I am faced with a similar issue, but not necessarily with just mill tolerances. One customer has drawings for parts dimensioned in fractions. Stated tolerance is usually +/- 1/32 and sometimes +/- 1/16. Within the same drawing, other dimensions are to two decimal places and other times to three decimal places.
It has been my understanding that the dimension rules the precision of the measurement device. i.e. for a dimension with a 1/16" tolerance, it is permissible to use a calibrated tape or rule incremented in sixteenths of an inch. If the dimension is written as a decimal fraction with a 2 place decimal, the appropriate device must have precision to read at least to the third decimal place and standard rounding rules apply and so on to the stated decimal precision.
My issue is the customer's Incoming QA Inspector reads every length dimension to 3 decimal places regardless of the stated units and tolerances. This includes dimensions indicated a "REF" which should have no implied tolerance. Mill tolerances are generally governed by the appropriate ASTM specification which almost never go to the third decimal place.
My position has been measure to the drawing or redraw and restate the tolerances needed, then I can tell you if the tolerances can be met.
I don't want to win the battle and lose the customer, not do I want to add cost chasing an unnecessarily tight tolerance.
It has been my understanding that the dimension rules the precision of the measurement device. i.e. for a dimension with a 1/16" tolerance, it is permissible to use a calibrated tape or rule incremented in sixteenths of an inch. If the dimension is written as a decimal fraction with a 2 place decimal, the appropriate device must have precision to read at least to the third decimal place and standard rounding rules apply and so on to the stated decimal precision.
My issue is the customer's Incoming QA Inspector reads every length dimension to 3 decimal places regardless of the stated units and tolerances. This includes dimensions indicated a "REF" which should have no implied tolerance. Mill tolerances are generally governed by the appropriate ASTM specification which almost never go to the third decimal place.
My position has been measure to the drawing or redraw and restate the tolerances needed, then I can tell you if the tolerances can be met.
I don't want to win the battle and lose the customer, not do I want to add cost chasing an unnecessarily tight tolerance.