DIY GMT Master Crystal Replacement

[TonyMonatana44]

Really nice work bro, congrats. Solid hit on both date mag and sitting height.

You didn't mention crystal gasket shaving. Did you thin it? Also I would try something different with the hytrel ring before buying a gen click ring. A slightly thicker hytrel ring (or fishline) will tighten up the bezel.

I was going to mention it before - I may have forgotten. Regarding rehaut polishing, once it's done to your satisfaction finishing it with some 600 or 800 grit sandpaper or a piece of Scotchbrite puts the horizontal grooves back nicely. It can take a little practice to make them even and level but it's the ultimate in making it gen-like. I've made a rehaut or two more smooth than it should be before using this final step.

Thank you! I couldn't have done it without you honestly. I thought I was going to be using the 2.7mm gasket because I've read that other members had issues with the seconds hand touching the xtal, but when I tested it out I didn't have any problems at all.

I actually bought all sorts of sizes of fishline, so I'll test that out. I used the hytrel ring that came with the watch. It was in immaculate shape so I didn't bother to replace.

The rehaut looks okay in my opinion with the horizontal grooves. I can't get it on camera but they're still there, and they're more present in direct sunlight. I can try that next go around when I mess with the movement in the future.

The xtal gasket I did not shave at all. I did put a thin coat of lithium grease all around the outer edge of the gasket to help aid the retaining ring slide in easier. Other than that, didn't touch the crystal gasket.

 

[TonyMonatana44]

Great work Tony.

Think I’m going to remove the movements on mine before attempting this.

Assume just a couple of movement holder screws that get “tightened” and spin the movement to remove yes?

Also did you remove the stem in winding or time set position? I don’t want to upset the keyless

I would def recommend removing the movement. It's fairly simple but the only pain in the ass is putting back the screws and the metal part that holds the movement to the case. I'm not sure what factory you're going to be working on but the CF GMT Masters aren't like gens where you "tighten" the screws and it loosens the case. Mine I had to unscrew both the movement screws and then take out the tiny screws and the holder. A VERY pointy and thin pair of tweezers is needed to put them both back in along with a magnification loop. Without those things i would 100% not be able to see what I was doing since it's so tiny. But it's doable and it's not hard to do. Just need some patience.

The crown I just unwinded to the "set time" position and then pressed the button with a pair of tweezers to pull out. However, I did find it better to twist the crown while you put it back inside the movement because it goes in smoother for some reason. I'm not a watch smith and I've never removed a crown or a movement from these newer GMT's but I didn't break anything, and if I didn't break anything you more than likely won't either considering I always break something when I DIY hahaha.

Oh - I also forgot to mention I oiled the winding rotor when I removed the movement. It was super noisy and unbearable honestly. It was a little loose as well and I ever so slightly tightened it, oiled it up with some non-toxic and oder less jewelry oil I had laying around, and voila - much more silent now.

 

[TonyMonatana44]

Here are some more pictures in sunlight/day setting.

IMG 9378

Image IMG 9378 hosted in ClickPix.org

clickpix.org

IMG 9379

Image IMG 9379 hosted in ClickPix.org

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IMG 9381

Image IMG 9381 hosted in ClickPix.org

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IMG 9382

Image IMG 9382 hosted in ClickPix.org

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IMG 9383

Image IMG 9383 hosted in ClickPix.org

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IMG 9384

Image IMG 9384 hosted in ClickPix.org

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IMG 9385

Image IMG 9385 hosted in ClickPix.org

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IMG 9386

Image IMG 9386 hosted in ClickPix.org

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IMG 9387

Image IMG 9387 hosted in ClickPix.org

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IMG 9388

Image IMG 9388 hosted in ClickPix.org

clickpix.org

Also don’t mind the paper towel pillow. I put the bracelet in my ultrasonic cleaner than dipped it in baby oil to stop the squeaks and to soften it up. It’s worked so far, just have to wait a day or two for the oil the drip out

 

[Artyfowl]

Excellent stuff mate you’ve done amazing work.

How did you get the crystal retaining ring off in the end? Razor blade / case knife?

Also pressing it back on?

 

[TonyMonatana44]

Excellent stuff mate you’ve done amazing work.

How did you get the crystal retaining ring off in the end? Razor blade / case knife?

Also pressing it back on?

Thank you sir! I feel like I could do the job in less than half an hour now.

Honestly just used a small flat head screw driver and gently wedged it under the retaining ring, then pried up every 3rd scallop or so, so it slide up evenly to reduce the chance of it bending.

I bought a cheap crystal press off of Amazon. I think it was like $50 or something along those lines. It’s one of the handles that screws down, and not an actual press. I read that the presses are likely to not put force down evenly. So I decided to buy a press that you have to screw down and it does apply force evenly. Made quick work of putting the retaining ring back on.

 

[Artyfowl]

Thank you sir! I feel like I could do the job in less than half an hour now.

Honestly just used a small flat head screw driver and gently wedged it under the retaining ring, then pried up every 3rd scallop or so, so it slide up evenly to reduce the chance of it bending.

I bought a cheap crystal press off of Amazon. I think it was like $50 or something along those lines. It’s one of the handles that screws down, and not an actual press. I read that the presses are likely to not put force down evenly. So I decided to buy a press that you have to screw down and it does apply force evenly. Made quick work of putting the retaining ring back on.

Yep I bought this press off Ali. I stripped it down and oiled it and it works really well for what I’ve done so far

 

[Artyfowl]

Just done a vsf sub. On to the gmt

 

[Artyfowl]

Crystal swapped. This wasn’t too bad. How do people get the bezel triangle aligned to 12 o’clock? Mines in between the clicks so it rests either side of 12 o’clock when in the clicked resting positions

 

[TonyMonatana44]

Crystal swapped. This wasn’t too bad. How do people get the bezel triangle aligned to 12 o’clock? Mines in between the clicks so it rests either side of 12 o’clock when in the clicked resting positions

I would advise to mark or remember roughly where your retaining ring was before removal so you can know where the dead center of 12 o clock was. I can't tell where yours is from your photo since it's at an angle, but you might have to twist the retaining ring either left or right to achieve that.

 

[Artyfowl]

Ah mine came off in the bezel due to all the gunk. No idea where it was

 

[Artyfowl]

Oh… I wonder if the retaining ring should go on in a certain position… if that’s off then no matter where the click spring goes it will always be off when it clicks inside each scallop. Bloody hell don’t want to remove that again

 

[Artyfowl]

Sorry Tony I’ve just repeated exactly what you said sorry, was thinking of the click spring. I greased the crystal gasket so perhaps I can just knock it around a few mm in situ

 

[TonyMonatana44]

Sorry Tony I’ve just repeated exactly what you said sorry, was thinking of the click spring. I greased the crystal gasket so perhaps I can just knock it around a few mm in situ

I would remove it completely and press it back in. You won’t be able to turn it while it’s pressed in.

mark where it is now and then press it back in.

 

[Autobús]

Or remove the insert from the bezel. Install the bezel, then align and reinstall the insert with the bezel in place.

 

[TonyMonatana44]

Or remove the insert from the bezel. Install the bezel, then align and reinstall the insert with the bezel in place.

That’s also a good way to do it. I just

 

[TonyMonatana44]

**I wouldn’t want to remove the bezel, the less parts I have to remove the better**

Sorry accidentally hit post and didnt finish the sentence lol

 

[TonyMonatana44]

@Artyfowl what height gasket did you end up using? Or did you use the factory rep one that came with the watch?

 

[Artyfowl]

The factory clean gasket. The watch is brand new so was in excellent condition

Slightly off topic. When putting the movement back in, I assume the retaining tabs go back on with the tabs sloping down at the far end? I got one in and had trouble getting the second to sit flush.

Would too much pressure affect the movement running? Everything is sitting flush and we’ll dial wise but I’m sure I had a running issue overnight where the movement stopped

 

[TonyMonatana44]

The factory clean gasket. The watch is brand new so was in excellent condition

Slightly off topic. When putting the movement back in, I assume the retaining tabs go back on with the tabs sloping down at the far end? I got one in and had trouble getting the second to sit flush.

Would too much pressure affect the movement running? Everything is sitting flush and we’ll dial wise but I’m sure I had a running issue overnight where the movement stopped

I saw one of your posts where you posted a pic of your swap. Great work on the job. However, I would swap out the crystal gasket to a 2.7mm atleast to make the mag date as close as gen as possible. Also it'll make the glass sit a little lower as the gen's do vs the reps coming in about 1.5-2 mm above the gens.

You can buy a clarks gasket on eBay. They're excellent quality and actually on par with the gen's gaskets.

 

[KJ2020]

The factory clean gasket. The watch is brand new so was in excellent condition

Slightly off topic. When putting the movement back in, I assume the retaining tabs go back on with the tabs sloping down at the far end? I got one in and had trouble getting the second to sit flush.

Would too much pressure affect the movement running? Everything is sitting flush and we’ll dial wise but I’m sure I had a running issue overnight where the movement stopped

You can put movement tabs in place in either orientation. Their original angle can sometimes be reduced or flattened completely with tightening. Normal tightening to the limit a screw can allow generally will not damage a movement.

What can happen, especially with a 4 hand stack (GMT) is that tightening the movement down can cause the second hand to contact the crystal. This can slow or halt the movement. It can also scratch the glass (amazingly) or ruin an AR coating.

Second hand catching on crystal