GD&T Symbols and Rules 4

Question 1

A 'basic dimension' in GD&T is identified on a drawing by:

Accepted Answer

Enclosing the value in a rectangular box

Answer

Basic dimensions are shown enclosed in a rectangular box and represent the exact theoretically perfect value from which toleranced dimensions are measured.

Question 2

What is the function of the 'tangent plane' modifier (T in a circle) in a GD&T callout?

Accepted Answer

The tolerance applies to a plane contacting the high points of the surface

Answer

The tangent plane modifier means the tolerance controls the orientation of a tangent plane that contacts the high points of the surface, not the entire surface form.

Question 3

Which GD&T characteristic uses two coaxial cylinders as its tolerance zone?

Accepted Answer

Cylindricity

Answer

Cylindricity requires all points of a cylindrical surface to lie within two coaxial cylinders separated by the specified tolerance.

Question 4

The 'projected tolerance zone' symbol (P in a circle) is most commonly applied to:

Accepted Answer

Threaded holes or press-fit pins to control mating part interference

Answer

Projected tolerance zones extend the position tolerance above a hole to the height of the mating pin or fastener, preventing interference during assembly.

Question 5

In GD&T, the term 'virtual condition' for an external feature at MMC is calculated as:

Accepted Answer

MMC size plus the applicable geometric tolerance

Answer

For an external feature (shaft) at MMC, virtual condition equals the MMC size plus the geometric tolerance, representing the worst-case boundary.

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

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

GD&T Symbols and Rules 4