Crystal for a Monocoque Case

[gpraceman]

Is there any particular crystal type that works better with monocoque cases?  Something that maybe has a thinner sidewall than usual?  I need to source a new crystal for my grandfather's watch.  The old crystal is 30.0 mm diameter and about 3.5 mm inner height.  Case bezel is about 29.45 mm.

I used a claw type crystal lift to remove the old crystal but unfortunately cracked it in the process.  Strike 1.  I found a replacement crystal, a GS high dome I believe, but I managed to crack it as well.  Strike 2.  For that one I used a crystal wrench type tool to try to insert it.

Not great photos I know.

[gpraceman]

I managed to get a replacement high dome crystal.  Had a bit of trouble getting it in.  Then noticed a piece of lint on the dial. Took the crystal back off, removed said lint and got the crystal back on.  Had to use my crystal press to make sure that it was fully seated.

[tIB]

I'm not an expert but think a tension ring type (which I think yours has) is the way to go. I had the same experience - got it all together and fluff noticed... couldn't remove with the claw thingy, though fortunately a syringe did the trick, phew!

[gpraceman]

1 hour ago, tIB said:

I'm not an expert but think a tension ring type (which I think yours has) is the way to go. I had the same experience - got it all together and fluff noticed... couldn't remove with the claw thingy, though fortunately a syringe did the trick, phew!

The original crystal did not have a tension ring.  I would think with a tension ring, you could not use a crystal lift to remove the crystal, as you experienced.  I think next time, I will use the compressed air trick to remove a crystal from a monocoque case.

[JohnR725]

On 9/18/2024 at 11:12 PM, gpraceman said:

monocoque cases

sometimes there would be a possibility if we knew whose case this was figuring out what Crystal was they are originally.

[tIB]

4 hours ago, gpraceman said:

The original crystal did not have a tension ring.  I would think with a tension ring, you could not use a crystal lift to remove the crystal, as you experienced.  I think next time, I will use the compressed air trick to remove a crystal from a monocoque case.

My only experience with a monocoque case was with an army issue watch - you're probably right about removal but perhaps they chose the tension ring as it would be less prone to failure and if it did fail they'd replace the watch rather than the part? 

 

Anyhow, glad you got it sorted. 

[gpraceman]

Thankfully, my grandfather's watch is all done.  It's a 1970's Elgin, with a beautiful copper plated Elgin 996 (AS 1902) automatic movement.  There's no signs of anyone else servicing the movement, so it was well overdue.  This watch was actually what got me interested in watchmaking.  It was my first mechanical watch.  I inherited it when my grandfather passed away.

I definitely learned some lessons on dealing with monocoque cases.