Why is it so hard to take off the back of a watch?
The answer is to keep the movement away from casual people tinkering with it.
And I mean YOU.
A mechanical watch is a sort of carefully balanced little mechanism which can be swayed by the presence of a minuscole blog of dirt. It runs on tiny pivots that would make an average needle look like a hulking behemoth.
And you really want that someone would open it to examine and touch this assembly with his fumbly and greasy fingers? No way, sir.
Yes, what you can see here is the longterm effect on a bridge of ONE careless fingerprint left on its surface.
This is the main reason why watch backs are difficult to pry open.
The need of protecting the service network
Even if you – the end user – possess the technical skills neeeded to perform some routinary operations on a watch, the watchmaking company instead makes its best to restrict you from doing it.
And the reason why is simple.
While in the past it was pretty normal that any watchmakerrepaired watches, in more recent times companies try to give this privilege only to their official authorized assistance network of technical service centers.
As you know, the markup on the object itself is not the main objective: the real deal is performing the routine assistance. And this is what the watch companies are pushing their retailers to do.
One of the easiest ways to do this is to create a closure that can be opened with a special tool only, which is not widely available. This is the case of the Rolex Oystercase, that needs a special die to clutch the indentations at the base of the back and let them rotate to unscrew the back from the case.
Rolex is not the only culprit doing this: Breitling and Longines have done it as well. This means that if you do not have that special key, you cannot open the back. But professional watchmakers do have the necessary keys to open different kinds of watches.
As you can clearly see, the back of an Oystercase is not easy to accesss. You need a proper tool to do that without scratching the surfaces.
The need to close the back safely
The last thought is that watchmakers had to develop a closing system that was both good enough to perform its duty, and cheap enough to be installed in an industrial production.
One of the main enemies of watches, before water, was dust. If dust went into a watch, it would impair its operation, and clog the oil used inside to lubricate its movement. So, companies had to find ways to keep the dust out of watches. And when the fad of water came, the experience they had was applied towards it.
This need brought companies into the manufacturing of the two main closure systems that you’d find: snap-on and screw-on.
Snap-on systems are the cheapest. They are composed by a lid that snaps on and off the case if you use enough pressure and skill. To facilitate this happening, they generally have an indent or a sort of nail where you can place an case opener tool , press and twist a bit. If you have done it carefully, the back would snap off without you scratching the watch (yes, this is the main issue – you definitely CAN scratch it deeply if you are not careful and accustomed to it).
Screw-on systems are generally more costly. They are composed by a back that is screwn on the case by using a special wrench. The backs have generally a few indents – normally six – where you can place the points of a special wrench, press hard and twist it so to unscrew the back. In the case of the Girard Perregaux above, there are eight – so you’d need a special key.
A screw-on back is much more water resistant than a snap-on one, as you would suppose, and many of them are protected by a rubber or silicone gasket to further insulate the mechanism from the water.
Beware of the gaskets
Remember that when you remove a watch back, in many instances you will find a silicone gasket which has been put there to protect the mechanism from water and dust getting in and rusting or clogging the delicate wheels of the movement.
A silicone gasket has a limited duration, generally five years – and must be periodically lubrified to keep int in good shape. If you do not, the water resistance of your watch is at risk, and water and dust could get in, with possibly dire consequences.
As said before, do not open a watch back if you do not know what to do, because you would probably damage its mechanism.
Another advice is that while Quartz watches are way sturdier than mechanical watches, so they survive much rougher handling as well. this means that their backs are generally easier to open, especially since you need to change the battery every now and then.
But mechanical watches make their best to deter you from opening them, and with very good reasons.
You can find much more about horology and its fascinating history in The Watch Manual, a thorough e-book that explains all the basics about watchmaking and its protagonists.