Hamilton 768 service

[LittleWatchShop]

I hate working on ladies watches, but this belonged to my aunt and the family asked me to service it.  She was a wonderful lady, so I made an exception.

All of the train wheels are covered with one plate.  I thought it was going to be a royal pain to assemble, but surprisingly it went together without a hitch.

When I dropped in the balance assembly, it ran really goofy and stopped and when running it was at 28,800.  What was going on.  Geez...the hairspring was sitting on top of the center wheel.  Well...everything is so small...so tight.  Anyway, I made it right and it is running fine.

 

[nickelsilver]

Ah, one of the about billion ~5x7?"' movements that were made between the 50s-70s. This is a Buren (they had a thing with Hamilton), but Fontainmelon and AS probably made 75% of them. Amazing that they could mass produce such small pieces! Back in the day when trade shops were churning out watch repairs for jewelry stores these little movements were done at about 75% of the price of a regular "men's" watch, insane. Never figured out the reasoning.

 

There were some pretty high grade ones too, from JLC and Zenith in particular. But these small guys rarely run very well. I remember doing one for Cartier, from their dark period in the 70s (AS 1012 movement dressed up a little). Impossible to get better than a 60s delta in 6 positions. With their approval I literally spent a week (I think I may have mentioned this before): changed fork, escape wheel jewels for domed with olive holes, changed balance jewels same, made 2 staffs, pushed the escapement adjustment to the ultra max, polished the fork slot, etc. Still had a 100 degree amplitude drop from horizontal to vertical, terrible delta.

 

Good job getting this one going! With 25 years experience I have dunked the hairspring on these guys a couple of times, always the "last time the balance is going in or coming out". They got repaired, but it was like a day of work. Glad yours didn't get hurt!

[LittleWatchShop]

Here are the timing results after one tweak.

DU PD PU DD

Edited October 4, 2022 by LittleWatchShop

[nickelsilver]

That looks about right

 

I was talking to one of the only guys I consider a genius in watchmaking a few years ago and asked for his advice on these little guys. He said, "take the movement out of the case, hands and dial off, and throw it in the trash". Hahaha. He did have some insight: the proportions are all wrong basically. The hairspring collet is huge for the balance size, bringing the hairspring center far from the balance center. Pivots end up large for a given wheel (especially balance). The whole escapement is often about the right size for a 13"' watch, where the old rule of thumb is the escape wheel diameter is around the radius of the balance wheel. On and on. He's right. But they did run, and people were satisfied with them.

 

For him one of the biggest things is the size of the hairspring collet.

Edited October 4, 2022 by nickelsilver

[HectorLooi]

I picked up about 100 pieces of assorted ladies movements a while back and about a quarter of them were these design. 

I now use them for donor parts. The hairspring stud screws have come in handy especially. As well as dial feet screws. I think the jewels would come in handy someday. 

My mentor made me practice on them after I became comfortable working on gent's watches. It was a great way to improve on tweezering skills.

[LittleWatchShop]

24 minutes ago, HectorLooi said:

. It was a great way to improve on tweezering skills.

Ha!!! No kidding!!!

[ifibrin]

14 hours ago, LittleWatchShop said:

hairspring was sitting on top of the center wheel

The hardest part of assembling or disassembling these movements is the balance cock: it’s very easy to get the hairspring out of flat when putting or removing the balance cock. If the hairspring gets even slightly out of flat, it will rub against the Center wheel, and cause snow on the timegrapher. Manipulating such a small hairspring is very difficult to get it back flat.

 

13 hours ago, nickelsilver said:

Back in the day when trade shops were churning out watch repairs for jewelry stores these little movements were done at about 75% of the price of a regular "men's" watch, insane. Never figured out the reasoning.

The lower price to service ladies movements in the past has always puzzled me as well. If anything, they require more work… Nowadays, if you bring a ladies movement in for servicing at an independent watchmaker, either he will refuse to service it, or charge you a lot more for a ladies movement.