How To Install A Wrist Watch’s Main Spring

These instructions will show you how to install a wrist watch’s main spring. A broken main spring cannot be repaired, so if you want your watch to run properly, you must replace the main spring.

As with most watch problems, it is best to take your broken timepiece to a professional watchmaker for repairs. However, if you are familiar with the inner workings of your watch and feel up to the challenge, these steps can help you install a main spring.

Materials needed to install a wrist watch's main spring:

  • Case knife
  • Magnifying glass
  • Watchmaker’s tools
  • Precision screwdrivers
  • Toothpicks
  • Tweezers
  • Empty egg carton
  • Small glass container
  • Cleaning solution
  • Lubricating oil
  • Old toothbrush
  • New main spring
  1. Open the wrist watch’s case back. Open the watch’s case back with a case knife. A hinge or raised lip will show you where to remove the watch cover. If the watch has a screw-down cover, unscrew the case from the bezel.
  2. Locate the wrist watch’s main spring. Use a magnifying glass to locate the wrist watch’s main spring. The main spring is tightly coiled steel inside a main spring barrel. Winding the crown can help you find the main spring, because the crown stem has a metal ledge that moves over the main spring ratchet wheel.
  3. Unwind the wrist watch’s main spring. With one hand, wind the crown a couple of notches. With the other hand, use a toothpick to gently nudge the metal ledge. The main spring should unwind.
  4. Remove the movement from the case. Use a magnifying glass to find the screws that attach the movement to the watch case. Loosen the screws with a precision screwdriver. Remove the movement from the case.
  5. Remove the dial from the movement. Turn over the watch movement. Use watchmaker tools to remove the hour, minute, and second hands from the dial. With a precision screwdriver, loosen the screws that attach the dial to the movement. Remove the dial.
  6. Remove the gears from the movement. Use tweezers to remove the gears from the movement. Start with the hour wheel, continue with the cannon pinion, and follow with a few of the bridges, or flat metal pieces. Then remove the barrel bridge.
  7. Remove the main spring from the movement. Use tweezers to remove the main spring barrel and wrist watch’s main spring. Remove the jewels, or small colored stones, from their holes.
  8. Clean the wrist watch’s parts. Sort the tiny wrist watch parts. Label the parts and place them in the compartments of an empty egg carton. Soak each part in a small container, such as a shot glass, filled with cleaner. Clean very dirty parts with an old toothbrush. Allow the parts to air dry after cleaning. Lubricate the jewel pinholes with oil.
  9. Install the new main spring. To reassemble the wrist watch, follow the removal instructions above in reverse order. In the process, replace the broken main spring with a new one. When the watch is reassembled, close the watch case cover, and wind the watch. It should work properly again.
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