Sizing Expansion Bands
You may want to custom-fit an expansion band that comes with a new watch. Other times the band breaks when you catch it on something, and you have to replace it or - if it's one of today's higher-priced versions - repair it. Sizing the band and repairing the links are performed using the same basic procedures.
Expansion bands are made of a series of bottom and top rectangular, tube-shaped links holding two leaf springs and four U-shaped clips per link. On top is a decorative cap.
To start the repair, you'll need a thin knife blade. Place the blade behind the flat end of a link and twist outward while pushing toward the fold in the hinge (see below). To remove the U-clips, use the knife to lever open the end of a top cap on one link and then open the opposite end on the bottom link on the adjoining link. Slide the two halves apart and the U-clips will be clear to grasp with tweezers.
To begin the repair, use a thin knife blade to pry open the flat end of the link. Note: Several expansion bands require complete removal of the top caps before replacing a link. These have larger top caps or an angled end flap. If in doubt, refer to the watch company's repair guides.
To replace the U-clips after sizing or repair, line them up. Be sure the clip on the bottom link inserts above the leaf spring in the top cap. Also be sure the clip from the opposite end inserts below the leaf spring on the bottom link. Slide the two links together. This can be tricky, but you'll be able to do it in fewer than 10 minutes with practice.
When closing the ends of the links, support one side on your bench top. Apply even pressure as you rotate your blade downward. When both sides are closed, place the band in a small, smooth-jawed bench vice. Close the jaws slowly to even out the closed end flaps.
Fitting The Band
A properly fitted expansion band should have no gaps between the links when placed on the wrist. If there's a gap, add a link. (Or recommend buying a larger size). Otherwise the band will bind the wrist, pull hair and be uncomfortable.
When sizing, hold the band around your wrist (see on the right) and count the number of links that "bunch up." Subtract two from this number and remove the remaining links using the procedure outlined above. Open the band, count out the links for removal, slide them out and rejoin the two halves.
After a few years of use, expansion bands begin to weaken and gaps appear between the links. Dirt and perspiration aggravate this deterioration. When an older band becomes uncomfortable, you can extend its life for a year or so by removing several links. Afterward, the links usually become so weak that replacement is the best answer.
Reprinted with permission from the Professional Jeweler Magazine. For more information, please visit the American Watchmakers-Clockmakers Institute (AWCI).