GlossaryKind of term: Manufacturing termRunout and total runout
What are runout and total runout?
Runout limits how far a surface may deviate while the part turns about its datum axis; total runout applies that limit over the whole surface at once.
Runout is a tolerance under ISO 1101 relative to a datum axis, shown as ↗ for circular runout and ⌰ for total runout. Radial circular runout limits, in each cross-section square to the axis, the surface to the space between two concentric circles about the datum axis whose radii differ by the tolerance value. Axial circular runout does the same on a face, in each cylindrical section about the axis. Total runout lays one zone over the whole surface: two coaxial cylinders for radial, two parallel planes square to the axis for axial. The requirement holds form and location together.
What does the standard say about runout and total runout?
ISO 1101 defines the zones and symbols, ISO 5459 the datum axis; often it is a common datum A-B across two bearing seats. ASME Y14.5 has the same two kinds, as circular runout and total runout. Total axial runout gives the same zone as perpendicularity of that face to the datum axis. Circular axial runout is looser: it applies circle by circle and does not fully catch a slightly concave or convex face. On a cone or other curved surface of revolution, runout applies normal to the surface unless the drawing states a direction. For circular runout the value is the largest permitted indicator movement over one revolution in each section; for total runout it applies over the whole surface without re-zeroing the indicator.
How do runout and total runout work in practice?
In turning, a tight runout often dictates how the part is held. Diameters finished in one chucking run out little relative to each other. When the part has to be turned round, the clamping error comes in: a standard three-jaw chuck often does not repeat closely enough for a tight value, and soft jaws bored to size, a collet, clocking in or turning between centres become the obvious options. Hardening can distort a shaft; grinding between centres after hardening is then a common final step. Measurement uses a dial indicator between centres or in V-blocks, or on a coordinate measuring machine, with the datum established as the drawing specifies.
What are runout and total runout often confused with?
Total runout is not cylindricity: cylindricity is a form tolerance without a datum, total radial runout also covers location relative to the datum axis. Nor is runout coaxiality: the indicator reading holds form and location together, so even an oval diameter on a perfect axis runs out.
How do you see runout and total runout in Blake?
In Blake turning, mill-turn and setup are separate lines in the estimate, with the setups you enter and accept per route. Grinding between centres, if subcontracted, enters the estimate as a separate line from your subcontract library, and without a price that line stays open. The result carries the estimate label. More on turning.
Frequently asked questions
How do you measure runout?
Rest the datum diameters in V-blocks, or hold the part between centres if they form the datum, and read a dial indicator over one revolution: highest minus lowest reading. For total runout, traverse it parallel to the datum axis over the whole surface without re-zeroing.
Can a three-jaw chuck hold a tight runout?
After reclamping, often not: a standard three-jaw chuck usually repeats too coarsely for it. Soft jaws bored to size, a collet, clocking in or turning between centres are then the better options. Finishing in one chucking avoids the clamping error.
What does runout on a face mean?
Axial runout: the indicator sits against the face while the part turns and picks up a face that is tilted or wavy relative to the axis. Total axial runout over the whole face matches perpendicularity to that axis at the same value.