scope:

These British Standards cover the dimensions, material, finish, testing and identification of aircraft stiffnuts with Unified threads. According to the materials used in their construction, the stiffnuts are classified as satisfactory for use at sustained temperatures within the following ranges:

a) - 75 °C to + 425 °C: corrosion-resisting steel nuts, silver plated or unplated

b) - 75 °C to + 200 °C: steel and corrosion-resisting steel nuts, cadmium plated

c) - 75 °C to + 125 °C: aluminium alloy, brass or bronze nuts.

NOTE All nuts are capable of remaining effective for servicing operations at - 40 °C.

Stiffnuts of the following types are covered by these British Standards:

a) hexagon nuts: ordinary, thin and cap

b) anchor nuts:

1) double-lug fixed: ordinary, thin and cap

2) double-lug floating: ordinary and thin

3) single-lug fixed: ordinary and thin.

c) stripnuts floating: ordinary and thin.

In these standards, the nut bodies, whether of normal hexagon form or not, have a thread strength as least as great as the corresponding standard nuts.