Material Condition Modifiers

What are Material Condition Modifiers?

The three modifiers are:

Understanding Material Conditions

For a Hole (Internal Feature)

• MMC = Smallest hole (most material remaining)
• LMC = Largest hole (least material remaining)

    ┌─────┐   ┌─────┐   ┌─────┐
    │ ○   │   │  ○  │   │  ○  │
    │small│   │ nom │   │large│
    └─────┘   └─────┘   └─────┘
      MMC      Nominal     LMC

For a Shaft (External Feature)

• MMC = Largest shaft (most material)
• LMC = Smallest shaft (least material)

    ┌─────┐   ┌─────┐   ┌─────┐
    │ ███ │   │ ██  │   │ █   │
    │large│   │ nom │   │small│
    └─────┘   └─────┘   └─────┘
      MMC      Nominal     LMC

MMC (Ⓜ) - Maximum Material Condition

The Concept

MMC provides bonus tolerance when a feature is NOT at its maximum material condition. The logic: if the hole is bigger (or shaft is smaller), there's more clearance for assembly, so position can be relaxed.

Example: Hole with MMC

Hole size: ⌀ 10.0 ± 0.2 (9.8 to 10.2)
Position: ⌀ 0.25 (M)

MMC = 9.8mm (smallest hole)

Total Tolerance = Stated Tolerance + (Actual Size - MMC Size)

LMC (Ⓛ) - Least Material Condition

The Concept

LMC provides bonus tolerance as a feature approaches maximum material. Used when minimum wall thickness or edge distance is critical.

Example: Hole Near an Edge

Hole size: ⌀ 10.0 ± 0.2 (9.8 to 10.2)
Position: ⌀ 0.30 (L)

LMC = 10.2mm (largest hole)

• Maintaining minimum wall thickness
• Ensuring minimum edge distance
• Thread engagement requirements

RFS (Ⓢ) - Regardless of Feature Size

The Concept

RFS means the tolerance applies at any size—no bonus tolerance is available. This is the default condition when no modifier is specified.

┌───┬────────┬────────┐     ┌───┬──────────┬────────┐
│ ⊕ │ 0.25   │ A      │  =  │ ⊕ │ 0.25 (S) │ A      │
└───┴────────┴────────┘     └───┴──────────┴────────┘
        (implied RFS)              (explicit RFS)

• Critical interfaces where bonus cannot be allowed
• Precision alignment features
• Non-mating features

MMC Modifier on Datums

The modifier can also apply to datum references:

┌───┬────────────┬──────────┐
│ ⊕ │ ⌀ 0.25 (M) │ A (M)    │
└───┴────────────┴──────────┘

Virtual Condition

For MMC:

• External feature VC = MMC + Geometric Tolerance
• Internal feature VC = MMC - Geometric Tolerance

Example: Pin
Size: ⌀ 10.0 ± 0.1 (MMC = 10.1)
Position: ⌀ 0.2 (M)

Virtual Condition = 10.1 + 0.2 = ⌀ 10.3

For LMC:

• External feature VC = LMC - Geometric Tolerance
• Internal feature VC = LMC + Geometric Tolerance

When to Use Each Modifier

Modifiers Allowed by Control Type

Key Takeaways

• MMC = Maximum Material Condition (smallest hole, largest shaft)
• LMC = Least Material Condition (largest hole, smallest shaft)
• RFS = Regardless of Feature Size (default, no bonus)
• Bonus tolerance = actual departure from MMC or LMC
• MMC is most common—used for assembly fits
• LMC is used for minimum wall/edge requirements
• Virtual condition defines worst-case boundary

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