Applicable to machine screws and machine screw nuts having ISO inch screw threads and hexagon head and slotted or recessed heads with type Z and type V recess. Mechanical properties are specified for steel, brass and aluminium alloy screws and nuts. Cross References:BS 919BS 1474BS 1475BS 1580:Parts 1 & 2BS 1580:Part 3BS 1768BS 3382:Parts 1 & 2BS 3643:Part 1BS 3643:Part 2BS 4183BS 5750BS 6322:Part 1BS 6605Patents Act 1977