Understanding the Fundamentals of Aircraft Fasteners

There are many fasteners used in aircraft. Most fasteners are visible during the preflight process. However, some are not visible to the naked eye. In this article, we will learn about the process of liquid honing, Vickers hardness tests, and zinc plating. We will also learn about thread rolled after heat-treating. Understanding the fundamentals of aircraft fasteners will help you recognize which fasteners should be removed before flight.

Liquid honing

Aircraft fasteners typically contain advanced plastics and titanium to withstand corrosion, abrasion, and the high temperatures found in air travel. These parts can reduce aircraft maintenance costs by being lighter than their counterparts. How to identify the hardware distributors on your plane? The specification number represents the part’s manufacturer.

The process is designed to achieve the required finish for precision aircraft fasteners, such as fasteners on commercial and military aircraft. The process involves using a tool with a beam and cap on one side. The weaker side is the one that experiences more bore distortion, so this connection provides an advantage. The process is also characterized by controlled force systems that ensure that the tool never overstresses itself or causes excessive bore distortion.

Vickers hardness tests

The Vickers hardness test for aircraft fasteners determines the strength of a material under a specific load. A Vickers hardness value is a number with an acronym referring to the triangle formed by a diamond indenter. The test measures the amount of force a material can withstand under a given load, usually expressed in kilograms per square millimeter. This number can be converted to several different types of force and is described in pascals. It is important to note that this test is different from HM because it considers the amount of plastic or elastic deformation that a piece can undergo after being indented.

The Vickers hardness test was developed in 1924 and is widely applicable to most materials. Its range of tests is one of the widest of any hardness test. It is governed by the ASTM standard E384 and can measure loads ranging from 1 gf to 120 kgf. Because of its versatility, the Vickers hardness test is a valuable tool for aerospace manufacturers.

Zinc plating

When you think of corrosion-resistant fasteners, you probably think of titanium or beryllium, but the reality is much more complicated. Titanium fasteners are incredibly light and perform exceptionally well under extreme temperatures. In contrast, beryllium fasteners are nearly 40% heavier and far more brittle. While beryllium fasteners do not require any special maintenance, zinc plating greatly increases the corrosion resistance of steel fasteners. In addition, zinc plating leaves a golden or shiny appearance to them, while chromium offers excellent corrosion resistance. But be warned: zinc coating thickness is directly proportional to the amount of zinc material present on the parts.

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The disadvantage of zinc plating for aircraft fasteners is that it can cause hydrogen embrittlement. This is a condition in which trapped hydrogen weakens the metal and causes it to crack. The zinc must be baked after plating to diffuse hydrogen throughout the metal to combat this issue. This process takes three hours. In addition, Paulo’s Murfreesboro division offers in-house salt spray testing.

Thread rolled after heat-treating.

A thread rolled after heat-treating in aircraft flanges is ten to twenty percent stronger than one produced using a ground or cut thread. Threads produced with rolled threads also have higher fatigue resistance, and there is no waste of stock during the forming process. The rolled threads are also more wear-resistant, as the surface is more complex than the cut or ground thread.

A thread rolled after heat-treating is a standard process used in aerospace fasteners. It extends the fatigue-resistance of threaded elements by introducing residual compressive stress during the process. Thread rolled fasteners can assemble connecting rods, cylinder heads, and main bearings in aircraft. Their high workforce makes them suitable for these high-stress applications.

Self-locking aircraft “jet nuts.”

Self-locking aircraft “jet nuts” are a type of bolt designed for tight quarters, such as on aircraft. These nuts are lightweight, compact, and highly durable. They are commonly used in high-stress applications and are often preferred over conventional locknuts because of their lower weight and smaller profile. However, despite these advantages, these nuts lack a warranty or traceability. 

Self-locking aircraft “jet nuts” feature a locking mechanism that activates when a bolt is tightened. A surface-bearing locking nut can rotate freely under normal conditions but is usually compressed against a bearing surface to activate the locking mechanism. Locking aircraft nuts can come in many subsets and models suited to various applications. However, unlike other aircraft nut styles, it is designed with a self-locking mechanism. Despite the name, this nut is self-locking, and its self-locking mechanism ensures that it will stay securely in place once it is fully tightened.

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