GDT:Modifiers Overview
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| Symbol | Modifiers Overview |
|---|---|
| Type | Modifiers |
| Category | Modifiers |
| Standard | ASME Y14.5 |
| Author | Admin |
| Datums | Datum reference modifiers and material condition modifiers |
| Modifiers | MMC, LMC, RFS, projected tolerance zone, tangent plane, unequal, free state, statistical |
| Tolerance zone | Modifier-dependent zone sizing and boundaries |
| Image | |
| Common mistakes | Using prohibited modifiers; mixing incompatible modifiers; missing diameter where required |
| Related | GDT:Position |
Summary
Modifiers refine how tolerance zones are sized, oriented, or interpreted.
Definition
Modifiers are symbols or text applied to tolerance values or datum references that change how a tolerance is evaluated, such as material condition, projected tolerance zones, or profile distribution.
When to use it
Use modifiers when functional requirements require bonus tolerance, constrained simulators, or special zone definitions.
Examples
Example: MMC on a hole position
Position with MMC allows bonus tolerance as the hole departs from MMC.
Example: Projected tolerance zone
Projected tolerance zone used for fastener engagement.
Common mistakes
- Applying diameter or projected tolerance zone to planar features of size.
- Mixing modifiers that are not allowed for the tolerance type.
- Omitting diameter on cylindrical features of size where required.