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CASTLE NUT 600X6 MS21025-24

Packaged Items
SinglePack of 2
Nut TypeThreadAxle TypePart No.


Castle type nuts manufactured to MIL Specification MS21025 using 4140 steel. Mild steel nuts are not acceptable for use on certificated aircraft. 1-1/4" dia. nuts for 500 x 5 axles, 1-1/2" dia. nuts for 600 x 6 axles.
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Backordered at Wicks so I ordered from here. Works as designed.

Taylor F Verified Purchase

CASTLE NUT 600X6 MS21025-24

October 8, 2023

I put these on my 1956 Cessna 172 and they matched up perfectly

Jason B Verified Purchase

CASTLE NUT 600X6 MS21025-24 (PACK OF 2)

March 21, 2023

Castle Nuts worked out as planned. Packaged well. Steven

Steven B Verified Purchase

CASTLE NUT 600X6 MS21025-24 (PACK OF 2)

February 28, 2023

Exactly what I needed. Thanks!

James J Verified Purchase

CASTLE NUT 600X6 MS21025-24

July 26, 2022

Fit my 172 Axle perfect.

Keith W Verified Purchase

CASTLE NUT 600X6 MS21025-24 (PACK OF 2)

July 5, 2022

I bought these because I needed 1-1/2-16 threaded nuts for a non-aircraft project. Its a hard to find thread size but Aircraft Spruce provided the solution..

December 31, 2020

Perfect as advertised.

William B
September 25, 2020

High quality and a perfect fit.

Ralph L
April 26, 2020

Great Product, Great Fit. Steve

Stephen F
March 21, 2020

Fit my Cessna 150 Axle fine - its a Cessna PN replacement. Allowed me to take off the ugly nut for wheel pants and put on a hub cap.

Bill C
November 29, 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: What are the dimensions on the Matco Castle 5/8-18 (Part Number 06-11815)? Specifically the height of the castle nut and the outer flat side.

The dimensions of 06-11815 are 9/16 inch height x 15/16 inch outer flat side. Looking at the drawings in the "Drawings" tab, these would H and F. For reference, G is 1-1/16 inch.

Q: Are the MS21025-24 axle nuts, your part number 06-11900, usable for certificated aircraft?

It is a Mil Spec part, so as long as the aircraft manufacturer calls for this as a replacement part, it would apply to a certified aircraft. Similar to AN bolts and nuts.

Q: What cotter key is to be used with 06-11815 5/8x18 axle nut?

MS24665-360 or -362 will work just fine

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