# Captive nut



## tel (Jan 23, 2012)

Been 'gunna' make one of these for a while now - the completion of Boggy's threading tool gave me the excuse!


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## lazylathe (Jan 23, 2012)

I had that sucker full screen, high resolution and could still not tell where the join is!!! ;D

Nice work Tel!!!
How about a pick of it apart??

Andrew


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## tel (Jan 23, 2012)

;D P'raps in a day or two, when it's run for a while!


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## AussieJimG (Jan 23, 2012)

There's a trick to it right? ???

Jim


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## doc1955 (Jan 23, 2012)

Nice job Tel I have seen these before but I will keep your secret I keep telling myself I need to make one with about a 3/4 nut for a paper weight at work.


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## Jeremy_BP (Jan 23, 2012)

I made one a couple months ago. Still can't stop fiddling with it.


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## Herbiev (Jan 24, 2012)

Great work. I saw one of these on that ABC show " the inventors" around 30 years ago but i dont think it won


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## dsquire (Jan 24, 2012)

tel  said:
			
		

> Been 'gunna' make one of these for a while now - the completion of Boggy's threading tool gave me the excuse!



Tel

Is that by any chance one of those rare 1/2-12 threads? :bow: :bow:

Cheers 

Don


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## tel (Jan 24, 2012)

Yes Don 'Rare and Collectable' - bid big and bid often!


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## arnoldb (Jan 24, 2012)

Thm: Nice one Tel

Looks better'n mine...

Regards, Arnold


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## John S (Jan 24, 2012)

What's rare about 1/2" x 12 ?

One of the first threads ever invented and far better than that abomination of 1/2" x 13 that many lathes can't even cut.


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## ksor (Jan 24, 2012)

Very nice work indeed ! :bow:

But I think it should have been in the "Tips and Tricks" ;D ;D

Now come on, how did you do it - pztt just between you and me !


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## Omnimill (Jan 24, 2012)

I've been meaning to make one myself. Can I give the game away? ;D

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

Next up was to be one of these:

http://streffp-chs.wikispaces.com/file/view/Sneaky+Puzzle+for+a+Machinist.pdf


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## tel (Jan 24, 2012)

Yes, I've been meaning to give that other one a go as well - might give it a try over the weekend


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## dsquire (Jan 24, 2012)

tel  said:
			
		

> Yes, I've been meaning to give that other one a go as well - might give it a try over the weekend



Tel

Very cagey there Tel. Will be interesting!  :big: :big:

Cheers 

Don


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## ksor (Jan 24, 2012)

-->Omnimill

Yeah, that was a good one - I'll try too in a 12mm version !


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## tel (Jan 24, 2012)

John Stevenson  said:
			
		

> What's rare about 1/2" x 12 ?
> 
> One of the first threads ever invented and far better than that abomination of 1/2" x 13 that many lathes can't even cut.



Bit of a joke there John - somebody posted a question on one of the forums about this 'weird' thread he had found in something or other - I forget the details, it's a while ago now.


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## Blogwitch (Jan 24, 2012)

If you want to keep your hands busy while sitting at your bench, and you want to try out your new DRO, then have a go at making this.


http://www.frets.com/HomeShopTech/StepByStep/TwoSlider/twosllider1


John


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## mklotz (Jan 24, 2012)

Known in the American South as a 'smoke-grinder'.


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## bezalel2000 (Jan 24, 2012)

I thought it was an ellipse drawing "compass" but the pencil appears to be missing from the handle end

 ???

Have you tried fixing a pencil to the end of the arm of that thing John?

Bez


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## mklotz (Jan 24, 2012)

Yes, mathematically it is an ellipsograph. The crank handle traces out a perfect ellipse.


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## Blogwitch (Jan 24, 2012)

I've never made one, but one day........

I don't know if there is a mathematical formula for it, but I did used to use two small nails, a length of string and a pencil for marking out rough ellipses onto a piece of paper.

There must be a way of working out the distance between the pins and length of string to give you what you want exactly.


John


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## Bluechip (Jan 24, 2012)

There is a way using a Directrix and a whole lot of convoluted maths ... IIRC  ??? Long, long time ago.

Some insight here.

http://mathworld.wolfram.com/Ellipse.html

Otherwise you can use this construction, much easier.

http://www.mathopenref.com/constellipse1.html

OK John ... you prefer the string bit eh ??

Me too ... 

BC


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## Blogwitch (Jan 24, 2012)

Ahah! Dave,

Now I understand my bit of string and two nails and how to do it repeatedly. 

Thanks

John


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## basement_guy (Nov 10, 2012)

I've never made thread on the lathe.  This was a fun way to learn.

The inside thread was made with a tap.  All outside thread with the lathe.
M6 inside an M10 outside.


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## terrywerm (Nov 11, 2012)

I found that the links to the puzzles/projects on the Frets.com page were no longer working and found that Mr. Ford has done some changing on his website and the captive nut puzzle is now located here:

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

The "Two Slider" has also moved and is located here:
http://www.frets.com/HomeShopTech/StepByStep/TwoSlider/twosllider1.html


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## rleete (Nov 11, 2012)

These are great to take to work.  Put it out in the open and let people fiddle with them.  Make up stories as to how it was made, but never reveal the real secret.


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## ChooChooMike (Nov 15, 2012)

Dang !! Forgot about that little puzzle  Had bought materials a few years ago and put them aside and promptly forgot to make one !


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## basement_guy (Nov 18, 2012)

I showed the pic of the captive nut to my colleague.   He wondered how i made it.
Tomorrow is his birthday so I made him this little present. It is M6 on the outside and M3 inside.


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