Material Condition Modifiers Flashcards

A shaft has a true position tolerance of 0.2 MMC. At MMC the shaft diameter is 20.0 mm. If the shaft is produced at 19.8 mm, what is the total allowable position tolerance?

Answer: 0.4 mm

The shaft has departed 0.2 mm from MMC, so the bonus tolerance (0.2) is added to the stated tolerance (0.2), giving 0.4 mm total.

Which material condition modifier requires the tolerance zone to remain fixed regardless of the feature's actual size?

Answer: RFS

RFS (Regardless of Feature Size) means the specified tolerance applies at every actual mating size with no bonus tolerance.

On an internal feature (hole), the LMC condition corresponds to which of the following?

Answer: Smallest allowable hole diameter

For a hole (internal feature), LMC is the smallest diameter because that represents the least material removed.

The virtual condition of an external feature controlled at MMC is calculated as:

Answer: MMC size plus the geometric tolerance

For an external feature (e.g., shaft) at MMC, the virtual condition = MMC size + geometric tolerance, representing the worst-case boundary.

Which modifier, when applied to a datum feature, allows the datum to shift as the feature departs from its referenced material condition?

Answer: MMC on a datum reference

Applying MMC (or LMC) to a datum reference in a feature control frame allows datum shift equal to the departure from that material condition.

A hole has a diameter tolerance of 10.0–10.4 mm and a perpendicularity tolerance of 0.1 at MMC. What is the perpendicularity tolerance when the hole is produced at 10.4 mm (LMC)?

Answer: 0.5 mm

At LMC (10.4 mm) the departure from MMC (10.0) is 0.4 mm, adding 0.4 bonus to the 0.1 stated tolerance gives 0.5 mm.

Under ASME Y14.5-2009, when no material condition modifier is specified for a feature of size, which modifier is implied?

Answer: RFS

ASME Y14.5-2009 established RFS as the default when no modifier symbol is shown in the feature control frame.

The term 'resultant condition' for an internal feature controlled at MMC refers to:

Answer: The worst-case inner boundary considering both size and geometric tolerance

The resultant condition of an internal feature at MMC is the worst-case inner boundary = LMC size minus the maximum allowable tolerance.

Which of the following GD&T tolerances is most commonly applied with an MMC modifier to take advantage of bonus tolerance for assembly purposes?

Answer: True Position

True position is most commonly modified with MMC because assembly clearance naturally increases when mating features depart from MMC.

An LMC modifier is most useful for controlling which engineering concern?

Answer: Minimum wall thickness and edge distance

LMC ensures minimum material (wall thickness, edge distance) is maintained, making it useful for structural or sealing concerns.

A pin (external feature) has a size range of 9.9–10.0 mm. At MMC, the straightness tolerance is 0.05 mm. What is the maximum allowable straightness tolerance when the pin measures 9.9 mm?

Answer: 0.15 mm

At 9.9 mm (LMC), departure from MMC is 0.1 mm; adding this bonus to 0.05 mm gives 0.15 mm total.

Which boundary is established by the MMC size of an external feature PLUS its applicable geometric tolerance?

Answer: Outer boundary / Virtual condition

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

When an MMC modifier is applied to a tolerance of flatness, what happens?

Answer: It is invalid — flatness cannot use MMC

Flatness is a surface form control that does not reference feature size, so applying MMC to flatness is not allowed per ASME Y14.5.

Datum shift is analogous to bonus tolerance. Which statement correctly describes datum shift?

Answer: It is the allowable movement of the true datum axis/plane due to the datum feature's departure from its referenced material condition

Datum shift is the permissible translation/rotation of the datum reference frame that occurs when the datum feature departs from its referenced material condition.

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

Answer: Ⓜ

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

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

Answer: The MMC of the hole minus the positional tolerance

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

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

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

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.

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?

Answer: Free State — it suspends Rule #1 for flexible parts

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

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?

Answer: MMC

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

A straightness callout of 0.1 Ⓜ is applied to a shaft with MMC of 25.0 mm and LMC of 24.6 mm. What is the maximum possible derived median line straightness tolerance?

Answer: 0.5 mm

Maximum bonus = MMC (25.0) − LMC (24.6) = 0.4 mm; total max = 0.1 + 0.4 = 0.5 mm.