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Tubular nuts...

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Kjelle:
Well, I might bet nuts, but when you can't buy what you need, you'll have to make it!
One annoying problem I have had för at least a couple of years, is the lack of tubular nuts in M3 dimention. M4 and larger, no problem, but M3... Nope. They are needed to fasten the light switch on my Italian bikes, due to CEV being a bit, shall we say, eccentric. Follow the link, and you'll see how they do it
http://www.pillondorino.com/index.php?_r=2511&id=81&cat=15
The lower picture is the complete holder, and the switch is screwed to it with the nuts from below, and the screws from above;
So I made some nuts.
It's one of the first things I have made from metal (ok, so I have made som bushings, but nothing more), and I had to hold a certain length...

Happy Bunny!

Kjelle

Lew_Merrick_PE:
Kjelle,

1) I assume that the attachment force restraining the switch does not have to be too great.
2) I assume that the screw to nut attachment needs to be (fairly) weatherproof.

If those two assumptions are correct, then machining a tubular nut should not be that great of a challenge.  In essence, you are taking a piece somewhat larger than a screw's stock, machining the hole-clearing diameter on it, and then drilling & tapping the M3 thread to the greatest depth reasonably possible.  You may have to reduce the length of the mating screw's body.

So long as you have 1.5X the major diameter of the thread (4.5mm in this case) in engagement, normal (even reaching towards high) loads should not be an issue.  [Impact or high cycle fatigue loading are the main concern here.]  Leaving 1-1.5X the major diameter of thread (3-4.5 mm in this case) between your pilot drill tip and the load face of the nut's head should leave you with plenty of strength even if your are entering the "high load" region.  A bottoming tap will leave you the longest "mating screw engagement (even though that is unlikely to be required).

Does that help?

Kjelle:
Thanks, Lew. I didn't think my humble attempt at makeing this would attract your attention!

The biggest reason for makeing those nuts, is the price of the parts. The parts in the link (both pictures) are approx €27! And I got to practice cutting off brass... Did go quite well.

Kjelle

Lew_Merrick_PE:

--- Quote from: Kjelle on November 22, 2015, 04:01:56 PM ---The biggest reason for makeing those nuts, is the price of the parts. The parts in the link (both pictures) are approx €27! And I got to practice cutting off brass... Did go quite well.
--- End quote ---

I am glad to hear it went well for you.  My tendency is to make them from 12L17 (Ledloy) steel and oxide finish them.  12L17 cuts like a dream, is easy to tap, and finished up beautifully.

Noitoen:
You could get a piece of tube, thread both sides and locktite a screw on one side.

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