Captive Nut

I know how both are done, but haven't tried it yet. That second one is fiendishly simple to do, but I'd never think of how to do it in a million years. The thing that stops me from making the first type is that I really want to do it without having relief at the ends of the threads such as the first picture, but I can't figure out for sure how I would do it without a retracting tool holder. I think I know, but maybe I'm making it harder than it should be. don't want to give anything away here. LOL

I made one years ago without the relief at the end but it turns out looking like a piece of threaded rod with a knob screwed on each end. The reliefs point out that the knob and the threads are one piece.
 
I will have to give in!
I will make one myself by making it without the thicker end at one side, weld, weld, weld.... turn it in the end.
Would that be one solution?

Kai
You could also run a nut onto a bolt and then forge the end of the bolt into a head. That isn't a machining solution, though.
 
Here's my version of the project:

I cut a couple of pieces of 5/8" diameter 304 stainless steel, faced and drilled one end of each:

captivenut01.jpg

Then I tapped them 5/16-18, using my hand tap aligned at the tailstock:
captivenut02.jpg

I took special care to face off the ends as smoothly as I could:
captivenut03.jpg

After screwing in a short section of threaded rod, I could screw the sections together:
captivenut04.jpg



The sections went together nicely, with no gap:
captivenut05.jpg



Mounting the assembled rod between centers, I took a light pass over the length to true up the sections:
captivenut06.jpg



My lathe had most recently been set to cut 20 tpi threads, so I just left it set that way and proceeded to cut some threads centered at the joint in the piece where I'd turned down the diameter a bit:
captivenut07.jpg

Then I stuck a short section of 7/8" brass hex stock in a collet, drilled, bored, and tapped it to match the threads I'd made on the rod:
captivenut08.jpg

Separating the two sections of the rod, I was able to check the threads as I cut, and when I got a nice loose fit, I trimmed up my brass nut.



Here's the whole thing, after I buffed up the rod ends and the nut:

captivenut10.jpg



Screwing it together with a bit of blue Loctite, and cleaning the threads completed my little puzzle:
captivenut09.jpg

With its loosely fitting nut, this gizmo is irresistibly fun to twiddle, and it's a little conversation starter. Even with my myopic close up vision, the joint is invisible.

http://www.frets.com/HomeShopTech/Projects/CaptiveNut/captivenut.html
 
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