Composite Position tolerance in GD&T - What is it?
Mufaddal Rasheed 
The concept of composite position tolerance is a widely applied concept in GD&T schemes of components with multiple features
When the component contains patterns of features like a set of holes then using the position control only controls the individual position of each hole with respect to the datum . The inter relationship between the features is not being controlled.
But when a composite feature control frame is used as shown below. The meaning changes.
Now the first line of the composite (2 line) control of position means the pattern position is being controlled within a tolerance zone of 0.2. Where as the second line denotes that the Feature to feature position is being controlled within a tolerance zone of 0.1
The true distance between the holes should be within a tolerance zone of 0.1
So now instead of controlling the holes individually the relationship between them in position is also controlled.
When there is a datum attached in second line. the meaning changes
That means that the pattern should be within the tolerance zone of 0.1 with respect to the orientation along with that the true distance between the holes should be within a tolerance zone of 0.1 .
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Geometric Dimensioning and Tolerancing: Advanced concepts
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Categories: : GD & Tolerancing