It's easy to replace a watch back, commonly referred to as a case back, on a Timex watch. However, you should thoroughly inspect the original case back to determine whether it's necessary to replace it. Although Timex watches are inexpensive timepieces, vintage models are becoming collectable. Switching the case back will significantly reduce its value because the date code ink-stamped on the inside will not match the rest of the watch's model and movement codes. Replacement case backs on newer models should match the original. These can be purchased from an authorised Timex dealer.
Use a jeweller's loupe to inspect the Timex watch back to determine whether it's a snap-down or screw-down model. Many Timexes have a small triangle stamped on the case back that points to a lip under which a blade can be placed to lift the snap-down versions. Older models may not have a lip. If there is no lip, then inspect the seam between the case back and case to find a suitable location to insert the blade to pry off the case back. Skip to Step 3 if the Timex is a screw-down version.
Insert the blunt blade under the lip. Push the blade downward. The case back will pop open. Insert the blade into the seam if there is no lip.
Insert the case back remover into the notched holes around the edge of the case back if the case back is a screw-down model. Rotate the case back remover counterclockwise until the case back is free. On older models without the notches, you can use the palm of your hand to rotate the case back off the case. Once the case back is removed, a rubber gasket will come off with it. Gaskets are usually found on newer models. Skip to Step 6 for screw-down models.
Wipe the new case back and edges of the case with a clean, lintless cloth. Place the case back on the case and use your thumb and forefinger to snap the snap-down version into place. This will work on vintage Timex watches. Newer snap-down models may require a watch press, which is outlined in Step 5.
Place the Timex watch crystal side down on the bottom pad of a watch press. Fit a pad, or die, into the top press pad holder. Ensure the pad covers the case back but doesn't extend beyond it. Align the replacement case back and gasket on the case. Gently lower the press onto the case and squeeze it shut.
Wipe the new case back and edges of the case with the cloth. Screw the replacement case back onto the case in the reverse order you removed it if you are replacing the screw-down version.
Never force open a stubborn case back. It will damage the watch.
Opening a newly-purchased Timex watch case back will void the warranty.