How to fabricate a set bridge for an old pocket watch Helvetia

[Brutus]

Hello again

My name is Doreen and I enjoy very much any topics about watch making and any discussion about watches in general. First I have to mention that I’m not a professional watch maker; I’m doing this as a hobby at home trying to learn as much as I can by reading books and looking up to any good advice.

This time I’m trying to challenge myself to find the right material to fabricate a set bridge for a pocket watch(Helvetia caliber 51-10 derivate from a caliber 51 ) that got broken and I can’t find any replacement for it. I’ve been looking over two years anywhere possible and I did not have any luck. I’m not to familiar with the metal options that I should use for this particular part. Somebody suggested to use Durnico or Durinox for this part(set bridge) since it has elasticity and good properties as for a spring part. Another suggestion that I had  is to use basic 1095 plain carbon steel which is what the original spring likely is, or similar to it.  I would like to have any good advice on this meter. What material do you think will be the best, and were I can purchase it from?

What tools I should use to cut and build this watch part?

 

Thank you in advance for any good advice.

Kind regards 

Doreen 

Edited December 2, 2020 by Doreen
spelling

[oldhippy]

Thin steel is what you want measure the thickness and have a look here I found this from another post on the forum 

 https://sheffieldshims.co.uk/

[Brutus]

25 minutes ago, oldhippy said:

Thin steel is what you want measure the thickness and have a look here I found this from another post on the forum 

 https://sheffieldshims.co.uk/

Thank you for your information. I just send them an email.

 I need this to be somewhere between 0.37mm to maximum 0.50mm thickness.

Regards Doreen 

 

[oldhippy]

If you can't get the thickness you want best to get thicker because you can always take it down, thin might make it flimsy and it might not work very well. 

[Brutus]

You are perfectly write about that.

[HectorLooi]

1 hour ago, oldhippy said:

Thin steel is what you want measure the thickness and have a look here I found this from another post on the forum 

 https://sheffieldshims.co.uk/

Hi OH! Do you think old clock mainspring steel would work? I have some watches missing the setting levers too.

[oldhippy]

If you have the right thickness, don't forget you will need to heat it first, also spring is most likely not to be flat, so be careful. I must admit I used steel sheet, that is what my master used to do so that is what I did,  we had plenty in the work shop I always saved cut offs, in this line of work you soon learn not to throw stuff away. These days you can use these model makers band saws and finish with a file. 

[jdm]

2 hours ago, Doreen said:

 I need this to be somewhere between 0.37mm to maximum 0.50mm thickness.

Buying sheets for just a tiny part makes little sense, you can get a feeler gauge for cheap and sacrifice the most suited blade. I do that all the time for shimming too.

[Brutus]

22 minutes ago, jdm said:

Buying sheets for just a tiny part makes little sense, you can get a feeler gauge for cheap and sacrifice the most suited blade. I do that all the time for shimming too.

I do have a small sheet of annaeled steel that is close to 0.40mm. The problem is I don’t know what type of steel it is. 

[jdm]

1 hour ago, Doreen said:

I do have a small sheet of annaeled steel that is close to 0.40mm. The problem is I don’t know what type of steel it is. 

What you need to make is a setting lever spring, not a bridge.

On your material cut a portion like the one that should bend and see if it's springly properly. If not you can try hardening it a bit and try again. But a feeler blade will work fine for sure.

The difficult part of this work is drilling and filing precisely, you will need an hand vice and a good set of needle files. Of course you can use the broken part for drilling and marking.

[Klassiker]

A technique I have read about, which seems promising to me, is to cut and finish the required profile in a relatively thick and sturdy piece, then use superglue to fix it to a thick plate for support. Then you can file down the thickness.

[nickelsilver]

You want a hardenable steel, preferably (strongly) in its annealed state. As close to final thickness as possible, as it's a long boring process to work it down.

 

Stick the old part on your blank metal. In school we used soft solder, but you can use superglue or whatever is handy. If you have the broken bit stick it in place as close as you can to its proper position. If you don't have it, you can approximate it from the Bestfit drawing. Now you can drill through the holes in the original part, and saw and file around the perimeter of the old part. One way we were shown was using a Dremel type cutoff wheel held in the lathe, with a slotted table in the T rest, and you grind away the blank. I never liked that as the wheel wears and the grinding dust and precision lathe bearings is a bad mix. It goes quite fast with a jeweler saw and file.

 

If you can only find pre-hardened steel, like feeler gage or old clock mainspring (yes it's a fine material), it would be best to anneal it first. Heat it to a dull red and let it cool as slowly as possible. If using clock spring now you can redress it pretty flat, finishing on various grits of abrasive paper to get it uniform.

 

Don't get nervous about making the spring arm too fine, if it's too thick it will be hard to pull into setting position and it could lead to premature wear on the detent and stem slot. Make it as close to original as possible. To reharden (or harden), heat to an orange color and quench in oil. Even if it's a mystery steel this will 99.9% of the time work fine for small pieces like this. I like to hold the part in a steel tube, I use old canisters from seltzer or whipped cream siphons (they are about 20mm diameter, cut the neck off, perfect for watch parts). If you want to get fancy fill the tube with wood charcoal powder before heating to orange, and the part will come out of the oil a nice grey color. If you don't use the tube then it's good to make a little basket out of iron wire to heat the part in; this helps ensure the heating is even all around. If it's dark in color after quenching, brighten it on fine abrasive paper, then heat in a little pan of brass filings over an alcohol lamp until it turns a nice blue color. Now you can finish it, a grained surface off of abrasive paper it nice, and use a toothpic in a hand motor and some polishing paste to finish the notches that work with the pin on the detent. This can also remove the blue from the sides and in the holes. Ah- if there are countersunk holes for the screw/s, do this (with and appropriate drill, hand held in a pinvice) before hardening.

 

 

 

 

[Brutus]

9 hours ago, jdm said:

What you need to make is a setting lever spring, not a bridge.

On your material cut a portion like the one that should bend and see if it's springly properly. If not you can try hardening it a bit and try again. But a feeler blade will work fine for sure.

The difficult part of this work is drilling and filing precisely, you will need an hand vice and a good set of needle files. Of course you can use the broken part for drilling and marking.

You are totally right ; I need to make a setting lever spring not a bridge. I did find an old set of feeler blades on my old tool box; a little bit rusty but I asume it will work fine for this purpose. I’m not sure of what metal it is made out of!
Thank you for your advice 

[Brutus]

1 hour ago, Doreen said:

You are totally right ; I need to make a setting lever spring not a bridge. I did find an old set of feeler blades on my old tool box; a little bit rusty but I asume it will work fine for this purpose. I’m not sure of what metal it is made out of!
Thank you for your advice 

I also have this sheet of annealed steel that is 0.99mm thick; three times more from the 0.37mm (original part thickness). Just wondering if it will be better perhaps to use this sheet of annealed steel; try to build the part. I’m thinking to use the annealed steel sheet as you advise me too even thought I have found the perfect thickness 0.37mm-0.38mm on the feeler blades set. I will also try to anneal the feeler blade to see if I can work with that better. If I can have the blade soft again I will avoid the final process of getting it down from 0.99mm to 0.37mm thickness.

Edited December 2, 2020 by Doreen
Typos

[Brutus]

10 hours ago, nickelsilver said:

You want a hardenable steel, preferably (strongly) in its annealed state. As close to final thickness as possible, as it's a long boring process to work it down.

 

Stick the old part on your blank metal. In school we used soft solder, but you can use superglue or whatever is handy. If you have the broken bit stick it in place as close as you can to its proper position. If you don't have it, you can approximate it from the Bestfit drawing. Now you can drill through the holes in the original part, and saw and file around the perimeter of the old part. One way we were shown was using a Dremel type cutoff wheel held in the lathe, with a slotted table in the T rest, and you grind away the blank. I never liked that as the wheel wears and the grinding dust and precision lathe bearings is a bad mix. It goes quite fast with a jeweler saw and file.

 

If you can only find pre-hardened steel, like feeler gage or old clock mainspring (yes it's a fine material), it would be best to anneal it first. Heat it to a dull red and let it cool as slowly as possible. If using clock spring now you can redress it pretty flat, finishing on various grits of abrasive paper to get it uniform.

 

Don't get nervous about making the spring arm too fine, if it's too thick it will be hard to pull into setting position and it could lead to premature wear on the detent and stem slot. Make it as close to original as possible. To reharden (or harden), heat to an orange color and quench in oil. Even if it's a mystery steel this will 99.9% of the time work fine for small pieces like this. I like to hold the part in a steel tube, I use old canisters from seltzer or whipped cream siphons (they are about 20mm diameter, cut the neck off, perfect for watch parts). If you want to get fancy fill the tube with wood charcoal powder before heating to orange, and the part will come out of the oil a nice grey color. If you don't use the tube then it's good to make a little basket out of iron wire to heat the part in; this helps ensure the heating is even all around. If it's dark in color after quenching, brighten it on fine abrasive paper, then heat in a little pan of brass filings over an alcohol lamp until it turns a nice blue color. Now you can finish it, a grained surface off of abrasive paper it nice, and use a toothpic in a hand motor and some polishing paste to finish the notches that work with the pin on the detent. This can also remove the blue from the sides and in the holes. Ah- if there are countersunk holes for the screw/s, do this (with and appropriate drill, hand held in a pinvice) before hardening.

 

 

 

 

That is quite of impressive and definitely good information you wrote down here. Thank you very much for taking the time to do that; very much appreciated. I’m sure a lots of hobbyist like me will definitely benefit out of this.

I will red this a few times, to familiarize myself with all the terms and all the process stages here. I have to admit, I never worked with metal before, never. Some of the terms are quite new to me; especially that the English is not my native language. I do spoke a few languages but for some reason the English was the hardest one to learn for me. So I do apologize for my broken English and my typos here. 
I’m pretty sure I will have more questions once I will start the building process. First I have to come up with all necessary tools I need for this challenging job. For now I just ordered a Jeweler's Saw Set that will include:

Wood Bench with Clamp

144 Pc. Saw Blades

Steel

Size: 1/0, 2/0, 3/0, 4/0, 1, 2

3" Working Length

PVC Pouch

Saw Frame with Tension Nut

Wooden Handle Adjustable
 

I hope those size blades will work fine for what I intend to do here; to cut the shape I need.
I do have a fine files set to.

Edited December 2, 2020 by Doreen
Typos

[jdm]

You will need small C clamps too for holding to the block. An hand held vice would be better, and needle files as mentioned.  Plus the equipment to drill. Leave a big part of the material to hold the work and cut it off at the end.

All in all that spring is not easy to make. Watch some videos by clickspring on YouTube to get an idea, but consider that what he normally does is much bigger, and in soft metal. 

An important aspect in beginning with this hobby is to start with reasonable projects that can bring reward quickly. Otherwise the learning curve becomes so steep and the amount of expensive tooling plus time required so large that most beginners give up and are not heard anymore. 

[Brutus]

42 minutes ago, jdm said:

You will need small C clamps too for holding to the block. An hand held vice would be better, and needle files as mentioned.  Plus the equipment to drill. Leave a big part of the material to hold the work and cut it off at the end.

All in all that spring is not easy to make. Watch some videos by clickspring on YouTube to get an idea, but consider that what he normally does is much bigger, and in soft metal. 

An important aspect in beginning with this hobby is to start with reasonable projects that can bring reward quickly. Otherwise the learning curve becomes so steep and the amount of expensive tooling plus time required so large that most beginners give up and are not heard anymore. 

I do have a few small c clamps along with a small vise table and a set of needle files as well. Thank you for your advice.

[rodabod]

I’ve made similarly shaped clock parts like detents before. If it were me, I’d buy some suitable quality “gauge plate” as we call it in the uk. If you haven’t worked with a piercing saw much before then I’d recommend scribing two parts in case you cock one up. Also, use quality European/American-made blades when working with high carbon steel. 

[praezis]

All good traditional practice. 
However in such cases I take some coordinates with a microscope, make a CAD drawing and have the part laser cut. 

Frank

[jdm]

1 hour ago, praezis said:

However in such cases I take some coordinates with a microscope, make a CAD drawing and have the part laser cut. 

Would you give an idea of the associated cost in case one of us need to provide an estimate?

[oldhippy]

2 hours ago, praezis said:

All good traditional practice. 
However in such cases I take some coordinates with a microscope, make a CAD drawing and have the part laser cut. 

Frank

That's all very modern. 

[Brutus]

3 hours ago, praezis said:

All good traditional practice. 
However in such cases I take some coordinates with a microscope, make a CAD drawing and have the part laser cut. 

Frank

The point is that I want to learn how to build this by hand...at least that is my goal here.

[praezis]

5 hours ago, jdm said:

Would you give an idea of the associated cost in case one of us need to provide an estimate?

Hi,

I looked it up: in 2018 I paid 30.- for setup and 3.- per piece (+tax).
Tolerance 20µ - what is sufficient here. 
Lower tolerance will multiply setup cost.

Highest cost will be measuring and CAD drawing time here.

Frank

 

[Tudor]

I used to cut mother of pearl for inlay on guitars with a similar jeweler's saw. It should work fine for this. It won't take too long- "rough-in" the part close to final size before you get into the detail work. Gluing it down is a fne idea, but once the holes are transferred, you may consider screwing through both pieces into a wood scrap underneath, to ensure nothing moves. With small parts, small inperfections can cause it to not even fit, let alone work.

Set the blade such that it is cutting DOWN into the material, against the support underneath. We used the handle under the supprt, so cutting with a "pull" stroke. If you prefer to "push", the blade would have to be reversed in your case.

We made our own support block (very similar to yours), since we had all sorts of wood working tools... and used an aquarium air pump to blow the dust away from the cut, so we could see what we were doing. (Pearl dust is not good to breathe by the way)

A drop of cutting oil where you are working will help with the cut, but not with visibility. See how it goes.

Darken the old part, which will be on top, with a black marker, or layout fluid, and polish the blank, underneath, with 600 (or finer) grit paper, to make it white. That contrast will help. Plenty of light of course.

Use a #4 (fine) Swiss pattern file for the last bit of work. Make sure to only push the file; never "saw" back and forth with it. Back and forth will ruin the file. That goes for any file by the way.

Final edge polish I would do with a fine Cratex stick. Basically, these are carbide dust suspended in rubber. It cuts reasonably quickly while giving a good finish. 

And, even if you don't polish all the edges, it is ABSOLUTELY CRITICAL to polish the termination of the spring bit where it meets the larger plate. Any scratch or imperfection here will lead to a crack and failure in the future. Use a 10X loupe and be sure there are no sharp edges, no burrs and no scratches.

To make it fancy, you can chuck the end of a round Cratex stick (sometimes a pencil eraser charged with abrasive works OK too) in a drill or Dremel, spin it and create a pearlage pattern quickly by overlapping the "swirls" created.

[Brutus]

2 hours ago, Tudor said:

I used to cut mother of pearl for inlay on guitars with a similar jeweler's saw. It should work fine for this. It won't take too long- "rough-in" the part close to final size before you get into the detail work. Gluing it down is a fne idea, but once the holes are transferred, you may consider screwing through both pieces into a wood scrap underneath, to ensure nothing moves. With small parts, small inperfections can cause it to not even fit, let alone work.

Set the blade such that it is cutting DOWN into the material, against the support underneath. We used the handle under the supprt, so cutting with a "pull" stroke. If you prefer to "push", the blade would have to be reversed in your case.

We made our own support block (very similar to yours), since we had all sorts of wood working tools... and used an aquarium air pump to blow the dust away from the cut, so we could see what we were doing. (Pearl dust is not good to breathe by the way)

A drop of cutting oil where you are working will help with the cut, but not with visibility. See how it goes.

Darken the old part, which will be on top, with a black marker, or layout fluid, and polish the blank, underneath, with 600 (or finer) grit paper, to make it white. That contrast will help. Plenty of light of course.

Use a #4 (fine) Swiss pattern file for the last bit of work. Make sure to only push the file; never "saw" back and forth with it. Back and forth will ruin the file. That goes for any file by the way.

Final edge polish I would do with a fine Cratex stick. Basically, these are carbide dust suspended in rubber. It cuts reasonably quickly while giving a good finish. 

And, even if you don't polish all the edges, it is ABSOLUTELY CRITICAL to polish the termination of the spring bit where it meets the larger plate. Any scratch or imperfection here will lead to a crack and failure in the future. Use a 10X loupe and be sure there are no sharp edges, no burrs and no scratches.

To make it fancy, you can chuck the end of a round Cratex stick (sometimes a pencil eraser charged with abrasive works OK too) in a drill or Dremel, spin it and create a pearlage pattern quickly by overlapping the "swirls" created.

Thank you for all the information and good advice; very much appreciated.

Im getting together all the necessary tools for the project.