Week 1 Tools - Bolts in Aviation

Study Notes

Bolt Materials: Standard aircraft bolts are most commonly made of steel, followed by corrosion-resistant steel, stainless steel, aluminum, and titanium.
Standard Bolts (AN): Commonly used in general aviation.
NAS Bolts: High tensile strength and close tolerance.
Special Bolts: Used in applications requiring tighter fits, often marked with an (S) on the head.
Aircraft Bolt Markings: Standard markings include X or *, corrosion-resistant bolts (-) and aluminum bolts (- -).
Bolt Use Restrictions: Do not use aluminum bolts for tension applications—this is usually removed for maintenance.
Bolt Head: Larger than the bolt's diameter, typically hexagonal, to aid in directional control during use.
Bolt Grip/Shank: Threaded portion of the bolt, often referred to as the grip. The grip diameter matches the bolt diameter.
Bolt Threads: UNC (coarse) and UNF (fine) threads are used; the thread gauge determines TPI (threads per inch).

General Purpose Hex Head Bolts (GPB): Used more broadly and identified by a 6-point hexagonal head.
Bolt Dimensions: Specific dimensions including diameter and length.
AN Bolt Material: Cadmium-plated Nickel Steel is a common material used; corrosion-resistant (C) and aluminum alloy (DD) materials are also used.
AN Numbering System: Example: AN4-20A. The numbering system includes diameter, material, and length information; an 'A' or 'H' at the end signifies if there is a hole in the bolt head.

Nuts & Bolts Classification: Divided into self-locking and non-self-locking types.
Non Self-Locking: Requires an external locking device (e.g., cotter pins).
Self-Locking: Integrated locking mechanism, commonly utilized in aircraft applications.
Self Locking Types: Two primary types: metal and nylon.
Washers: Used in many applications, mainly to protect and ensure proper contact. The most common types are AN960 and AN970.

Safety Features: Prevent failure of secured devices, providing backup and security during events such as fire suppression.
Lockwiring: An example of a safety feature to prevent unwanted assembly.
Types of Lock Wire: Stainless steel, Inconel, and Monel are types of lock wire to know.
Standard Wire Diameters: 0.020”, 0.032”, 0.041” are common diameters.
Turnbuckles: Purpose is to adjust cable tension; used in control cables on aircraft.
Witness Wire: Designed for visible confirmation of securement during inspections to prevent damage and misuse of other equipment.
Witness Wire Application: DO NOT use lock wire when deploying witness wire.

Witness wire is used to ensure that the cover remains in place, such as during a fire suppression.
Minimal breaking force is ideal for witness wire to prevent damage to equipment.

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