Forming a mainspring bridle

[Neverenoughwatches]

Hi watch people,  what would be the preferred method here , pros and cons ? The options are 1. a riveted end piece 2. A loose piece fitted into a formed socket  3. Bend and crimp the end of the mainspring to be used.   I've started to experiment with a piece of mainspring cut from the one that i am going to use to replace the original set spring taken from an Oris 291 pic2. old spring left, new uncut spring on the right. My first attempt is idea no. 3 which seems to be the easiest to carry out. I'm not quite sure what the spring is made from, it has a slight gold tinge colour to it, but it was easy to anneal and double over. The original spring has been modified by a prevo ( previous repairer ) picture 3, this has a piece riveted to it. The spring I'm going to replace it with was too long but the profile dimensions matched up, the bridle on it is factory doubled over and punched pic1. I'm optomistic that the remaining shape of the replacement will be ok  . After annealing the end of the test piece, it's then shaped with a slight taper to both sides and a knife edge at it's tip created to help catch the barrel wall ledge pic4 then folded over pic5 and pressed tight at the fold to crimp it pic6. shows the original modified riveted spring top and the test piece ready to reharden below it.The shaping is to overcome any error that may occur with squaring up with the mainspring after folding, tbh probably not necessary as the steel is soft enough to easily straighten up. The end is then rehardened and tempered to light blue. Next attempt is to rivet a piece,  a lot more accuracy I'm sure will be required here.

Edited May 29, 2024 by Neverenoughwatches

[HectorLooi]

Maybe because I have a spot welder, my prefered method has always been to spot weld another piece cut off from an old mainspring.

[Neverenoughwatches]

13 minutes ago, HectorLooi said:

Maybe because I have a spot welder, my prefered method has always been to spot weld another piece cut off from an old mainspring.

This way removes the process of any material changing heat treatments . I assume the heat from spot welding is so localised it doesn't change any properties of the spring. 

[HectorLooi]

2 hours ago, Neverenoughwatches said:

This way removes the process of any material changing heat treatments . I assume the heat from spot welding is so localised it doesn't change any properties of the spring. 

The heat is so intense and sudden that it can harden the spot.

[Neverenoughwatches]

2 minutes ago, HectorLooi said:

The heat is so intense and sudden that it can harden the spot.

Doesn't affect any other part of the spring though ?  I guess you would have had problems by now though if it did. I like the idea of riveting, it's about as close to spot welding as you can get without a spot welder .  Negates the heat treatment .

[RichardHarris123]

For interest, I looked up spot welders. The cheap ones, used for battery packs, amongst other things, have decent reviews.  Probably not very powerful but should be enough for a mainspring.  

[Neverenoughwatches]

1 minute ago, RichardHarris123 said:

For interest, I looked up spot welders. The cheap ones, used for battery packs, amongst other things, have decent reviews.  Probably not very powerful but should be enough for a mainspring.  

I like gadgets but I'm tryin to keep that down , for the odd time that i have done this ....... Though i might be doing it more often, its a simple process that saves waiting time and cost of a new one. 

14 minutes ago, Neverenoughwatches said:

I like gadgets but I'm tryin to keep that down , for the odd time that i have done this ....... Though i might be doing it more often, its a simple process that saves waiting time and cost of a new one. 

maybe something like this that welds upto .15 nickel strips.

[nickelsilver]

Spot welding is the best, and is how Generale Ressorts does it. Rivetting is good, but it's an absolute bear getting the holes in the spring and tongue, centered in the spring, then making a rivet that fits well while being as low profile as possible and actually holding up to use. I would by far rather make a balance staff than rivet a tongue on a mainspring.

 

There are a number of spot welders aimed at watchmaking on Aliexpress, I've been meaning to get one. They can do dial foot soldering (using a carbon rod) and spot welding.

[Neverenoughwatches]

1 minute ago, nickelsilver said:

Rivetting is good, but it's an absolute bear getting the holes in the spring and tongue, centered in the spring, then making a rivet that fits well while being as low profile as possible and actually holding up to use. I would by far rather make a balance staff than rivet a tongue on a mainspring.

Thanks nickelsilver I thought it might be a tricky job, but now that you've made it sound so......well riveting i guess,  that i  just have to try it

14 minutes ago, nickelsilver said:

Spot welding is the best, and is how Generale Ressorts does it. Rivetting is good, but it's an absolute bear getting the holes in the spring and tongue, centered in the spring, then making a rivet that fits well while being as low profile as possible and actually holding up to use. I would by far rather make a balance staff than rivet a tongue on a mainspring.

 

There are a number of spot welders aimed at watchmaking on Aliexpress, I've been meaning to get one. They can do dial foot soldering (using a carbon rod) and spot welding.

I have these i forgot about , making life a bit easier.

[HectorLooi]

35 minutes ago, RichardHarris123 said:

For interest, I looked up spot welders. The cheap ones, used for battery packs, amongst other things, have decent reviews.  Probably not very powerful but should be enough for a mainspring.  

I repaired one of the rechargeable spot welders for my mentor a couple of years ago. It used a flat, 12V lead acid cell, like those found in uninterruptible power supplies.

I was surprised that at the maximum setting, it was more powerful than my dental tabletop unit.

The only problem with these spot welders is the power supply. The battery is so small that it is easy to overcharge it and cause sulphation. And if not charged regularly, it would go dead and short out.

[Neverenoughwatches]

4 minutes ago, HectorLooi said:

I repaired one of the rechargeable spot welders for my mentor a couple of years ago. It used a flat, 12V lead acid cell, like those found in uninterruptible power supplies.

I was surprised that at the maximum setting, it was more powerful than my dental tabletop unit.

The only problem with these spot welders is the power supply. The battery is so small that it is easy to overcharge it and cause sulphation. And if not charged regularly, it would go dead and short out.

Mains power supply then ?

[Knebo]

Well, I can't compare the three approaches you (@Neverenoughwatches) mention and the rest of you all are more experienced+advanced than I, but I can tell you that I've once implemented your approach No3 on a Vostok watch and it has worked really well. I just heated it with a simple lighter and then bent it backwards. Done. 

[Neverenoughwatches]

43 minutes ago, Knebo said:

Well, I can't compare the three approaches you (@Neverenoughwatches) mention and the rest of you all are more experienced+advanced than I, but I can tell you that I've once implemented your approach No3 on a Vostok watch and it has worked really well. I just heated it with a simple lighter and then bent it backwards. Done. 

Should maybe have been rehardened and tempered. There is a lot of stress at that point of holding the mainspring, too soft and it could possibly unfold and break when fully wound up

[nickelsilver]

You wouldn't be able to reharden just the bit that has been annealed, without annealing a bit further along. By the time to get to the center the whole thing would be annealed- except the center! They work fine un-hardened at the end, it's actually less likely to break, and you would almost certainly break something in the winding system before deforming anything.

[Knebo]

Here's a picture of it:

[nevenbekriev]

Instead of just folding the spring end back, it is beter to use this way, shown in old book. Jus folded back end often breaks after some time

The small aditional piece can be hardened (rather not anealed). No hardening of mainspring neither of internal , nor  outer end needed as @nickelsilversaid.

I prefer riveting and drill the holes without anealing. Never thought that there may be problem with centering the holes, may be that's why I never had

 

Edited May 29, 2024 by nevenbekriev

[Neverenoughwatches]

2 hours ago, nickelsilver said:

You wouldn't be able to reharden just the bit that has been annealed, without annealing a bit further along. By the time to get to the center the whole thing would be annealed- except the center! They work fine un-hardened at the end, it's actually less likely to break, and you would almost certainly break something in the winding system before deforming anything.

The piece i heated up is really soft, maybe overheated it ? I thought whatever i heat to cherry red and cold quench would fully harden. So anything beyond where it hits red would be annealed ?

1 hour ago, nevenbekriev said:

Instead of just folding the spring end back, it is beter to use this way, shown in old book. Jus folded back end often breaks after some time

The small aditional piece can be hardened (rather not anealed). No hardening of mainspring neither of internal , nor  outer end needed as @nickelsilversaid.

I prefer riveting and drill the holes without anealing. Never thought that there may be problem with centering the holes, may be that's why I never had

 

 

1 hour ago, nevenbekriev said:

Instead of just folding the spring end back, it is beter to use this way, shown in old book. Jus folded back end often breaks after some time

The small aditional piece can be hardened (rather not anealed). No hardening of mainspring neither of internal , nor  outer end needed as @nickelsilversaid.

I prefer riveting and drill the holes without anealing. Never thought that there may be problem with centering the holes, may be that's why I never had

 

Thats my option 2 Nev to form a socket to fit a piece into. So with it not being a sharp bend the steelp doesn't reach a yield point and break ? 

[oldhippy]

The K way is what I was taught. I never thought of a spot welder which I'm sure would be the best bet, but how often are you going to use it £50 plus is a bit much if that is all you are going to use it for. 

[Jon]

21 minutes ago, Neverenoughwatches said:

So anything beyond where it hits red would be annealed ?

Heating to cherry red and leaving to cool at room temperature will anneal the metal.

[Neverenoughwatches]

33 minutes ago, Jon said:

Heating to cherry red and leaving to cool at room temperature will anneal the metal.

Experimenting with this piece of spring which has a slight golden colour ( blue steel ?) even momentary heat from a lighter to blue softens the steel enough to bend easily without breaking it so much so that it takes several reverse bends to make it snap. Trying the same with an alloy spring is different again , that stuff needs to reach cherry red.

3 hours ago, nickelsilver said:

You wouldn't be able to reharden just the bit that has been annealed, without annealing a bit further along. By the time to get to the center the whole thing would be annealed- except the center! They work fine un-hardened at the end, it's actually less likely to break, and you would almost certainly break something in the winding system before deforming anything.

Spot on Nicklesilver even the slightest of heat anneals this spring.

45 minutes ago, oldhippy said:

The K way is what I was taught. I never thought of a spot welder which I'm sure would be the best bet, but how often are you going to use it £50 plus is a bit much if that is all you are going to use it for. 

I would say its easy enough without the welder so unless that comes in for another use probably not worth the investment, problem is i love gadgets.

Loving my proxon drill and stand, one of the best tools i have bought. 

2 hours ago, nevenbekriev said:

Instead of just folding the spring end back, it is beter to use this way, shown in old book. Jus folded back end often breaks after some time

The small aditional piece can be hardened (rather not anealed). No hardening of mainspring neither of internal , nor  outer end needed as @nickelsilversaid.

I prefer riveting and drill the holes without anealing. Never thought that there may be problem with centering the holes, may be that's why I never had

 

Ready to rivet, i have to say thanks Nev for stopping me throwing away these cheap carbide drills, its not really the drill thats the problem it's how they are applied and the user of them. They do need a fast speed and a very steady hold with as little run out as can be achieved. With that they work perfectly , ive just sharpened a 0.5mm drill on a diamond slitting disk that dentists use also recommended by you. Been sharpening drill bits since i was 13, never done a 0.5mm before drilled the spring off no problem.