Product Code:SAE J390
Title:Dual Dimensioning
Issuing Committee:Technical Standards Board
Scope: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 J 916. Herein is guidance for converting from one system to the other while maintaining functional interchangeability.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 drawing. The scope does not include the 'chart method'聴whereby drawings are dimensioned only in SI units聴with conversions to inch-pound units provided in chart form (usually computer generated) on the drawing. Further information on the chart method is found in SAE Handbook Supplement J1066, 'Recommended Guidelines for Company Metrication Programs in the Metalworking Industry.' The purpose of this document is to provide an authoritative guide for uniform application of dual dimensioning on engineering drawings. SAE recognizes that a decision regarding preparation of engineering drawings during metric transition is an individual judgement 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.