Concentricity

[jayprince]

1) What would be the most accurate calculation method for defining circles/cylinders for the purpose of determining the concentricity of 2 circles/cylinders??? Would it be Min_Sep ? (Minimum Separation)

2) Would the number of "hits" used to define a circle/cylinder need to be a prime #? (I have been told this is the case) ?

[kbotta]

If you are referring to ASME Y14.5M-1994 (on your drawing) than you cannot measure concentricity with 2 circles. Pcdmis does not correctly determine the geometric characteristic of concentricity. That would involve measuring 2 opposite pts and constructing a mid point - at every point around the dia (and how many pts are there on your dia???) and making sure the "point cloud" is inside of the tolerance zone specified in the FCF.
It's one of the worst things (and symmetry) as programmers that we can see on a drawing. Of course, I guess it would be ok if retirement is right around the corner
kb

[kbotta]

BS7172:1989 recommends 7 to detect up to 6 lobes.
Personally, I use 9...

[jayprince]

Thanks for your help kbotta!!!
Jay

[kbotta]

no prob..