GD&T - Geometric Dimensioning and Tolerancing Material Condition Modifiers Questions and Answers

Question 1

Which of the following applications is the primary reason for specifying a geometric tolerance at Least Material Condition (LMC)?

Accepted Answer

To guarantee a minimum wall thickness is maintained between two features.

Answer

Least Material Condition (LMC) is used when a minimum amount of material is critical for the function of the part. A common application is controlling the position of a hole near the edge of a part to ensure the wall does not become too thin, which could compromise its strength.

Question 2

A feature control frame for a positional tolerance specifies Ø0.2 mm. No material condition modifier symbol is present. The controlled feature is a hole with a size of 15.0 ±0.3 mm. If an inspector measures the actual size of the hole to be 15.2 mm, what is the total permissible positional tolerance?

Accepted Answer

Ø0.2 mm

Answer

According to ASME Y14.5 Rule #2, Regardless of Feature Size (RFS) is the default condition for all geometric tolerances unless an MMC or LMC symbol is specified. At RFS, the stated geometric tolerance is the total tolerance available, regardless of the actual produced size of the feature. No bonus tolerance is gained as the feature departs from MMC or LMC.

Question 3

An external feature (a pin) is specified as Ø8.0 ±0.2 mm. A perpendicularity tolerance of Ø0.1 mm is applied at Least Material Condition (LMC). If the pin is produced at its largest size (Ø8.2 mm), what is the total allowable perpendicularity tolerance?

Accepted Answer

Ø0.5 mm

Answer

The LMC for the external pin is its smallest size: 8.0 - 0.2 = 7.8 mm. The actual produced size is 8.2 mm. The bonus tolerance is the amount of departure from LMC, which is |8.2 - 7.8| = 0.4 mm. The total allowable tolerance is the stated tolerance (0.1 mm) plus the bonus tolerance (0.4 mm), which equals 0.5 mm.

Question 4

What is the primary advantage of specifying a geometric tolerance of zero at Maximum Material Condition (e.g., ⌖|Ø0Ⓜ|A|B|C|)?

Accepted Answer

It forces the tolerance to be entirely dependent on the feature's departure from its MMC size.

Answer

Specifying a zero tolerance at MMC means that if the feature is produced at its exact MMC size, it must be located or oriented perfectly. The entire permissible geometric tolerance is derived as "bonus" tolerance from the feature's actual departure from its MMC size. This maximizes the available size tolerance for manufacturing while ensuring the functional requirement (like assembly) is met by controlling the virtual condition.

Question 5

A material condition modifier (MMC or LMC) can be applied in the feature control frame for which of the following geometric tolerances?

Accepted Answer

Perpendicularity

Answer

Material condition modifiers (MMC and LMC) can only be applied to tolerances that control features of size. Orientation tolerances (perpendicularity, parallelism, angularity), position, and straightness (when applied to an axis) are examples of tolerances that can use these modifiers. Form controls like flatness, circularity, and cylindricity control surfaces directly, are always applied RFS, and cannot use material condition modifiers.

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

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

GD&T - Geometric Dimensioning and Tolerancing Material Condition Modifiers Questions and Answers