Position tolerance of a sphere with respect to Taper datum feature axis

[sunnynitian]

Hi Everyone,

I am creating a drawing for a ball joint's ball stud, wherein my critical functional surfaces are sphere and taper.
Based on my functional requirement, I have selected taper as datum feature A- that define a point and axis and constrain
5 DOF. my logic to define datum feature B is that axis from datum feature A is defined so now I can define a position tolerance with respect to that axis and define my datum feature B.
but by doing that I have not defined the basic dimension for the sphere center assuming that the datum simulator is going to establish the sphere center. I don't want to measure the sphere center
from the point established by the taper. Profile tolerance on the taper is missing.I am attaching my drawing for your reply. Thank you.

 

[3DDave]

Making the sphere the initial datum feature solves most of your problem. Position and profile tolerances to [A] will create a simultaneous requirement for the DRFs of the various features, minimizing overall tolerance stackup.

 

[AndrewTT]

How can you verify if the position of the sphere is correct if you don't know where its true position is? You will need a basic dimension from the datum point that is generated from the datum feature A cone. If you stick with positioning the sphere feature you will need to add an "S" in front of the diameter symbol of the position geometric tolerance (Sø).

If you don't like the idea of describing the true position of the sphere from a point in space (or possibly obscured by the M16 threaded portion of the part) you could use a customized datum reference frame (sections 4.21-4.23 ASME Y14.5-2009).

 

[powerhound]

I second AndrewTT's suggestion of customizing this datum reference frame. If we call translation along datum axis A z then let it constrain x, y, u, and v and give z to datum B. Then you can reference everything to A|B|.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech