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January 2000

Timepieces: Education & Repair

Plastic Gears Grate Jeweler

Newer materials aren't as bad as you might think and have some good aspects too. You should understand the differences between metal and plastic gears

Dear David Christianson:

Do you think watch manufacturers really think plastic gears will outlast metal gears?

I think movements are being made more cheaply than ever and wonder if we are going back to a throwaway
society.

Sincerely,
Paul Rowe,
Lane Jewelers
Beaver Falls, PA

The sentiment that plastic gears are cheaper and inherently inferior to metal ones is common among watchmakers who take even a glance inside a currently made quartz watch.

In defense of the movement makers, there are several real economic reasons behind the plastic movements and some amazing technological developments.

Watch engineers are quick to emphasize the plastic is specially engineered and formulated to be molded to precise dimensions without shrinkage or deformation. They are "machinable" and self-lubricating to some extent, making them more free of friction than metal grinding against metal. These parts are also less expensive to make than their metal counterparts.

Making Sense

In light of the mechanical and physical requirements of quartz technology, these newer movements make sense.

A quartz movement is typically and by design more fragile than its mechanical cousin. Mechanical movements are powered by a mainspring, which exerts a rather powerful side torque on a series of gear wheels. A quartz watch, however, is powered by a weak electric motor that turns the same kind of gear wheels but with little side torque.

These major differences require the user to lubricate and clean a mechanical movement frequently to avoid wearing out the wheel surfaces.

The quartz watch operates with so little torque there is virtually no wear to the movement. But because of the low torque, the watch is more vulnerable to contamination than a mechanical model. The tiniest dirt, lint or rust particle can stop a quartz watch instantly or cause intermittent operation. Likewise, the electronic circuit is susceptible to moisture in the form of water, perspiration and humidity.

Style Rules

Nearly all quartz movements keep excellent time and are relatively inexpensive compared with the price of the watch. In fact, the cost and value of a quartz watch are in the styling and case, not the movement.

More expensive quartz watches use better cases, machine-fit bezels, tightly secured crystals and backs, and gaskets on all seams to resist moisture and contamination. And in general, as you go up the price scale to luxury brands, the maker uses increasingly heavier layers of precious metal plating, better-quality stainless steel and solid precious metals.

What's Its Lifetime?

In theory, quartz movements could last as long as mechanicals but in real life they don't. Consumers don't replace the gaskets and batteries often enough. The former leads to contamination inside the watch; the latter can create leakage or "salting." Sometimes a battery left unchanged can reverse the polarity of the electronic circuit.

Further, movement manufacturers don't necessarily want their movements to last "forever." To keep their factories operating, manufacturers must keep producing replacement movements and introduce new models. Repairers must continue to replace rather than repair old quartz movements. This is more economical to the consumer and the retailer. It's generally quicker and less costly to replace than try to repair the movement inside a quartz watch.

Link to Repair Industry

But just because repairs can be made quickly and easily doesn't mean you don't need to be able to identify problems and make repairs – or arrange for the repairs to be done. As goes the repair industry, so goes the movement industry – though they may have a different perspective on their own futures.

If the level of repairs declines to where all mechanical movements are sent away to the watch manufacturer for repair, perhaps quartz movements will replace automatics or mechanicals in more new timepieces.

Though the reviving popularity of mechanical movements is strong, if the repair side of the business can't handle the influx of mechanicals, manufactures may just prefer to use quartz – even in higher-priced models.

By David Christianson, Certified Master Watchmaker, President, American Watchmakers - Clockmakers Institute

David Christianson is fourth-generation owner of Christianson Jewelry, Kendallville, IN. In addition to serving as AWI president, he is a certified master watchmaker and a fellow of the British Horological Society. He discusses watch repair for the sales staff in this column each month. Send questions, suggestions and comments to Professional Jeweler, 1500 Walnut St., Suite 1200, Philadelphia, PA 19102; timepieces@professionaljeweler.com.



Copyright © 1999 by Bond Communications.



 

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