After the second washing, the watchmaker can proceed to assembling the automatic group, during which the correct operation plays between the parts are restored, proceeding first with lubricating all the parts: from the central pinion to the stones, to the escape wheel, lubrication is essential for minimizing friction which causes the moving parts to wear out. First the watchmaker mounts the crown pipe. He starts from the dial side, from the wheels of the 24 hour gear train, making sure that the pins enter perfectly.
Then he turns the movement to mount the barrel and the crown wheel. At this stage the last part to be mounted is the anchor, whose levers are lubricated with special grease, used only for this part. The watchmaker puts a drop of lubricant on the output lever turning the escape wheel and repeating the operation three times for a full spin of the wheel. This is enough to distribute the lubricant to the teeth of the wheel.
During this operation he must be very careful that the lubricant does not slide away to the anchor pin or one it, because it has to be dry while spinning. Finally we proceed with reinserting the balance spring, which was lubricated on a stone and against a stone with a special tool which drops the same amount of lubricant, so that everything remains perfectly clean and without any leaks. A special treatment (recommended by Rolex) is performed on the inverters which are lubricated with a specific product in which they soak for a couple of minutes before being dried with hot air. Then the lubricated rotor is put back together with its pin.
Once assembled, the movement is subjected to the final adjustment which lasts for 24 hours. Fully charged, the watch is placed on the chronocomparator in six positions (crown up, crown down, crown on the left, crown on the right, dial upwards, dial downwards) to detect the daily average deviation. The same operation is performed after 24 hours of operation. The adjustment is made for a daily deviation between 0 and +5 seconds per day.