and potentially orientation and location, of the entire surface.

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

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

GD&T - Geometric Dimensioning and Tolerancing Profile Tolerancing Applications Questions and Answers