BS 4320:1968 (R2012)

Relates to bright metal and black metal washers for use with ISO metric bolts, screws and nuts. The washers are basically divided into 3 categories of size: 'normal', 'large' and 'extra large' diameter series and the bright washers are further divided by including a 'light range' which have thicknesses approximately 60 per cent of the 'normal range' thicknesses. The bright metal washers cover the range for bolts, M1 to M39, and the black metal washers cover the range M5 to M68. Appendix gives details of sizes greater than 68 mm diameter, up to and including size M150.