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PeterS

Carbon mainsprings

Question

I disassembled an old scrap movement and this is my first encounter with a carbon mainspring.
There is plenty of information on the modern alloy mainsprings across the web but I’m not finding much info about the carbon ones.

1. Disassembly – trying to disassemble it the same way as with Nivaflex it popped out unexpectedly (possibly due to my handling and the small size, about 8mm barrel).

2. Assembly – What’s the best way to get the spring into the barrel? Tools can be purchased for modern alloy mainsprings but I can’t find anything for carbon. Perhaps one of the antique K&D winders that can be seen on Ebay?

3. Barrel arbor fitting – the arbor loosely fits into the coil (pics below) unlike the Nivaflex. I don’t know whether this is how it should be with carbon springs or whether the spring is stretched.

It could do with a new mainspring but as this is a scrap movement, I don’t intend to spend money on it, it’s for practice only.

20190713_164258 (Copy).jpg

20190713_165232 (Copy).jpg

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Just tighten the spring for better grip on arbor.

Can be wound in manually, rinse and grease afterwards, start from outer coils to wind in.Greasing wont be as thorough but hardly the end of the world.

Wear protective gogles.

I assume it is manual wind.

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Yes, this is manual wind.

How do you tighten it? I believe the carbon is very fragile.
After tightening it might work on a Nivaflex winder, at this moment it’s too loose and the eye doesn’t catch the hook.

Manually as place the spring against the barrel inner wall and start winding it in? I can put dots of grease on the barrel and the lid but I’m not sure what you mean by rinse.

Is there a particular tool for winding carbon springs?

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Nothing special about winding a carbon steel spring other than the fact that they may break especially if old and set.  The center eye that fits the arbor is probably sprung on this old spring and since it is a scrap movement, you should take your round nose pliers and practice closing it a bit.  Go gently and in small increments.  if you can successfully close the center eye without breaking it, it should then fit a MS winder very nicely.


RMD

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55 minutes ago, rduckwor said:

Nothing special about winding a carbon steel spring other than the fact that they may break especially if old and set.  The center eye that fits the arbor is probably sprung on this old spring and since it is a scrap movement, you should take your round nose pliers and practice closing it a bit.  Go gently and in small increments.  if you can successfully close the center eye without breaking it, it should then fit a MS winder very nicely.


RMD

Sounds like a good plan. I’m going to have to look for some suitable pliers, the pair I have is certainly not up to the job.

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