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Old 08-21-11, 05:28 PM   #1
Drakonchik
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What Exactly Is the Thread on a Standard Issue Bicycle Spoke?

I'm using stainless bicycle spokes to make something completely unrelated to wheel-building.

Let's just say it's a fastener, and it will live on a bicycle. I want to use stainless spokes because they are excellent, predictable material for strength and welding etc.

I would like to nut off the thread-end of the spokes with stainless steel nuts (for my application I cannot use chromed brass nipples or aluminum).

Therefore I need to know the exact thread of the standard issue bicycle spoke. (Spoke gauge doesn't matter -- 1.8mm and 2mm both work for me.)

I checked Sheldon's site but no answer. I don't have a thread-measuring tool, so a did my best with a ruler: there seem to be about 19 threads per 9mm of length. Which might indicate .5mm threads. However the diameter of the threads does not appear to fall on any standard metric increment. Diameter seems to fall pretty close to 1/16th" actually. Wondering if the thread is actually a tiny English/Whitworth spec that was set in motion 80+ years ago and the bike industry could never "jump tracks" onto metric.

Hopefully someone will jump in here with a 1 sentence, one spec, on spec answer.
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Old 08-21-11, 05:33 PM   #2
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56 tpi
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Old 08-21-11, 05:42 PM   #3
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Thanks, that is helpful. 1 divided by 56 equals .017857", which equals .045357cm. Since the latter is a non-standard increment, I assume the spec is English or Whitworth, therefore not metric. And that therefore the diameter likely English as well -- perhaps 1/16"?

Can anyone confirm the official diameter at the threads?
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Old 08-21-11, 05:42 PM   #4
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2.2mm x 56 tpi Common 2mm spoke threading

Odd that the thread spec mixes metric and English. It is what it is.

See bottom, 9/10ths of the page: http://www.parktool.com/blog/repair-...hread-concepts
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Old 08-21-11, 05:55 PM   #5
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I been surfing around industrial thread standard resources. This is one of the industrial standards in use in the world currently, and this is what I think the standard bicycle spoke thread is:

2-56: 0.0860 or 43/500 in diameter; 56 threads per inch

.0860" happens to be extremely close to 2.2mm, which is why Park Tool also appears to be correct.

Also by direct measurement spoke thread diameter under my mic is .086". (It was counting tiny threads which was difficult without the right tool.)

Thanks, MudPie, for the rad Park Tool link, I'll be revisiting that page for other stuff too!

So to conclude (note to self!) -- if I'm going shopping for matching nuts, it's 2-56 standard nuts which I will need to find.

Last edited by Drakonchik; 08-21-11 at 06:01 PM.
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Old 08-21-11, 06:19 PM   #6
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It's a United States Standard, UNC-2B Unified Thread Standard, #2 Coarse, aka #2-56. Here's a link to the standard for reference. It's your basic #2 machine screw thread.

One reason small threads like spoke threads are a funny diameter is that they're generally formed (rolled) rather than cut. (all spokes have formed threads). Forming threads raises the metal, with the blank diameter running through the mid-line. #2 screws are made using an 0.80 blank which is the same as a 14g wire.
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Old 08-21-11, 06:30 PM   #7
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I did the 2.2 / 25.4 = .0866 and it didn't look familiar, other than it is 1/10 the sine 60 = .8660, which made me wonder more about the choice of diameter.

I almost made a bold statement: "if you need nuts for 2.2mm x 56 tpi, you might have to make your own", good thing I didn't!

Good that 2-56 will work. It's a coarse thread (UNC),

That Park site is great for torque specs, repair and maintenance help, and technical data in general.

Good luck in your project.
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Old 08-21-11, 07:02 PM   #8
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#2-56 tip

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Old 08-21-11, 08:07 PM   #9
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Thanks all!
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