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Symbol Geometric Characteristic Description Typical Use Case Integration in CAD Inspection Notes
⏤ Flatness Ensures a surface is uniformly flat within the specified tolerance. Critical for sealing surfaces or bearing fits. Applied using surface tools for flatness analysis. Checked with a surface plate and gauge.
⊥ Perpendicularity Ensures a surface or feature is at 90° to a datum. Used for aligning holes or surfaces in assemblies. Ensures perpendicularity through datum alignment in CAD. Measured with a square or CMM.
// Parallelism Ensures a surface or feature is parallel to a datum. Ensures parallel alignment of mating surfaces. Checked by setting parallel planes in CAD models. Checked with a surface plate and gauge blocks.
○ Circularity Ensures all points on a circular feature are equidistant from the center. Applied to shafts, bores, or cylindrical parts. Analyzed using roundness measurement tools in CAD. Checked with a roundness measuring tool.
∅ Cylindricity Ensures a feature is both round and straight along its length. Important for shafts and cylindrical components. Modeled with precise cylindrical constraints. Checked with a roundness/cylindricity gauge.
⌒ Profile of a Line Controls the contour of a line element in a cross-section. Used for controlling the profile of gears or blades. Designed using line profiling and cross-sectional tools. Measured using an optical comparator or profilometer.
~⌒~ Profile of a Surface Controls the shape, size, and form of a surface. Used for aerodynamic or freeform surfaces. Generated with surface profiling features in CAD. Measured using a profilometer or CMM.
Ø⏤ Position Specifies the allowable deviation of a feature’s location. Used for hole placements and ensuring assembly alignment. Defined using positional constraints in CAD software. Inspected using a CMM or optical comparator.
↕ Concentricity Ensures features share the same axis or center. Ensures the alignment of coaxial holes or shafts. Checked using axis alignment tools in CAD models. Checked with a dial indicator or CMM.
∠ Angularity Ensures a feature is at a specific angle relative to a datum. Used for angled features such as chamfers or inclined planes. Defined by angular constraints and visual inspection tools. Measured using an angle gauge or sine bar.
↔ Symmetry Ensures balanced dimensions or features about a centerline. Ensures balanced features such as grooves or keyways. Balanced via symmetrical constraints in CAD. Inspected using a comparator or CMM.
⚭ Runout Controls surface variation on a rotating part. Applied to rotating parts such as pulleys or gears. Simulated with rotational axis checks in CAD tools. Checked with a dial indicator during rotation.
⚯ Total Runout Controls variation across an entire surface of a rotating part. Ensures total surface accuracy for rotating components. Modeled using surface accuracy constraints. Measured using a CMM or advanced runout gauge.