BS 4A 116:2012

NOTE 1 The values in British units are to be regarded as the standard. Table A.1 provides a ready means of calculating the approximate millimetre equivalents of the inch dimensions. More accurate conversions should be based on the tables in BS 350.

NOTE 2 In place of the customary, but incorrect, use of the ton as a unit of force, the unit called a ton force (abbreviation tonf) is used in this British Standard. It is the force which, when acting on a body of mass one ton, gives an acceleration equal to that of standard gravity.