CNC: Circularity and Cylindricity – the difference
Circularity: Every circular cross section of the part must lie between two concentric circles spaced the ‘circularity’ distance apart. In this example, the circularity is 0.25 mm. All cross sections (like A-A and B-B in the figure) must lie within two circles 0.25 mm apart. Circularity is 2-dimensional. You are only checking to see if the cross sections are OK, not whether their centres lie on a straight line.
Cylindricity: Every circular cross section of the cylinder must lie between two concentric cylindersspaced the ‘cylindricity’ distance apart. In this example, the cylindricity is 0.03 mm. All cross sections (like A-A and B-B in the figure) must lie within these two cylinders 0.03 mm apart. Cylindricity is 3-dimensional. You are checking to see if the cross sections are ok AND that they lie on a straight line
The rod in the picture below might be OK for circularity, but will not be OK for cylindricity.
Circularity can also apply to spheres and cones, while cylindricity applies only to cylinders.
This post was prompted by a suggestion of Mr. K. Vijayakumar in my last post.
Text and pics. source: CADEM NCyclopedia multimedia CNC training software.
