Twisted Stem?

[tpt]

Hello folks,

Starting out on my BHI 'technician grade' distance course here and I've got hold of 2 practice pieces. A quartz Seiko and a mechanical 'Chronostar' which has an automatic movement cal. 2788 which I'm presuming is ETA although I've yet to learn where to look for that gem of information...

Apologies if I get terminology a bit wrong to start with but I have a quick question...

The squared section of the winding stem has a slight twist in it. (counter clockwise. oddly)  would it be manufactured like this? or do I need to look at replacing? 

Many Thanks

 

Tim

[Irishcain]

I think you'd need to look at replacing it. I've never heard of a twist in a stem like that.

[tpt]

Many thanks. 

I wish I had a camera that could take a macro pic for you. 

[rogart63]

Many thanks. 

I wish I had a camera that could take a macro pic for you. 

Do you have a loupe ? Put it in front of the mobilecamera . Or any other camera that has a small enough lens . 

Edited March 4, 2015 by rogart63

[tpt]

Do you have a loupe ? Put it in front of the mobilecamera . Or any other camera that has a small enough lens . 

brilliant. here goes...

Edited March 4, 2015 by tpt

[ash145]

Certain eta movements do have a twist in the stem. A "Helicoidal Stem" I think they call them. Something to do with the winding mechanism.

[tpt]

Thanks Ash. That must be what's going on here. 

Love this forum! 

BR

Tim

[Geo]

Now that's interesting.

Never having seen one, can someone please tell me why it is designed with a twist ?

Is it for operating a quick set system?

Edited March 4, 2015 by Geo

[rogart63]

brilliant. here goes...

twisted stem 2.JPG

That stem is shot .Takes a lot of force to twist like that . Nice picture with the loupe :)

Edited March 4, 2015 by rogart63

[clockboy]

I see one on a marvin watch and all worked fine and looked un damaged so left as is.

Why designed like this I just don,t know 

[Geo]

That stem is shot .Takes a lot of force to twist like that . Nice picture with the loupe :)

I'm not convinced Rogart, I think it is meant to be like that. The twist is anti-clockwise, you couldn't cause that damage in the watch because the clutch would free wheel.

[Mark]

I will confirm that this is by design, if you order a new one - it will be twisted just like that.

 

Here is a packet from my parts draw:

 

 

[Vich]

Odd stem but apparently manufactured that way.  There is a bit on the net about it but finding out why it is made like that is harder to establish.  I did find this patent that seems to give an answer, whether its the right one I can't be sure but it certainly sounds like a good explanation.

 

US2655784.pdf

 

Cheers,

 

Vic

 

 

[bobm12]

Maybe the designer had a twisted mind?! :)

 

Good one Vic, it does explain it from what I see. Thanks for sharing.

 

Cheers,

 

Bob

[rogart63]

Learn something new today :-)

[tpt]

For my first watch uncasing I'm happy to have generated such interest!

 

While we're on the subject of twisted things... who'd like to tell me if they think this can be saved??

From Junghans cal. J30 BZ aircraft clock.

Mark? 

 

Edited March 4, 2015 by tpt

[bobm12]

If at all possible I wonder about the time and trouble it would take...on the other hand, maybe it can be sourced (the hairspring alone) to be refitted? Let's hear the experts' opinions...

[Mark]

I suppose it could with enough time and patience, not something I would relish :)

[tpt]

is it possible to direct message on here Mark. I'd quite like to know what you'd charge? I can send relish.  ;)

[Geo]

I did find this patent that seems to give an answer, whether its the right one I can't be sure but it certainly sounds like a good explanation.

Great find Vic. :)

I'm absolutely sure you have found the right answer. It takes a bit of digesting, it would be a lot easier to see it in the metal.

[MortenS]

I believe that the purpose of the twist on the stem is to aid the engagement of the clutch with the intermediate wheel when the crown is pulled into time setting position.

 

Morten