BS 3A 125 to 3A:1981+A1:2013

Specification for Stiffnuts (Unified threads) for aircraft. | Status: Confirmed, Current

1 Scope 1.1 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:

1. a) – 75 C to + 425 C: corrosion-resisting steel nuts, silver plated or unplated
2. b) – 75 C to + 200 C: steel and corrosion-resisting steel nuts, cadmium plated
3. 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.