outofround

Out of round, often written as out-of-round, describes a circular object's cross-section that is not perfectly circular. In cylindrical parts, this means the diameter varies around the circumference, a condition commonly described as ovality or roundness error. Out-of-roundness is a key concept in quality control, bearing and shaft design, and other rotating assemblies.

Measurement and related concepts: Roundness is typically specified as a tolerance band around a nominal diameter. Runout describes the deviation observed when the part is rotated relative to a datum and is divided into radial runout and axial runout. Ovality refers to the difference between the maximum and minimum diameters encountered around the circumference. Eccentricity describes an offset between the part’s center and a reference axis. Common inspection methods include dial indicators, coordinate measuring machines (CMM), profilometers, and multi-point form testers.

Causes and effects: Out-of-roundness can arise from machining errors, tool wear, improper fixturing, thermal expansion, residual stresses, or deformation during handling. In rotary components, it can cause vibrations, noise, accelerated wear, reduced bearing life, seal leaks, and poor fit with mating parts. Tight tolerances on roundness are important in precision engineering to prevent interference and ensure smooth operation.

Standards and correction: Tolerances for roundness and related measurements are defined in standards from organizations such as ISO, ASME, and ANSI. Correction typically involves re-machining (turning, grinding, or lapping), re-finishing, or precise reshaping, followed by re-inspection to verify compliance.

See also: Roundness, circularity, runout, ovality, concentricity, tolerance.