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(play), in machines and mechanisms, the departure of the surfaces of rotating or vibrating cylindrical parts from their proper relative positions.
Radial runout is the difference between the greatest (Amax) and least (Amin) distances from points on the actual surface to the reference axis of rotation in a section perpendicular to this axis (see Figure l); it results from eccentricity of such a section with respect to the axis of rotation.
End runout is the difference between the greatest and least distances from points on the actual end surface located around the circumference of a specified diameter (D) to a plane perpendicular to the reference axis of rotation (see Figure 2); it results from the nonperpendicularity of the end surface with respect to the reference axis and deviations of the end shape along the line of measurement.
Runout is a detrimental effect in machines and mechanisms; it tends to increase wear and failures in machine parts.