DIY GMT Master Crystal Replacement

[TonyMonatana44]

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.

Not to derail what @KJ2020 just posted, but if you look at the groove where the tabs sit inside the actual watch case, you can see that there is a slot where the little metal thing goes. I would take a pair of tweezers and first put the flat end of the metal part inside of that groove, then let the metal part go and it'll sit or be close to the screw hole after you get it in the groove. If it's off orientation to the screw hole, you can move it around to be perfect, but be careful not to remove the flat part from the case groove.

I would do this under a magnifying glass or scope. It's insanely hard to do and to see without a mag.

Also @KJ2020 - to your point about the seconds hand touching the xtal - I installed a 2.5mm gasket with mine, and also tightened the movement down as much as I could. It's not stopped the seconds hand and the watch still tells accurate time, which leaves me to believe that it's not touching. Does this seem right? I've spent hours on RWI reading posts where whenever someone used a gasket lower than 2.7mm, they had problems. I wonder why mine wasn't the same.

 

[Artyfowl]

Thanks chaps. Mine’s definitely catching when it gets to the cyclops. Just witnessed it (and nope my crystal isn’t upside down )

 

[KJ2020]

Also @KJ2020 - to your point about the seconds hand touching the xtal - I installed a 2.5mm gasket with mine, and also tightened the movement down as much as I could. It's not stopped the seconds hand and the watch still tells accurate time, which leaves me to believe that it's not touching. Does this seem right? I've spent hours on RWI reading posts where whenever someone used a gasket lower than 2.7mm, they had problems. I wonder why mine wasn't the same.

I wondered about the too but I have seen a 2.5mm gasket work before. IDK if anything has changed with recent releases like a slightly taller rehaut or slightly shorter hand collars. In any event, once a crystal sits on the rehaut ledge it can't go any lower no matter how short the gasket is so if the second hand is sweeping beneath the rehaut ledge (and it's level) there can't be an issue. Fully pressing each hand down completely can help achieve this goal. Paying close attention to the hour hand is critical ofc. Dial clearance is slight, and dial scratching can ocurr easily.

 

[TonyMonatana44]

Thanks chaps. Mine’s definitely catching when it gets to the cyclops. Just witnessed it (and nope my crystal isn’t upside down )

That is super off. Do it touch even if you remove the screws? I would take them out and just let the movement sit inside the case. Check if it causes any issues. If it doesn't, i would tighten the screws down evenly, first left side, then right, then a little more on left and then right to make sure there is even pressure on both ends.

If that doesn't work, then take pics and show us of the caseback so we can try and help out.

 

[TonyMonatana44]

I wondered about the too but I have seen a 2.5mm gasket work before. IDK if anything has changed with recent releases like a slightly taller rehaut or slightly shorter hand collars. In any event, once a crystal sits on the rehaut ledge it can't go any lower no matter how short the gasket is so if the second hand is sweeping beneath the rehaut ledge (and it's level) there can't be an issue.

Yeah this is the height difference between the stock CF Xtal with CF gasket (1.86mm) and the 2.5mm from Clarks with the Deep xtal. Major height difference so I'm not sure either. Could be that the hands were shortened from the factory?

 

[Artyfowl]

Thanks Tony

Here is a pic I’ve just got back from picking the kids up and it’s stopped again. This is where it seems to always catch.

 

[Artyfowl]

It must only be slightly as If I tap the watch face it kicks it back in to motion. At first I thought it was an iffy movement but it always stops at exactly the same place

 

[Artyfowl]

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.

I’m pretty sure the prof crystal is sitting right on the rehaut ledge so physically won’t go any lower. I’m building up the energy to strip it all down again this eve so will update what I find

 

[TonyMonatana44]

I’m pretty sure the prof crystal is sitting right on the rehaut ledge so physically won’t go any lower. I’m building up the energy to strip it all down again this eve so will update what I find

Hmm. I'm certain that you might've over tightened the side near the mag more than the other side, and it's basically not even, or the movement is at an angle.

What I would do is just remove the case back and remove both screws from the movement. Look at the watch face upside down so that the movement sits as it would be if it were screwed in, see if it still catches or if you have issues. You should not be having this problem if you used the CF crystal gasket as it's super high at like 2.86mm.

I installed a 2.5mm gasket and used a thicker Deep crystal at 1.8mm and still didn't have issues.

Keep us posted.

 

[Artyfowl]

Hmm. I'm certain that you might've over tightened the side near the mag more than the other side, and it's basically not even, or the movement is at an angle.

What I would do is just remove the case back and remove both screws from the movement. Look at the watch face upside down so that the movement sits as it would be if it were screwed in, see if it still catches or if you have issues. You should not be having this problem if you used the CF crystal gasket as it's super high at like 2.86mm.

I installed a 2.5mm gasket and used a thicker Deep crystal at 1.8mm and still didn't have issues.

Keep us posted.

Will do my man thank you. Just preparing my scrubs for theatre

 

[Artyfowl]

We go again!

 

[TonyMonatana44]

We go again!

God speed my friend. I would have some fishline on hand to replace that Hytrel ring. It can only take so many beatings taking the bezel off and on

 

[KJ2020]

We go again!

You can test your insert alignment with a given crystal retaining ring orientation by placing all the parts together except the bezel gasket (hytrel ring). This will allow you to adjust the crystal retaining ring's rotational position without all the hassle and risk of a full press each time. Refit the the hytrel when the retaining ring is good just before the final press.

I chose to realign an insert this way once and it took 8 - 10 retaining ring adjustments to produce a perfectly centered insert. It isn't fun but if you're dealing with a gen insert for example, it can be worth the trouble to avoid cracking the insert during a removal or reinstall.

It's way less trouble IMO to just remove the insert from the bezel and save the reinstall til the last step.

 

[TonyMonatana44]

You can test your insert alignment with a given crystal retaining ring orientation by placing all the parts together except the bezel gasket (hytrel ring). This will allow you to adjust the crystal retaining ring's rotational position without all the hassle and risk of a full press each time. Refit the the hytrel when the retaining ring is good just before the final press.

I chose to realign an insert this way once and it took 8 - 10 retaining ring adjustments to produce a perfectly centered insert. It isn't fun but if you're dealing with a gen insert for example, it can be worth the trouble to avoid cracking the insert during a removal or reinstall.

Is there any benefit to pulling just two of the tabs on the bezel spring vs all 3? I need a more solid "click" on mine and it just seems too lose and wobbly.

I put it up against my gen spring that I have and they dont seem to be too far off in diameter either.

I will try the thicker fishline for the hytrel ring to see if that stops the bezel from playing left and right after I swap to my Gen Crystal I have coming in hopefully a few days.

 

[KJ2020]

Is there any benefit to pulling just two of the tabs on the bezel spring vs all 3? I need a more solid "click" on mine and it just seems too lose and wobbly.

I put it up against my gen spring that I have and they dont seem to be too far off in diameter either.

I will try the thicker fishline for the hytrel ring to see if that stops the bezel from playing left and right after I swap to my Gen Crystal I have coming in hopefully a few days.

This is how the click ring needs to be adjusted.

Bending the ring between the oval pin bases forces them to hug the retaining ring scallops more tightly. You don't need to worry about over-bending it but take care not to crease it. The underside groove in the bezel where the ring fits will only allow so much of a bend and will bend it back to fit when it's installed.

You should re-read my post about fishline. Pay particular attention to the part about not forcing a bezel down if there is significant resistance. You can end up with no play, no rotation, and no removal. There's a solution but it's not particularly pleasant. I've had to do it twice.

Using fishline as a hytrel ring

 

[TonyMonatana44]

This is how the click ring needs to be adjusted.

Bending the ring between the oval pin bases forces them to hug the retaining ring scallops more tightly. You don't need to worry about over-bending it but take care not to crease it. The underside groove in the bezel where the ring fits will only allow so much of a bend and will bend it back to fit when it's installed.

You should re-read my post about fishline. Pay particular attention to the part about not forcing a bezel down if there is significant resistance. You can end up with no play, no rotation, and no removal. There's a solution but it's not particularly pleasant. I've had to do it twice.

Using fishline as a hytrel ring

Yeah that's what I did to my spring as well. I also tried pulling on the tabs to see if that would fix anything. I guess i'll just have to get a gen spring for this watch as well.

As for the fishline, I got a lot of different sizes. I will try from the smallest to the largest diameter and see which one plays best.

 

[Artyfowl]

Well chaps all adjusted and rebuilt. I’ve left it sitting to check it runs true.

There was so much grease from the factory I think the hyrtel was well protected. I’ve had the bezel off about 8 times now and it still clicks back in perfectly.

I got my ruler out and measured absolute dead centre on the case and managed to get the retaining ring position bang on after 2 tries. Result!

Got the movement tabs in better. Only one was a pain, seems like the tab is slightly too long to manage to sit flush on the movement above the threaded hole. Gave the edge a slight sand and sitting well.

Thanks for the assistance. Fingers crossed the seconds hand doesn’t get caught

 

[TonyMonatana44]

Well chaps all adjusted and rebuilt. I’ve left it sitting to check it runs true.

There was so much grease from the factory I think the hyrtel was well protected. I’ve had the bezel off about 8 times now and it still clicks back in perfectly.

I got my ruler out and measured absolute dead centre on the case and managed to get the retaining ring position bang on after 2 tries. Result!

Got the movement tabs in better. Only one was a pain, seems like the tab is slightly too long to manage to sit flush on the movement above the threaded hole. Gave the edge a slight sand and sitting well.

Thanks for the assistance. Fingers crossed the seconds hand doesn’t get caught

Glad to hear it!! I will be doing mine again soon to change to Gen crystal. I will more than likely swap my hytrel ring that came with the watch to thicker fishline to make the bezel stick more and not move around.

 

[Artyfowl]

I have to say, the Ali bezel remover has been superb. Pops the bezel off smoothly and evenly. Has helped it survive so many removals I reckon. It’s the slightly more solid one. Not the £20 eBay / Amazon job… of which I have still unopened

I have one more gmt, my Pepsi to do (I’ll do that tomorrow) then the only crystal swap I have left is for the….

Dun dun dunnnnnnn

DSSD

 

[TonyMonatana44]

I have to say, the Ali bezel remover has been superb. Pops the bezel off smoothly and evenly. Has helped it survive so many removals I reckon. It’s the slightly more solid one. Not the £20 eBay / Amazon job… of which I have still unopened

I have one more gmt, my Pepsi to do (I’ll do that tomorrow) then the only crystal swap I have left is for the….

Dun dun dunnnnnnn

DSSD

I just use a kitchen knife and hope for the best