ADJUSTED – Adjusted to compensate for temperature, positions and isochronism. A watch is said to be ‘adjusted in 5 positions’ if it has been rated in the two horizontal and tree of the possible vertical positions – i.e. dial up, dial down, pendant up, pendant left, pendant right and pendant down. ‘Adjusted for temperature’ means that the compensation has been observed in at least three temperatures.
ADJUSTABLE POTENCE – See POTENCE
AFFIX – A small bimetallic blade, one end of which is fixed to the rim of the balance: used to correct the temperature compensating properties of the main compensating arrangement.
ALARM WATCH – A watch that will give an audible sound at a pre-set time.
‘ALL-OR-NOTHING’ PIECE – In a repeating watch, a device which ensures that the striking is released only if the lever or push-piece for the repeating action is fully depressed. Without this mechanism, if the actuating lever or push-piece is insufficiently depressed an incorrect number of hours is sounded. With this improvement, the watch has to strike all or nothing. Both Tompion and Quare incorporated it, though Julien Le Roy is often credited with the invention.
AMPLITUDE – The maximum angle by which a balance swings from its position of rest. By observing the arms of a balance it is possible to estimate this angle. See ARC.
ANNEALING – Heating and cooling a metal slowly to relieve internal stress.
ANTI-MAGNETIC – Not affected by magnetic field. If those parts of a watch most affected by a magnetic field (balance, balance spring and escapement) are made of non-magnetic materials the watch is termed ‘anti-magnetic’, although more strictly ‘anti-magnetic’ up to a specified strength or field. The earliest non-magnetic balance springs were gold as used by John Arnold. Subsequently palladium alloy was invented by C.A. Paillard in 1877.
APPLIQUE – Applied ornament to a case, or applied chapters, numerals or decoration to a dial.
ARBOR – The spindle, shaft or axle upon which the wheels of a watch train are mounted. The mechanical axle of a moving part; on the balance it is called the staff, on the lever it is called the arbor.
ARC – The arc of a balance is twice the amplitude (q.v.). A balance with an amplitude of 270 degrees has an arc of 540 degrees (11/2 turns of the balance).
ASSAY – Analyzing a metal for its gold or silver content.
ATTACHMENT – The ‘point of attachment’ or ‘pinning-point’ is the point at which the balance spring is pinned to the collet on the balance staff.
AUTOMATON – Animated mechanical objects and figures; actuated by the going, striking, musical or repeating train. See JACQUEMART.
AUTOMATIC WATCH – A watch which is wound by the movement of the wearer. Also known as a ‘self-winding’ watch. John Harwood patented a self-winding wrist watch in about 1928. Patent No 218,487 of 1923.
AUXILIARY COMPENSATION - For middle temperature errors found on marine chronometers. An additional and subsidiary compensation sometimes fitted to a bimetallic balance to eliminate the middle temperature error (q.v.).
BACKPLATE – See TOP PLATE
BALANCE – A plain wheel with two or three spokes known as ‘arms’. Coupled to its spring, the balance of a watch is the controlling device; its oscillation, its to and fro swinging properties, regularise the movement of the train powered by the mainspring, and hence the timekeeping ability of the watch. A plain balance, or a monometallic balance, is an uncut ring, with or without timing screws. It may be made of brass, steel, gold, nickel or palladium. A modern alloyed metal such as ‘Invar’ or glucydur produces a balance which for all practical purposes is unaffected by temperature changes. A ‘compensated’, cut bimetallic balance has its rim made of two metals of different coefficient of expansion (brass and steel) fused together. The rim is cut near each arm of the two-arm balance, the other end, the tree end moves inward or outward on a rise or fall (respectively) in temperature, thus altering the moment of inertia of the balance by shifting the mass of the rim closer to or away from the centre. This counteracts the effect of temperature changes upon the elasticity of the steel balance spring. Brass has a higher coefficient of expansion than steel, and is on the outer side of the rim. Screws or weights on the balance rim enable the compensating property to be adjusted. An ‘unsprung balance’ is a balance without a spring – i.e. before the introduction of the balance spring in 1675. See also FOLIOT and ‘S’ BALANCE.
BALANCE COCK – The bridge that holds the upper jewels and the balance and secured at one end only. See COCK.
BALANCE SCREWS – See TIMING SCREWS
BALANCE SPRING – Also called the hairspring; the spring governing the balance. Both Robert Hooke and Christian Huygens have been credited with the invention of the balance spring as the controlling agent for watches. The Abbé de Hautefeuille also claimed priority, though it seems fairly certain that his conception was for a straight as opposed to a spiral spring. It also appears that Hooke's original idea of 1658 was a straight spring. It is certainly established beyond doubt that Huygens devised a practical means of applying a spiral spring and employed Thuret of Paris to make a watch with such a spring in 1675. Hooke had in 1664 propounded the first law relating to springs: ut tensio sic vis (‘as the tension is, so the force’). Put more simply: The force which a spring exerts depends upon the amount it has been wound up. Hooke's Law is only partially true as applied to a watch balance spring. A balance spring is a week spiral spring attached at its inner end to the balance staff and its outer end to the balance cock or movement plate. The sprung balance regulates the timekeeping, the period of each swing depending upon the ratio of the moment of inertia of the balance to the stiffness or elasticity of the spring. The elasticity of any given spring depends basically upon the material from which it is made and upon its effective length. See ISOCHRONOUS, COMPENSATED BALANCE and COMPENSATION CURB. The earliest balance spring were sometimes made of copper but mostly of steel. Gold springs were occasionally used in the later 18th and 19th centuries. C.A. Paillard invented a palladium spring - which is non-magnetic – in 1877, and of recent years alloys of nickel steel, chronium, manganese and other elements have rendered balance spring impervious to temperature changes, magnetic fields and damp. Dr. C.E. Guillaume did the original research on nickel steel alloys in 1896. ‘Elinvar’ (‘elasticité invariable’) was the name given to his springs. The earliest springs (with the verge escapement) had three or four coils; with the later escapements about fourteen are general. A helical spring is one formed into a helix and is normally found with the chronometer or detent escapement. In about 1782 John Arnold discovered by empirical methods that isochronism could be achieved by a helical spring with the two terminal coils or ends incurved. A.L. Breguet introduced a spiral spring with an overcoil as an aid to isochronism. The overcoil spring has the outer coil raised and turned in towards the centre, which ensures the concentric development of the spring as the balance oscillates. In 1861, Edouard Phillips gave the theoretical conditions for end curves for both helical and spiral spring to render them isochronous. Jules Grossman and L. Lossier took these investigations further. A steel spring will lose its elasticity in heat and become more ‘springy’ in cold: hence the need for temperature compensation.
BALANCE STAFF – The staff of the balance wheel. The spindle or arbor upon which the balance is mounted.
BALANCE WHEEL - A device shaped like a wheel that does for a watch what a pendulum does for clock.
BANKING PINS - The two pins which limit the angular motion of the pallet. With the verge escapement, a pin protruding from the outer edge of the balance. The extreme arc of balance swing is limited by stops on the balance cock, against which the pin would ‘bank’ if the arc were excessive. In later escapements, an equivalent provision is included and in the lever escapement the device of two banking pins is used to limit the angular movement of the lever. Occasionally, instead of two pins, banking takes place against walls forming part of the movement plate or of the pallet cock.
BAR – Bridge as distinct from a cock which has a foot by which it is secured to the movement plate.
BAR MOVEMENT - A type of movement employing about six bridges to hold the trai also known as a Lepine Calibre.
BARREL - Drum-shaped container that houses the mainspring.
BARREL (GOING) – A cylindrical box (barrel) with a toothed disc (a wheel) on the outer edge. The disc is the ‘great wheel’ and the box contains the mainspring. The barrel (box) turns freely on its arbor, the mainspring being hooked to the barrel at its outer end and to the arbor at its inner end. The great wheel meshes with the first pinion of the watch train. In a watch movement with going barrel, the fusee (q.v.) is dispensed with. The barrel in fusee watches is plain barrel without teeth. In winding a going barrel, the barrel arbor is turned round, drawing the spring away from the rim of the box and coiling it round the arbor. A click and ratchet prevent the arbor from recoiling while the mainspring is being wound and when it is fully wound. The tensioned spring, in striving to ‘unwind’, expends its force in turning the barrel, this same force being utilised to drive the watch train via the great wheel. The barrel makes as many turns in unwinding, of course, as were given to the arbor in winding. See also STOP WORK and SET UP.
BARREL (HANGING) – A going barrel, fixed to the movement only by its upper portion. Also known as ‘standing barrel’.
BARREL (RESTING) – The great wheel is mounted on an arbor, the power transmitted to the wheel by ratchet and click. The spring is enclosed in a barrel which is screwed to the plate.
BARROW REGULATOR – An early from of regulator of balance spring watches. Two pins (curb pins) held upright in a slide embrace the end section of the balance spring which is straight, not coiled. The slide moves along a worm (endless screw) which has squared end to take a key. An index engraved on the movement plate indicates the amount the slide may be moved with the aid of a key, as the effective length of the spring is altered for regulation. A watch still retaining its Barrow regulator is very rare.
BASSE-TAILLE ENAMEL - Translucent enamel laid over a ground engraved to enhance the pictorial effect.
BASSINE - A type of watch case that is rounded on the edge and smooth.
BEET - The multiple sound of the escapement action heard as the 'tick'. Refers to the tick or sound of a watch; about 1/5 of a second. The sound is produced by the escape wheel striking the pallets.
BEETLE HAND - The type of hour hand faintly resembling a stag beetle; usually associated with the poker-type minute hand. See POKER.
BELL METAL - Four parts copper and one part tin used for metal laps to get a high polish on steel.
BEZEL - The rim that covers the dial (face) and holding the glass.
BIMETALLIC - Formed of two metals, brass and steel, whose different coefficients of expansion are utilised for compensating the effects o temperature changes on a steel balance spring. See BALANCE. Mostly in the early eighteenth century alternatively, a bimetallic strip, formed by riveting or fusing, was utilised, which bent under the influence of temperature changes. This strip was known as a compensation curb (q.v.)
BIMETALLIC BALANCE - A balance composed of brass and steel designed to compensate for temperature changes in the hairspring.
BLIND MAN'S WATCH - A Braille watch; also known as tact watch.
BLUING or BLUEING - By heating steel to about 540 degrees, the colour will change to blue.
BOTTOM PLATE - See TOP PLATE
BOUCHON - Also 'Bush'. Hard brass tubing inserted into watch plates to from pivot holes - i.e. bearings for pivots.
BOW - The metal ring hinged, pivoted or looped to the pendant (q.v.) of the watch case, by which the watch may be attached to a chain or fob.
BOX CHRONOMETER - A marine or other type chronometer in gimbals so the movement remains level at sea.
BOX JOINTED CASE - A heavy hinged decorative case with a simulated join at the top under the pendant.
BREGUET HANDS - Hour and minute hand slightly tapered, the end a disc eccentrically pierced to from a crescent. Also called 'moon hands'.
BREGUET KEY - A ratcheting watch key permitting winding in only one direction. A watch key in the upper and lower portions of the shaft are connected by a ratchet clutch kept in gear by a compressed spring, so that the upper part will turn the lower part in the correct direction for winding, but if the upper part is turned in the opposite direction, the ratchet slips without moving the lower part. This ensures that no damage will result from turning the key in the wrong direction. This key is also called a 'tipsy' key, presumably since it ensured a watch against damage when owned by inebriates! A similar from of key was patented in England in 1789 by S.B. Harlow.
BREGUET SPRING - A type of hairspring that improves timekeeping also called overcoil hairspring. See BALANCE SPRING.
BREGUET STOP-WORK - This from of stop-work (q.v.) has two toothed wheels, one of eight teeth fixed to the barrel arbor and one of ten teeth fixed to the barrel itself. Projections on the two wheels meet after four turns, thus limiting the extent to which the mainspring is wound.
BRIDGE - A metal bar which bear the pivot of wheels and is supported at both ends. See COCK.
BRISTLE - See HOG'S BRISTLE
BULL’S EYE GLASS - Used on old type watches; A flattened dome glass in shape, but with a small circular flat ground in the centre. Popular in England between about 1685 and 1750 and for inexpensive watches in the first half of the 19th century.
BUSH - See BOUCHON
BUTTON, WINDING - Round, or rounded, knurled or milled button fixed to a shaft or stem by which a watch is wound or the hands set. Sometimes called a ‘set-hand button’. Used in keyless watches.
CADRATURE - Under-dial work, viz. repeating work.
CALENDAR WATCH - A watch that shows the date, month and day.
CALIBRE - The size and type of design of a watch movement. The term was used by Sully in about 1715 to denote the dimensions and layout of a movement; more recently the term has been used to indicate the shape of the movement or even the designer’s name - e.g. Lepine calibre (q.v.) - or the origin of the movement.
CAM - A part shaped with an irregular contour so as to give the requisite reciprocal irregular movement to a lever in contact with it.
CANISTER CASE - An early form of case, drumshaped. Not dissimilar to a tambour case (q.v.), but not hinged.
CANNON PINION - A pinion, part of the motion work carrying the minute hand. Its hollow arbor, or pipe, is merely a friction fit on the centre wheel arbor, thus allowing the hand to be set.
CAP JEWEL - Also called the endstone, the flat jewel on which the staff rests. See ENDSTONE.
CAPPED MOVEMENT - A movement provided with a dust cap (q.v.).
CARTOUCHE DIAL - Found on continental watches, French in particular. White enamel plaques with blue or black numerals, the plaques being fired on to the metal dial. On champlevé dials, the maker’s name is usually engraved on a cartouche which has been polished in contrast to the matted centre of the dial.
CENTRE PINION - The pinion in the going train (see TRAIN), driven by the great wheel. Normally it is centrally placed in the movement.
CENTRE SECONDS - A seconds hand pivoted in the centre of the dial concentric with the hour and minute hands, and traversing the dial in one minute. Sometimes called a ‘sweep seconds’. The hour and minute hands may be on a subsidiary dial.
CENTER WHEEL - The second wheel; the arbor for the minute hand; this wheel makes one revolution per hour.
CHAFF-CUTTER - See ORMSKIRK and DEBAUFRE ESCAPEMENT
CHAIN (Fusee) - Looks like a miniature bicycle chain connecting the barrel and fusee.
CHAISE-WATCH - A large watch used for travelling. Not to be confused with a carriage clock.
CHAMPLEVE - An area hollowed out and filled with enamel and then baked on. An area of metal which has been hollowed out with a graver to take enamelling: champlevé enamel. ‘Champlevé dial’ is a metal dial with portions removed to leave others standing proud of the main surface - i.e. the hour numerals and minute markings. The hollowed-out numerals are then filled with black or coloured wax, or pitch.
CHAPTER RING - The ring upon which the hours and minute graduations or half and quarter-hour divisons are engraved. An alternative name is ‘the hour ring’.
CHASING - Engraving in relief.
CHATELAINE - A chain for suspending watch or piece of jewellery. In addition to the watch, the winding key, were often attached. Normally the decoration on the watch case is en suite with the decoration on the châtelaine. See also FOB CHAIN.
CHINESE DUPLEX - A form of duplex escapement invented by C.E. Jacot in 1830. It was commonly used for watches exported from Fleurier to China. The locking teeth are double, thus resembling a fork. After the first prong of the fork passes the roller, the escape wheel is immediately locked again, so that a second swing of the balance is necessary to unlock the whole tooth or ‘fork’ before impulse can be given. A second elapses between each complete unlocking, but the intermediate stage is detectable by a slight movement of the centre seconds hand: otherwise, the watch appears to beat seconds.
CHRONOGRAPH - A movement that can be started and stopped to measure short time intervals and return to zero. A stop-watch does not keep the time of day. A watch which, in addition to the time-of-day hands, has a centrally mounted seconds hand. This can be started, stopped and returned to zero by means of a push-piece or slide. A subsidiary dial is provided which records the number of revolutions (each of a minute) made by the centre seconds or chronograph hand. A more correct term would be ‘chronoscrope’. See also SPLIT-SECONDS.
CHRONOMETER - Among English watchmakers and collectors, a chronometer is understood to be a watch or portable clock (hence a ship’s, marine or box chronometer) which has a detent escapement (q.v.) although the use of the word preceded the detent escapement. Of recent years there has been a tendency - regretted by many ~ to use the word in the French or Swiss sense to indicate a watch which has obtained an official rating certificate issued by the observatories at Geneva or Neuchatel. Etymologically, any instrument for measuring time.
CHRONOMETER ESCAPEMENT - A detent escapement used in marine chronometers.
CHRONOSCROPE - See WANDERING HOUR DIAL
CLICK - A pawl or lever with a ‘beak’ which engages in the ratchet-shaped teeth of a wheel, it being under the tension of a spring, and pivoted. The usual purpose of a click, its spring and the ratchet wheel is to allow the wheel to turn in one direction only. On watches the ratchet wheel is fixed to the arbor of the mainspring barrel, thus enabling the mainspring to be wound; the tension of the mainspring is held up against the tensioned click.
CLOCKMAKERS’ COMPANY - The Worshipful Company of Clockmakers was granted its Royal Charter in 1631, with David Ramsay as its first Master. Prior to its incorporation, the craft of clock and watchmaking was controlled by the Blacksmiths’ Company, and it would seem that boys were apprenticed as Blacksmiths in the earlier years. In the City of London apprentices were admitted through the Guilds, and after they had served their term they were granted the freedom of the craft. The Clockmakers’ Company had the right to regulate the manner, order and form in which the craft should be conducted within the realm of England. It had powers to make laws and ordinances for all persons using the Art within a ten-mile radius of the City of London and had wide powers touching the ‘Trade, Art or Mystery’, The Company had the right to make a general search and view all productions made in this country or brought in from abroad: it had powers to seize and to destroy unworthy work or cause it to be amended. None but admitted members might sell their wares within the City or ten miles thereof. An apprentice was bound for seven years and, after admittance as a Freeman, served a further two years as journeyman and then produced his masterpiece before being admitted as a workmaster. A Brother was allowed to engage only one apprentice, a Warden or Assistant Warden two only.
CLOCK WATCH - A watch that strikes the hour but not on demand. Not to be confused with a repeating watch. Clock-watches were made from the earliest period.