In the second example the feature would always contain opposed points. This feature may be located using profile of a surface or position as shown.
If You Use Position, Make Sure You Have a Feature of Size (#115)
(In accordance with Y14.5M-1994 standard)
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Position is used to locate features of size. A feature of size must contain opposed points. The radius in the first drawing may or may not contain opposed points depending on the actual part variation. Position would be a misguided approach to controlling the location of this feature. Making the dimensions basic and using profile of a surface is a better approach.
