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Packaged Items
SinglePack of 5
TypePart No.Thread SizeCotter Pin Size
Stainless SteelAN310C41/4-28


Fabricated from steel and cadmium plated per QQ-P-416A, Type II, Class 3. AN310 castle nuts are used with drilled-shank bolts, clevis bolts, eye bolts and studs. The slots in the nut accommodate a cotter pin for safety purposes. The thinner AN320 castellated shear nut, with half the tensile rating of the AN310 nut, is used with clevis bolts and threaded taper pins which are subject to shearing stress only.

Less 20% for quantity 100/Part No.
California Prop 65 Warning Symbol

WARNING: Cancer and Reproductive Harm -

Reference Chart


I am building a small scale radial engine. About 8 horsepower. These will be the prop nuts. They look fantastic. Mike Brainerd

Mike B
March 8, 2021

As usual, very fast shipping and well packed, a company I can always rely on.

Malcolm C
March 8, 2020


Sport I
November 15, 2019

you are doing great getting everything here at reasonable rates and on time . USPS Priority does great Thanks

Bob B
November 7, 2019

July 12, 2019

Sport I
April 20, 2019

I am sure they will work when I need to use them . Wrong size for this job. MY fault.

March 8, 2019

All hardware arrived quickly and as listed and in good condition!

Tim O
February 7, 2019

Nice and shiny....

Stick N
August 11, 2018

Very happy with the kind friendly service and fast shipping that Ms Henley provided..Super Girl.

James B
August 4, 2018


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Are these castle nuts unified national fine thread?

Yes, they are standard AN UNF thread.

Q: What are the hex sizes and height for the AN310-6 and 310-8 castle nuts?

AN310-6 would use a 9/16 wrench and is 13/32 tall

An310-8 would use a 3/4 wrench and is 9/16 tall.

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