Eterna 1472U, long term project

[Boz]

I've taken possession of an Eterna wristwatch belonging to a family member, in need of a service. It's in a sorry state externally. It barely runs and has terrible variation in between positions. It has been serviced in the past. There are four servicing marks in the case back and scratches on all of the bridges. It definitely requires deep cleaning. On examination, I found two significant challenges requiring attention, which are damage to the barrel bridge and the setting lever spring. Spares are no readily available for this movement and donors rarely come on the market. Plus it's time for me to move on from fault finding and parts replacement on to greater challenges.

1: The mainspring barrel bridge pivot hole is ovalised. The barrel arbor is no longer orthogonal to the plate and bridge. There is obvious wear to the upper side of the bridge from the ratchet wheel. 

I've resolved this issue by fitting a bushing to the bridge. I practiced the technique, refining each time on a couple of old citizen movements before working on the eterna: Having mounted the movement on a wax chuck I centred it on the lower barrel pivot using a wiggle stick, ensuring the movement was fully flat on the chuck:

I then fitted the barrel bridge, and bored it out to about 2.7mm to regain the centring. I then bored the hole to 2.99mm using a seitz reamer. Following Perplexr's instructions on youtube, adapted to the tools I have available  I turned a brass bushing 3.00mm in diameter and 0.44mm in thickness, pressed it in to place and broached it to size ready for a test fitting. If the fit is good I'l deburr it and re-plate the bridge.

 

Happily the barrel now sits square, rotates freely without side play and with correct end play

I then finished the bore with a burnishing broach, deburred and replated the bridge. Regrettably I scratched the surface of the bridge when boring the hole. You can see the scratch running up from the chamfered circle where the bushing meets the original material of the bridge. Oh well, it's only one more of many. It niggles me as I managed not to to do this on the practice pieces.

Part 2 of the challenge (the setting lever spring) is rather daunting and I'm struggling to find the materials. I'll post it as a question in the other forum.

 

Edited August 2, 2022 by Boz
Removed extraneous photo

[dadistic]

Bravo!

[watchweasol]

Hi   well done indeed , setting lever springs have been fabricated from feeler gauge material by members in the past, maybe give that a try. 

[Boz]

Thanks @watchweasol I can give that a try

 

Also apologies for the confusion, its a 1274U not a 1472U. Still rare but not actually non existent.

[Boz]

Really making good progress on this now. Barrel bridge and setting lever spring are sorted. I replaced the mainspring with the one recommended by cousins (and also on Watchboy's database) and sadly the watch knocked somewhat at full wind. I replaced the spring with one 0.005mm thinner and it now runs well, with about 295 degrees in the horizontal positions and 265 in the vertical. Timekeeping is good, so it's time to reassemble it. 

The only fly in the ointment is a broken movement fixing screw. I've had a few attempts at making one to match, from pivot steel. I used a razor blade knocked on a #4 file to cut the slot, and a cheap Indian die.  First attempt is a good fit but it doesn't look too smart. I made the cap too thin and the finish is rough:

Second attempt, still rough:

So I've been experimenting with duplicating a variety of screws and finishing them more finely, however I'm struggling to get the crisp finish the original screws have. I I just burnish them with a ruby stone and then an arkansas stone the finish is crisp but not fully polished. If I mirror polish them I lose the crisp edges. I'm using improvised tools (green rouge on a cocktail stick in a rotary tool:

Any suggestions for a better way to do this with basic tools would be gratefully received. 

Edited August 24, 2022 by Boz

[Shane]

Can you tap three or four hols in a piece of stock.  In a triangle or square pattern that would just circumscribe your finger tip.  Depending on the pattern, make three or four screws at a time, thread them all in an polish on a piece of glass.  I've seen the tool that is supposed to be used for this and it looks very expensive and hard to find.

[dadistic]

Simple DIY screw polishing tripod, great idea. 

 

[Neverenoughwatches]

On 8/2/2022 at 3:26 PM, Boz said:

I've taken possession of an Eterna wristwatch belonging to a family member, in need of a service. It's in a sorry state externally. It barely runs and has terrible variation in between positions. It has been serviced in the past. There are four servicing marks in the case back and scratches on all of the bridges. It definitely requires deep cleaning. On examination, I found two significant challenges requiring attention, which are damage to the barrel bridge and the setting lever spring. Spares are no readily available for this movement and donors rarely come on the market. Plus it's time for me to move on from fault finding and parts replacement on to greater challenges.

1: The mainspring barrel bridge pivot hole is ovalised. The barrel arbor is no longer orthogonal to the plate and bridge. There is obvious wear to the upper side of the bridge from the ratchet wheel. 

I've resolved this issue by fitting a bushing to the bridge. I practiced the technique, refining each time on a couple of old citizen movements before working on the eterna: Having mounted the movement on a wax chuck I centred it on the lower barrel pivot using a wiggle stick, ensuring the movement was fully flat on the chuck:

I then fitted the barrel bridge, and bored it out to about 2.7mm to regain the centring. I then bored the hole to 2.99mm using a seitz reamer. Following Perplexr's instructions on youtube, adapted to the tools I have available  I turned a brass bushing 3.00mm in diameter and 0.44mm in thickness, pressed it in to place and broached it to size ready for a test fitting. If the fit is good I'l deburr it and re-plate the bridge.

 

Happily the barrel now sits square, rotates freely without side play and with correct end play

I then finished the bore with a burnishing broach, deburred and replated the bridge. Regrettably I scratched the surface of the bridge when boring the hole. You can see the scratch running up from the chamfered circle where the bushing meets the original material of the bridge. Oh well, it's only one more of many. It niggles me as I managed not to to do this on the practice pieces.

Part 2 of the challenge (the setting lever spring) is rather daunting and I'm struggling to find the materials. I'll post it as a question in the other forum.

 

Well done matey, dont beat yourself up about the scratch, you've made a cracking job of it.

[Boz]

2 hours ago, Shane said:

Can you tap three or four hols in a piece of stock.  In a triangle or square pattern that would just circumscribe your finger tip.  Depending on the pattern, make three or four screws at a time, thread them all in an polish on a piece of glass.  I've seen the tool that is supposed to be used for this and it looks very expensive and hard to find.

I'll give it a go, I'd not thought of polishing on glass, and I can see the three or four screws would keep it level and maybe give the nice clean edges