HOME PAGE  ::  THE WATCH CABINET  ::  GLOSSARY  ::  ESCAPEMENTS  ::   ENGLISH WATCH REPAIR   :;   HALLMARKS   ::  LINKS



A BRIEF GLOSSARY OF TECHNICAL TERMS

Words in red and in italics have an entry of their own elsewhere in this Glossary.

AIGUILLES

(French) The hands of a clock or watch.   The cuvette of a Swiss or French key-wound watch is sometimes stamped
AIGUILLES as a warning that the hands are set through the nearby hole rather than by placing the key directly over the
exposed end of the cannon pinion in the centre of the dial.

ALARUM

Horologists seem to prefer this Shakespearean spelling for a clock or watch that sounds a warning bell at a pre-set time.
Alarum mechanisms are found on some of the earliest mechanical timekeepers and were being fitted to watches before 1600.

AMERICAN GAUGE

A system of gauging the sizes of watch movements.   Size 0 equals 1.167" or 29.63mm and each step upwards or
downwards consists of a step of 0.0333" (0.846mm);  size 18, the largest in common use, is 1.688" (45.72mm).   Sizes
below 0 are expressed (in diminishing order) as 2/0, 3/0 and so on downwards, 1/0 being omitted.   The American
gauge, like the Lancashire gauge which was its source, measures the diameter of the front plate. — This is a greatly simplified
account;  for more detail, with a table correlating the different systems, I recommend this page in Wayne Schlitt's Elgin site.

ANCRE

The French term for the lever escapement in its usual 20th-century form, with the arm that carries the pallets mounted at a
right angle to the lever itself so as to give a rough likeness to an anchor.

ARBOR

The axle or shaft on which a wheel or pinion is mounted.

ARCADING

A distinctive treatment of the minute track on some 18th-century watches;  between each pair of hour numerals the track is
shaped in an ornamental semicircle.   This pattern is especially associated with Dutch watches (example).

ARNOLD, John

(1736-1799) Chronometer pioneer.   Born in Cornwall, Arnold first distinguished himself in 1764 with a tiny repeater set
into a ring, which he presented to King George III.   He invented a helical balance-spring which came nearer to true
isochronicity than anything else before Breguet (who greatly admired him) produced his overcoil spring, and he may or
may not have devised the spring detent escapement independently of Earnshaw.

BALANCE

The component which, in a mechanical timekeeper without a pendulum, controls the speed of the mechanism by its
oscillations to and fro.   Since the early 1600s it has invariably consisted of a spoked wheel (for an earlier form see
Foliot).   Until the 1670s the balance-wheel performed this task alone, relying (not very successfully) on the weight of
its rim to provide a flywheel effect and give it a uniform motion;  since then the hairspring has provided this uniformity.

BALANCE-SPRING

An alternative name for the hairspring.   The latter term is preferred in the U.S.A. but is not unknown in Britain;  in 1857
the humorous writer Tom Hood used the name ‘Harespring’ [sic] for a watchmaker.

BALANCE-STAFF

The arbor of a balance-wheel.   It is a steel rod, usually very thin (to minimise friction) and therefore easily damaged,
especially in English full-plate watches where it often succumbs to accidental pressure on the unsupported cock.

BANKING PIN

A pin whose function is to prevent an oscillating component – a balance-wheel or part of the escapement – from swinging
too far.   It may be mounted on the moving part itself and designed to strike an obstacle if the arc threatens to become
too great;  thus some verge balances carry banking-pins.   Another kind is fixed to one of the plates and acts as a
stop for (e.g.) the lever of a lever escapement.

BARRED MOVEMENT

A movement in which the traditional bottom plate is replaced by a number of small brass blocks screwed into place, each
supporting one wheel.   The type was developed by Breguet as a variant of the Lépine calibre and became almost universal
in Swiss watchmaking by about 1850.   Also called ‘bridge movement’.

BEAT

The ‘tick’ of a clock or watch, produced as a pallet comes into contact with the escape-wheel.

BEETLE HAND

A pattern of hour hand used in many 18th-century English watches.   Something like a figure-of-eight laid on its side,
with prongs projecting from it, lies across the main shaft of the hand near its outer end;  this is supposed to resemble the
wing-cases and legs of a beetle.

BERTHOUD, Ferdinand

(1729-1807) Swiss watchmaker who invented a form of spring detent escapement independently of his English
contemporaries Arnold and Earnshaw.   Founder of a long-enduring family firm, he is equally important for a series of
technical writings on horology — in contrast to Breguet, of whom Berthoud reproachfully commented “He has published
nothing”.

BEZEL

The retaining ring in which the crystal or glass is mounted.   It forms part of the case and was usually hinged
to the main body until about 1880, after which screw-threaded or snap-on bezels gradually came into use.

BIMETALLIC

Made of two different metals, usually brass and steel, with the idea that their differing rates of expansion and contraction
in response to temperature changes will more or less cancel each other out, immunising the component in question
(usually a balance-wheel) against overall variation in size and hence in speed of oscillation.   A bimetallic balance usually
has a rim consisting of conjoined strips of the two metals, split at two points to allow it to expand and contract without
distortion, and with small gold screws spaced around it for purposes of fine adjustment.   Such balances were used in
precision timekeepers from about 1800 but did not become general until nearly a century later.

BOSLEY REGULATOR

A form of regulator consisting of a movable arm pivoted round the centre of the cock, its outer end forming a pointer which moves
over a graduated scale (sometimes marked Slow[er] and Fast[er], or in French R[etard] and A[vant]);  near this end are fixed the
curb-pins.   Joseph Bosley patented this arrangement in 1755 but it is rarely seen before 1780;  over the next half-century,
however, it completely ousted the old Tompion regulator.

BOTTOM PLATE

In a full-plate or three-quarter-plate movement, the plate farther from the dial.

BOW

The loop for attachment to a chain, mounted on the pendant of a watch case.   The bow is often an approximate guide to
the date of the watch;  various ornamental shapes were used from about 1680 to 1820, after which a plain circular bow
was generally adopted.

BREGUET, Abraham Louis

(1747-1823) Swiss-born clock- and watchmaker noted for his individual ideas and incomparable craftsmanship.   He
refined and popularised the Lépine calibre, using it to create watches of austere beauty (his movements are quite
undecorated) and remarkably modern appearance.   He was an early champion of the lever excapement, although he also
made great use of the cylinder, applying (though he did not invent) the ruby roller as found in most Swiss movements of 1840-1900.
His most influential invention is probably the Breguet or overcoil balance-spring, used in many quality watches of the 20th century

BREGUET HAND

A hand terminating in a triangular pointer protruding from a circle, the latter having a hole cut in it slightly off-centre so
that the rim is at its narrowest where it meets the pointer.   The pattern was very widely used in both clocks and watches
for about fifty years from 1800.   Also called moon hand.

BREGUET KEY

A winding-key incorporating a ratchet so that if turned the wrong way it revolves harmlessly instead of straining the
train;  used by Breguet but apparently a slightly earlier English invention.

BREVET

(French) Patent.   Stamped on the cuvette, the word is sometimes mistaken for a maker's name (ancre and remontoir also
lend themselves to this misconception);  as it happens there really was a Paris watchmaker named Brevet, although as
he lived in the seventeenth century he is unlikely to cross the path of the average collector.

BRIDGE

A brass or nickel block screwed to the top plate of a movement, with a hole in it (often jewelled) to support one end of the arbor
of a wheel.

BRIDGE COCK

A cock which is secured to the movement at two points on opposite sides.   Bridge cocks were preferred by most
European makers form about 1680 to 1820, whereas English makers inclined to what I have called the cantilever cock,
with only one securing point.

BRIDGE MOVEMENT

The same as barred movement.

BULLSEYE

A glass or crystal of convex form with a panel ground flat or slightly concave in its centre, much used between about
1760 and 1820 but still found on some Swiss watches fifty years later.

CALIBRE

The physical make-up of a watch movement;  as a person may be said to be of stout, slim, massive or slight build, so a
watch can be described as being of large, small, deep, slim etc. calibre.   The word is most often found as part of the
phrase Lépine calibre.

CANNON PINION

A pinion which is a friction-fit on the arbor of the centre wheel and has a tubular extension (whose shape gives rise to the
name) passing through the central hole in the dial, on which the minute-hand is fitted.   On English key-wound watches
the top of this extension is squared off to receive the key for setting the hands.

CANTILEVER COCK

This, I must confess, is not a recognised technical term but a coinage of my own for something which otherwise seems
to have no specific name:  the English type of cock which is secured to the dial at one point only, by means of a screw
passing through a hole in the large wedge-shaped foot, and whose table is prevented from collapsing onto the
balance-wheel only by its own rigidity.

CENTRE WHEEL

The second wheel of the train, driven (by means of a pinion which shares its arbor) from the great wheel.   The arbor forms
the spindle around which the hands revolve.

CHAMPLEVÉ

This has two meanings:  (1) A technique of enamel decoration used on very early watches.   The metal body of the item to
be so decorated is carved away, leaving its original surface only as a series of narrow walls between hollowed-out cells
which are then filled with enamel — hence the French name (‘raised field’).   (2) A type of dial much used in the
eighteenth century in which each hour and minute numeral is surrounded by a narrow platform following its outline, the
rest of the dial being recessed and (usually) textured or engraved.   The numerals themselves are engraved within the
platforms and then filled in, not with enamel but with black wax.

CHAPTER-RING

The circle of hour numerals on a dial, or the part of the dial which contains these numerals.

CHINESE MARKET

From the middle eighteenth century onward a taste for European (initially English, later Swiss) clocks and watches
spread among the upper classes in China, with the Ch'ing emperors setting the example.   ‘Chinese’ watches usually have
very ornately engraved plates or bridges and often incorporate a distinctive kind of duplex escapement
which makes the centrally-mounted second hand move in jerks like that of a modern electronic watch.
Chinese dials, unlike Turkish, retain the Roman numerals customary in the West.   These watches are sometimes
misinterpreted as Japanese.

CHRONOGRAPH

A watch that is both a normal timekeeper and a stop-watch.   Invented by Henri Piguet in 1861, it was a large
watch with a centre seconds hand and a slider on the edge of the case to operate the stop-work.   The minute/second
divisions on the dial are subdivided into fifths.   ‘Chronograph’, unlike ‘chronometer’, does not necessarily imply that
the watch is more of a precision instrument than one not so described.

CHRONOMETER

A portable timekeeper designed for the purpose of finding a ship's longitude at sea – a task which calls for exceptional
accuracy under widely varying climatic conditions.   Some authorities hold that only an instrument fitted with a detent
escapement deserves to be called a chronometer;  others argue that anything which performs like a chronometer (and
can be proved to do so in strict laboratory trials) is a chronometer.   True ship's chronometers generally have no cases,
the movement being suspended directly in a mahogany box.

CLICK

A spring-loaded pawl or tongue used in conjunction with a wheel with angled teeth (in which the click engages) so that
the wheel can be turned one way only.   Most familiar in association with one of the two large wheels usually visible in a
stem-wound movement.

CLOCK-WATCH

A chiming watch, distinguished from a repeater in that it sounds the hours etc. automatically as the appropriate time
arrives, whereas a repeater does so only when a plunger is pressed.   Some of the earliest portable timekeepers are
clock-watches.

COCK

The shaped bracket which supports the bottom bearing of the balance-wheel and to some extent protects the wheel
itself.   A cock consists of a ‘foot’ (or, on French, Swiss and some German and Dutch movements until the 1820s, two feet)
screwed to the movement and a ‘table’ extending over the balance.   Until about 1790 the table covered the entire
wheel and was elaborately pierced and engraved;  then, as compensated balances crept into use, the table was made
narrower so as to give access to the timing-screws and piercing died out, although engraving of some kind persisted
even into the 1900s.

COLLET

A retaining-ring, usually of brass;  especially the one which holds the inner end of the balance-spring on the staff.

COMPENSATED
BALANCE

A balance-wheel constructed in such a way that its diameter (variations in which can affect its rate) remains constant at
all temperatures, despite the tendency of its material to expand and contract with heat and cold.   This is usually done
by making the rim of the wheel out of two different metals (brass and steel) fused together so that their differing
expansion rates cancel each other out.   This rim is split at two points so that the resulting fluctuations cannot cause it
to buckle.   This kind of balance appeared shortly before 1800 but took nearly 100 years to penetrate throughout the
market;  the Americans were the first to adopt it more or less as standard (c. 1880).   See next entry for an earlier form
of compensation.

COMPENSATION CURB

An early form of temperature-compensation, using a bimetallic strip with one end fixed to one of the plates and the
other, which is free, carrying the curb-pins.   The controlled expansion and contraction of the strip adjusts the position of the
pins on the hairspring and so maintains its effective length.   This device was first used in a watch designed by John Harrison
in about 1755.

COMPLICATED WORK

Strictly, any function in a clock or watch other than the recording and display of hours, minutes and seconds;  e.g. calendars
(the most common kind), week-day indicators and moon-phase indicators.   The description is sometimes applied to
an instrument which has only the normal functions but displays them on more dials than usual, e.g. by
showing hours and minutes on two separate dials.

CONE

In a watch fitted with a fusee, the tapered, spiral-grooved drum onto which the chain is wound and whose
parabolically-curved profile provides the progressive gearing effect.   The cone incorporates the great wheel.  

CONSULAR CASE

The standard pattern of case in 19th-century British watches.   The body of the case consists of an open ring to which
the back and bezel are both hinged;  a third hinge carries the movement so that this can be swung out for inspection.
Inside the back there is a fixed inner panel, the dome, usually pierced with a hole for the winding-key.

CONTRATE WHEEL

A wheel with teeth standing upright on its rim, so that it resembles a comb bent into a circle.  Most often found in verge
watches, where the fourth wheel is of contrate form.

CONTROLLER

The oscillating component – balance-wheel, foliot, or in modern watches an electronic vibrator – which, in conjunction
with the escape-wheel, meters out the motive power of the watch and makes it a timekeeper.   Where there is a separate
carrier for the pallets, as in the lever escapement, this can be considered as part of the controller.

COQUERET

A steel plate shaped like a keyhole, mounted on the cock of an 18th or early 19th-century French or Swiss watch.   The
circular end fits over the balance-staff and is pierced for the pivot;  the other end is screwed to the cock.   With the
screw loosened the coqueret can be rotated, allowing for some adjustment of the staff.

CROWN

The milled knob on the pendant of a stem-wound watch, turned by the fingers to wind the watch and (usually) to set the hands;
for the latter purpose it is pulled out or occasionally pushed in.   Stem-winding is one of the few 19th-century English
innovations in domestic (as opposed to specialist and precision) watch-making, having been invented by Thomas Prest in 1820,
but it was rarely applied before 1880.

CROWN WHEEL

The escape-wheel in a verge watch is sometimes so called because of the shape of its teeth.

CRYSTAL

A rather modern term for the transparent cover over the dial of a watch (usually called simply ‘glass’ until the late 19th
century).   Plastic ‘crystals’ began to appear soon after 1900 and are now often found as replacements on older watches.
True rock crystal was sometimes used in very early watches for the glass or even the whole case.

CUPER family

The extraordinary achievement of this French watchmaking family, hitherto buried in the pages of Baillie's Watchmakers
and Clockmakers, deserves to be put on wider display.   Established in Blois before 1600 (Barthélemy, the earliest, was
born in 1555), they continued to ply the same trade in the same town for nearly three hundred years, ceasing only with
the death of Charles Raoul Cuper in 1875.   Collateral branches found their way to London, Geneva and even
Constantinople.

CURB PIN

The part of a regulator which controls the operative length of the balance-spring.   Generally there are two such pins
side by side, the spring passing between them so that they restrict its motion;  they are mounted on an arm or
quadrant which can be moved, so that they slide along the length of the spring and allow a greater or lesser proportion
of its length to vibrate freely.

CUVETTE

The hinged inner back cover of a 19th-century Swiss or French watch, pierced with holes for winding and setting (if the
watch is key-wound) and often engraved with the maker's name, number, type of escapement and number of jewels.
Some people also use the name for the removable dust-cap of an English watch.

CYLINDER

A type of escapement, especially popular in Switzerland between about 1840 and 1890, in which the teeth of the escape-
wheel interact with a cut-away cylinder which forms part of the balance-staff.


A-C   D-F   G-L   M-Pe   Pi-R   S-T   U-Z