Thread Details For Vintage Car Wheel Spokes

Hello, when i used to build wheels for push bikes we would ocasionaly need an odd size spoke that we either didn't have or wasn't made, we always used a thread rolling machine (hand held thing) to put a thread on a londer spoke we had cut down. It might be todo with the small diamitor vs high loading or that we were threading stainless steel, not sure which.

I don't remember using more than one die set for different diamitors. But their probably available in different pitches, they were 3 metal rollers with the thread pattern on, you migt be able to get the correct set and buy a bike shop mechanic a beer :) , the tools were quite comon , every bike shop I worked in had one.

Stuart

Just had a google, the work end of the tool looked like this , http://simplybearings.co.uk/shop/pr...O0HFxVznNm7X1M2wHWPWDdT9IDalX2kehEaArbf8P8HAQ
 
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I do have one of those bicycle thread rolling tools. A photo of mine is attached. It has a rib underneath that clamps into a vice and the spoke (1.8mm - 2.3mm diameter) is clamped with the one winged nut on the left end. This is too small and light duty to do spokes for cars and motorbikes, which tend to use 3/16" high tensile steel. The thread pitch is very much finer for the bicycle spokes - I believe it is 8BA or very close to it.

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n.glasson said:
I do have one of those bicycle thread rolling tools. A photo of mine is attached. It has a rib underneath that clamps into a vice and the spoke (1.8mm - 2.3mm diameter) is clamped with the one winged nut on the left end. This is too small and light duty to do spokes for cars and motorbikes, which tend to use 3/16" high tensile steel. The thread pitch is very much finer for the bicycle spokes - I believe it is 8BA or very close to it.

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Interesting to know their high tensile steel, i didn't realise they were that much bigger in diamitor, i just helped a friend rebuild/tension his electric bike wheel which had quite short and fat spokes (about 1/8 to 3/16 maybe) that wasn't too fun, the amount of torque required to get some stretch into the spokes was soo high i thought thhe nipples were going to start poping out of the rims :)

The one thing with the rolling tools is I never remember a thread going wrong (in the putting into spoke).

Awaiting pictures of awsome looking wheels :)

Stuart
 
This thread was used for small diameter threads (below 0.25 inches diameter). The thread has radiused roots and crests and has a flank angle of 47 degrees and a half degrees. The thread size varies from BA number 23 (0.33 mm diameter with a pitch of 0.09 mm) to BA number 0 (6mm diameter with a pitch of 1 mm). Relative to the Whitworth thread the depth of the BA thread is smaller size for size. The thread form is now redundant and has been replaced by Unified and Metric threads.The form of the thread is shown in the diagram:

If

p = pitch of the thread

d = depth of the thread

r = radius at the top and bottom of the threads

then:

d = 0.6 p

r = 2 p /11

Here is a link to standard BA Thread sizes http://www.trfastenings.com/pages/BA+Thread+Sizes

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If you just want to clean up the threads on the nipples. I would make my own cleaning tap using the information that I posted. Turn and thread a piece of O-1 rod to specs shown and then gash the thread to form a tap. Heat treat it and use it to clean the threads.
 
I am wondering if the threads are stretched.
They may have started life as a 60*, and then got stretched to ~65* when torqued. Would not be the first oddity one could encounter on a British car. The British after all are the only ones to successfully use an alloy that can rust even when under a thick layer of oil. We used to always joke that MB and AM parts are made from unobtainium.
It would not surprise me if it was some aerospace thread similar to the MJ thread.

Have you tried contacting Aston Martin? A lot of manufacturers maintain a library or museum for their classics. If you reach the right person there, they might be able to answer your question.
 
Spoke section shown in my microscope pic is from a brand new unused spoke so it is not stretched. It is probably more likely that the thread rolling machine is very well worn. Aston Martin won't be much help - I am rebuilding an Austin. I have been playing with some of the worst spokes and finding that M5 is so damn close to the original thread that it is hard to distinguish between them. I can run a M5 die nut on a spoke and it threads firmly into a new nipple and I can run a M5 tap thru a nipple and it threads on nicely to a new spoke. I'll run with M5 and see how it goes.
 
/Doh
Seems I read to fast. I just assumed the 7 was an Aston Martin I had not heard of. Just looked up Austin, looks pretty bleak on getting info from the company...
 
This is the car. It is a 1929 Austin 7 - built into a special in the 80s. In the photos it has 17" wheels on the front and 16" on the back. I plan to make it 17" all round to make it lighter and so I don't need to carry two spares. As pictured, without fluids or battery - it weights 400kg. It won't go particularly quick but it will seem like it!

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