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This may be a silly question but I can’t seem to find a good size with either metric or SAE for the AN3 and AN4 bolts as well as the 1032 lock nuts. 10mm seems to be the closest for AN3 but just a tad too big. Not sure if there a special aviation tools that would grab better. Thanks

Walter

3/8”

Hi Walter,

I could be wrong but ... The AN in AN3 stands for Army Navy. The old AN standards predate the more current Mil standards. Back then Americans hadn't even considered metric measure.

The correct size for AN3 is 3/8". The correct size for AN4 is 7/16".

The AN bolts are hardened steel. I've never had a problem with rounding off the heads. If you are having problems better check the torque chart for the bolts, or maybe the quality of your tools. YMMV.

Best of Luck,

Wes

7/16 for AN4. Metric tools need not apply.

AN bolts end in a number that specifies the bolt shank diameter in 16ths of an inch. For the bolt head, add 3/16ths to the bolt diameter (example: AN4 = bolt shank diameter of 4/16ths. Add 3/16ths for the head and you get 7/16ths for the wrench/socket).

As mentioned, proper torque values are often lower than people think, especially for the smaller bolts. Check out FAA AC43-13 (you can find it for free online or buy it in book form). Torque values/limits are listed in a table in the “Bolts” part of the document, near section 7-40 titled “Torques”.

When in doubt, AC43-13 is the “go to” reference for all fastener info, strengths/limits, and recommended standard practices. If the aircraft manufacturer doesn’t list exact steps and values, assume AC43-13 standards apply.

Enjoy,

—Noel

Thanks so much to all. Appreciate the help.

Walter