Does anyone recognise this captive-nut please

Given the paint-job … I am almost sure that this lump came from an aircraft fitter.

It has a half-inch diameter hole, with this natty little insert carrying a captive nut.

… I scraped some paint off, in the hope of finding an identifying mark, but there is none.

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Simple questions:

1. is it a standard part, and does it have a name ?
2. does it, as I suspect, just push into the hole, to be retained by spring pressure ?

Grateful for a simple answer … but if none is forthcoming, I will probably remove some more paint and try pulling !!

MichaelG.

Can't be much help I'm afraid; just been in contact with a friend of mine, in Cornwall, who until recently was an aeronautical tech of some sort, on current RAF aircraft.
He's never seen anything like it, but wondered if it might have originated in a wooden framed plane, such as a Mosquito or Wellington.
What's the larger item which houses it?

Bill

Just a lump of metal, Bill … no longer identifiable,

I am led to believe it’s an off-cut from a bucking block.

Thanks for trying.

MichaelG.

Edited By Michael Gilligan on 09/01/2023 21:43:56

It’s a barrel nut. This picture is an aircraft nut & bolt that used to help hold the wings on a PC-12 aeroplane, for example.

Edit: I have just retrieved it from the windowsill where it lives.  The thin metal part holds the nut in the bore when the bolt is not inserted.

Edited By DrDave on 09/01/2023 22:17:22

Thanks DrDave … that looks spot-on

I just didn’t know the name.

Looks like my assumption that it would just slide out is O.K.

MichaelG.

That's annoying, I'd searched for barrel nut, but not "aircraft captive barrel nut", all the words, but not in the correct combination.

https://www.lisi-aerospace.com/en/product/barrel-nuts/

Bill

Looking at the pictures, it would be interesting to see if there is anything built into it to stop it being installed upside down (i.e. that prevents the bolt entering from the wrong side). Maybe the last thread is malformed like a T-nut.

The nut is made in 3 parts. There is the barrel which has a slot in the back. A high tensile "nut" sits in the slot. A flat strip spring clip holds the nut in barrel and locate the whole assembly in the hole. On most of these the exit side of the nut is deformed. This is primarilly a threadlocking feature but also makes it very difficult to put the male thread in from the wrong side.
One note on this and aircraft fasteners in general. Steel aircraft fastners are generally Cadmum plated and that green paint contains chromium. Both these are toxic so take sensible precautions wash your hands after handling etc.

If you want a dheaper non aircraft similar part intended for D shaped holes and T slots, but can be used upside down, look at D nuts for use in machine building extrusion
Random example www.amazon.co.uk/sourcing-map-Elastic-Aluminum-Extrusion/dp/B07KWVQG6V other suppliers are available.

Robert G8RPI.

When I remove them [there are two, one towards each end of the long hole] I will post a photo to illustrate the construction.

There seem to be many variations on the theme, so we won’t know the detail until then.

Following the very useful responses last night, I bumped the insert gently with a drift and it moved quite easily.

More anon

MichaelG.

Thanks for the additional notes, Robert

MichaelG.

That sounds like Eric Morecambe explaining to André Previn that he was playing all the right notes but not necessarily in the right order.

Mike

I took a close-up of the working side of the nut to show its features. The dark grey nut can float slightly on the barrel section to allow for mis-alignment of the bolt. A pair of roll pins retain the nut (you can see one in the upper right of the nut). You can see why they cost an arm & a leg.

everything aircraft cost an arm and a leg after all it has to be made the best it possible to make it. long way down when something goes wrong

A good example of design to do the job. The bolt is taking sheer load , the captive nut is simply stopping it from moving and subject to very little load. NEAT !

Slightly different design and a lot bigger than the ones I'm used to. No room for pins on the smaller ones but installation forces are probaly a lot lower.

Unfortunatly not everthing on aircraft is made to be the best possible. The cost of aircraft parts is mainly down to certification costs A.K.A "the paperwork" not the basic production costs. It's getting worse all the time. It is one reason why aerospace is so conservative and does not always use leadingedge technolgy. Oid technology components are used long beyond their product life as a non-aircraft item because of the cost of analysing, testing and certification of a more modern replacement.

Robert G8RPI.

If I may correct you, Lee, this is a tension bolt. If the shank is loaded in shear, something has gone wrong with the design! When installed, the bolt is torque tightened to a specified value, normally high enough to prevent the joint gapping under the maximum expected tension loading. The barrel nut has to carry the full tensile load in the bolt. The barrel nuts would be used in places where it is difficult to install an ordinary nut, for example.

For reference, on aircraft at least, a shear bolt would be installed in an interference fit hole and the nut screwed on.

Hi, I don't know much about aircraft construction or maintenance, but I think DrDave is correct. High tensile bolts are normally used where the shear forces are taken by the two components having enough friction to resist shear forces, and to do this, the bolt is in tension, and such bolts should not have shear forces applied to them. These are also known as High Strength Friction Grip bolts.

Regards Nick.

I am pleased to confirm that:

1. Both of my barrel-nuts slid nicely out of the 1/2” hole, with only light tapping applied
2. The plain hole is actually more useful to me
3. The design of the barrel-nuts is similar, but not identical to that shown by Dr Dave
4. One of them carries a part number
5. The line-spacing on that paper is 3/8”

Thanks everyone … mission accomplished

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Everything aircraft usually carries a number. Thin plain washers being an exception. It can be the part number, but more usually it is the production or batch number. Each item being recorded in the build log of the particular item. Be that a fuel system, undercarriage, propeller, etc.

Regards

Gray,