How to Choose Airframe Bolts: What You Should Know

AN bolt by Monroe

Airframes are held together by a variety of fasteners. Airframes, of course, encompass fuselages, wings, undercarriages and empennages. Many of these components are held together by threaded fasteners known as airframe bolts. If you’re building an airplane, you’ll need to choose the right airframe bolts for your project.

Thread Standard

You can find airframe bolts in different thread standards. Some of them use the American National Coarse (ANC) standard, whereas others use the American National Fine (NF) or American Standard Unified Fine (UNF) standard. There are nuances between each thread standard. The thread standard determines the spacing and overall design of an airframe bolt’s threading.

Fully vs Partially Threaded

Regardless of the thread standard, airframe bolts may have a fully threaded shank or a partially threaded shank. The former is more common than the latter. More airframe bolts have a fully threaded shank than a partially threaded shank. Nonetheless, there are still some airframe bolts that don’t have threading covering their entire shank. A partially threaded shank means the threading only covers some of the shank.

Drilled Shank

Some airframe bolts have a drilled shank. When inspecting the bottom part of the shank, you may notice a small hole in them. The purpose of a drilled shank such as this is to support a pin. You can typically use a cotter pin with airframe bolts that have a drilled shank. After installing the airframe bolt, you can slide a cotter pin through the drilled hole. The cotter pin will help to secure the airframe bolt.

Head Style

Don’t forget to consider the head style when choosing airframe bolts. The head style, of course, will determine the type of tool that you’ll need to install a given airframe bolt. Most airframe bolts have a hexagonal head. They don’t have a recess. Rather, they have a solid, six-sided head. But there are still airframe bolts in alternative head styles, so don’t overlook this feature when ordering them.


One of the most important things to consider when choosing airframe bolts is the material. While all airframe bolts are strong, they are available in different materials. Some of them are made of stainless steel, whereas other airframe bolts are made of high-carbon steel. You can even them in aluminum alloy materials and titanium.

Airframe bolts are commonly used in the construction of airplanes. They are heavy-duty threaded fasteners that, like other fasteners, are designed to hold two or more parts together. When choosing airframe bolts, consider the thread standard, whether they have a fully or partially threaded shank, whether they have a drilled or solid shank, the head style and the material.

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