Breitling Navitimer 806

[Bonefixer]

A friend of a friend has entrusted me with the service/restoration of what was his grandfather's Breitling Navitimer 806. It was just lying around in a drawer, missing its glass and two of the hands, but incredibly it runs and the Chrono seems to function. 
 

I've started dismantling it and have learned that I'm not the worst amateur watch fixer in the world - the dial had been glued down!

 I'm planning to strip down and clean the movement - I should be competent to do that. Clean and re-lume the hands. Source a new glass - acrylic I think - and do very little to the dial apart from maybe a cotton bud and water. 
 

Any advice from the good people here before I crack on? I did tell him the potential value of this and suggest he might get a proper watch maker to sort it. I've offered no guarantees apart from I shouldn't make it worse. 

[Mercurial]

It can be difficult to keep track of all the different screws on a movement like this, you can save yourself a lot of trouble by putting each screw back on the movement after removing the part it secures. 

This ensures every screw stays in the position you found it in, but if the watch was serviced by someone willing to glue the dial on, it’s possible that some of the screws are already misplaced.

You mentioned that the chronograph functions. That being the case, I suggest you keep all the eccentrics that adjust the depthing and engagement of the chronograph works in the position they’re in, unless you have experience with setting up and adjusting a chronograph. 

Take plenty of photos, and you should be fine during reassembly. 

I hope that helps,

Mark

[rehajm]

…watch the YouTubers who have serviced this one, maybe a couple of times.  It helps to be familiar when you dive in. Also can help when you forget where that screw goes…

[Bonefixer]

Update!

 I've dismantled it, cleaned all the glue off, and rebuilt and lubricated the base movement. I'll leave the chrono part for another day. It's running well - great amplitude and keeping time, but it's got a beat error of 4.8ms. 
 

How important is it to correct this? I'm worried that the potential for making things worse having to take the hairspring off and on repeatedly to adjust this. Would anyone here accept it at that?

[LittleWatchShop]

16 minutes ago, Bonefixer said:

How important is it to correct this? I'm worried that the potential for making things worse having to take the hairspring off and on repeatedly to adjust this. Would anyone here accept it at that?

I am an amateur, so there's that. I do not get fixated on amplitude, lift angles, and beat error. However, 4.8ms would bug me if it were my watch. But you must judge your own skills to appreciate the possibility of going backward. I suggest, that you button it up let your friend enjoy the watch for now. As your skills progress, come back to it and correct it.

I assume that this watch has a fixed hairspring pin. Some modern watches have an adjustable pin along with adjustable regulator. These are trivial to get in beat.

On 4/4/2025 at 10:19 PM, Mercurial said:

It can be difficult to keep track of all the different screws on a movement like this, you can save yourself a lot of trouble by putting each screw back on the movement after removing the part it secures. 

I own a valjoux 726 my dad gave me on my 18th birthday (a looooong time ago). I broke the ratchet wheel with an aggressive wind 4 yrs ago. I have been waiting for my skills to progress before doing a service. I am close. Your advice is well placed and I will apply it.

[watchweasol]

Hi. What’s the movement. ETA. 7750 etc as a service sheets would be handy to have for reference.

[Bonefixer]

Venus 178

[Mercurial]

Depending on the age of the movement, the Venus 178 can be found with either a fixed or a mobile stud carrier. 

If the movement you’re working on has a mobile stud carrier, as seen in the image below with the blue arrow, you can move the stud carrier to adjust the beat error. It moves like a regulator arm, it rotates around the incabloc setting. 

Only a small movement is necessary to correct a 4.8ms beat error. You can use apiece of pegwood to make the adjustment, just be sure you don’t slip towards the hairspring. 

If the movement has a fixed stud carrier, indicated by the green arrow below, then of course you must move the hairspring collet on the staff to adjust the beat error. 

Mobile stud carrier : 

Fixed stud carrier :

A beat error of 4.8ms isn’t a big deal. The watch will need a few extra turns of the crown to get it running, but beyond that it won’t have much impact.

I would adjust the best error to <1ms, but it isn’t worth risking a damaged hairspring it if you don’t feel comfortable doing it yet  

I hope this helps,

Mark

[Bonefixer]

Thanks Mark. I think I’ll leave the beat error for now - it’s a fixed stud so I’d have to adjust the collet position. 
 

The watch has bigger problems. On reassembly I’ve found that the hour counter reset hammer is broken - I didn’t do it, the main hammer part was just not there. Can’t easily identify a replacement part. And the subdial hands. The running seconds hand needs an extended pivot tube as the pivot is below dial level. Can’t find one of them either. I’ve found a central seconds hand that might fit it - going to have a go at cutting, filing and polishing it to make it work. 

[Mercurial]

I’ve sent you a link to a supplier that has the hour reset hammer in stock.

Hands for Breitling Venus 175 watches seem to be easy enough to find and the running seconds hand will fit the cal. 178.

Mark

Edited 3 hours ago by Mercurial
Added information regarding hands

[tomh207]

If the Venus 175 hands fir then hands for the sea-gull ST1901 should fit too and be available on Aliexpress. Sea-gull bought the Venus 175 tooling and rights to make the sea-gull 1963 military chronograph.

Tom