Bent Barrel Tooth

[AdamC]

Hello,

Another first for me. I'm attempting to repair a friend's antique watch, and not until after cleaning did I notice a bent tooth on the barrel. The original mainspring had snapped and I wondered if any damage had occurred when this happened, but on inspection, the jewel holes all look fine, it's just this tooth shown in the photos that concerns me now.

So my question/dilemma is, do I attempt to straighten it, and if so, what would be the best technique to do this without causing further damage or snapping the tooth off? I'm very much doubting that leaving it alone will be an option as I'm sure that the watch will stop when the centre wheel pinion meshes with it, though I've not actually reassembled the train yet.

I guess my biggest hope would be to get a replacement barrel. I'm pretty sure the movement is from c.1928 as it has a gold hallmarked case to date it. And although I also know it's an early ETA movement, I am unable to identify the calibre (see photo). Again, if anybody recognises it, that would be fantastic.

Many thanks,
Adam

 

 

Edited August 12, 2020 by AdamC
Photos edit

[oldhippy]

That group of teeth all look in bad shape. I had a few old screwdrivers that I blunted the blades right down and would use whatever one would fit the best and use it as a lever to bend it back. You could try ebay for a donor movement. You never know one or more of our kind members might have a movement with the part and they might be able to help you.   

[AlexeiJ1]

Just be very careful. I ruined a rare Rolex barrel trying to do the same.
I had to fork out $400 to replace it. It doesn't have to be perfectly straight, just slightly more inline. Every bend will stress the metal and could crack it.

[Nucejoe]

I cut a piece of fine sandpaper 1×4 cm to use as a file.

Bend back in little and file some, just enough to get it do its job. 

 

 

[AdamC]

You could try ebay for a donor movement. You never know one or more of our kind members might have a movement with the part and they might be able to help you.   

Looking on the Ranfft website, it looks like the movement might be an ETA 128. The top plate looks identical though the bridges differ on the bottom plate and mine doesn’t have a sub second hand. There’s one of these on ebay so may take a chance for a barrel donor if the straightening goes horribly wrong.


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[AdamC]

Well I think I've successfully done it. Thanks for all your words of advice. My method was to first assemble the train wheels and bridge and check they were freely spinning - all good. Then I tried the barrel held by its bridge without adjusting the tooth and as expected, the spin came to a hard stop and lightly bounced back. The gap of the good teeth is around 0.4. My 0.5 screwdriver blade got over half way between the gap of the bad tooth so using this I did a straight firm push (no back and forth levering as I hoped the wedge of the blade would push apart). On pushing the 0.5 home, I moved onto the 0.6 and repeated. Then onto the 0.8 (sweating by now as it seemed to take more pressure to drive home). At this point, I tried it against the train, and again, the same happened with the bounce back. Feeling my luck was going to run out soon, I applied a tiny drop of HP 1300 oil on both sides of the 1.00 screwdriver blade in the vain hope it may ease the blade in, and it did seem to ease the push home. On examining, I recalled @AlexeiJ1's advice that it doesn't have to be perfectly straight, just more inline, and it did appear improved so trying with the train again, it spun freely with no resistance past the imperfect teeth. Of course I won't know if the performance will be affected until she's up and running but for now, I'm pleased with the result. I've attached a photo of the straightened tooth.