Why? Are you going into outer space It may be a problem, plexi crystals are usually held in by a chamfered bezel, i.e. they spring out into the bezel when installed. Sapphire crystals are usually bonded into the bezel. Al Archer will give expert advice though.
Usually this question is asked the other way around - people want to replace the acrylic with sapphire. I don't know of anyone who does what you are asking as some sort of specialty service. Sapphire crystals are not usually glued to the bezel or case - that is typically only done on very cheap watches or by someone who doesn't take them time to affix the crystal properly. Most sapphire crystals are pressed in place with a hard plastic gasket, although there are other ways. And that is really the point that makes this difficult to answer - there are many different ways of fixing a crystal to a watch, so unless you can talk about a specific watch, the question can only be answered by "maybe?" Another point about acrylic crystals - difficult to say they are "usually" held by a chamfered bezel. Many are, but most Omega watches use an armored crystal with a tension ring, and there is no chamfer involved with these. There are even more options with acrylic crystals than with sapphire, so it's something that can be very different depending on the watch. Cheers, Al
It uses a tension ring, so the yellow, silver, or black ring on the inside of the crystal. This type of crystal is straight sided, and is pressed directly into the case using a press - held in by friction and not a chamfered bezel. Speedmaster is a common example. Cheers, Al
I'd like to replace toss the sapphire on my FOIS and replace it with what Omega should have used. I much prefer the way the light reacts on acrylic. Sapphire is much too reflective, even with the coating they gave it. It's the main reason the watch sits in a drawer.
Won't work - the opening in the case is too big for the acrylic crystal that goes in a typical Speedmaster. Time to flip the watch and get another one with an acrylic crystal. Cheers, Al