| Symbol Glossary |
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What follows is a short summary of feature control symbols used in GDT. As was mentioned in the introduction, this is not intended to be an exhaustive presentation of GDT, but rather a concise, clear explanation of GDT's most important yet often misunderstood points. Therefore, we do not explain in detail all of the symbols listed below. In the "Type of Feature" column, "Individual" means that this type of tolerance does not need to be referred to a datum. Individual GDT tolerances are the easiest to understand for a beginning GDT user. "Related" designates a type of tolerance that must be referred to a datum. "Individual or Related" can be of either type, depending on the situation. |
| SYMBOL | VERBAL DESCRIPTION |
TYPE of TOLERANCE | TYPE of FEATURE | NOTES |
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Position | Location | Related | Commonly used. |
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Concentricity | Location | Related | Difficult to inspect. |
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Circular Runout | Runout | Related | |
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Total Runout | Runout | Related | Includes Circular Runout |
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Perpendicularity | Orientation | Related | |
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Parallelism | Orientation | Related | |
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Angularity | Orientation | Related | |
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Profile of a Surface | Profile | Individual or Related | |
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Profile of a Line | Profile | Individual or Related | |
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Flatness | Form | Individual | |
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Straightness | Form | Individual | |
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Roundness or Circularity | Form | Individual | |
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Cylindricity | Form | Individual |
