Omega Chronostop (Cal. 920) with Loose Canon Pinion

RunningOnTime · Jul 1, 2021

Hello! I have been working on an Omega Chronostop that I recieved from my grandfather a few months ago. The timepiece is gradually coming together, however it seems that the cannon pinion is loose. The two common symptoms that my watch has shown is no resistance when I set the time by pulling/turning the crown and the hands slowing down or even stoping despite the rest of the movement operating normally. I have tried to find either photos or videos online regarding cannon pinions, and I was wondering if anyone has had experience servicing calibre 865 or 920 (the date wheel version) canon pinions. Is it theoretically posssible to tighten the canon pinion so as to not purchase any new/old stock or is a new part inevitable? Also, in the case that a new canon pinion is needed, would it be possible to replace said canon pinion without disassembling the rest of the movement? I will post a photo a little later when I have time.

Thank you all so much in advance!

--Gavin Timmons

ChrisN · Jul 1, 2021

RunningOnTime
Is it theoretically posssible to tighten the canon pinion so as to not purchase any new/old stock or is a new part inevitable?

Thank you all so much in advance!

--Gavin Timmons

Yes, you can tighten the cannon pinion and this is not an unusual issue. Even if you bought a new one, it could be too tight or too loose and both issues can be resolved.

Do you have a staking set?

Cheers, Chris

RunningOnTime · Jul 1, 2021

ChrisN
Yes, you can tighten the cannon pinion and this is not an unusual issue. Even if you bought a new one, it could be too tight or too loose and both issues can be resolved.

Do you have a staking set?

Cheers, Chris

I do not have have staking set. How much would that set me back if I were to buy one and would this work with all canon pinion designs? Also, would this involve me removing the canon pinion, and if so, could this be done without completely disassembling the movement? The movement is fully assembled and I would not be quick to jump on having a chronograph disassembled unless completely necessary.

Thanks,

Gavin Timmons

ChrisN · Jul 2, 2021

Hello Gavin

Did you assemble this movement? If you didn't remove the cannon pinion, then how did you clean and lubricate the second wheel?

If you didn't assemble it, then just return the watch to the watchmaker who did and explain your issue.

Tightening a cannon pinion is easy but reading your latest post, I would recommend that you first get a book about repairing watches or, take your watch to a watchmaker. I'd be concerned if I explained this and you damaged your watch because you don't have the background knowledge to do it.

Cheers, Chris

RunningOnTime · Jul 2, 2021

ChrisN
Hello Gavin

Did you assemble this movement? If you didn't remove the cannon pinion, then how did you clean and lubricate the second wheel?

If you didn't assemble it, then just return the watch to the watchmaker who did and explain your issue.

Tightening a cannon pinion is easy but reading your latest post, I would recommend that you first get a book about repairing watches or, take your watch to a watchmaker. I'd be concerned if I explained this and you damaged your watch because you don't have the background knowledge to do it.

Cheers, Chris

Hello Chris,

I do have some experience at disassembling watches and cleaning them, however I have never done a chronograph before. As far as I know, I do not believe my grandfather had the watch serviced in a while (I could be wrong though). Most of the components that I was repairing were not directly related to the movement, and as a result, I have not had to disassemble the movement for cleaning and lubrication. Than canon pinion puts me in a little pickle as I am not confident about servicing a nice chrono movement. I have college in the fall, so money is also an issue if I get it done by another watchmaker. Even after looking endlessly at watchmakers handling the movement (and its near identical twin, the Calibre 865), I still am not too keen on getting the screwdriver and tweezers out. I've also tried reaching out to a local watchmaker, however I have not had any response yet.

Thanks,

-- Gavin

ChrisN · Jul 2, 2021

Hi Gavin

It sounds as if you have enjoyed working on your grandfather's watch and trying to bring it back to life. I saw your other thread about a dial screw as well. It's a nice thing to do as it sounds like an heirloom that you can enjoy for many, many years.

Removing the cannon pinion and tightening it doesn't involve stripping the whole movement and it is probably a similar design to what you've seen before as the vast majority of calibres have this style. It is not part of the chronograph system and is part of the basic movement.

However, the issue you're having may be a blessing in disguise as the movement hasn't been serviced for some time (you say) and so it is likely dry and dirty. If you run it like this, you will probably be wearing out components that will be expensive to replace and you'll get a very big bill in the future.

It might be better to keep it as a static display until you have the money to have it properly serviced. As I said above, you can enjoy this watch for many years if you get it sorted correctly so, waiting a few years will not seem like a long time in the scheme of things.

Best regards, Chris

RunningOnTime · Jul 2, 2021

Hello Chris,

This project has been a really fun experience that I've enjoyed over the past few months. I have the last (hopefully) parts for the watch and will have them installed shortly. I will also heed your advice in keeping the watch in a more stationary state until a service becomes more affordable for my situation or I gain the experience/confidence to service chronos (going to college will make sure that it is out of my meddling hands 🤪). I'd like to say a big thanks to all of the help you all gave me in both threads I started for this project. I enjoy working on and around mechanical movements, and being able to reach out to others when I needed help made the experience that much better! I know that I'll definitely continue to use these forms to share and receive advice on some of the coolest watches around.

Take care,

-- Gavin Timmons

RunningOnTime · Jul 6, 2021

Hello,

Just replaced the cannon pinion and it seems to have done the trick. I plan to get the watch serviced once I'm out of college and can afford it. Also, is there any advice on a good brand of brass tweezers? My last pair started to bend too much for the force applied and I feel like they are going to break before I really want them to. A few weeks ago they were solid as can be...

Archer · Jul 6, 2021

Personally I use bronze, because as you have found brass don’t hold up all that well. I use Bergeon bronze tweezers for general assembly work.

Cheers, Al

RunningOnTime · Jul 6, 2021

Archer
Personally I use bronze, because as you have found brass don’t hold up all that well. I use Bergeon bronze tweezers for general assembly work.

Cheers, Al

Hello @Archer,

Thanks for the tip. I'll keep a lookout for them once this pair goes out.

-- Gavin Timmons

Omega Chronostop (Cal. 920) with Loose Canon Pinion

RunningOnTime

ChrisN

RunningOnTime

ChrisN

RunningOnTime

ChrisN

RunningOnTime

RunningOnTime

Archer

RunningOnTime

Similar threads

Omega Chronostop, Year 1969, Cal 920, Case Ref 146.009-146.010

5x signed vintage 1970 OMEGA Chronostop Genève Ref. 146.009/10 - Cal. 920

New Arrival: Omega Chronostop De Ville Cal 920 Italian "Fontana"

Omega cal 920 "Jumbo" Chronstop 41mm - Strap and Bracelet

Omega chronostop date cal. 920 central hand trouble