Runout and datum D

[[An...]]

See attached.

Pic_9-5.pdf

[[SH...]]

Perpendicularity between axis and the plane control or in other words phaseout control..

[[An...]]

it means that the total planned run-out must be within a tolerance of 0.04mm to the axis of rotation of cylinder "D".
The total planned run-out and the total radial run-out have the same symbol.

[[Ma...]]

Datum D in the example defines the secondary datum of the axis of rotation. Without it the cumulative axial runout characteristic would be incompletely defined as there would be no axis clearly specified to rotate about.

[[Mi...]]

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I'm only familiar with runout to a single datum (axial).

How would the measurement be different if datum D were the primary datum, and C wasn't included? In the figure, does the plane normal define the direction of the axis, but the midpoint of D define the center of rotation?

[[Ma...]]

I'm only familiar with runout to a single datum (axial).

How would the measurement be different if datum D were the primary datum, and C wasn't included? In the figure, does the plane normal define the direction of the axis, but the midpoint of D define the center of rotation?
[/quote]

Good question. The answer to your second question is yes. Here is why this is important. Using single axial runout for this example, imagine an axial surface on the end of a shaft. This axial surface is slightly conical in shape rather than flat. If the conicity error of the axial surface is perfectly true to datum D it will not show any runout. Any radial displacement of the axis of rotation from there would cause an increase in the observed axial runout due to the conicity error. In this case the error caused would be eliptical in shape (cross section of a cone).