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Posted

So I bought a small Bergeon winder set and have the opportunity to wind a replacement mainspring as I broke the end tab (the little tab at the end and outside of the spring, maybe called a bridle?) off the original spring for an Elgin wristwatch, movement 412B.

I'm having the same problem I had with the first one. When I wind it in the winder, it will not just wind into the winder barrel because of the tab/bridle which wants to catch. So I stop a little short and then try to push the end of the spring in with tweezers. I do wind the handle in the opposite direction first to take pressure off of the spring, but I can't seem to move it with tweezers. I've watched a couple of videos where it looks easy but it's not.

Maybe I need stronger tweezers but it seems it should not be this difficult. For what it's worth I am using what looks like a NOS spring, but it does say alloy if that makes any difference. Any ideas?

I watched Mark's video on winding and of course it looked too easy 🙂

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Posted

Have you tried not unwinding the spring before you try to coax the bridle in, by unwinding you are not leaving any space for the bridle.

 

Posted

"Have you tried not unwinding the spring before you try to coax the bridle in, by unwinding you are not leaving any space for the bridle."

No, I would have thought the opposite would be true, but after I lube the spring I'll give it a try.  Since this is for training I left the spring dry but that could be why nothing wanted to move.

Thanks.

Posted

The tension you put on the spring when winding will pull it slightly away from the wall of the winder. If you let the tension on the arbour lessen then the spring will try to unwind to its relaxed state and all that spring tension will be on the wall of the winder vastly increasing the friction.

 

Tom

Posted

You must be right because through a lot of trial and error that's exactly what I found, so thank you.  I also confirmed it by pulling up Mark's lesson on winding as well.  The other thing I leaned is that once the end of the spring/bridal is inside the winder barrel, then release tension from the handle "slowly" or the bridal can move and pop back out.  I probably did 10 tries to get it right and in the course of all that slammed the bridal into the notch and broke two of them.  I'm now out of springs for this old ebay beater that I've been practicing on but I think I have a process figured out now...

  • Like 1
Posted

Oh, I'll have to go find them.  And how do you actually weld something so tiny???

Ahh, just did a little googling and there are jeweler's spot welders, of course.  Another rabbit hole 🙂 but looks really interesting.  I just found a thread here started by neverenoughwatches on "Forming a mainspring bridle" that's informative.  I think I'll put that on my "todo later when I get the lathe" category.  

Posted
1 hour ago, linux said:

And how do you actually weld something so tiny???

I use a dental spot welder just because I have one. But a spot welder for joining lithium batteries in battery packs will also work. These are not expensive and easily available from AliExpress. 

The difficult part is actually lining up the mainspring and the bridle so that they are straight.

Portable Battery Spot Welder DIY Mini Welding Machine 18650 Battery Pack Welding Tool 5000mah Weldable 0.25mm
https://a.aliexpress.com/_mqjeO2x

 

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