GD&T Material Condition Modifiers 4

Question 1

Which symbol is used in a feature control frame to indicate the Maximum Material Condition modifier?

Accepted Answer

Ⓜ

Answer

The circled M symbol (Ⓜ) is used in a feature control frame to designate the MMC modifier per ASME Y14.5.

Question 2

In a functional gauge for a position tolerance at MMC, the gauge pin diameter for a hole pattern would equal:

Accepted Answer

The MMC of the hole minus the positional tolerance

Answer

The gauge pin diameter equals the virtual condition of the hole = MMC hole size minus the positional tolerance (for an internal feature).

Question 3

A feature control frame reads: position | 0.3Ⓜ | A | BⓂ. What does the Ⓜ on datum B indicate?

Accepted Answer

Datum shift is allowed based on datum B's departure from MMC

Answer

An MMC modifier on a datum reference (B Ⓜ) permits the datum reference frame to shift by the amount datum feature B departs from its MMC.

Question 4

Under the envelope principle (Rule #1), a feature of size must not violate its MMC perfect form boundary. Which material condition modifier explicitly overrides this rule?

Accepted Answer

Free State — it suspends Rule #1 for flexible parts

Answer

The Free State modifier (Ⓕ) suspends Rule #1 for non-rigid (flexible) parts measured in the free (unconstrained) state.

Question 5

Two mating parts use a clearance fit. The designer wants maximum allowable positional error when parts are easiest to assemble. Which modifier should be applied?

Accepted Answer

MMC

Answer

MMC provides maximum bonus tolerance when parts are at their smallest shaft / largest hole (most clearance), maximizing allowed position error when assembly is easiest.

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

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

GD&T Material Condition Modifiers 4