BS 3692:2001 ISO metric precision hexagon bolts, screws and nuts – Specification

BS3692 gives the general dimensions and tolerances of precision hexagon bolts, screws and nuts with ISO
metric threads in diameters from 1.6mm to 68mm inclusive. Mechanical properties are given only in respect of carbon or alloy steel bolts, screws and nuts, which are not to be used for special applications, such as those requiring weldability, corrosion resistance or ability to withstand temperatures above 300ºC or below 50ºC.


Steel precision bolts, screws and nuts are supplied with the following finishes:

Heat-treated bolts and screws. Components heat-treated after manufacture are customarily dull black, although the manufacturer may machine some of the surfaces of the larger size bolts and screws after heat treatment.

Bright finished bolts and screws. This term is used to describe bolts and screws which are finished bright on all surfaces or which have a finish on the hexagon, produced by bright drawing.

Nuts. These may be bright on all surfaces or dull black when heat-treated.

Other finishes. If the purchaser requires bolts, screws or nuts of steel (or other material) to be coated, they should state the type of coating required in their enquiry and order and it is recommended that reference be made to BS EN ISO 4042, in this respect.

If steel bolts, screws or nuts are required finished bright all over, the purchaser should state this in their enquiry and order.