Tension-ring crystal replacement tool. Any options?

[MrRoundel]

Greetings, gents.

I'm in the process of replacing a tension-ring crystal on a vintage 1954 Girard Perregaux wristy. I was not aware that it used such a crystal until after I popped it out in a couple of pieces. Bugger was really in there. I tried finessing it out with a standing pliers style GS press but no luck until I bore down a bit harder. I had also tried a crystal clamp but it wasn't able to squeeze the crystal down enough to press it out, even with taps of a nylon hammer head.

Unfortunately the case bezel grew a bit since I first took what I thought was a good measurement of it and ordered that size crystal. And of course the crystal I got is too small. On the next measurement I found out that the bezel grew about .2mm since the first measurement. As I read up on installing tension-ring/armored crystals I discovered that you don't have a lot of tolerance for a crystal that is too large. .1mm is the maximum oversize from bezel that one should use. This, according to the Sternkreuz catalog details. It also seems that I might not be able to use my GS press, nut-cracker/plier style to install it. In addition, I read that it's quite difficult to install them using the nylon dies that come with the inexpensive case presses. Do I have any chance in fitting the right crystal with the nylon dies (Some dies do have the chamfer to fit over the edge of the crystal and reduce its diameter a touch.) or do I have to buy a "real" crystal press that's heavier duty, or at least uses threads for applying the pressure?

The case is a nice 14K case that I don't want to distort. I think I now understand how it is that some watch cases have broken lugs, etc. People probably using the wrong press and/or applying too much pressure. Any suggestions are appreciated. Many thanks. Cheers all.

 

MrR

 

[Klassiker]

There are already a few threads on here discussing this. Mark also made a video. As you say, size is important. Get the size you think you need, and one size bigger. You can rub down the o.d. if necessary. The press you have with the angular contact dies should do the job if the crystal is the right size. The claw tool is the wrong one for this job. You need to get the crystal lined up with the bezel, and the pressure from the die needs to be equal all around.