Bolt and Nut Identification (page 2 of 3)

GENERAL INFORMATION

03-12

Encapsulated bolts and screws

Encapsulated bolts and screws have a micro-
encapsulated locking agent pre-applied to the 
thread. They are identified by a coloured section 
which extends 360

°

 around the thread. The locking 

agent is released and activated by the assembly 
process and is then chemically cured to provide the 
locking action.

Unless a specific repair procedure states otherwise, 
encapsulated bolts may be re-used providing the 
threads are undamaged and the following procedure 
is adopted:

l

Remove loose adhesive from the bolt and 
housing threads.

l

Ensure threads are clean and free of oil and 
grease.

l

Apply an approved locking agent.

An encapsulated bolt may be replaced with a bolt of 
equivalent specification provided it is treated with an 
approved locking agent.

Self-locking bolts and screws

Self-locking bolts and screws, i.e. nylon patched or 
trilobular thread can be re-used providing resistance 
can be felt when the locking portion enters the female 
thread.

Nylon patched bolts and screws have a locking agent 
pre-applied to the threads. They are identified by the 
presence of a coloured section of thread which 
extends for up to 180

°

 around the thread.

Trilobular bolts (i.e. Powerlok) have a special thread 
form which creates a slight interference with the 
thread of the hole or nut into which it is screwed.

DO NOT  re-use self-locking fasteners in critical 
locations (e.g. engine bearings, flywheel). Always 
use the correct replacement self-locking nut, bolt or 
screw. 

DO NOT  fit non self-locking fasteners in applications 
where a self-locking nut, bolt or screw is specified.