GDT:Symmetry
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| Symbol | Symmetry |
|---|---|
| Type | Location |
| Category | Location |
| Standard | ASME Y14.5 |
| Author | Admin |
| Datums | Primary datum required |
| Modifiers | None (rarely used) |
| Tolerance zone | Median plane/axis symmetry about datum |
| Image | |
| Common mistakes | Using symmetry where position or profile would be more appropriate |
| Related | F4:Symmetry Validation |
Summary
Symmetry controls how a feature’s median points are distributed about a datum center plane or axis.
Definition
Symmetry compares the median points of the toleranced feature to the datum reference plane or axis so they fall within the specified tolerance zone.
When to use it
Use symmetry only when the distribution of median points about a datum is critical. It is rarely required in modern GD&T practice.
Examples
Example: Symmetry about a datum plane
Symmetry applied to a feature relative to datum A.
Common mistakes
- Using symmetry instead of position or profile.
- Missing or unclear datum references.