How Watches Work
In addition to their exterior beauty, watches are also an incredible feat of engineering and craftsmanship.
Many complicated parts must all work in tandem in order to not only tell time,
but perform the myriad other functions that many of today’s watches perform.
This section contains an overview of the major parts of a watch, as well as an
explanation of how watches operate.
Watches contain many parts that work together to tell time, as well as perform
other useful functions. These could include a chronograph, altimeter, alarm,
day/date calendar, phases of the moon, slide-rule, etc. Here are descriptions
of the major internal and external parts and their functions. For more detailed
explanations, you can also visit our
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External Watch Parts
The cover over the watch face is called the crystal. There are three types of
crystals commonly found in watches: Acrylic crystal is an inexpensive plastic
that allows shallow scratches to be buffed out. Mineral crystal is composed of
several elements that are heat-treated to create an unusual hardness that aids
in resisting scratches. Sapphire crystal is the most expensive and durable,
approximately three times harder than mineral crystals and 20 times harder than
acrylic crystals. A non-reflective coating on some sport styles prevents glare.
A watch's hands are the pointing device anchored at the center and circling around the dial
indicating hours, minutes, seconds and any other special features of the watch.
There are many different types of hands:
A hand that is slightly tapered
A narrow hand sometimes referred to as a ‘stick hand’
A wide, tapered hand with a facet at the center running the length of the hand
Cutout hands showing only the frame
Hand made of skeleton form with the opening filled with a luminous material
The surface ring on a watch that surrounds and holds the crystal in place is
called the bezel. A rotating ratchet bezel moves in some sport watches as part
of the timing device. If rotating bezels are bi-directional (able to move
clockwise or counter clockwise), they can assist in calculations for elapsed
The nodule extending from the watchcase that is used to set the time, date,
etc. is called the crown. Most pull out to set the time. Many water-resistant
watches have crowns that screw down for a better water-tight seal.
The watch face that contains the
numerals, indices or surface design is called the dial. While these parts are usually applied,
some may be printed on. Sub-dials are smaller dials set into the main face of
the watch. These can be used for added functions, such as elapsed times and
Case (or Watchcase)
The watchcase is the metal housing that contains the internal parts of a watch.
Stainless steel is the most typical metal used, but titanium, gold, silver and
platinum are also used. Less expensive watches are usually made of brass that
has been plated with gold or silver.
A bracelet is the flexible metal band consisting of assembled links, usually in
the same style as the watch case. Detachable links are used to change the length of the
bracelet. Bracelets can be made of stainless steel, sterling silver, gold, or a
A strap is simply a watchband made of leather, plastic or fabric.
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Internal Watch Parts
A watch’s main timekeeping mechanism is called its movement. Today’s
watch movements fall into two categories: Automatic mechanical or quartz.
Automatic mechanical movements mark the passage of time by a series of
gear mechanisms. Most automatic movements are wound by the normal, everyday
movement of your wrist, which charges the watch’s winding reserve. Quartz
movements are powered by a battery and do not stop working once removed
from your wrist.
The regulating organ of a watch with a mechanical movement that vibrates on a
spiral hairspring is called the balance wheel. Lengthening or shortening the balance
spring makes the balance wheel go faster or slower to advance or retard the
watch. The travel of the balance wheel from one extreme to the other and back
again is called oscillation.
This series of small gears in both quartz and mechanical movement watches is
responsible for transmitting the power from the battery (in a quartz watch) or
spring (in a mechanical watch) to the escapement, which distributes the
impulses that mark the time.
This part of the watch restricts the electrical or mechanical impulses of the gear
train, metering out the passage of time into equal, regular parts.
The motion work is a series of parts inside a watch that receive power from the escapement and
gear train, which distribute and generate the watch’s power. The motion work is
responsible for actually turning the watch’s hands.
The mainspring is the energy source responsible for powering the watch movement
(as opposed to a battery in a watch with a quartz crystal movement). The spring
is wound, either manually (using the winding stem) or automatically, by the
motion of the wearer’s wrist. Potential energy is stored in the coiled spring,
then released to the gear train which transmits the power to the
escapement and motion work, which turns the hands on
the watch dial.
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How a Watch Works
Watches essentially tell time by
the integration of three main components: an energy source, a time regulating
mechanism and a display. The energy source can be electronic (as in a battery)
or mechanical (as in a wound spring). A watch’s main timekeeping mechanism is
called its movement. Today’s watches fall into two categories: Mechanical
movements and Quartz movements. Here’s a breakdown of how each type of movement
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Mechanical (Automatic) Watches
Mechanical watches are made up
of about 130 parts that work together to tell time. Automatic mechanical
movements mark the passage of time by a series of gear mechanisms, and are
wound by the movement of your wrist as you wear it. The gear train then
transmits the power to the escapement, which distributes the impulses, turning
the balance wheel. The balance wheel is the time regulating organ of a
mechanical watch, which vibrates on a spiral hairspring. Lengthening or
shortening the balance spring makes the balance wheel go faster or slower to
advance or retard the watch. The travel of the balance wheel from one extreme
to the other and back again is called oscillation. A series of gears, called
the motion work, then turns the hands on the watch face, or dial. See illustration
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Quartz Crystal Watches
Quartz watches work with a series of electronic
components, all fitting together in a tiny space. Rather than a wound spring, a
quartz watch relies on a battery for its energy. The battery sends electrical
energy to a rotor to produce an electrical current. The current passes through
a magnetic coil to a quartz crystal, which vibrates at a very high frequency
(32,768 times a second), providing highly accurate timekeeping. These impulses
are passed through a stepping motor that turns the electrical energy into the
mechanical energy needed to turn the gear train. The gear train turns the motion work,
which actually moves the hands on the watch dial.
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