SAE J 390:1999-05-01

This document covers a dual dimensioning practice that provides both U.S. customary inch-pound units and SI metric units for all dimensions on the field of the drawing. The scope does not include the various methods by which computer programs are used for dual dimensioning. In one method that has had some usage, drawings are dimensioned in SI (metric) units, with conversions to U.S. customary inch-pound units provided in a computer-generated chart on the drawing. The purpose of this document is to provide an authoritative guide for uniform ap plication of dual dimensioing on engineering drawings. SAE recognizes that a decision regarding measurement units is an individual judgment based on needs and circumstances. While providing this information, SAE takes no official position concerning dual dimensioning. Issuance of this publication should not be construed as advocacy. This document establishes a uniform method of combining inch-pound units and metric units of measure on the same engineering drawing. In this document "metric units" means the International System of Units (abbreviated SI) as described in SAE TSB 003. Herein is guidance for converting from one system to the other while maintaining functional interchangeability.