H
Hacking - a feature that stops the seconds
hand when the stem is pulled out as far as it will go. This allows you to set
the exact time to a time signal or other accurate time device. When the time
signal reaches the exact same second that you have set on your watch push in the
stem to start your watch. This is not a common feature on older watches.
Hairspring - Also called the balance spring. A small spring that is attached
to the balance wheel.
Hand -
the indicator that moves over the dial to point
at the hour, minute or second. Watches generally have three hands to show the
hours, minutes and seconds. Hands can have very different shapes: pear, Breguet,
sword, skeleton, baton, arrow, etc.
Helium Escape Valve - Prior to surfacing
from great depths in a pressurized enclosure, such as a diving bell, toxic gases
that have been formed in the enclosure are removed and helium is mixed into the
air. The helium molecules are lighter than air and can therefore penetrate the
watch. When the pressurized enclosure surfaces and is depressurized the helium
rushes out of the watch so quickly that the glass on the watch pops out as well.
The watch was built to withstand external pressure, not internal pressure. The
glass popping out can be avoided by opening the Helium Escape Valve on the watch
during resurfacing, which allows the helium to escape but prevents water from
entering the watch.
Hesalite - a brand name for a type of acrylic. Omega chose hesalite for the
crystal on their Moon Watch because of its resistance to shocks and extreme
temperatures.
Horns (Lugs) –
Projections on the watch case.
There is a spring bar between the 2 horns
that is used to fix the strap or bracelet.
Horology - the science of the measurement
of time.
Hour Markers - Arabic numerals, Roman numerals or symbols
placed around the dial to mark the hours.
Hunter Case - Pocket watch fitted with a front
cover to protect the glass. It can be opened and closed with a spring release by
pushing the crown in with your thumb.