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Archer
··Omega Qualified Watchmaker
Oh my not good technique/practices shown in that link guys...maybe I can give you some tips for fitting crystals and case backs...
So first, all rigid plastic gaskets are one use only items. Like those for a snap on case back, a plastic crystal gasket relies on compression/deformation to provide the tension to hold the crystal in or the case back on. Once they have been used once, they are never as tight if used again, which can lead to water resistance issues.
Secondly, if your crystal is out of flat when pressing it in, please do not do what they show there and press the crystal on one side. It needs to be removed, and personally if this happens (not often really, but sometimes it does) then you start over with another new gasket. So when ordering a new crystal gasket, I recommend ordering 3 instead of 1 - that way you have some spares for the next watch, or if the one you are working on gets damaged you have another one on hand right away.
So crystal gaskets can come in different cross sections, so they can be an "I" cross section, or sometimes they are an "L" cross section. In either case, the gasket goes into the case first, and always pay attention to see if there is a chamfer on the gasket. Of course the chamfer is there to help ease the crystal into the gasket, so it has to be facing up. When installing a snap on case back with a plastic gasket, the gasket is mounted on the case back, not in the case. The chamfer is of course facing towards the case, not the case back.
The key to a good press is rigidity, and alignment of the shaft to the base, so the perpendicularity of those two components. I can't speak for this press, but the Horotec press I used to have was decent (it was not the screw in type, but one with a handle you pressed and the plunger was spring loaded - I think it was about a $500 press), but putting in thicker dive watch crystals often resulted in damaged gaskets. After using the Bergeon rack press at Omega training to fit crystals (I had used one in school also, but just for case backs and for that it seemed like overkill) it was clear I needed to get one. The difference is astounding at how easy crystals are to install, even very thick PO crystals.
So the key is to get the crystal lined up as flat as possible to start with, and take your time pressing the crystal in. If you think your press might not be 100% aligned, then press the crystal a bit, then rotate the case 90 degrees, then press again, and repeat until the crystal is all the way down. Make sure it's flat as you are pressing, and when done you can confirm this from the inside - if there is no inner rehaut then it's easier to check if the crystal is all the way down all the way around. If it is in all the way, you are still not done!!
Leave the case/crystal set up in the press with no pressure on for 10 minutes, then go back and seat it again. Depending on how tight the gasket is, the crystal may lift up slightly - the gasket will sort of expand again lifting the crystal, in particular with tall gaskets used on dive watches. When I go back for the second pressing, I listen for a tell tale "click" of the crystal seating on the case, and then I know I'm done.
One other thing to keep in mind is that dies can be damaged, so when doing something like is shown in that link where they are not pressing on the whole crystal with the die, it's easy to damage it doing stuff like that, so now you will have made the problem worse for the next time. Some people swear by aluminum dies, but I use mostly plastic dies and as long as they have brass threaded inserts to screw onto the press, they are usually good quality and stay aligned if treated well.
Hope this helps.
Cheers, Al
