Extreme positional variation from a deformed hairspring

[ifibrin]

I was practicing disassembly and reassembly of a Tissot 2700, an extremely small ladies movement, when the balance cock flipped. Long story short, after initial attempts to fix the hairspring, the terminal curve was extremely deformed, and the movement wouldn’t even run. After many more hours of adjusting the terminal curve, and introducing many kinks and straightening them out, I managed to reform a terminal hairspring on the tiny hairspring.

Now the movement has extreme positional variation, (-40 s to +200s) over six positions, change in beat error over different positions, and lower amplitude (230deg) in the vertical positions compared to the horizontal (290deg). I’m quite hesitant to try and fix the hairspring even more, because I’m not sure if the hairspring can take more manipulation.

If this was in a professional setting, what would you do? At some point it would be better to get a new hairspring if possible, as time is money, but this may not always be possible? In a sense, this hairspring manipulation was my first successful attempt at forming a terminal curve, but you can’t  keep retrying as the hairspring will eventually have metal fatigue...

[ifibrin]

I haven’t closed the boot, but this is the final shape of the terminal curve. You can see small twists and kinks even after straightening.

Edited March 30, 2022 by ifibrin

[Nucejoe]

1 hour ago, ifibrin said:

I haven’t closed the boot, but this is the final shape of the terminal curve. You can see small twists and kinks even after straightening.

Surely you know, unless a kink in terminal curve is right inside the regulator slot it wont create any problem. 

Hairspring rubbing or fouling itself seem to be the cause in this case.

 

[HectorLooi]

There appears to be an overlap of the 1st and 2nd coil at the position near the stud.

With the balanced wheel removed and the hairspring on the balance cock, is the collet centered properly?

Unfortunately, it's hard to get a new hairspring and even more so for a ladies watch. I think you are almost there. Centre the collet properly and see if there is still an overlap of the outer coils. Ganbatte!

[ifibrin]

33 minutes ago, Nucejoe said:

Surely you know, unless a kink in terminal curve is right inside the regulator slot it wont create any problem. 

Hairspring rubbing or fouling itself seem to be the cause in this case.

 

The ladies movement is too small for me to see if the hairspring is fouling itself, but that’s a reasonable guess. The terminal curve doesn’t seem to be bouncing evenly between the pin and curb though. I’m also not sure if the hairspring is entirely flat…

it’s difficult to install the balance cock without the Center wheel teeth catching on the hairspring, further contributing to potentially distorting the hairspring everytime the balance cock is installed. I suppose getting around 15 rounds of practice with this movement is already quite a lot.

26 minutes ago, HectorLooi said:

There appears to be an overlap of the 1st and 2nd coil at the position near the stud.

With the balanced wheel removed and the hairspring on the balance cock, is the collet centered properly?

Unfortunately, it's hard to get a new hairspring and even more so for a ladies watch. I think you are almost there. Centre the collet properly and see if there is still an overlap of the outer coils. Ganbatte!

I haven’t removed the hairspring from the balance wheel, all manipulation was done with the balance wheel still attached to the hairspring, without the balance cock.

The hairspring doesn’t have an overlap of the first and second coil near the stud, it’s an optical illusion from the photo, because the coil is near the edge of the balance cock.

[HectorLooi]

57 minutes ago, ifibrin said:

I haven’t removed the hairspring from the balance wheel, all manipulation was done with the balance wheel still attached to the hairspring, without the balance cock.

You have to remove the hairspring from the balance and put it on the cock to test the centering and to form the end curve.

I can't imagine doing hairspring work without a microscope.

[spectre6000]

I can imagine fixing a hairspring without a microscope, as I've attempted it many times. Never was successful, but attempted it.

[DanT]

On 3/30/2022 at 11:06 AM, spectre6000 said:

I can imagine fixing a hairspring without a microscope, as I've attempted it many times. Never was successful, but attempted it.

Same.  I've got a Gruen Curvex (350) balance assembly on my bench at the moment that is currently winning the fight.