AN4 Bolts (1/4-28)

Hex head aircraft bolts are manufactured from high-strength 4037 or 8740 alloy steel, with 8740 being the most commonly used. Each bolt is centerless ground and threaded after heat treatment to ensure precision and durability. They feature a minimum tensile strength of 125,000 PSI and are cadmium plated in accordance with QQ-P-416A, Type II, Class 3 specifications.

These bolts are available with either a drilled shank for cotter pin use or an undrilled shank for stop nut applications, as well as with or without a drilled head for safety wire. To specify an undrilled shank, add the letter “A” after the dash number. For bolts with a drilled head, add the letter “H” after the AN number (example: AN3H-15). The letter “C” indicates Type 431 stainless steel, which contains magnetic iron.

The length of AN aircraft bolts is measured from under the head to the end of the shank, while the “grip” refers to the unthreaded portion of the shank.