Replace lead gasket

[rogart63]

Think this a a lead gasket? Could i replace it with a rubber gasket or should i try to find a new lead gasket?  Watch is an old Tissot. Seen them before but not in this condition. 

 

[Tudor]

I've never seen one, but standard O-rings are identified by inner diameter and cross section.

There are certain parameters for O-rings as well. I have an old print copy, but I think it's online too: Parker O-ring handbook.

Just finding one that "fits" is only part of the issue. The other it that it actually seals for you. Check out that book and learn more than you ever wanted to know about O-rings... (you can probably identify the one you need from that book as well)

[rogart63]

13 minutes ago, Tudor said:

I've never seen one, but standard O-rings are identified by inner diameter and cross section.

There are certain parameters for O-rings as well. I have an old print copy, but I think it's online too: Parker O-ring handbook.

Just finding one that "fits" is only part of the issue. The other it that it actually seals for you. Check out that book and learn more than you ever wanted to know about O-rings... (you can probably identify the one you need from that book as well)

A flat gasket would probably be better. Will take a look  and see what size it need. cousinsuk have gaskets. 

 

[vinn3]

Quote

unless the case is machined for an o ring  a flat gasket would be better.  vin

 

[oldhippy]

Vinn3 is quite correct a new flat gasget should be fitted. It is possable if an O ring is fitted when you screw the back down it might leave a gap due to not having enough room for the O ring to sit correctly.  

[jdm]

 

13 hours ago, Tudor said:

I've never seen one, but standard O-rings are identified by inner diameter and cross section.

There are certain parameters for O-rings as well. I have an old print copy, but I think it's onlie too: Parker O-ring handbook.

O-rings of all sizes https://www.cousinsuk.com/category/o-ring-rubber-gaskets

But as mentioned already, old watches (and still most new ones) don't use O-ring, rather flat gaskets.

 

[Tudor]

Unless the groove is inappropriate (read the selection details in the Parker book) an o-ring will Work quite well. 

No dimensions were posted or I’d select it for you. If for example the groove is disproportionately deep, a backer ring could be used. 

You will have a far more difficult time finding a square profile gasket that seals better, due to requiring precision in all dimensions. 

But if you find a source with a wider selection of square profile gaskets than what Parker offers I’m all ears for many projects, not just watches. 

PS there is a superior design called the “quad ring” which looks like four small o-rings grouped together in a square profile. I do t think the selection is as broad but those are superior to both o rings and correctly sized flat profile seals. 

I did a lot of work with high pressure gasses and water in the past...

[jdm]

14 minutes ago, Tudor said:

Unless the groove is inappropriate (read the selection details in the Parker book) an o-ring will Work quite well. 

...

Many old (and cheap new) watches have no groove at all. In these as suggested, a flat gasket is better. Really no book is needed to choose correctly, just common sense and the readily available sizes  as posted above.
Another discussion could be had on the material used, synthetic rubber, NBR, Viton, and others. Fortunately in 99% of the cases there is no need to worry about that, the common type is OK.
I do work on diver's and regular watches. For either type I try to deliver them as much as water resistant as reasonably possible.

[rogart63]

A flat  rubber gasket will probably be okay. Need to buy a new mainspring so i will check the size and order that from cousinsuk. 

[ro63rto]

Aren't the"red" gaskets made for this ?
Harder than rubber and flat.

[Deggsie]

Are you sure it’s lead. I have one similar in an old rotary men’s watch. I was thinking it’s compressed dense rubber... but may be wrong. I had not thought about the possibility of it being lead


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[rogart63]

Not 100% sure it's lead. But it ain't rubber gasket. Those i have seen a lot of. This Tissot is from the 30-40 i think. Probably never open before. Seen that vintage Omega used lead as gaskets  in the 30. 

[Deggsie]

Really no book is needed to choose correctly, just common sense

There are rectangular section (flat), square section and circular section (O) seals. Then there is material spec’, and also shore hardness. The book really is worth a quick look at... imho


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[Deggsie]

Not 100% sure it's lead. But it ain't rubber gasket. Those i have seen a lot of. This Tissot is from the 30-40 i think. Probably never open before. Seen that vintage Omega used lead as gaskets  in the 30. 

Ok. This is interesting. I’m going to take my seal onto the quality lab at work on Monday, they’ll be able to measure it and weigh it to the nearest knat nads.

From the volume and mass, I can derive density. That’ll help determine if my seal is lead. From what you say, my seal looks and feels very much like lead


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[Tudor]

Lead or not, I doubt very much you will find a NOS replacement. If not an o ring with a backer ring (if needed) then perhaps a Teflon o ring will suit it. That will compress like lead (but easier) and provide a good seal. You could even stack two as they will crush/deform to fill the space. 

If it doesn’t need to be water tight, you could get a roll of Teflon faucet packing cord, cut to length and go with that. That’ll be fine for splashing (hand washing) but not immersion.

Color of a gasket does not indicate hardness. Silicone ones are typically red-orange but even they have several durometers available. 

The Parker book explains it all- static (like this) dynamic, internal and external glands- so you can design your grooves and what and how they are placed, to provide optimal “crush” etc for the desired purpose. I’ve read the book and designed with it. I didn’t write the book but I have perhaps a better understanding than a casual user of the lowly o ring...

[jdm]

5 hours ago, Deggsie said:

There are rectangular section (flat), square section and circular section (O) seals. Then there is material spec’, and also shore hardness. The book really is worth a quick look at... imho

For watch casebacks, which are our practical interest here, the most used are O an flat sections. I gave a purchase link for the first type above, while for flat types check https://cousinsuk.com/category/watch-parts/flat-rubber-gaskets

 

[rogart63]

Finally watch ready with new mainspring and new rubber gasket. Worked perfect.