Multi-start screw threads

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Mick F
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Multi-start screw threads

Postby Mick F » 5 Aug 2019, 11:30am

Mrs Mick F gave me an empty nail varnish remover pad box - she often gives me small containers for nuts, screws and washers etc - and I noticed the lid has a four-start thread. A previous one she'd given me has a three-start thread. Looking about, I've found a big plastic tub we keep dog treats in, and that's got a massive eight-start thread. Marmite jars only have single-start threads, whereas jam jars have four-start or more.

I got to thinking about mechanical stuff, and then bikes of course. Sturmey Archer hubs have a two-start thread on the ball ring. Are there any other examples of multi-start threads on a bike?
Mick F. Cornwall

Brucey
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Re: Multi-start screw threads

Postby Brucey » 5 Aug 2019, 11:34am

yes, IIRC the original style of sprocket fitting on a Rohloff hub has a six-start thread.

The helical splines on a Helicomatic hub and inside a Chris King rear hub are also a kind of multi-start thread too.

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Mick F
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Re: Multi-start screw threads

Postby Mick F » 5 Aug 2019, 3:08pm

Rohloff eh?
Interesting.

I suppose that as well as the SA hub need them to stop them tightening so much that you can't undo them.
This then begs the question of why don't freewheel sprocket clusters have them too?
Mick F. Cornwall

Brucey
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Re: Multi-start screw threads

Postby Brucey » 5 Aug 2019, 8:09pm

cost, I expect.

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brynpoeth
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Re: Multi-start screw threads

Postby brynpoeth » 5 Aug 2019, 9:43pm

Please to post images and a bit more explanation, hoping to learn something new again :wink:
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Brucey
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Re: Multi-start screw threads

Postby Brucey » 5 Aug 2019, 10:05pm

Image
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Tom17
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Re: Multi-start screw threads

Postby Tom17 » 12 Aug 2019, 10:12pm

Fountain pen caps

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Mick F
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Re: Multi-start screw threads

Postby Mick F » 13 Aug 2019, 11:41am

Brilliant! I never thought of those.
Just looked at my Parker ballpen I've had for donkey's years, and that too has a two-start thread.
Mick F. Cornwall

alexnharvey
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Re: Multi-start screw threads

Postby alexnharvey » 13 Aug 2019, 11:45am

The cost of a multithread die for fountain pen making is shocking.

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Re: Multi-start screw threads

Postby Brucey » 13 Aug 2019, 11:48am

alexnharvey wrote:The cost of a multithread die for fountain pen making is shocking.


If you think the cost is shocking, you should try using one. They require quite a bit more force than normal. AFAICT most multi-start screw threads are machine-cut, not die cut.

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