A watch case cannot simply be opened once you’re already on your feet. Before the first movement, you need to clean your workstation, select the appropriate tools, and treat the watch as something vulnerable to improper pressure. A case opening isn’t merely the entry into the interior of a movement. It is also an operation that could lead to scratches along the side or back of the case back or disturbs a gasket, introduces dust, or otherwise complicates what may otherwise have been a non-issue.
First, establish what sort of back your watch has. There are various back designs, with some watches incorporating snap backs; others, a few screws and others a threaded case back that requires a corresponding case back opener. Not every style will be opened properly by the same tool. For instance, forcing a blade under a screw-down back will result only in damage rather than success and, similarly, carelessly using a case back opener on the wrong notches might lead to slippage and leave deep, unwanted marks. Before attempting anything, take time to carefully examine the back under a loupe and determine how it is supposed to open.
A clean set up is especially important, since what’s inside the case is far more delicate than what’s outside. If you open the watch case there is a risk that dust, lint and fingerprints could find their way inside, where the movement, dial-side, gasket and battery are all exposed. Use a dust blower to prevent dust from blowing into your work area when possible, keep sleeves with fabric away from your bench area, and avoid setting your watch or case components down onto surfaces that shed fibers. If you use finger cots or gloves, make sure they are clean and are not interfering with your grip.
To begin the preparation process, a helpful exercise is to place a closed watch case on the bench mat and hold it down while positioning a case opening tool against the back. Do not make a full application of force but merely position the tool, so that you are able to assess your wrist angle and what way the tool would slip and slide in a sudden movement. Be sure that you have not placed the other hand into the path for which the watch might slide. A little preparation here may keep you from accidentally doing a sudden twist, resulting in a case that’s scratched or a watch that flies across your bench.
Even at this level, it’s necessary to inspect the gasket. This is located either inside the back of the watch or within the case; the gasket could have been stretched from a former disassembly, fallen out, collected dirt or might not be correctly placed once you have finished reattaching the case. You must avoid the assumption that, because you’ve opened the case, it is also water-proofed, particularly if you don’t have the means to test it. You need to make it a habit of inspecting the gasket to make sure it has not been damaged, keeping it as clean as possible and avoiding its pinching and understand that just because you have properly placed your case back again does not mean that your water resistance is guaranteed.
If your watch has a battery, you shouldn’t be in a rush to replace it upon first inspection. Take note of how the battery is held in place, where its contact lies and any clip or miniature screws. Take your time to avoid the risk that, should an instrument that has slipped from your hand do anything more damage than an old battery. Don’t apply unnecessary force if you aren’t able to make a movement with the least possible resistance and should be ready to look more carefully instead.
Practice opening a watch case on an older watch with minimal value before working with a watch that is personally or monetarily meaningful. It doesn’t really matter how quickly you’re able to get that cover off; rather the aim is to gain an understanding of how the case back feels as it is manipulated, how the tool feels seated, what the gasket looks like and just how much dust has gathered. A successful first opening is not one that allows you to get it off the fastest, but instead one that results in the watch being opened, with your case remaining without marks, components remaining in place with the least risk of moving around, and with that same watch being ready to close once more.