Bristol Industries Fasteners

phone 01494 882498 for your UK representative, Comtech International. 

Bristol Industries Fasteners manufactures Engine (high temperature) & Airframe Self Locking Nuts. Self-locking nuts provide tight connections that will not loosen under   vibration. Airframe self-locking nuts meet critical specifications for strength, corrosion resistance, and heat-resistance. New self-locking nuts must be used each time components are installed in critical areas throughout the   entire   aircraft.  Self-locking nuts are found on flight, engine, and fuel control linkage and attachments.

There are two general types of self-locking  nuts.  There are the all-metal nuts and the metal nuts with a nonmetallic  insert, Hex, Double Hex, Barrel nuts used to bolt thin sheet metal parts to larger, often billet or forged, parts. Shank nuts are where the swaging of shank nuts is carried out by deforming the end of the shank using a 60° swaging cone. Shank nuts are swaged with the aid of a swaging tool either manually or by machine. Swaging cones and anvils of the swaging tools are replaceable. Spline, Channel and Anchor are all self-locking configurations. Bristol Industries fasteners are manufactured from Aerospace Grade Materials which include CRES or 300 series Stainless Steel.

The 300 series stainless steels (CRES) are not strong enough to be aerospace structural materials in most applications, but screws and bolts of 300 CRES are used for fastening covers and small brackets for electronics. Inserts are often made of 300 CRES. 300 series CRES is not heat treatable and can only be strengthened by cold forming.

400 series CRES can be heat treated up to about 150ksi before low elongation becomes a problem. 400 series CRES materials have only 12% chromium, which allows some surface rusting.

A-286, Inconel and Waspalloy are all aerospace superalloys. MP-35® & MP-159®

are very high strength superalloys (up to 260ksi at RT), and can be used up to 1100°F. They also have good resistance to fatigue, stress corrosion cracking, and general corrosion.

Bristol Industries fasteners are for commercial or military aircraft.

Aerospace Self-Locking Nuts

Self-locking nuts, as the name implies, do not need a locking device. The most common method of locking is derived from a fibre insert. This insert has a smaller diameter than the nut itself so that when a bolt enters the nut it taps into the fibre insert producing a locking action. This fibre insert is temperature limited to 250-deg. F. The designation of these nuts is AN365 and AN364. Both of these nuts are available in stainless. The AN364 is a shear nut not to be used in tension.

All metal locking nuts are used forward of the firewall and in other high temperature areas. In place of a fibre insert, the threads of a metal locking nut narrow slightly at one end to provide more friction. An AN363 is an example of this type of nut. It is capable of withstanding temperatures to 550-deg. F.

The dash number following self-locking nut defines the thread size. Self-locking nuts are very popular and easy to use. They should be used on undrilled bolts. They may be used on drilled bolts if you check the hole for burrs that would damage the fibre. One disadvantage, self-locking nuts should not be used on a bolt that is connecting a moving part. Am example might be a clevis bolt used in a control cable application.

Bristol Industries Fasteners make the B-Prime Fastening System of self-locking nuts and torque-controlled tools.