Mainspring inner coil

[transporter]

Quick question, how do you guys tighten the inner coil of a new mainspring to fit the arbor?

Every mainspring I’ve bought has never had the inner coil at the correct size to fit the arbor. 
I,ll be honest I’ve snapped a good few attempting to re size the coil, I’m now turning to heat to soften it up whilst it’s still held in its transit packaging.
 

[mikepilk]

The answer is - very carefully. Don't just squeeze on the outside of the inner coil, or it will kink an be wrecked. If you put a rod in to stop it kinking, you usually can't get it to deform enough.

You shouldn't need to heat it, the ends of the springs are soft enough to reshape.

I have an Eterna where the arbor is much smaller than inner coil size. I broke two springs before getting it right.

I use some fine round nose pliers - put the point in to the inner coil and gently twist to reshape the coil

[Nucejoe]

Check this bending pliers.

https://images.app.goo.gl/91HpYZ8Q72YpXM4i7

Inspired to make me one out of a worn long nose pliers.

[mikepilk]

I couldn't find any bending pliers any near fine enough (2mm). So I bought pliers with two tapered rounded ends.

[Nucejoe]

Oh shoot that one gives  an error, dynamic link something. 

Here is another one.

https://www.etsy.com/listing/612239311/wire-working-pliers-wrapping-looping?ref=share_v3_lx

[Jon]

Those pliers that @Nucejoehas posted is exactly what I use, but sometimes the inner coil needs a little more and I use round nose pliers in the same fashion @mikepilkhas said. It's very easy to break that inner coil though, as the hole/slot weakens it.

[transporter]

 Cheers for your input guys. Looks like we are all basically doing the same thing, I have a set Of them wire bending pliers although mine are far to large to deal with a watch mainspring.

I will try my fine round nose pliers on the next spring, I will grip the spring before the hole and then start to turn it as the arbor would whilst the spring is in the barrel. 
Hopefully this will work without another breakage 

[clockboy]

In my experience the inside curve must be supported by something round such as the shaft of a screwdriver. Without this support it either reduces out of shape or as you have found it snaps. I use brass tweezers and just gradually reduce. I have never annealed a spring. 

[transporter]

Well I just tried to reshape the end of the old spring using the round nosed pliers, basically holding the spring just before the end ( abit like leaving clearance for the hole ) .
I then started to attempt the reshape, 3 times and it snapped! 
now I’m not hamfisted when it comes to this work but in my experience this shouldn’t happen.
I then put a small amount of heat on the spring and could manipulate it perfectly around the pliers to the correct size required.
So the Jury it seems is out on this subject, I haven’t yet tried winding the new spring onto one of my vintage K&D winders, I wonder if that would reshape the inner coil without damage or heat?

[mikepilk]

Hmm, I've never annealed the end of a spring, but then I've broken a few, and @clockboy says he's never annealed.

If you anneal it, would you would need to harden/temper it, so that it would keep it's shape and not break with fatigue due to bending? Don't know, maybe not?  Not sure how easy it would be to temper the end of a thin spring.

I've just tried putting tight bends in three scrap mainsprings I found. Two bend easily, the third snaps easily, and seems impossible to bend, unless I anneal it. 

Some springs are softer than others - if your mainspring winder is bigger than the inner coil, some inner coils increase in size, some don't

Edited December 21, 2021 by mikepilk

[transporter]

Sounds like your spring is the same as mine, I’ve just tried at different points and it snapped at every point!!

I will see if I can hold the arbor with a pin vice from the rear of the barrel and then with the cap off pull and hook the main spring onto the arbor, then place the cap back on and wind with the pin vice, hopefully this will reshape the coil to the arbor without snapping the damn thing.

[clockboy]

When bending the inner spring the inside of the coil must be supported or it will break. A balance tac is good because you can fully support when adjusting. Also very gradual persuasion it also required I usually use brass tweezers or I have used occasionally hairspring tweezers which have convex and concave tips. See pic:

 

[mikepilk]

1 hour ago, clockboy said:

When bending the inner spring the inside of the coil must be supported or it will break. A balance tac is good because you can fully support when adjusting. 

Round nose pliers (as the OP was using), do support the inside of the coil. Doesn't stop it breaking though 

[transporter]

1 hour ago, clockboy said:

When bending the inner spring the inside of the coil must be supported or it will break. A balance tac is good because you can fully support when adjusting. Also very gradual persuasion it also required I usually use brass tweezers or I have used occasionally hairspring tweezers which have convex and concave tips. See pic:

 

Gotta say if I had a set of dumont hairspring tweezers I wouldn’t be using them on mainsprings, I guess due to their price I’d be looking after them. I assume you do look after yours.

13 minutes ago, mikepilk said:

Round nose pliers (as the OP was using), do support the inside of the coil. Doesn't stop it breaking though 

Yes, they do support and yes the spring still breaks. 
I’ll have one more chance to get a new mainspring in today as I have one coming from cousins and the customer is expecting the watch back tomorrow, I can always put back the lead time but I hate doing that.

[mikepilk]

Looking in 'The Watch Repairer's Manual' by Henry B Fried, the way to adjust the inner coil end :

There's no mention of annealing. Though he does say that the outer end of the spring does need heating if it needs folding  over.

I've tried the method shown in Fig 32. It works if the spring is 'soft' and pliable, but not if it is more brittle and 'springy' - you need to bend it tighter than the arbor diameter to get it to keep it's shape. 
It's also difficult not to scratch the barrel. 

It would be interesting to hear from someone who's been to watchmaking school to hear if this was covered.

Edited December 22, 2021 by mikepilk

[transporter]

Ooohhh, I’ll have a look, I do peruse his books and the others from time to time, 
I shall have to take more notice in future, thanks for bringing that to my attention

[clockboy]

OK I have uploaded a couple of vids on youtube showing my method. The first spring is quite big  with a height of .45 x .20 strength . the second vid is a smaller spring a height of 1.1 x .10 strength. Apologies for the quality but it was recorded on my iPhone using a stand also the second vid is not published until the 24th. so it might not show.

 

https://www.youtube.com/watch?v=kjoUvRwogXA

 

 

 

 

[mikepilk]

Good idea using the balance tack (though I usually stab myself ). The taper gives you a good range of diameters.

Some springs seem so hard that even taking all precautions they are likely to break. I wonder, if you have such a spring, if annealing is the right way to go, and is it then necessary to harden/temper the end after ? 

If not annealing, I wonder if a bit of heat would help - heat the tools in boiling water ?

Edited December 23, 2021 by mikepilk

[transporter]

Thanks for the very helpful video, another bench trick not found in manuals. 
i did eventually Resort to a little heat just a flash and that allowed it to reduce
I notice in the video you are manipulating a steel spring, mine is a modern alloy one, I don’t know how much of difference that makes, but with the remains of the old  spring I tried everything to reduce its size apart from heat and every time it just snapped.

i will try the balance tack approach in the future though so thank you for that tip

[clockboy]

The springs I used were from my stock of springs. Before this method I broke many springs but since using this method it works every time including the modern springs. Personally I am not sure if heating a spring alters it’s spring effect.

[transporter]

Well I definitely be using your technique in the future, time will tell on how the spring handles in the barrel. 

[DaveL]

I found a pair of pliers concave bottom jaw round upper from RioGrande worked perfect thank for all the insight and info Dave , cheap about 6 bucks