Safe zone activated. Crystal replacement.

[way2wyrd]

Ok so I'm pretty comfortable with disassembly, oiling , reassembly, I've gotten a 6mm lathe and got it going well i think need to practicemore tho. 

I'm just clueless when it comes to crystal replacement.  Just no clue and it scares me a bit  .  

I understand measuring the ID and OD , tension ring if needed.  

It's the identifying the type of crystal. (Pocket watch, seiko, caravelle ladies, vulcain cricket)  height style etc has me lost.

On top of that the multitude of ways to install and tools available. 

Talk me off the ledge.  Can anyone explain it in a way that doesn't hurt my head. 

--jeff

 

[Simeon]

The vast majority of vintage watches use common, lentile round acrylic crystals. These should be sized to be about 0.1mm larger than the measured opening they are installed in. These are best installed with a press with an upper die sized to fit over the outer edge of the crystal, bearing down on the sloping section towards the outer diameter. The die will tend to compress the diameter slightly (depending upon the shape) as it is being pressed downwards. You can also use a smaller diameter die (or a convex rubber or Bakelite die) on the bottom to accentuate the deformation of the crystal by pushing upwards in the middle. Then the case or bezel is lifted upwards so that the crystal fits within the bezel. Then the tension is released on the press and the crystal expands again and wedges itself into the bezel. 

Tension ring (or armoured) crystals are typically fitted to water resistant watches (or at least those with that prentention like compressor cased watches)   These are installed with a press in similar way to the lentile crytals but they will deform less due to the tension ring being present. These are basically just man-handled into the opening with force from your press, so make sure that the case is well supported  and not holding on lugs or the crown (it’s best to remove the movement while installing). These often install with a crack as they are pushed into place, so you get to slowly remove the press and check it has been correctly pressed in or you have broken it!
 

Flat mineral glasses are the easiest of the lot. Check you have a gasket present (it might be worth replacing it anyway). Measure the inside diameter of the gasket and get the same or next biggest size of crystal. Measure the depth of the opening (or the old crystal ) to set the thickness of the glass. This is then pressed in with a die just slightly smaller than the OD of the crystal and with the case well supported underneath. Press it into position and periodically release the pressure and rotate the watch in the press and reapply pressure so that  the crystal is pressed in consistently all around the diameter. 

This will do you for the vast majority of vintage watches you will encounter. There are more complicated pieces such as ‘top glass’ crystals that fit over the case and then have a bezel pushed down over them like an external tension ring.  These are tackled in a similar approach to the others with a combination of techniques but measuring and getting the correct crystal is a lot harder.

it’s definitely tricky to get the right size crystal, so I will typically buy additional crystals in the next bigger and smaller sizes. They are usually cheap and don’t impact on shipping costs if you have a few others thrown in an order so getting some ‘spares’ isn’t a bad idea.  I am going to buy a boxed assortment from Cousins which has 10 of each size  for the typical size crystals that I work with. That way, I will have one on hand for any typical project watch with a standard crystal. 

[nickvon]

Hello all. I too am a noob and I am working on my first watch. I have successfully disassembled, cleaned, badly oiled and reassembled an ETA 2375, and reinstalled in back in the "top loaded" case. The crystal trickery also has me baffled. I bought  an Hw and N 294 replacement crystal as those were the outer diameter of the original crack and scratched crystal. There is a what I assume is a chapter ring (or is it a tension ring) which is stepped, which slots in between the dial and the inner diameter of the case, which holds the movement more securely, and then the bezel that then goes on top. After much pressure from my chinese press which is probably completely the wrong thing to use, and slightly denting the back of the case, I soon realised the new crystal inner diameter was not wide enough to press onto the case. So my question is how does one find the inner diameter of the crystal when shopping for them, where are they displayed, or coded? On the cousins website I can easily find the outer diameter but not the inner. How do I know if I need one with or without a tension ring? Do I need s stepped crystal, and does step refer to a step on the ID or OD?

 

Apologies for so many questions, but it's a minefield! Many thanks.

[AndyGSi]

It's always best to start a new post than add to someone else's.

Good photos of the case and parts are also needed so we can see what you're working with.

Edited October 21, 2024 by AndyGSi

[Neverenoughwatches]

Ok so if its a tension ring you are holding ? then you're trying to fit this that came with the original crystal into a non armoured crystal. What you have ordered are just snap in normal and high domes. 

Armoured crystals that are used on water resistance cases come with their own tension ring fitted. Lets have a look what you need.

Double check your measurements from the original crystal using an accurate digital vernier gauge. Check the size externally in multiple places around the circumference of the crystal to find a good average. With the armoured crystal you order it needs to be right as there is no flex in the tension ring, the safe option is to order the one you think plus a size above and a size  below.....so 3 glass orders. There is the potential to reduce the crystal diameter if required but you will be risking the water resistance of your watch which should be pressure tested with a glass change anyway if you are intending to have it exposed to water. Andy's comment...new thread and evaluating the situation from scratch... can't be bettered IMHO. 

The best advice i can give you if watch repair is going to be a regular hobby for you, is to order yourself a Sternkreuz catalogue from cousins and study it front to back and back to front. Dont skip any of the table of contents,  foot notes, glossary or shape/lettering codes. The knowledge gained will go a long way towards preventing future mistakes and wasted dosh. 

 Rich

Edited October 22, 2024 by Neverenoughwatches

[nickvon]

Apologies I thought it was more an open disussion for similar questions. That said thank you Rich, you helped the penny drop and thanks for the Sternkreuz catalouge suggestion, super helpful resource. I was indeed trying to fit a snap-in when I should have been using a top-glass. Snap-in's I've relised are held in place by the outer part of the glass, whereas the opposite is true for top glass which are effectively placed over part of the case.

It's still not 100% clear for me if my watch needs a topglass or an armoured crystal. I'm eering towards topglass because although the metal ring does fit inside the inner diameter of the old crystal, it also slots around the dial like a chapter ring to hold the movement fast, and also the crown wouldn't almost certainly let water in, so we're not going for water-resistant. One can also purchase a topglass crystal with a specific inner and outer diameters, although in my case I need to go 1mm wider OD copared to the old crystal to get the right ID. With regards to the armoured glass, I understand now why you said buy it in 3 sizes to ensure you find the best fit as this inner diameter is not given in the catalouge.

Again, thanks very much, very useful info.

Nick