Runout is a composite tolcrance used to control the functional relationship of one or more features of a pan to a datum axis.

6.7.1 Runout Tolerance. The types of features controlled by runout tolerances include those surfaces constructed around a datum axis and those constructed at right angles to a datum axis. See Fig. 6-46. Basis of Control. The datum axis is established by a diameter of sufficient length, two diameters having sufficient axial separation, or a diameter and a face at right angles to it. Features used as datums for establishing axes should be functional, such as mounting features that establish an axis of rotation. Rotation About an Axis. Each considered feature must be within its runout tolcrance when the part is rotated about the datum axis. This may also include the datum features as a part of the runout tolerance control where so designated. The tolerance specified for a controlled surface is the total tolerance or full indicator movement (FIM). Types of Runout Control. There are two types of runout control, circular runout and total runout. The type used is dependent upon design requirements and manufacturing considerations. Circular runout is normally a less complex requirement than total runout. The following paragraphs describe both types of runout. Control of Circular Elements.

Circular runout provides control of circular elements of a surface. The tolerance is applied independently at each circular measuring position as the part is rotated 360°. See Fig. 6-47. Where applied to surfaces constructed around a datum axis, circular run out may be used to control the cumulative variations of circularity and coaxiality. Where applied to surfaces constructed at right angles to the datum axis, circular runout controls circular elements of a plane surface (wobble). Total Runout for Composite Control of Surfaces. Total runout provides composite control of all surface elements. The tolerance is applied simultaneously to all circular and profile measuring positions as the part is rotated 360°. See Fig. 6-48. Where applied to surface, constructed around a datum axis, total runout is used to control cumulative variations of circularity, straightness, coaxiality, angularity, taper, and profile of a surface. Where applied to surfaces at right angles to a datum axis, total runout controls cumulative variations of perpendicularity (to detect wobble) and flatness (to detect concavity or convexity). Applied to Portion of Surface.

Where a runout tolerance applies to a specific portion of a surface, a thick chain line is drawn adjacent to the surface profile on one side of the datum axis for the desired length. Basic dimensions are used to define the extent of the portion so indicated. See Fig. 6-47. Application. The following methods are used to specify a runout tolerance. Control of Diameters to Datum Axis. Where features to be controlled are diameters related to a datum axis, one or two of the diameters are specified as datums to establish the datum atis. and each related surface is assigned a runout tolerance with respect to this datum axis. Figures 6-47 and 6-48 illustrate the fundamental principle of relating features in a runout tolerance to a datum axis as established from a single datum diameter (cylinder)

Runout Tolerance 0015

Rotate part

Applies to portion of surface Indicated —f

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  • Glen
    How to control surface flatness and wobble?
    8 years ago
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