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LiamB

Hole ended mainspring

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Hello, I need to replace a mainspring in a Waltham pocket watch and have revived a new spring inside of one of those rings. However the mainspring is a hole end and I have no idea how to get it to engage with the hook when installing it into the barrel. I have only installed Swiss mainsprings before. 

Any help would be greatly appreciated! 

Thanks

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You should push the spring in like any other, but it can be a little tricky to align the hole with the barrel hook because as the spring expands into the barrel it will tend to unwind slightly.

I find that it is best to turn the spring slightly so the hook lines up just past the edge of the hole in the spring (towards the coiled spring, not the spring end) before fitting.  As the spring is wound up it will then tend to align naturally with the barrel hook if it wasn’t quite there after fitting. Clearly if the hole starts the other side of the hook you would need it to slip a complete turn when winding to catch on the hook.

 

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  often,  on a vintage pocket watch,  you will find that the main spring had been  shortened rather than replaced.  this requires you to aneal the "hook end"  before broaching a hole or making a "fold".   there are several other potential problems for a "first time" mainspring replacement on a vintage watch.   this very good forum can adress them.  vin

 

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Is this a modern replacement spring or a original spring?

I'm attaching an image this is an original waltham spring and it's shaped different than a modern spring. So to hook into the steel barrels typically found on waltham watches ideally the mainspring should look like the image. The modern spring will just have a hole and it usually will never catch. Then if you look where the bend is you'll notice that the hole edge has a taper that is to wedge into the protruding part of the barrel. So you can try shoving your modern spring in but usually that will not work at the minimum you need to file the taper.

 

Waltham mainspring.JPG

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On 10/7/2018 at 3:49 AM, StuartBaker104 said:

You should push the spring in like any other, but it can be a little tricky to align the hole with the barrel hook because as the spring expands into the barrel it will tend to unwind slightly.

I find that it is best to turn the spring slightly so the hook lines up just past the edge of the hole in the spring (towards the coiled spring, not the spring end) before fitting.  As the spring is wound up it will then tend to align naturally with the barrel hook if it wasn’t quite there after fitting. Clearly if the hole starts the other side of the hook you would need it to slip a complete turn when winding to catch on the hook.

 

Thanks, that method worked very well. The spring slipped right in place!

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