valjoux 7750 cover plate question

[Danh]

Evening Folks

i was not expecting this tonight whilst swapping a watch case on one of my watches, and before I physically investigate thought it wise to ask.

whilst replacing the weight finishing off the watch tonight I realised the screw was not tightening properly, or so I thought.

on examining the chronograph cover plate it appears the post for the weight is loose and turning that the weight should tighten onto.

has anyone seen this before please?

is it a usual thing to happen or has the post on the cover plate snapped and I need a new cover plate?

as ever thank you for any replies

Dan

[SSTEEL]

The bridge with the oscillating weight retaining screw thread post, this can be replaced, a new one pressed fit, but in your instance, you would be better off replacing the bridge itself.  I have only come across the problem you are having once, and I simply replaced the bridge.

I did look closely at the bridge from the underside, and it looks like the thread post is renewable, but have never seen the post being sold on its own before.

[Danh]

Thanks for the reply, I have had a closer look without dismantling and it appears that the Jewel under may have broken also.

i have emailed May to see if the bridge is in stock (8500), not sure where else to source one if May does not.

[SSTEEL]

Who's  May?

Try cousins, or Gleave&Co, failing that, eBay.

Edited September 25, 2016 by SSTEEL

[Danh]

May is at http://www.nwcsupplies.com/

mans thanks will try the others too

[SSTEEL]

Ah thanks, I take it you are stateside?

 

Edit, just noticed its an English site that, have you ordered from them before?  I'm always open two other sources for parts

Its little hard to navigate that site, but worthy of a bookmark

Edited September 25, 2016 by SSTEEL

[Danh]

I am in Cumbria, May was the only place I could source parts for an AS5008 at one point.

arrived the next day, great service

[Danh]

I think I have found one, but May says the jewels are "not red in colour"

trying to find out what colour the jewels are, has anyone come across different colour jewels?

[SSTEEL]

Let me check an ETA bridge I have here, give me a few minutes.

[SSTEEL]

Its difficult to see from the photos, but the jewel colour should be red.

 

DSC07263 by Micky Aldridge, on Flickr

DSC07262 by Micky Aldridge, on Flickr

ETA Auto Wind Bridge by Micky Aldridge, on Flickr

[Danh]

Thanks that what I thought, still not heard from May as too what colour hers is

i personally have only seen red before

[bobm12]

Hi guys,

I believe the transparent jewels are better quality since -- don't quote me on this one, it is from memory! -- the white transparent jewels are cast and the red are pressed from "dust" like particles. They are both man made "rubies".

Cheers,

Bob

[Danh]

Thanks Bob, your the only reference I can find - been searching like mad

Dan

[bobm12]

Ah! I found it:

http://forums.watchuseek.com/f2/smoke-mirrors-part-1-eta-grades-explained-458060.html

Check this out Danh!

I just forgot! You are Welcome, Danh!

 

[Danh]

Thanks Bob

thats a great bit of info, truly most appreciated 

Dan

[Marc]

That's an interesting article Bob but it doesn't actually explain the difference in the colour of the jewels, it is referring to the difference in clarity. Polyrubies are translucent, almost waxy in appearance, the synthetic rubies are clear, like red wine. Both are red in colour.

In my own watch mechanicing endeavours I have encountered red, blue, and white (or clear as in colour, not clarity) jewels. Red jewels are rubies. Blue jewels are sapphires. And white jewels are diamond, these I have only encountered as balance end stones on much older higher end movements. Some sapphire jewels are very pale in colour, and because they are also very thin, they can look colourless, thus easily confused with diamond.

Diamond is of course carbon. Rubies and sapphires are essentially the same as each other as they are both aluminium oxide (or corundum) with the difference in colour resulting from trace elements within the crystal structure (chromium in rubies, and nickel, iron, copper, etc in sapphire giving rise to colours from blue to yellow and green). As sapphires and rubies are effectively the same stuff, with the same physical properties, I can't really see why one should have any advantage over the other, except maybe cost, and that may simply be due to economy of scale of manufacture. Maybe the use of sapphires is to create the perception of higher quality since they are more expensive? Who knows.

The most common use (that I have seen) for sapphires is for pallet stones in older watches. Then for balance end stones, and this may have been to create the impression of diamond (which is harder and more expensive) in this highly critical part of the movement. Sapphire end stones are a pig because their lack of any strong colour can make them very difficult to see, especially when they are in a jar of naphtha for cleaning (thankfully not how I do it any more). Diamond end stones tend to be less of a problem from a visibility point of view as they are usually in a setting.

I have also seen sapphire pivot jewels though. They have tended to be in more modern movements, but I have as yet to find any convincing argument to suggest that they provide any practical advantage over rubies.

 

[Geo]

I liked your post Marc, most informative.

[Marc]

Thanks Geo,

it was something that I looked into a while ago when I thought that maybe someone had used glass for end stones on an old pocket watch. Turned out it was diamond, and researching it shed light on all the other colour variations that I had seen in pivot and pallet jewels.

[Danh]

More brilliant info, thank you very much 

[bobm12]

Absolutely, Marc, I just didn't think it was a higher end stone in this case but a matter of the process. Thanks for setting the record straight.

Cheers,

Bob