Mainsprings: How to Tighten Radius At Arbor?

[mzinski]

I wish I were submitting my way of doing this but instead I'm here to ask how to do this: what is the technique for tightening the curve at the arbor side of the mainspring? The new mainspring (MS-48T) is to large a radius where it meets the arbor and does not lock on. I need to tighten the curve to lock on to the arbor. I've heard heating the spring red hot then bending is a technique that works - but it was from an unverified source. 

What is your method of doing this? 

Thanks! 

[oldhippy]

Round nose pliers.  Be very careful these new springs do not like to be altered and sometimes they snap. 

[Willow]

yes as oldhippy has said be careful i have had a couple snap on me, good luck 

[Nucejoe]

check this 3 step curving pliers,

https://www.amazon.co.uk/Forming-bending-looping-concave-Prestige/dp/B00MMU1384

[oldhippy]

Currently unavailable.   

[lexacat]

https://www.amazon.co.uk/Beadsmith-3-Step-Looping-Pliers-Concave/dp/B005025UFI/ref=sr_1_4?crid=2KULBZ27WTK4P&keywords=Wire+Bending+looping+concave+Round+Nose+Pliers&qid=1674739738&s=kitchen&sprefix=wire+bending+looping+concave+round+nose+pliers%2Ckitchen%2C405&sr=1-4

Same same but different. Should be currently available

[mzinski]

So I have those plier and tried to adjust - it snapped. 

Decided to try the annealing then tempering process. I heated the tip of the inner coil red hot with a butane torch. Let it cool, bent into shape. After annealing it was pliable and held position. After getting it bent into shape I heated red hot again then plunged in water for a fast cool. Dried it with denatured alcohol to rid it off the water - I'll install and test tonite. 

[Malocchio]

Are you using those pliers with pocket watch mainsprings? They look a bit too big for wrist watches. I haven't had great success in reducing the coil diameter. The material seems too brittle to be manipulated without heat. I tried with heated tweezers but there wasn't enough heat. Maybe I'll try a soldering iron next time. That way I could keep the heated area pretty confined.

[mzinski]

21 hours ago, Malocchio said:

Are you using those pliers with pocket watch mainsprings? They look a bit too big for wrist watches. I haven't had great success in reducing the coil diameter. The material seems too brittle to be manipulated without heat. I tried with heated tweezers but there wasn't enough heat. Maybe I'll try a soldering iron next time. That way I could keep the heated area pretty confined.

Yes, amongst a few other jeweler's pliers. Totally agree, it's too big for wristwatch mainsprings. 

I used a butane soldering iron in torch mode. It create a very hot but small and directed flame that I was able to aim at the inner coil and heat one coil. I was concerned going in to it it'd effect the whole spring or heat up a large area but it was totally fine. 

[mikepilk]

On 1/26/2023 at 6:06 PM, mzinski said:

So I have those plier and tried to adjust - it snapped. 

Decided to try the annealing then tempering process. I heated the tip of the inner coil red hot with a butane torch. Let it cool, bent into shape. After annealing it was pliable and held position. After getting it bent into shape I heated red hot again then plunged in water for a fast cool. Dried it with denatured alcohol to rid it off the water - I'll install and test tonite. 

It will be brittle after you hardened it. I would temper it before you fit it, to prevent possible breakage.

I have an Eterna Cal 12804, effectively an ETA 2804, but for some reason they made the barrel arbor much smaller - something like 2mm. I broke 2 springs before one worked. I just use tapered round nose pliers.

It's hit an miss, but annealing was a good idea.

[mzinski]

2 hours ago, mikepilk said:

It will be brittle after you hardened it. I would temper it before you fit it, to prevent possible breakage.

I have an Eterna Cal 12804, effectively an ETA 2804, but for some reason they made the barrel arbor much smaller - something like 2mm. I broke 2 springs before one worked. I just use tapered round nose pliers.

It's hit an miss, but annealing was a good idea.

Any recommendations on how to best do so? I annealed it by making red hot and allowing to cool. I hardened it by making it red hot then quenching it. I read tempering requires a slow cooling but haven't found clarity on how to heat then cool. 

[nickelsilver]

The alloy in modern springs (Nivaflex) is precipitation hardened over a period of a couple of hours at around 500C in a vacuum oven. You won't really get any hardness by heating to red and quenching, like with high carbon steel. In fact the annealing process is to heat to 1000-1100C (which would be red hot) and rapid cool, i.e. quench.

 

It should be totally fine though annealed at the center; after the first turn of wind it's held in place on the arbor by the further wraps of spring, and it's still plenty strong enough to hold onto the hook. That small length not being "springy" will have no effect on performance.

[mikepilk]

1 hour ago, nickelsilver said:

The alloy in modern springs (Nivaflex) is precipitation hardened over a period of a couple of hours at around 500C in a vacuum oven. You won't really get any hardness by heating to red and quenching, like with high carbon steel. In fact the annealing process is to heat to 1000-1100C (which would be red hot) and rapid cool, i.e. quench.

Interesting information. Thanks for that, I would never have guessed. I assumed it was a carbon steel.

[nickelsilver]

On 1/28/2023 at 12:53 AM, mikepilk said:

Interesting information. Thanks for that, I would never have guessed. I assumed it was a carbon steel.

There are quench hardenable stainless steels, but not used for watch springs. The old blue steel springs are high carbon steel, and you can often see at the center where the temper has been drawn back further to facilitate shaping the coil.

 

I'm not sure who came up with the first modern "unbreakable" mainsprings, but it was likely Elgin with their Elgiloy alloy. It's similar to Nivarox, a few percentage points off here and there, but with the notable addition of manganese (and in metallurgy a few percentage points can make a lot of difference). Elgiloy is still in production but is used for lots of high tech stuff now, not mainsprings. These alloys are known as Cobalt alloys, as the cobalt content is higher than all the other alloying elements- and much more than iron.

Edited January 29, 2023 by nickelsilver