The old time watchmakers call an overhaul a C.O.R. (clean, oil, and regulate.) How it's done, the movement is taken completely out of the case. The watch is completely disassembled and all the parts are placed inside a metal wire meshed basket and and then the basket is placed inside a bigger unit that is filled with cleaning fluid called a cleaning machine. All the parts are flowing through the cleaning fluid while the unit spins back and forth for a given amount of time,(the same concept as a washing machine). The unit stops spinning after the parts are clean and then radiant heat is passed through the basket to dry the parts. Then the watch is carefully put back together. While in this process, he is applying very small drops of oil to certain parts of the movement that need this done to, such as all the jeweled pivots (except the pallet fork pivots), mainspring, certain gears, and the keyless works (the system in the watch that contains the crown and stem for setting). 3 different kinds of lubricants with different kinds of viscosities are used depending on what parts he is lubricating. After it's completely assembled and lubricated and is in working order, then the movement is placed on a timing machine for regulation.
Here the watch's timing and beat frequency is checked. This is done for accuracy. If the watch doesn't pass his timing test, then appropriate action is then necessary to rectify the problem such as an adjustment to the balance wheel, by turning what they call microstella screws inward or outward depending on how fast or slow it's running and other adjustment in regard to beat frequency that go over my head, (but I'm still learning).
After the movement is finished, then the watch case is buffed and polished and then dipped into an ultrasonic cleaning machine (without the movement installed of course). New gaskets for the crystal, caseback, and crown are installed. Also, I forgot to mention the case tube and crown are replaced too. (the casetube is the threaded metal part that the crown screws on. In other words, it's the small threaded tube that sticks out of the case for the crown to screw on)
Beware of freelance watchmakers nowadays. Instead of disassembling the entire movement, what they do is just dip the entire movement into this hi tech cleaning solution that contains some space age lubricant like teflon or something, and by doing this, they don't have to take the time to disassemble the movement. It's a very cheap way out, that in my opinion doesn't do a thorough job. Like taking a shower with a raincoat on so to speak. So if you do have an independent watchmaker service your Rolex, make sure he is one of a type that takes his time and does a complete job, by completely disassembling the movement instead of the "dipping" procedure. Also make sure both the case tube and crown is replaced and all the gaskets. You never know sometimes. They may use the same gaskets and parts and say it was replaced.
From: http://www.turfers.com/nuggets/posts/124.html
