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
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
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.
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
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
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
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; firstname.lastname@example.org.
Copyright © 1999 by Bond Communications.