Multi-start screw threads

[Mick F]

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?

[Brucey]

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.

cheers

[Mick F]

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?

[Brucey]

cost, I expect.

cheers

[Cyril Haearn]

Please to post images and a bit more explanation, hoping to learn something new again

[Brucey]

[Tom17]

Fountain pen caps

[Mick F]

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.

[alexnharvey]

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

[Brucey]

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.

cheers