Drawing Interpretation

[[Ja...]]

I am looking at a sphere, Position to datums A and B. A is an I.D. thread pitch diameter (permission granted to use minor) and B is a face. The sphere is drawn at a NONBASIC dimension to the face.

The FCF dictates a planar tolerance zone. How is this so? A diametral zone would be appropriate for Position of sphere to A. Planar zone would be appropriate for sphere to B, but that dim is nonbasic.

I'd assume spherical zone, but what does the print say?

[[Br...]]

Actually a sphere should have a spherical tolerance zone for position. The FCF should have a "SØ" immediately preceding the tolerance. The centerpoint of the sphere must fall within a spherical tolerance zone.

Mathematically you are probably used to calculating the position error as something like "2*SQRT(deltaX^2+DeltaY^2)". With a Sphere you have another axis of position error within the DRF that is controlled. This would be expressed as "2*SQRT(deltaX^2+deltaY^2+deltaZ^2)"

If the intention is to have a square or rectangular shaped tolerance zone as opposed to the spherical one, it must be indicated with seperate FCFs indicating the direction and magnitude of each positional tolerance relative to specified datums.

The feature also MUST be located back to the DRF by basic dimensions.

[[Ja...]]

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Thanks Brett, that's exactly what I thought. There is constantly a lack of understanding throughout our prints of a spheres location in space. Nobody ever wants to change the print, and typically it is flowed down to us this way from outside sources. Would you just measure this in a spherical zone, against what the print says but following what the standard (that the print is written to) implies?

[[An...]]

See attached.

Contribution_18_10_2019.pdf

[[Ja...]]

Andreas, I'm not sure what you are trying to say.

[[An...]]

See attached.

Contribution_18_10_2019_a.pdf

[[An...]]

See attached.

True_Pos_and_Sphere_1.pdf