This British Standard specifies requirements for the construction, for the accuracy at the reference temperature of 20 degrees C and for the protection of metric and imperial precision vernier callipers with external and internal contact faces. The metric callipers measure lengths up to a maximum of 1 000 mm using a main scale and vernier scale graduated to read to 0.02 mm. The imperial callipers measure lengths up to a maximum of 48 inches using a main scale and vernier scale graduated to read to 0.001 inch.
The vernier division of 0.02 mm marked on the metric calliper corresponds to a 0.001 inch vernier division on the imperial calliper, whereas the actual conversion is 0.001 inch = 0.0254 mm.
Methods of testing and information on the use of callipers are given in the appendices to this standard.