Angularity is a GD&T orientation control that holds a surface, axis or centre plane at a stated basic angle to a datum. The zone is two parallel planes, the tolerance apart, tilted at that exact angle, so the result is a fixed width in millimetres or inches rather than a plus-or-minus angle.
Angularity says: this inclined face must lie between two parallel planes set at exactly the basic angle (for example 30°) to datum A. Because the zone is a constant width, the allowed angular error gets smaller as the face gets longer, which is usually what the function needs.
It also controls flatness of the face, since every point must be inside the two planes. It does not control where the face is; that is the job of size dimensions, position or profile of a surface.
Strictly, perpendicularity and parallelism are angularity at 90° and 0°. Use those symbols for those angles, and angularity for everything else.
For a surface, the zone is two parallel planes, the tolerance value apart, inclined at the basic angle to the datum. The angle itself carries no tolerance; it is shown in a box as a basic dimension.
For an axis, the zone is either two parallel planes or, with a diameter symbol, a cylinder inclined at the basic angle.
Angularity always needs at least one datum, because an angle has to be measured from something. A secondary datum is added when the rotation of the zone around the primary datum matters.
| Modifier | With angularity |
|---|---|
| MMC or LMC | Allowed when applied to the axis or centre plane of a feature of size, such as an angled hole. |
| Tangent plane (T) | Checks only the plane touching the high points, so form error is ignored. Useful for faces that bolt to another part. |
| Diameter symbol | For an angled axis with a cylindrical zone. |
Example: a 30° chamfer face, 40 mm long, angularity 0.1 mm to datum A
Result: The face passes angularity. The basic 30° angle has no ± of its own; the 0.1 mm band does all the work.
Every GD&T symbol page: GD&T symbols chart
Yes, always. An angle must be measured relative to a datum feature.
The zone is two parallel planes a fixed distance apart. That gives the same allowed movement at the end of the face whatever its length, which matches how most assemblies work.
Technically yes, but perpendicularity is the symbol meant for 90°, and parallelism for 0°.
Yes. All points of the face must be within the zone, so the face can be no less flat than the angularity value.
Set the basic angle on a sine bar so the face reads level, then indicate across it; or measure it on a CMM relative to the datum.
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