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Open & Shut the Case

By David Christianson, Certified Master Watchmaker

Timepieces can be damaged during a routine battery change. To help you with this common but often inadequately performed task, let's examine the first steps toward changing quartz watch batteries more efficiently and without costly errors.

Watch Case Basics

Watch Case Basics

The watch case houses and protects the delicate and intricate quartz watch movement. Depending on the construction of the case, it can protect against ambient dust or even submersion in water if the case is well sealed.

The case consists of a clear lens (or crystal) over the dial (see illustration), a case band or case frame (the main frame of the case) and a caseback that allows access to the inner movement (the actual workings of the watch). The hand-setting knob and linkage are called a crown and stem. They extend through the case frame and into the movement.

The crystal, case frame, crown and caseback must remain intact to protect the movement from contamination. The least bit of contamination can cause the watch to stop and require the expertise of a professional watchmaker to clean and relubricate the movement.

Most quartz watches have a thin rubber seal or gasket sealing the crown and caseback to the main case frame. The crystal is sealed with a gasket, cement or friction pressure, depending on the case and crystal design. Any cracked, stretched, hardened or loose gasket needs to be replaced to keep the integrity of the case intact.

The Two Cases

Before opening a watch case, you must clean any contaminants off the caseback. Wipe with a soft cloth or clean with a stiff bristle brush or a brass brush, depending on the accumulation of contaminants. There are two basic watch cases:

  • One is snapped into the case frame.
  • One is screwed into the frame.

Removing A Snap-On Case Back

Remove the snap-on case back by inserting a thin-bladed knife into a notch located between the case back and the frame. Rotate the blade to lever the case back away from the frame. This is usually an easy procedure. Still, observe these precautions:

  1. Use a lifting motion with your knife blade when prying off the case back. And don't brace your knife on one of the case lugs, which could break.
  2. Don't allow the knife blade to slide under the case back and into the watch movement inside.
  3. Be sure your knife blade is firmly in the notch before prying. Otherwise, the blade will skip off the edge of the case back and gouge it.
  4. If you can't get a good grip on the back with your knife blade, quit! Refer the problem to a professional watchmaker.
  5. Specially designed snap-on case back opening systems eliminate many of these problems. Most major watch brands offer their own systems, or you can contact your watch supply centre.

Removing A Screw-On Case Back

Remove the screw-on case back using a wrench, either hand-held or benchmounted. A few precautions:

  1. The jaws of the case wrench must line up with the notches in the case back. Apply firm downward pressure to the wrench as you unscrew the back. Without enough pressure, the wrench is likely to slip and gouge the back of the watch - and maybe your hand.
  2. Many screw-on case backs are so tight you'll need to hold the watch in a special case vice when using a hand-held wrench. (Case vices are available through any major watch supply source.) Your hand may be strong enough to hold the case, but the torque applied while unscrewing such a tight case back will cause the watch to twist in your hand and can break the watch band where it attaches to the case.
  3. Using a bench-mounted screw-on case opening system will eliminate these problems.

Replace The Case Back

Even after you clean the area with a brush, a ring of contamination may remain around the case opening. Wipe this away with a cloth or a sharpened pegwood stick. Keep the case opening perpendicular to the bench top and rotate it so the contamination falls away from the case, not into it.

When replacing case backs, carefully remove the case back gasket, brush the edges and lubricate the gasket with a silicon sealant. This assumes the gasket is not stiff, cracked or broken. If the gasket is damaged, it would be best for a watchmaker to replace it.

Snap-on case backs can often be replaced with finger pressure, but keep fingers off the crystal - it can break under pressure. Align the stem notch in the back with the stem or the back will not go on properly.

If finger pressure won't snap the back on, use a case or crystal press. Align the watch in the press so there's no pressure on the crystal. This operation is critical, and a good press will avoid repair delays. If the case won't go on, you'll need to send it to a watchmaker.

With the screw-on backs, it's important to tighten the case back about half a turn after you feel it tug on the gasket. Too much tightening will cause the gasket to stretch and curl, reducing its effectiveness.

Reprinted with permission from the Professional Jeweler Magazine. For more information, please visit the American Watchmakers-Clockmakers Institute (AWCI).