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First time acrylic crystal replacement


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I have a watch with an acrylic crystal that is cracked and a few places and I'd like to try and swap it with a brand new one. It's not an expensive one so even if it goes south it's fine although I have swapped mineral glass crystals (with a press) and even though the principle is slightly different I'm sure I won't have any issues.

Right off the bat I'm thinking I need just 2 things: the new crystal and a special kind of cement/glue.

I looked on cousins as it is the best store for me and I found G&S Hypo Cement. Is this what I need ?

I think I'll need some help picking the crystal as well. It looks to be normal domed acrylic crystal from the outside but I know that there are several types. The watch is a 70s Swiss obscure brand.

From what I've seen I'll have to pay attention to the edge of the crystal and pick the right one for it. Am I right ?

Also one bonus question: how does one usually take the old crystal off ? Do you dip the case into something that kills glue like paint thinner or acetone ? Do you apply a bit of pressure ?

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It all depends what type of crystal it is if its a non armoured type then most are held in place with no glue at all they are slightly compressed around the edge when fitting or removing with a tool called a crystal lifter such as the following,

http://www.ebay.co.uk/itm/Watch-Glass-Fitting-Tool-Dome-Acrylic-Crystal-Plastic-Lifter-Fitter-Lift-Remover-/271265794833?hash=item3f28b38b11:g:pLAAAMXQHeBSG~Qs

I have both a Bergeon lifter and a cheap chinese one off ebay the chinese one is actually more useful as it opens out further and can be used to fit larger crystals on pocket watches the only time I have had to use crystal cement was when I could not find a crystal of the exact size I needed so had to secure it.

Edited by wls1971
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I know this tool. These are used for the different kind of crystal. The one that gets "inserted" inside the case and comes on top of the case so to speak.

To be honest this is a diver watch with a bezel and I think it might be possible that the crystal goes from the outside, not inside, not sure as I'll disassemble it tomorrow.

I guess I'll have to wait until tomorrow to see what type it is.

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If it is a plain domed acrylic crystal then you should be able to push it out from the inside with your thumb with minimal pressure, but will need the above tool to replace. You can usually spot the tension ring type as the ring is quite visible, these need a little more effort to push out, and best replaced with a press. Post some pictures if you need more help.

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 If the watch is a divers watch then you will have to remove the movement and maybe also the bezel and remove the crystal and insert a new one with a crystal press the crystal may have or may not have a gasket to form a water proof seal depending on the depth rating of the watch.

 

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It is one of those so-called divers watches but only resistant to 75 so not an actual divers.

I am planning on removing the movement and the bezel as that'll offer me a better view of everything.

Would it be correct to assume that it most likely has a crystal that gets inserted from the exterior like many modern watches ?

If I have uncertainties I will post a picture tomorrow.

Edited by Chopin
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14 hours ago, wls1971 said:

It all depends what type of crystal it is if its a non armoured type then most are held in place with no glue at all they are slightly compressed around the edge when fitting or removing with a tool called a crystal lifter such as the following,

http://www.ebay.co.uk/itm/Watch-Glass-Fitting-Tool-Dome-Acrylic-Crystal-Plastic-Lifter-Fitter-Lift-Remover-/271265794833?hash=item3f28b38b11:g:pLAAAMXQHeBSG~Qs

I have both a Bergeon lifter and a cheap chinese one off ebay the chinese one is actually more useful as it opens out further and can be used to fit larger crystals on pocket watches the only time I have had to use crystal cement was when I could not find a crystal of the exact size I needed so had to secure it.

I bought one of these Chinese clones and it was useless. The teeth weren't sharp enough to grasp the acrylic. I tried to sharpen them but the metal was too soft. I ended up buying a second hand Bergeon

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1 hour ago, mikepilk said:

I bought one of these Chinese clones and it was useless. The teeth weren't sharp enough to grasp the acrylic. I tried to sharpen them but the metal was too soft. I ended up buying a second hand Bergeon

I bought my Chinese one from redrooster on ebay and it has been fine if not I would have sent it back the Begeon one I have is good but the jaws do not open up wide enough for pocket watches so is limited in use to me.

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58 minutes ago, Chopin said:

Here is a picture of the front. I hope it's enough. From what I can see the crystal seems to be a "front loader" and I think it gets replaced using one of those claw tools.

Am I correct ?

WP_20170722_12_31_00_Pro.jpg

It definitely comes out the front, it looks like it *might* have a rension ring inside, but can't see that clearly from the picture.

Give it a good push from the inside with your thumb and it will pop out.

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2 hours ago, mikepilk said:

I bought one of these Chinese clones and it was useless. The teeth weren't sharp enough to grasp the acrylic. I tried to sharpen them but the metal was too soft. I ended up buying a second hand Bergeon

Haha! The teeth on my Chinese one were really sharp and I had to deburr them, but it works fine

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^^ What Stuart said. Push it out (if it has a removable case back) and look for a tension ring inside the crystal which pops out. If so, replace with Sternkreuz ATC at one size larger (0.1 or 0.2mm) than the measured diameter. You can sometimes re-fit with a case back press (sometimes called a crystal press, but not the type which forces crystals to become concave like a Robur). 

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Alright. It came out and it does have a tension ring on the inside of the crystal so to speak. Should I try and salvage it ? Can I do that or do the new ones come with one included ?

Also, does this still mean that the claw tool would be the best to use as I'm assuming it has to "shrink" the crystal a litle bit so that it will fit inside the case...?

Edited by Chopin
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Sry I can't edit my post anymore.

I've added a photo as well just so that someone might tell me that I'll order the right one as I'm not very good at this.

My calipers measured it at 31.0mm diameter but It doesn't show the 2nd digit unfortunately and last time I had to order a glass 1mm larger. Should 31,1mm diameter be safe ?

Currently I'm stuck at this category on cousins.

https://www.cousinsuk.com/category/tension-ring-armoured-watch-glasses

WP_20170722_16_48_46_Pro.jpg

Edited by Chopin
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The standard ATC should be fine. I found it best not to go more than one size up from the case measurement, and fit it with a case press. The crystal tool didn't work at all.


Sent from my iPad using Tapatalk

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I don't know of a resource that gives good details of the standard Sternkreuz crystal dimensions. Even their own catalogue is pretty thin on information for standard crystals http://www.sternkreuz.de/accordion/assets/Sternkreuz_Gesamtkatalog G22.pdf

As above, ATC looks like it should be fine. Your new crystal will come with a ring, but you may find reusing the old one helpful if the new one doesn't look or fit right. Some crystals come with a split ring so you can file a little away at the join if it won't quite fit in the case.

You should choose a crystal 0.1mm bigger than the hole in the case. The old one is unlikely to have shrunk due to the tension ring, so this should be a good guide.

 

 

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I only wish they had named these things in a way that gave away what the difference is or at least either the producer or these websites could offer more details.

Anyway, it looks like I shall be ordering a standard ATC then. The case hole shows 30,7mm but the crystal is 31,0mm. Which one is it then, hehe ?

I'm thinking of just getting a 31,1mm...

Edited by Chopin
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Putting a tension ring crystal on with a claw tool is almost impossible. You need a press. A die that press a little from the outside of the round part of the crystal to make the it bend a little inwards. 

If the crystal is 31,0 mm and you have a good set of caliper i think a 31,0 would be fine but maybe you should order a 31,1 to. Just to have an option if it doesn't work. Been there done that as they say. 

 

Edited by rogart63
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If it's too tight to fit, then sand the outer perimeter of the crystal to size. You can also bevel the edge where the crystal enters the bevel at 45 degrees, especially if you are using a crystal press to fit as it helps it to slide in initially. 

For cases with a removable case back, I would try a crystal/case press first. Then use a crystal lifter if that fails. For cases with non-removable case backs such as 1970's Omegas, I would try to use a crystal lift as there's a small risk with using a crystal/case press of damaging the dial or hands.

For measuring, measure the hole size and rotate the bezel to find the largest point. Add 0.1mm (or you may have to add 0.2mm if that's all that's available). The current crystal may not be original, so it may not be the best reference for size.

 

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The case back is removable and everything has been removed so there is no worry of damaging anything (mostly).

I will try a watch glass press first. Sadly I have to buy one as I don't own one yet.

Indeed I was thinking that if the crystal is too big I'll just sand the edge a little bit. I also thought of the 45 angle thing in case it just wouldn't fit but I have no worries about that.

I just hope I'll get the right diameter crystal as last time I was a bit unlucky haha.

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Well the crystal arrived and I finally managed to install it. Indeed it was the standard one so thank you guys.

However I'm now having some trouble putting back the bezel. It's the type that has spring wire on the inside to keep the bezel attached to the case.

Any tips for this ? Not my first time re-installing one but this one just won't do it...

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