Runout vs. flatness
Runout vs. flatness
(OP)
I have a print of a part that is similar to a cylinder. One flat end of the cylinder has a flatness tolerance. The other end has a circular runout tolerance.
I think I understand circular runout if it is applied to the curved part of the cylinder. But I don't see how it applies to the flat surface of the cylinder. And if it does, how does it differ from flatness?
The runout tolerance uses the other flat surface as its primary datum. It uses an outer diameter as its secondary datum. The print appears to have been created in the late 1960's.
I appreciate your help.
I think I understand circular runout if it is applied to the curved part of the cylinder. But I don't see how it applies to the flat surface of the cylinder. And if it does, how does it differ from flatness?
The runout tolerance uses the other flat surface as its primary datum. It uses an outer diameter as its secondary datum. The print appears to have been created in the late 1960's.
I appreciate your help.





RE: Runout vs. flatness
Time to revise the dwg to current stds.
Chris
Sr. Mechanical Designer, CAD
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RE: Runout vs. flatness
Or you can control the perpendicularity of the cylinder to the flat surface, but you would still need to control cylindricity. The other end could then be controlled with runout relative to the cylinder.
RE: Runout vs. flatness
I would change the runout to just the axis of the shaft not the flat. Using the flat and axis as a datum seems to wrong.
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Heckler
Sr. Mechanical Engineer
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RE: Runout vs. flatness
RE: Runout vs. flatness
The flat end of the cylinder is your main datum, placed on a turntable concentric with the axis of the cylinder and turntable, then runout is measured at the other end.
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RE: Runout vs. flatness
RE: Runout vs. flatness
You say that the runout uses the opposite surface and the diameter as datums, which is appropriate. Your inspector should jig up the part and run a dial indicator on the flat surface. The runout specification indicates the maximum Full Indicator Movement (FIM).
The only problem I can see is that ASME Y14.5M-1994 was not active in the '60s. Your original designer may have meant someting else.
JHG