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Size - Individual Control

Position - Individual Control

Another Circularity Tip  

Another Straightness Tip

   Size and Form Are Individual Controls.

All of the tolerances defined in the Y14.5 standard have a purpose. In general, they control size, form, orientation and location. Often people give various tolerances more credit than they deserve. The key to proper application of GD&T is understanding the relationships and limitations of each of the controls. The standard is very clear on the limitations of size and form controls. They are individual controls. They do not relate features to one another. A designer may think that by specifying a size and quantity symbol, the resulting part will look like the model on the right. Unfortunately, since size is an individual control and does not control the interrelationship between features, the model shown below may result. Even if the straightness and circularity controls are added, the lower model may be produced and still meet the drawing's requirements. This drawing is merely stating that each of the 8 cylinders must meet size, straightness and circularity individually. In order to assure that you get a part closer to the model at the right, a coaxial control must be used. 
What the designer wants.  What the designer might get according to the print. 

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