CZ - Common Zone requirements

[hunty42]

Image link -

https://flic.kr/p/2oCzyj9

I was hoping someone can tell me how to interpret the CZ / Common Zone tolerances from some drawing in the image so I can program my CMM machine correctly, the CZ tolerance is new to me but has started showing up of a lot of drawing and I cannot much information about it.

Tolerance 1 is for a group of holes but I do not know why the CZ modifier is used in a composite tolerance as the tolerance already regards the holes as group.
Tolerance 2 is also for a group of holes but I do not know why the CZ modifier is used instead of a composite tolerance.
Tolerance 3 is similar to 1 but for a surface instead and the CZ requirement is in the upper segment instead of the lower.

 

[MOester]

For #1 it means that the pattern (alignment of all the holes) to each other is more important than where the pattern is to the rest of the features. 1,0 to XYZ means the first hole could be displaced 0,5 mm "down" and the second hole 0,5 mm "up" and meet the 1,0 to XYZ. But this would then NOT meet the 0,5 CZ. Hole 1 and hole 2 are 1 mm away from each other.

#2 is hard to answer without seeing more of the print. Again, it means that the 5 cylinders are all within 0,5 of each other. If you are making one massive cylinder object, scanning circles in all 5 of them, it may best fit the cylinder and hide this. What they are after is similar to 1 above. They are more concerned the cylinders are all aligned to each other. I would think you would want to measure all 5 individually and check worst case displacements relative to the cylinder made from all 5 collectively.

#3 you got me. I'm not familiar with what the XYZ/c is.