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Making watch case gaskets.


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I've got an unusual size gasket (31.6mm inside diameter x 34.8mm outside diameter x 0.5mm) that I can't find on Cousins so I decided to try and make my own.

I bough two A4 sheets of 0.5mm thick nitrile rubber, an Olfa compass cutter and a cutting mat. I didn't think it would be easy and I wasn't wrong. After about 20 attempts I think I've managed to make a suitable gasket...

The gasket on the left is the original, the middle one is my best and the one on the right is uneven.

The best technique I could come up with is to cut a square of rubber and stick it to the cutting mat with double sided tape. After honing the blade once I cut out the largest diameter. Then, after honing the blade again I cut out the inner diameter. I then carefully removed the outer rubber then inner rubber.

There are better cutters online but they're pretty expensive and there's no guarantee they'd cut better.

Not sure if I'd ever need to make another but any tips would be appreciated.IMG_20210711_145334.thumb.jpg.89e929baec5eaac1561af2ff89fae9d6.jpg

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The way I've made gaskets in the past is with a punch. You'd need a circular blade cutter of the exact OD/ID size though... I've not seen them that large, nor have I seen them adjustable.

This may border on heresy, but what about RTV? I assume there's a channel for the gasket. A fine layer of grease on one face will allow it to release. 

Another may be to 3d print a gasket mold, then fill it with RTV or two part silicone...

I'm sure there are other ways as well...

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1 hour ago, spectre6000 said:

The way I've made gaskets in the past is with a punch. You'd need a circular blade cutter of the exact OD/ID size though... I've not seen them that large, nor have I seen them adjustable.

This may border on heresy, but what about RTV? I assume there's a channel for the gasket. A fine layer of grease on one face will allow it to release. 

Another may be to 3d print a gasket mold, then fill it with RTV or two part silicone...

I'm sure there are other ways as well...

Does RTV set? Could I form some sort of mould to the correct dimensions? 

I can't see dies/punches working for me due to the cost.

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2 hours ago, Plato said:

Does RTV set? Could I form some sort of mould to the correct dimensions? 

Yes. Not sure what country you're in, but pick a FLAPS (Friendly Local Auto Parts Store), and peruse the chemical section. Permatex is the brand I usually see around here. There are different formulations for different applications; most of which aren't exactly applicable. The baddest stuff going is the Ultra Black formulation, but watches are a different kind of engine...

You'd need to make a set of ID/OD forms, and plan for some sort of release strategy... Cooking spray maybe? Teflon? Then goop it in, and scrape off the excess with a razor blade or some such. It'll stay pliable and resistant to oil/water for a good long while in conditions far beyond what any watch would have thrown at it.

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I've made gaskets and valve parts from dental impression silicones. Some of them were used in extremely harsh environments, like the insides of an autoclave, and they performed better than the original part.

I recently restored a Bulova Accuquartz 224. The gasket had expanded and was very difficult to reseat. I tried cutting my own gasket with a similar circle cutter but the blade tends to go off on a tangent ( literally ). Esslinger had the gasket for $6.95 but the shipping cost to Singapore was $36. I ended up buying from a seller on ebay. 

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