How to tighten a watch mainspring onto an arbor?

[HorologicalHobby]

Recently my bergeon mainspring winder set has expanded the arbor loop/hook, and in trying to make it catch the arbor on an automatic mainspring, I broke it. I was barely able to get it to move before it broke. Is there an easier way to do this?

[clockboy]

Not sure of the problem you encountered could you post a pic.

[Tiktok]

Also not sure what you are trying to say but if you mean the arbor on the mainspring winder has made your mainspring too big to catch on your barrel arbor then you aren't using the correct mainspring winder. You can somtimes get away with tightening them a bit but more often than not it will break or come back as a return job because it's snapped weeks/months down the line. If you dont have the correct size mainspring arbor for a job then just order a new mainspring for that calibre and put it in straight out of its ring.

[HorologicalHobby]

Sorry for the confusion, I pulled a stock photo and highlighted what I meant.

The mainspring winder opened up that center loop, and made the arbor slip. With the bergeon set, like mark's, the winding handles are paired to a similarly sized winding barrel. There's no way to use a smaller handle, or you would need to use a smaller winder, and that would crush the mainspring.

 

[chadders1966]

Hi

I've read a number of posts on different sites (including clockboy on this one I think) that the arbors on these sets, even brand new ones, are sometimes too big - I have to agree. I do have some special pliers for tightening the ends of mainsprings but am reluctant to use them much as the springs are so hard and brittle.

Obviously the size of the winder is dictated by the size of the barrel but I have found with practice that you can use a handle from a smaller winder if you are careful, but it is fiddly and not ideal. Not sure what the answer is, other than buy a new mainspring as it only seems to affect more modern watches. Adjustable arbors maybe ;)?

Stephen

[clockboy]

OK got it. This does happen now & again & what I do is to close the gap using brass tweezers BUT most importantly have some thing round inside the bend for support or the spring will snap. I have found either a thin piece of pegwood or a cocktail stick works fine. & just gently a bit at a time re-shape & close the gap.