GD&T Material Condition Modifiers 2 — Questions and Answers
Question 1: 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?
- 0.2 mm
- 0.4 mm (Correct answer)
- 0.6 mm
- 0.8 mm
Correct 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.
Question 2: Which material condition modifier requires the tolerance zone to remain fixed regardless of the feature's actual size?
- MMC
- LMC
- RFS (Correct answer)
- Free State
Correct answer: RFS
RFS (Regardless of Feature Size) means the specified tolerance applies at every actual mating size with no bonus tolerance.
Question 3: On an internal feature (hole), the LMC condition corresponds to which of the following?
- Largest allowable hole diameter
- Smallest allowable hole diameter (Correct answer)
- Virtual condition boundary
- Midpoint of the tolerance range
Correct answer: Smallest allowable hole diameter
For a hole (internal feature), LMC is the smallest diameter because that represents the least material removed.
Question 4: The virtual condition of an external feature controlled at MMC is calculated as:
- MMC size minus the geometric tolerance
- MMC size plus the geometric tolerance (Correct answer)
- LMC size plus the geometric tolerance
- LMC size minus the geometric tolerance
Correct 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.
Question 5: Which modifier, when applied to a datum feature, allows the datum to shift as the feature departs from its referenced material condition?
- Free State (F)
- RFS
- MMC on a datum reference (Correct answer)
- Statistical Tolerance
Correct 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.
Question 6: 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)?
- 0.1 mm
- 0.3 mm
- 0.5 mm (Correct answer)
- 0.4 mm
Correct 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.
Question 7: Under ASME Y14.5-2009, when no material condition modifier is specified for a feature of size, which modifier is implied?
- MMC
- LMC
- RFS (Correct answer)
- Free State
Correct answer: RFS
ASME Y14.5-2009 established RFS as the default when no modifier symbol is shown in the feature control frame.
GD&T Material Condition Modifiers 2
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?