Tissot 27A - Balance spring help

[Boydie]

Hi guys, I'm hoping you can help.

I have a lovely Military ATP Lemania on the bench. Has a Tissot Tissot 27A (none shock protection) movement.

It runs for a few hours. Very very low amplitude. The first coil of the balance spring is touching the teeth of the 2nd wheel. The other coils are below the 2nd wheel. I saw immediately that the spring has been bent and maybe tried to be corrected at some point. See attached image of the watch, you should be able to see. 

I removed the balance complete and removed the balance. I can see the spring is quite poorly shaped. Also there is a brass pin as well as a stud, never seen this setup before holding the spring to the stu, I wonder if it's a bodge, or not?

Looks like the two balance regulator pins might have been bent to lean forward, not sure why, or is this original? See image.

I don't know if this is the original spring but bent, or if this is the wrong spring?

It seems to look like a very bent Breguet type spring, in that the first coil goes over the other coils. I might be wrong and I don't want to mislead you by suggesting Breguet style.

I don't know for sure what a Tissot 27A balance spring should look like. This is a problem I have every time I have to fix any bent spring, I don't know what it should look like from new.

I found an image online (ebay) from a selller of Tissot 27 movement parts, see here. One was completely flat, the other was like a Breguet. I've attached the image of the Breguet looking one (called 'ebay image').

I'm wondering if mine should be shaped like a Breguet, and so should it look like the attached? Do you know what a Tissot 27A balance spring should look like?

How would you approach this problem/fix? I cannot see a spare Tissot 27A spring online for sale. I'm wondering if there is another spring that is the same? How would you suggest I search?

What is the swiss movement code for balance hair springs? I usually use Cousinsuk but they don't list the 27A only the 27 and lots of others like 27. Is there a good site that lists all the swiss codes for watch parts? Like cannon pinion is 240, where can I look up any watch part code?

See attached images of the balance from my watch, maybe these will help you answer.

Hope you can help.

 

Cheers,

Boyd 

[Nucejoe]

 Various  grades of this caliber was put in many brands, some were Bereguet with multiple adjustments, some were elabore grade with less adjustments.

 I am not sure but apparently  the piece your working originally came with flat coil, then some watch destroyer tried fitting an overcoil in, so made a mess . 

BUT then what do I know, 

To save energy, I keep one eye open for answer from learnt members.

Rgds

[watchweasol]

Hi judging by the pictures the last one is a breguet style, yours may have been like it but difficult to make a judgment as the others look as though yours may have been so the balance cock stud point and regulator looks like a flat one.   Inconclusive I know but without looking at it in the flesh difficult.

[nevenbekriev]

What You have is Breguet hairspring , the bridge and regulator on it is seem to be for Breguet too. It is possible that someone has changed the entire balance and thus the hairspring with it, and he had to enlarge the diameter of the overcoil as per the regulator and stud hole, but he didn't know what shape is needed

The spring should be corrected like the one from ebay photo, this type is widely used in pocket and old wrist watches where the overcoil is on the same high as the center wheel and the wheel is big and no place for the overcoil. 

 

Edited December 15, 2023 by nevenbekriev

[CYCLOPS]

I think it should be an over-coil hairspring or Breguet style based on the hairspring regulator pins, most flat hairsprings have what's called a boot style type pins where one side turns to open the regulator pins, I hope this helps, I would try to shape like the last picture and don't forget to re-adjust the beat, the balance should be the same as 27-2 and 27-21T according to the balance staff listed [ best-fit #667D ] non-inc. 

[Boydie]

On 12/15/2023 at 3:02 PM, Nucejoe said:

 Various  grades of this caliber was put in many brands, some were Bereguet with multiple adjustments, some were elabore grade with less adjustments.

 I am not sure but apparently  the piece your working originally came with flat coil, then some watch destroyer tried fitting an overcoil in, so made a mess . 

BUT then what do I know, 

To save energy, I keep one eye open for answer from learnt members.

Rgds

Many thanks, this helped me!

On 12/15/2023 at 3:56 PM, watchweasol said:

Hi judging by the pictures the last one is a breguet style, yours may have been like it but difficult to make a judgment as the others look as though yours may have been so the balance cock stud point and regulator looks like a flat one.   Inconclusive I know but without looking at it in the flesh difficult.

Thanks, this is helping me!

On 12/15/2023 at 5:02 PM, nevenbekriev said:

What You have is Breguet hairspring , the bridge and regulator on it is seem to be for Breguet too. It is possible that someone has changed the entire balance and thus the hairspring with it, and he had to enlarge the diameter of the overcoil as per the regulator and stud hole, but he didn't know what shape is needed

The spring should be corrected like the one from ebay photo, this type is widely used in pocket and old wrist watches where the overcoil is on the same high as the center wheel and the wheel is big and no place for the overcoil. 

 

Thanks this really helps and is encouraging me!

20 hours ago, CYCLOPS said:

I think it should be an over-coil hairspring or Breguet style based on the hairspring regulator pins, most flat hairsprings have what's called a boot style type pins where one side turns to open the regulator pins, I hope this helps, I would try to shape like the last picture and don't forget to re-adjust the beat, the balance should be the same as 27-2 and 27-21T according to the balance staff listed [ best-fit #667D ] non-inc. 

Thanks this really helps and is encouraging me! I’m going to reshape it like the Breguet style and then adjust the beat error, I can already see the beat error is out loads! Ta guys!