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Position of a pattern of features to a datum (a plane normal to the features in this case) controls location of the pattern to itself (feature to feature) as well as orientation to the datum (perpendicularity). See attachment. Datum A is the underside of the part.
This is illustrated in the standard in the following figures; 4-22, 4-26, 5-28. Also it is the very definition of position in that it controls both location and orientation. The main confusion with this occurs with people who use position to control the orientation of a single feature to a single datum. For this requirement, perpendicularity should be used. In this instance, both position and perp will mean the same thing. As soon as I have two or more features, then position and perp have two different meanings. Since perp is an orientation control only, the pattern could be located anywhere and still pass the requirement. Position would define the tolerance zones perp to the datum and basically located to each other.
This is illustrated in the standard in the following figures; 4-22, 4-26, 5-28. Also it is the very definition of position in that it controls both location and orientation. The main confusion with this occurs with people who use position to control the orientation of a single feature to a single datum. For this requirement, perpendicularity should be used. In this instance, both position and perp will mean the same thing. As soon as I have two or more features, then position and perp have two different meanings. Since perp is an orientation control only, the pattern could be located anywhere and still pass the requirement. Position would define the tolerance zones perp to the datum and basically located to each other.
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