MS21042 jet nut, sort of...

[rocketbob]

I have a dwindling bin of some MS21042-like nuts, but with a twist...they have a washer stamped onto them. Where I got them from had no idea what they shipped me, and didn't know anything about them. They're very handy in limited access areas where its a pain to put a washer on and thread the nut on at the same time. I'd like to get some more but I haven't been able to find any info on what they're called or a part #. Anyone familiar with these?

[avee8tor13]

Give this a try. I used these in a number of areas.

http://www.aircraftspruce.com/catalo...es/MS21042.php

[Rick6a]

Originally Posted by rocketbob

I have a dwindling bin of some MS21042-like nuts, but with a twist...they have a washer stamped onto them. Where I got them from had no idea what they shipped me, and didn't know anything about them. They're very handy in limited access areas where its a pain to put a washer on and thread the nut on at the same time. I'd like to get some more but I haven't been able to find any info on what they're called or a part #. Anyone familiar with these?

Bob,

Its basic part number is ST3M774 indicating it was originally designed to a McDonnell-Douglas specification. It is entirely possible you may have seen the nut sold as surplus aircraft hardware on eBay.

For our purposes, an MS21042 aka NAS1291 works just fine. Always considering weight, I used mininuts in almost all areas where Van’s routinely calls out AN364 or AN365 nuts. A mini nut or "jet nut" or "jap nut" weighs in about ½ an AN364. Attaching a washer to it is not difficult. All it takes is one drop of super glue to afix a washer to the nut. Doing so makes its installation in difficult to reach areas much easier to accomplish.

[avee8tor13]

Rocketbob, I did not look at your picture very close. I did not noticed the additional washer. Were you able to find any?

[rocketbob]

Originally Posted by Rick6a

Its basic part number is ST3M774 indicating it was originally designed to a McDonnell-Douglas specification. It is entirely possible you may have seen the nut sold as surplus aircraft hardware on eBay.

Yep, I think I got them on ebay a few years back. Thanks for the info Rick.

Originally Posted by avee8tor13

Rocketbob, I did not look at your picture very close. I did not noticed the additional washer. Were you able to find any?

Nope, haven't found any, now that I have a part # to look for.

[jimgreen]

Seems to me the built in washer just increases the bearing area. It doesn't function in the same way as a normal washer which is there to protect the surface from galling as the nut is tightened. Shoot me down someone.

[Kevin Horton]

Originally Posted by Rick6a

Typically installed on slightly tapered surfaces, perhaps the official name of this hardware item can clarify:

ST3M774---NUT ASSEMBLY-HEX, SELF ALIGNING, SELF-LOCKING, 450?

Self aligning - installed on tapered surfaces - what kind of magic does this thing use? How does it work?

[Rick6a]

Originally Posted by Kevin Horton

Self aligning - installed on tapered surfaces - what kind of magic does this thing use? How does it work?

For a pictorial example of a self-aligning nut assembly, see post #8 here:
http://www.vansairforce.com/communit...t=tapered+shim

Bob,

I apologize for originally putting out bad information in my first response to your query. Upon closer examination of your photograph, I realized I misinterpreted this spec which does describe a self-aligning ST3M774:

The example shown in your photo is NOT an ST3M774. Your photo seems to more accurately suggest this type of common aircraft nut:



I suggest you simply research the piece of hardware using the following key words: "6 Point Nut Captive Washer." I regret the confusion I may have caused.

[rocketbob]

If the jetnuts I have are self-aligning, I can't see how they could handle much more than a degree or two of misalignment. I assume its because the nut crushes against the washer surface as its tightened.