Longines

[speedy88]

Hello!
I wonder if anyone can help me with my project! I´ve got a Longines "Comet", Ref. 8475, here, I guess you know this watch? Please view picture!
This is a new old stock watch! The problem is, somebody missused it! The hour "hand" is running to one ó clock, then stops....! The problem is, one tooth underneth this hour disk ist broken off/damaged! This thing is made of plastic, there is no chance to repair! If it was brass or other metal, there would be no major problem to fix it! Now i am looking for this hour disk or a set of hour and minute disk! It has been made in different colours, yellow, green, blue, red..... But I would take any colour! Even mix it! :-)
Would you please check your store for this? Maybe you know somebody, who can have this....! 
Thanks for your help!
Have a great day!
Peter
 

[Chopin]

Anything can be repaired. If the tooth is small (I know, they're very small) a new one could be made and glued to the wheel ?

Perhaps a 3D printer would help ? One that can work with really small parts. One with a high resolution basically.

[speedy88]

Thanks

for your answer, I'll geht back to you later!

Best,

Peter

[speedy88]

Here are some Photos, maybe you make some thoughts about......!

[Chopin]

What does it look like on the other side ? At first flance it can be made on a 3D printer provided that you make a 3D model of it (or scan it with a laser scanner).

You could also try and find a gear with teeth that are the same diameter and size. Cut those off and attach them to this one.

You could smooth out the surface where the tooth was broken and then when you get a gear with the same teeth you "extract" one of the teeth and glue it. (with a glue that does not melt plastic)

This is what I would do, probably but I can be a little unorthodox so don't take my word for it, necessarily.

Other options are finding a donor movement or maybe even this specific part.

[Tmuir]

A 3D printer would not be able to print a wheel of that size, the resolution is not good enough, maybe a high end commercial one could, but what you would pay to get it printed you could probably buy a whole new watch.

Dovetailing in a new tooth might be a possibility, but I think trying to find a donar watch might be a better option, although I'm guessing its not a very common watch.

[Tmuir]

Here is a donor one for sale, but its not cheap.

https://www.ebay.ie/itm/Longines-Comet-Retro-Deco-Yellow-Large-Mens-Wrist-Watch-for-Parts/332773238612?hash=item4d7ad4a754:g:88gAAOSwZHxbey6u

[rogart63]

Maybe find a wheel that has the same pitch and number of teeth. Have repaired a few seiko 6139 inner bezels with superglue but not sure that it would work on this kind of wheel? Very cool watch so it would be nice  if it could be repaired: 

[speedy88]

Thanks everybody!

What about using the gear from a normal hour wheel of the same caliber? I guess, this has been made for regular hands!?

Does anybody know?

Peter

[rogart63]

1 hour ago, speedy88 said:

Thanks everybody!

What about using the gear from a normal hour wheel of the same caliber? I guess, this has been made for regular hands!?

Does anybody know?

Peter

That was about was i was thinking. Remove the old and make the hole bigger. Maybe screws to hold in place.

[clockboy]

If you can give us the measurements and amount of teeth etc there is slim chance but a chance that one of us could have match in one of our scrap boxes. 

[speedy88]

Ich have many of these wheels in my store, just need some time tomorrow find the right one! It's not so easy to glue it in plastic! There ist not enough Material to put screws in!

[StuartBaker104]

I woke up this morning with an idea in my head for this...

1. Use a small amount of RTV silicone moulding rubber to create a mould from a good part of the wheel.

2. Drill a small hole a short way radially inwards from the damaged teeth, then join it to the damaged area with a slot that is smaller than the hole

3. Clean all the joining surfaces with IPA

4. Fit the mould around the damaged area and fill with epoxy resin.  Warm the resin slighty with a hairdryer to help it flow.  The hole drilled above will allow you to create a piece that will stay in place even if the bond between the epoxy and plastic isn’t brilliant.

Might be worth a practice with an old brass wheel first

[measuretwice]

I know this assumes a lot of equipment, but if I had to fix that, I'd make a new wheel in plastic, delrin or nylon, something that machines easily, turn off the old and epoxy in place.  A lot of work, but from the recent sale it would seem a watch well worth fixing.

 

[nickelsilver]

If I was doing that I'd turn off the teeth in a lathe, and lightly press fit a brass replacement. There shouldn't be any force at that gear, it was broken due to the disc being stuck or improperly installed in the past.

[vinn3]

it would be a good training project with a lathe, mill and a gear hob.

[speedy88]

could anybody do that for me? I have not much experience with working on lathe and mill.....

But I can try to find a gear, maybe a hour wheel with the right number of teeth, diameter and pitch!

I guess, it will not cost a fortune, right? :-)

Best,

Peter

[nickelsilver]

5 hours ago, speedy88 said:

could anybody do that for me? I have not much experience with working on lathe and mill.....

But I can try to find a gear, maybe a hour wheel with the right number of teeth, diameter and pitch!

I guess, it will not cost a fortune, right? :-)

Best,

Peter

Hmm, let's imagine that you found an hour wheel with the same number of teeth and it's the same diameter or slightly larger.

Chucking that disc will be tricky, it can't be deformed and won't fit in regular stepped chucks or a bezel chuck (the hand protrusion would be a hinderance). Easiest then would be to make a friction chuck out of plastic like PVC, where the part can sort of snap in. This is done (by me at least) often to hold acrylic crystals that need to be modified on their diameter or internally to accept an original tension ring. The teeth would be turned off, and a little more.

Then the hour wheel would probably need a trip to the rounding up tool to bring it to size, as finding exactly the right size is less likely than finding one slightly larger, and it would preferably be tested on the watch itself requiring a bushing be made to fit it over the little hour wheel already in the watch. It would then need to be bored to be a light friction fit on the part and possibly reduced in thickness, then carefully pressed on.

The above would probably be 2ish hours for someone equipped and proficient and motivated.

If no wheel was found one would need to be cut. For someone with a good stock of cutters on hand and machinery ready to go for cutting, chopping out a toothed ring would probably be another couple of hours start to finish. One nice thing about hour wheels is they are so forgiving that they can be divided with a simple slitting saw of the right thickness and finished in the rounding up tool.

 

Figure 2-5 hours then. In my experience the better the watchmaker the more often he's gotten burned on jobs that should have been smooth sailing, and the more likely they'll quote toward the high side- and also the more likely they'll do the job right. Most watchmakers I know quote around 100 bucks an hour (close enough the same to be in USD, CHF, or EUR).

I don't know any, but am absolutely sure there are guys in Germany who can do this job. Is there any sort of watchmaker referral service there, like the AWCI in the U.S. ?