Angularity
Angularity is a GD&T orientation tolerance that controls how far a surface, center plane, or axis may deviate from a specified basic angle relative to a datum. The tolerance zone is typically two parallel planes at the basic angle for a surface, or a cylindrical zone for an axis. It does not simply mean the angle dimension is ±X°; it controls the entire feature's orientation and form within that zone.
On the CNC shop floor, angularity is critical when a non-90° angled feature must maintain consistent contact for fit, sealing, or load path. Typical applications include wedge faces, dovetail flanks, chamfer lands, and inclined sealing surfaces. Achieving angularity requires careful fixturing, datum control, and toolpath strategy. The angle is set from the machine setup, but GD&T verification is against the datum structure, so a part can be at the nominal angle yet fail if surface waviness or fixture skew pushes it out of tolerance. Probing-based work coordinate correction and 5-axis simultaneous machining are often used to hold tighter angularity than manual fixturing. Inspection methods include CMM, indicator setups, or sine-based methods, and the result is expressed as a distance across the tolerance zone rather than in degrees.
Is angularity the same as an angular dimension tolerance?
No. Angularity is a GD&T orientation control relative to a datum; an angular dimension tolerance only limits the numerical angle.
Does angularity require a datum?
Yes. Angularity is always defined relative to a datum reference.
What does angularity control on a surface?
Angularity controls that the entire surface fits between two parallel planes oriented at the basic angle to the datum, which also implicitly controls form error within that zone.