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AN7-31A
Aeronautical Standard Machine Bolt
Description
Hex head aircraft bolts are made of high-strength type 4037 or 8740 alloy steel (type 8740 is most commonly used). The bolts are centerless ground and threaded after heat treatment. Minimum tensile strength 125,000 PSI. Cadmium plated per specification QQ-P-416A, Type II, Class 3. Available with shank drilled for cotter pin or undrilled for stop nut application, and with or without drilled head for safety wire. Specify bolts to have undrilled shank by adding letter "A" after the dash number. For bolts with drilled head add letter "H" after the AN number. See illustrated examples. "C" represents Type 431 Stainless Steel (contains iron which is magnetic). 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. See table for conversion of length and/or grip to proper AN callout. Note: Drilled bolts listed above are drilled shank only. To order drilled head only or both drilled head and shank bolts, please use our AN Bolt Selector by clicking the link below
Specifications
| Fastener Length | 3.219 |
|---|---|
| Features Provided | Finished head |
| Grip Length | 2 9/16, 2.562 |
| Hardness Rating | 26.0 rockwell c minimum and 32.0 rockwell c maximum |
| Head Height | 0.234 inches minimum and 0.266 inches maximum |
| Head Style | Hexagon Head |
| Length | 3 7/32 |
| Material | Steel |
| Material Specification | Mil-s-5626 mil spec 1st material response or mil-s-6049 mil spec 2nd material response or mil-s-6050 mil spec 3rd material response or mil-s-6098 mil spec 4th material response or mil-s-6758 mil spec 5th material response or ams 6300 assn std 6th material response |
| Min. Tensile Strength (psi) | 125000 pounds per square inch |
| Nominal Length | 3 7/32 |
| Surface Treatment | Cadmium or chromate |
| Thread Class | 3a |
| Thread Diameter | 0.438 |
| Thread Direction | Right-hand |
| Thread Length | 0.657 inches minimum |
| Thread Qty | 20 |
| Thread Qty Per Inch (tpi) | 20 |
| Thread Series Designator | UNF |
| Thread Size | 7/16 |
| Width Between Flats | 0.615 inches minimum and 0.627 inches maximum |
Cross-reference
Similar parts
Parts with matching key dimensions — often from a different standards family. Candidates for comparison only; verify the full specification before substituting.
- AN7-31 AN 7/16-20 · 0.099 in · Hexagon Head · Steel
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Catalog data updated 2026-07-05. Report a data error