GDT:Parallelism
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Revision as of 21:10, 14 January 2026 by Admin (talk | contribs) (Created page with "{{Author Credit |author=Admin }} {{GDT Infobox |symbol=Parallelism |type=Orientation |category=Orientation |standard=ASME Y14.5 |author=Admin |datums=Primary datum required |modifiers=Diameter for cylindrical FOS; ST where allowed; material condition modifiers per feature type |tolerance_zone=Two parallel planes (planar) or a cylindrical zone (axis/feature of size) |image=<!-- TODO: add diagram file name --> |mistakes=Missing datum referenc...")
| Symbol | Parallelism |
|---|---|
| Type | Orientation |
| Category | Orientation |
| Standard | ASME Y14.5 |
| Author | Admin |
| Datums | Primary datum required |
| Modifiers | Diameter for cylindrical FOS; ST where allowed; material condition modifiers per feature type |
| Tolerance zone | Two parallel planes (planar) or a cylindrical zone (axis/feature of size) |
| Image | |
| Common mistakes | Missing datum reference; using the datum feature as the toleranced feature; missing diameter on cylindrical FOS |
| Related | F4:Parallelism Validation |
Summary
Parallelism controls the orientation of a surface or axis relative to a datum. It keeps the toleranced feature parallel to the referenced datum.
Definition
For planar features, the tolerance zone is two parallel planes offset from the datum. For axes or cylindrical features of size, the zone is a cylinder oriented parallel to the datum.
When to use it
Use parallelism to align a surface or axis to a datum reference, such as keeping a face parallel to a base plane or a shaft axis parallel to a datum axis.
Examples
Example: Planar surface parallel to datum A
Parallelism applied to a face with datum A as the reference.
Example: Cylindrical feature of size parallel to datum A
Parallelism applied to a shaft axis with the diameter modifier.
Common mistakes
- Missing the primary datum reference.
- Applying parallelism to the same feature as the datum.
- Omitting the diameter modifier for cylindrical features of size.