What they should do is use the current SI-10 definitions of conversion vs. substitution. The old Hard vs. Soft was very confusing and
"B.7 Conversion versus substitution Transitioning from traditional inch-pound units to SI requires changing quantity values from one system to another. This can be done by direct conversion, using the factors and rules of this annex to determine an appropriate equivalent value with an SI unit. Another transition method uses substitution. In substitution, a new rational metric size is used for the value of the measurement for the item being converted. While conversion maintains the original standard value (rounded appropriately for accuracy and precision as defined in this annex), substitution defines a new standard value for the measurement. Substitution should not be confused with rounding." From: owner-u...@colostate.edu [mailto:owner-u...@colostate.edu] On Behalf Of John M. Steele Sent: Thursday, April 10, 2014 7:49 AM To: U.S. Metric Association Subject: [USMA:53702] Soft and hard metric conversions http://www.csemag.com/single-article/soft-and-hard-metric-conversions/8203d3c07c36773c13673e99ca608165.html Quote: "Soft metric" is not a mix of imperial and metric measurements, and the Dept. of Defense does not recommend it for engineering drawings. They would be better off forbidding it than not recommending it. Our CAD system would not allow inch entry or dual dimensioning. There were a few cases of unusual multiples and submultiples of 25.4 mm, but the engineer had to convert by hand (to increase the pain) and enter in metric. Most learned.
