Mastering Aircraft Bolts and Nuts: A Comprehensive Guide
By Alan Bettis · 2024-03-20
Explore the intricate world of aircraft hardware with a focus on bolts and nuts. Learn about different types of bolts, including AN and NAS standard bolts, clevis bolts, and the importance of grip length in aircraft construction.
A Comprehensive Guide to Aircraft Hardware: Bolts and Nuts
- Let's delve into the fascinating world of aircraft hardware, focusing on bolts and nuts. When it comes to aircraft bolts, they are generally categorized as either general purpose AN (Air Force Navy) bolts or NAS (National Aircraft Standard) close tolerance bolts, which are commonly used in aircraft structures. Bolts are distinguished by specific code markings on their heads. For instance, an AN standard steel bolt is identified by a cross or asterisk symbol on the bolt head, as illustrated in Figure 42 of the FAA documentation. On the other hand, an NAS close tolerance bolt is recognized by an X inside a triangle on the head of the bolt. Finally, a corrosion-resistant AN standard steel bolt is indicated by a single raised dash on the bolt head.
A Comprehensive Guide to Aircraft Hardware: Bolts and Nuts
Understanding Clevis Bolts and Grip Length in Aircraft Construction
- In aircraft construction, clevis bolts play a crucial role in ensuring structural integrity and safety. Unlike standard steel bolts, clevis bolts have a round head that is either slotted or recessed to accommodate specific screwdrivers. When identifying a clevis bolt, look for the round head—illustration number three in Figure 43. Clevis bolts are designed for sheer load applications only and should never be used in tension applications. When used with a fork-end cable terminal, secure the clevis bolt with a shear nut tightened to a snug fit, followed by a safety cotter pin. Additionally, the grip length of a bolt, which is the unthreaded portion, must be equal to the thickness of the material it extends through. This ensures proper structural support and prevents strain on the assembly.
Understanding Clevis Bolts and Grip Length in Aircraft Construction
Understanding Bolt Measurements and Thread Classes
- When examining the specifications of a bolt, it's crucial to focus on the shank length and threaded length rather than the overall length. The shank length encompasses both the threaded and non-threaded sections, with the non-threaded part referred to as the grip length. To determine the grip length, simply subtract the threaded length from the shank length. For example, if the shank length is 1 and 3/16 inches and the threaded length is 5/8 of an inch, the grip length would be 9/16 of an inch. To convert this fraction to a decimal, divide 9 by 16, resulting in 0.5625. Understanding thread classes is also important when dealing with bolts. The class of a thread indicates the clearance or tolerance in manufacturing, determining whether a wrench is needed to tighten the nut or if it can be done by hand. Class 1 represents a loose fit, Class 2 a free fit, and Class 3 a...
Understanding Bolt Measurements and Thread Classes
Understanding Aircraft Bolts and Lock Nuts
- When it comes to aircraft bolts, class 3 - the medium fit, is the standard choice for manufacturing. For the FAA written exam, knowing about class 3 bolts is essential. Additionally, fiber type lock nuts are a common choice, with their locking feature achieved through an unthreaded fiber locking insert inside the nut. It is important to note that fiber type locking nuts should not be used on aircraft if either the bolt or nut is subject to rotation. When installing nuts and bolts, the standards for how much the bolt studs and screws should protrude through self-locking nuts can be found in advisory circular 43.13-1b. This advisory circular provides acceptable methods, techniques, and practices for aircraft inspection and repair. It is crucial to distinguish between advisory circular 43.13-1b and 43.13-2a, which pertains to aircraft alterations. General standards regarding bolt protrusion through self-locking nuts can be located in aircraft specifications or type certificate data sheets.
Understanding Aircraft Bolts and Lock Nuts
Mastering the Art of Aircraft Nuts and Bolts
- When it comes to aircraft maintenance, the devil lies in the details. Specific standards are critical, especially when dealing with aircraft hardware. The key is to refer to resources like advisory circular 43.13-1b for crucial details such as the protrusions of bolt studs and screws through self-locking nuts. Generally, aircraft bolts should be installed with the head facing upward or forward to ensure that they stay in position even if the nut loosens. Additionally, torque values for nuts and bolts should be based on dry, clean threads—void of any grease or oil. If specific torque values are not provided, one can always turn to advisory circular 43.13-1b for guidance. In the scenario where a cotter pin hole is not aligned within the recommended torque range, the accepted practice is to change washers and try again. Understanding these nuances is essential when working with aircraft hardware.
Mastering the Art of Aircraft Nuts and Bolts
Conclusion:
Enhance your knowledge of aircraft maintenance by mastering the intricate details of bolts and nuts. Understanding bolt measurements, thread classes, and the correct installation of nuts and bolts is crucial for ensuring aircraft safety and structural integrity.