Unsuccessful crystal replacement on a ARF Milgauss

[ROXOLO]

I purchased this ARF Milgauss last year for my second half. it's a gorgeous watch except the crystal which is green AR coated and is an immediate tell for those who know the brand.
So as I broke the stem and the watch needed to go to my watchmaker, I decided to buy a "gen-like" crystal: I found one on Chrono24, "aftermarket replacement green sapphire for Milgauss", which came from China (of course). The price was 100$ + shipping. The crystal finally arrived and I sent the watch to my watchmaker.
Unfortunately, I received a message yesterday that he tried to install the crystal but it was very slightly too large and the edge exploded :-( (see pictures).

If anyone here ever successfully tried replacing the crystal on a ARF Milgauss 904L, I would like to know where did the crystal come from, if it was gen spec, if there was some modding needed... I've seen a milgauss for sale here with gen crystal bt it was a BP not an ARF.

I also need to know if the crystal is somehow not gen spec, or if (most likely) it is the watch. Both come from China so, you never know...

 

[ROXOLO]

I wrote the "crystal was slightly too big", I guess I should have wrote "slightly too small".

 

[freediver]

I am not an expert, but did he measure dimensions before installing?

 

[ROXOLO]

Well, I'm not sure, but he's a good watchmaker, I've seen some work he did for other people, and most of the time he's a magician.
I guess I'm tryin to know if:

1) the watchmaker made a mistake (I seriously doubt so)
2) the ARF Milgauss simply won't accept gen (or gen spec) crystal (most plausible explanation)
3) the crystal I bought is in fact a lousy quality part in which case I'd try to get a refund from the seller
and, also, if 4) a DJF green sapphire crystal would fit (would ARF and DJF possibly use the same case? doubtful)

 

[Rx4Time]

If I'm going to point a finger at which part I think is at fault, I'm going to blame the crystal having some microscopic imperfections. I cannot speak to the milgauss, but I know for a fact other ARF models will accept genuine crystals without modification.

 

[KJ2020]

A crystal install on this type of watch (Exp II, Air King, Milgauss) would go like this:

1. Fit the gasket to the crystal.
2. Slide the gasket onto the raised case lip that anchors it.

Those steps can be reversed but either way it should end up looking exactly like it does in the pic minus the shattered edge.

3. Place the bezel over the crystal and onto the gasket where resistance will prevent manual pressing very far. Try to get it level to accommodate a crystal die sitting flat on all of the bezel.

4. Use a crystal press and a hollow center die that contacts the bezel and not the crystal, and press the bezel home. The bezel on these models serves as the retaining ring. Models with rotating bezels have a separate retaining ring but the sequence is the same.

Note that this would be the normal sequence for "everyday" watchmakers working on a rep. A highly skilled watchmaker with expensive Rolex tools might use one of those tools that uses suction to remove the whole bezel/gasket/crystal assembly in one piece, then it gets put on that way also.

Which gasket was used, the ARF or different? If the crystal was too big it would not have fit the space properly.

Sometimes the bezel won't go on level so one end gets pushed down further.

This is OK as long as you make sure the bezel clears the crystal on the side that's up. The white circle graphic was added on the pic below to highlight the top of the crystal. Note that you can still see some of the gasket all the way around.

If you really want to compare the sizes of the crystals, the best way is put the undersides together after cleaning any loose debris away. Line up the outer edges on a flat surface (piece of glass, tile, etc) and take a pic. That will tell you if the size is correct. A crystal should not shatter like that in an install. It looks like it had contact with the bezel.

 

[ROXOLO]

The thing I don't understand, if a crystal is "too small", how can it sit in the rehaut at all? I mean, the gasket shouldn't even fit around it... I don't know. I trust my watchmaker to be able to do things the right way, but still...

 

[KJ2020]

If the green ARF gasket was used, then it would seem the crystals are the same size. That's why I asked about the gasket. And you are right if the crystal was too small that should be readily noticeable by excess play on the top rehaut ledge. Without measurements or a crystal comparison pic we can only speculate.

The first thing I always do when replacing a crystal is measure the old and the new, then do a test fit with the gasket. I've used smaller new crystals than the old one was to achieve gen-spec, but that requires two gaskets or some extra glue to fill the gap. Crystals are not usually off by random amounts, but usually whole or maybe half mm increments. Even really cheap crystals are usually not wrong from stated size.

Two gaskets in the install below. Once the bezel is on, you would never know if you weren't looking for it.

 

[Oascom]

To me it looks like crystal cracked from the top down. Meaning something pressed it I bet the bezel just like kj explained.

Plus it's just on side... Maybe little accident with the press.

 

[tripdog]

If the crystal was too big - or too small, then it wouldn't have fitted the case, and the crystal is fitted in the case, as can be seen in the pics.

Either the crystal had defects or the watchmaker is not a magician, just clumsy.

 

[ROXOLO]

Hmmmm... so that would mean I'm being lied to... I don't know the guy personally but he has a facebook page and people keep posting about how great he did with their watch, I've seen pictures of a Noob Daytona that looked like it was brought back from the dead and the watch ends up looking brand new... the guy has stellar reputation. according to him, the original crystal fitted on the ARF is 32,7mm, and the aftermarket crystal that broke is 31,8mm. That's easy enough to check once I receive everything back, but I wonder, how can a trained eye not see a difference of almost a millimeter? that's not a subtle difference I would say - certainly not in watchmaking context.

It sucks, not only because of the price I paid for the crystal (only 100$ but still, I'm not rich) but the watch was last year's Christmas present to my loved one, and we were looking forward to make it "more gen-like".
I guess I can still sell this one and get the DJF version (that appeared on the market just a week after I purchased this one... bullocks)

 

[KJ2020]

I fail to see how a crystal can break if it's 0.9mm smaller than one that fit inside the same bezel opening without something contacting it that shouldn't have. Not to mention a crystal that much smaller would not have been a proper fit for the case and installation should not have been attempted, at least not without a plan to account for the size deviation and a consultation with you.

 

[tripdog]

At a guess I'd say that he's installed the crystal with the gasket in place, put it in his crystal press, and when applied pressure the crystal dropped down lower than it should (because it's almost a full mm smaller) the upper lip of the crystal came into contact with the upper outer edge of the rehaut and this is what cracked the crystal on the outer edge - this part of the crystal is very fragile.

 

[ROXOLO]

Tripdog, yes, that sounds very plausible. He should have measured the crystal before trying to install it: we all know that they are not all made equal.

 

[KJ2020]

The 1mm difference could be explained by the ARF crystal having a different edge profile. That's exactly the case in the example I posted above where I used two gaskets, and that's why I had to use them.

The gen and gen-spec sapphire crystals (on the left) have a stairstep edge profile so the gasket tucks in mostly underneath the top of the crystal. Many rep crystals have a straight edge and the whole thickness of the gasket sits outside the crystal perimeter.

So a gen 29.5mm crystal is actually 30.5mm in diameter at its widest uppermost point. Same measurement you get from a rep straight edge crystal. Note that these measurements are for Subs, GMTs and other models. IDK what a gen Milgauss crystal measures offhand.
​
I've done this several times and not ever had a 1mm smaller diameter crystal bottom fall through or be able to fit past the rehaut ledge, with or without a gasket on it. The gen-spec crystal would fit loosely in the space and wouldn't need any pressing until the bezel comes into play. So the bezel is still a possible culprit here as well IMO.

But I can see it happening either way. Bottom line is there appears to have been metal to glass contact on the top crystal edge which should not have been allowed to happen.

 

[RobSe1]

The Chipping looks like the force came from underneath and broke it from bottom to top. So the way tripdog descript is logical. The edge had contact to the upper edge of rehaut and cracked it upwards while pressing the crystal in.

 

[KJ2020]

The Chipping looks like the force came from underneath and broke it from bottom to top. So the way tripdog descript is logical. The edge had contact to the upper edge of rehaut and cracked it upwards while pressing the crystal in.

The crystal would not have needed any pressing in though. Especially if it was smaller then the opening. Look at this sequence of pics with a properly sized crystal. The gasket and crystal just slip right over and onto the rehaut, not even any hand pressing needed.

It's the bezel that gets pressed on these and unless it or perhaps a metal die (which should not have been used to press a metal bezel, even through a cloth), touches the crystal, there should be no force of any kind exerted on the crystal. Not even excessive circumferential pressure because the gasket is closing in on a 1mm smaller diameter.

 

[ROXOLO]

Oh well, what's done is done. I'm sad about not being able to mod the watch the way I wanted... an option would be to buy a new Milgauss from DJF, but I noticed: they made the crystal as it should (or at least, closer) but the dial is flawed (no one ever said it it seems, but if you compare with a gen, the ARF dial is better. Hour markers on the DJF are a tiny bit too long, are the wrong colour, and are slightly too far from the minute markers. SELs also seem better on the ARF, more recessed.
Or I could get the DJF, and swap in the ARF dial (both versions are a2836) but then it begins to be a very expensive Milgauss.

 

[KJ2020]

When you get it back, measure the rep crystal (bottom of the edge stairstep profile if there is one) then find out what the gen measures. Then you can know exactly what size to buy again if you choose to. I've had very detailed conversations with vendors about parts shapes and sizes.

Sub007 would probably tell you

https://forum.replica-watch.info/fo...ies/8991971-gen-rolex-milgauss-116400-crystal

 

[KJ2020]

Hmmmm... so that would mean I'm being lied to... I don't know the guy personally but he has a facebook page and people keep posting about how great he did with their watch, I've seen pictures of a Noob Daytona that looked like it was brought back from the dead and the watch ends up looking brand new... the guy has stellar reputation. according to him, the original crystal fitted on the ARF is 32,7mm, and the aftermarket crystal that broke is 31,8mm. That's easy enough to check once I receive everything back, but I wonder, how can a trained eye not see a difference of almost a millimeter? that's not a subtle difference I would say - certainly not in watchmaking context.

It sucks, not only because of the price I paid for the crystal (only 100$ but still, I'm not rich) but the watch was last year's Christmas present to my loved one, and we were looking forward to make it "more gen-like".
I guess I can still sell this one and get the DJF version (that appeared on the market just a week after I purchased this one... bullocks)

The gen is 31.8mm. That is what the 318 means in the part number

https://forum.replica-watch.info/fo...-milgauss-green-sapphire-crystal-b25-318-1-c1

That measurement is taken on the lower part of the crystal edge, where the smaller diameter of the stairstep profile is. So if the ARF is really 32.7mm, it would seem that it is a straight edge profile with the same upper diameter as the gen. This is typical of some rep crystals - they look the same on top as the gen but are cheaper to make than the meticulously cut indentations of the gen or gen-spec edge. These two different types of edges would be interchangeable only if a second gasket is used as I showed previously. The second gasket just fills up the space in the lower crystal detent.