The Spring Bar
The band usually is attached with a push pin called a spring bar. Each end of the bar collapses inward under pressure and then extends when placed into the holes of the watch case lugs. The lugs are the two metal "legs" that protrude from each end of the watch case.
Check The Lug Holes
Often these holes need to be cleaned. Bracelets loosen as the lug hole fills with grime and dirt during everyday wear. These holes need to be clean before any new spring bar and strap can be attached. Pull out your small screwdriver set and select one with a blade just slightly smaller than the diameter of the lug hole. Place the blade in the holes and rotate the screwdriver to remove grime. If needed, press down to be sure the hole is deep enough to hold the new spring bar.
Before replacing the old spring bar, be aware many types are available. Perhaps the bracelet loosened because the spring bar was not the correct size or diameter in the first place. You may have bought a replacement band elsewhere that was fitted with thin or weak bars that "telescope" to fit nearly any case size. You'll do best if you replace these bars with stronger ones that fit properly. You don't want the problem to recur in six months.
Bars are sold in different sizes and styles. Generally, heavy watches require heavier spring bars. Choose the largest diameter that fits snugly through the end of the bracelet or strap. For length, find the longest bar that still fits between the lugs. To do this, measure the lug distance with a caliper. Then measure the spring bar from one extended end to the end of the solid central piece.
Note whether the bracelet or strap is sized incorrectly, and be aware of the possibility of future problems if inappropriate. Often, the strap is too narrow or the spring bar is too short. This places too much pressure on both ends of the spring bar. Select the correct size strap or bracelet or replace it if requested.
Remove The Bar
To remove the spring bar, use a common spring bar tool, a knife blade or a sharp screwdriver. Slide the blade between the lug and the band and retract the bar enough to free it from the lug. Push with a finger as you retract the spring bar.
Sometimes the tight space between lug and bracelet makes this operation difficult. A thin saw blade can cut the bar quickly. However, never use nippers to cut the spring bar on bracelets or bands that are attached to the watch because the lugs might break in the process.
Again, check with your materials supplier, watchband maker or the watch supplier for tools specific to the type of watches or bands you carry - and keep these in your toolbox.
Replace The Bar
Insert one end into the clean lug hole as you hold the strap or bracelet in place. Hold the other retracted side next to the knife or tool you're using.
Carefully and steadily slide the end of the bar from the tool into the lug hole or just near it. Use finger pressure to hold the strap or bracelet in position.
Adjust the bar end to snap into place with your tool blade. If the end of a metal band is narrower than the lug opening, the spring bars will break repeatedly.
Reprinted with permission from the Professional Jeweler Magazine. For more information, please visit the American Watchmakers-Clockmakers Institute (AWCI).