BS 2856:1973 (R2012)

Provides a procedure for the conversion of inch and metric sizes on engineering drawings which will give the essential accuracy required for precise dimensional interchangeability. The standard gives specific guidance on the optimum fineness of rounding the converted size, and recommends a procedure for conversion which takes the form of simple rules covering successive steps in the conversion. Examples of the application of the rules are given for a variety of cases. Tables of conversion from inches to millimetres, and vice versa, are included in an appendix to facilitate the work.