Tolerance question

[BODIE]

Can you put a (4) place tol on a (2) place dim.
For example
I have a <dia>1.50 can I make it concentric .0002 to datum 'A'.
Datum 'A' being <dia>1.5005/1.5003.

 

[ewh]

Bodie,

Technically you can, but concentricity may not be the best control to use, unless extreme accuracy of the centerline is required. Your feature is only dimensioned to two places, which leads me to believe that such extreme accuracy is not really necessary. It will be quite involved and expensive to inspect that feature to a concentricity of .0002. Controlling the feature with runout or true position may achieve what you want at less cost. AMSE Y14.5M-1994 (para 5.12.1) states:

Irregularities in the form of an actual feature to be inspected may make it difficult to establish the location of that features median points. For example, a nominally cylindrical surface of revolution may be bowed or out of round in addition to being displaced from its datum axis.
In such instances, finding the median points of the feature may entail a time-consuming analysis of surface variations. Therefore, unless there is a definite need for control of the features median points, it is recommended that a control be specified in terms of a runout tolerance or a positional tolerance.

I hope that helps!

Eric