AN hex head bolts in different series are offered under AVIATIONEU NEW ERA product series. Sourced from quality vendors, these bolts are manufactured to the US Army-Navy (AN) standard, predecessor to Mil-Spec (MS), superseded by the National Aerospace Standard (NAS). Commonly used in aviation for either tensile/shear load applications. Made from high-strength type 4037 or 8740 alloy steel or 431 Stainless Steel (CRES) and cadmium plated for superior corrosion resistance (compared to commercial grade zinc plated bolts) they are offered with shank drilled for cotter pin or undrilled for stop nut application, and with a drilled head for safety wire or without. Minimum Tensile Strength (Steel and CRES) - 125,000psi. The length of AN aircraft bolts is measured from under the head to the end of the shank. The "grip" is the unthreaded portion of the shank. Threads are pressed into the steel, not cut, thus maintaining strength throughout the entire shank. The surface under the head of AN bolts is designed to be a bearing surface to reduce non-uniform stress as the bolt is torqued thus reducing premature fatigue. The following letters are used in the product part numbers.
"A" after the dash number for bolts with undrilled shank
"C" for bolts made of 431 Stainless Steel (CRES)
"H" after the AN number for bolts with drilled head (eg. AN4H-15)
AN3 through AN20 Series bolts are superseded by NASM3 through 20 Series. The part numbers in both series have not been changed.
AN3 through AN20 (REV. 12), Military Specification Sheet: Bolt -Machine, Aircraft [superseded by NASM3 through 20]. This specification covers aircraft machine bolts part numbers, AN3, AN4, AN5, AN6, AN7, AN8, AN9, AN10, AN14, AN16, AN17, AN18, and AN20. AN3 THRU AN20 is canceled and superseded by NASM3 THRU NASM20. The Part Identification Number (PIN) for AN3 THRU AN20 REV. 12 and the part number for NASM3 THRU NASM20 are identical. The part numbers have not been changed.