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


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On 12/2/2020 at 7:17 AM, 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.

 

 

 

 

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Your suggestions is to “Stick the old part on your blank metal” and work around it...

My question is: how to unglued the original part once I’m done? 

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9 minutes ago, Doreen said:

My question is: how to unglued the original part once I’m done? 

You could glue them together with shellac and then heat them up to separate them when you're done.

Or use a CA glue (super glue) and soak in acetone to separate them.

GS hypo cement might even work in which case use IPA to dissolve the glue.

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17 hours ago, Marc said:

 

You could glue them together with shellac and then heat them up to separate them when you're done.

Or use a CA glue (super glue) and soak in acetone to separate them.

GS hypo cement might even work in which case use IPA to dissolve the glue.

Thank you for your reply and advice. Very much appreciated.

I would probably use super glue; that is the only one I have for now.

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5 minutes ago, Doreen said:
17 hours ago, Marc said:

 

You could glue them together with shellac and then heat them up to separate them when you're done.

Or use a CA glue (super glue) and soak in acetone to separate them.

GS hypo cement might even work in which case use IPA to dissolve the glue.

Expand  

Thank you for your reply and advice. Very much appreciated.

I would probably use super glue

In that case acetone (or nail varnish remover) is solvent. 

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I made one a year ago for a watch i can't remember the movement on now.  Was a pretty small one . But worked nice. I used a blue paint for marking out roughly the size. I used a dremel to cut it out with. Hardest part was to make the holes. So i made them first . DSC00488.thumb.JPG.6abacf98fa96047dc1cafb91f751f789.JPGDSC00487.thumb.JPG.bfae199844959ac7c52180897e2406ea.JPGDSC00485.thumb.JPG.24a55b9c6957f1b50babf6589662beee.JPG

Edited by rogart63
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3 hours ago, rogart63 said:

I made one a year ago for a watch i can't remember the movement on now. 

From a feeler gauge... These are a mechanic lifesavers. I buy too much Chinese stuff like pillar drills, vices, even the baby lathe. I'm totally used to shim up play everywhere. Some of that it's  just me that can't stand sloppy and lose machinery.

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3 hours ago, rogart63 said:

I made one a year ago for a watch i can't remember the movement on now.  Was a pretty small one . But worked nice. I used a blue paint for marking out roughly the size. I used a dremel to cut it out with. Hardest part was to make the holes. So i made them first . DSC00488.thumb.JPG.6abacf98fa96047dc1cafb91f751f789.JPGDSC00487.thumb.JPG.bfae199844959ac7c52180897e2406ea.JPGDSC00485.thumb.JPG.24a55b9c6957f1b50babf6589662beee.JPG

Great job, you did there. Thank you for the advice.

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On 12/5/2020 at 2:57 PM, Doreen said:

Great job, you did there. Thank you for the advice.

My first step on this process.

1.I tried to draw the best I could the original part to the annealed steel (I used the right thickness from the feeler gauge). To draw the broken part that is missing from the original, I used the drowning from the swartchild watchmaker guide. I actually copy the drawing to the steel. It was quite of challenge to do it but I managed. 

By posting every step on this process and explaining the best I can to my knowledge, it may benefit someone else on this matter. So I hope you all agree and help on the way with good and constructive advice as you all did here. Once again I would like to thank all for the impressive response to this subject.

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Edited by Doreen
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2 hours ago, rogart63 said:

Great work. Looking forward to see the finished part.

Thank you. I’m still waiting for my tools that I ordered to arrive; until than I can‘t really move on. I’m very excited about this project. I hope I can build this up; if not at least I tried. 
 

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On 12/8/2020 at 8:07 PM, Doreen said:

Thank you. I’m still waiting for my tools that I ordered to arrive; until than I can‘t really move on. I’m very excited about this project. I hope I can build this up; if not at least I tried. 
 

Some tools just arrived. 
I’m ready to start the process. 
I glued the original part against the steel using super glue and I now I made my first cut... Fingers crossed 
This will take some time...

 

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8 hours ago, Doreen said:

I glued the original part against the steel using super glue and I now I made my first cut... Fingers crossed 

I suggest that you line a side of the original part to an edge of the material, where it better matches both shapes. That will save you some sawing and finishing.

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2 hours ago, rodabod said:

The other thing which I might do (but is not essential) is to drill holes close to the radii which need to be formed - the two detent points. Plus you need to drill holes in it anyway.

Thank you for your advice. Already drilled the holes.

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Question 

I should harden the steel first before testing the part on the watch or I should first make sure is working properly on the movement and than harden the new part steel? I’m just afraid not to brake the tiny little arm.
How I should proceed?

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8 minutes ago, nickelsilver said:

I often test them before hardening, no problems. If it will break unhardened it will break hardened. Definitely easier to retouch when it's still soft.

Thank you very much for the advice.

Ready to do the test. Fingers crossed.

F29934C1-91F6-4538-9932-7714764BAFFF.jpeg

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48 minutes ago, nickelsilver said:

I often test them before hardening, no problems. If it will break unhardened it will break hardened. Definitely easier to retouch when it's still soft.

Time for hardening the steel. 
After hardening it is necessary to temper it?

If so how I should do that at home?

 

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