Regulating a mechanical watch is a relatively easy task that requires little skill and plenty of trial and error. Most mechanical watches are vintage timepieces manufactured before 1970. Although most watches produced today are battery-powered quartz models, mechanical watches remain in production. A tiny spring-loaded engine, called a "movement," powers a mechanical watch. A mechanical watch in good running condition may gain or lose between five and eight seconds a day. More time gain/loss may require a slight adjustment of the regulator.
Wind up your mechanical watch and set it aside for 24 hours to determine how much time it is losing. Time it against a quartz watch or clock. If the watch loses or gains less than eight seconds in 24 hours don’t bother regulating it. If it gains or loses several minutes, there is something wrong with the movement and regulating it won’t solve the problem. Take it to a watchmaker for repairs.
Place the watch on a table before you decide to open it for adjustment. Gravity and position play a role in the accuracy of a mechanical watch. According to Rolex, the watch may gain a few seconds if you lay it face up and running for 24 hours. It will lose a few seconds if the watch is set on its side with the crown (winding knob) facing downward. It will lose more seconds if the watch is set on its side with the crown facing up.
Use a case blade to open a snapdown case back of a mechanical watch if your positioning experiment does not work. Use a watchmaker’s rubber ball, a wadded up ball of duct tape or rubberized jar opener to twist off counterclockwise a screwdown case back.
Place the watch face down on a clean, flat surface. Use a jeweler’s loupe or magnifying glass to find the regulator. The regulator will be a notch next to the balance wheel with a “+” and “- ” on either side. Most watches, however, have a thin bar between the “+” and “-“. Many luxury watches don’t have regulators and must be serviced by a watchmaker. Step 5
Use a toothpick or similar clean tool and move the bar a tiny fraction towards the “+” to make the movement gain time or towards “- ” to slow it down. Use a screwdriver if the regular is a notch.
Set the watch aside for two hours and time it again to determine the gain/loss of seconds. Keep the case back off. Record the gain/loss and multiply it by 12 to determine how many seconds are gained or lost in 24 hours. Continue making incremental adjustments until the gain/loss is less than eight seconds. Your final adjustment should be made only within 60 to 120 seconds .
Novice watch collectors should practice on a cheap watch or one in poor condition for practice before attempting the real task.
Never force anything on a watch. You will break something. Send stubborn watches to a watchmaker.