Allen bolts, also known as socket head bolts or socket head cap screws, are fasteners that feature a cylindrical head with an internal hexagonal drive. These bolts are tightened and loosened using an Allen wrench (hex key) rather than a traditional wrench or screwdriver. They are widely used in machinery, automotive, construction, and industrial applications due to their high strength, compact design, and ability to handle high torque without stripping.

Allen bolts offer several advantages over traditional hex bolts or screws. Their internal hex drive allows for better torque application without damaging the bolt head, making them ideal for high-load applications. They also require less space for installation, which is useful in compact or tight areas. Additionally, Allen bolts provide a clean and professional finish since the head sits flush with the surface, reducing the risk of snagging or injury.

Allen bolts are manufactured using various materials depending on their application and required strength. Common materials include alloy steel, which offers high tensile strength and is often coated with black oxide for corrosion resistance. Stainless steel Allen bolts provide excellent rust resistance, making them ideal for marine and outdoor environments. Titanium Allen bolts are lightweight, highly corrosion-resistant, and used in aerospace and medical applications. Brass and aluminum variants are also available for decorative or electrical applications.