ÉBAUCHE. Movement blank, or rough movement in the incomplete stage - 'in the grey'. In the early 19th
century the ebauche was made up of two plates with pillars and bars, barrel, fusee, index, click and ratchet wheel
and assembly screws. The parts were roughly filed and milled. In England during the 19th century, Lancashire
became the centre of the movement trade. One of the best known makers was Joseph Preston & Sons of Prescot,
founded in 1829. Their movements were stamped J.P. The work was much sub-divided.
END SHAKE. Axial play, or necessary clearance between the ends or shoulders of an arbor and the bearing
surfaces.
END STONE. An end-plate made of a jewel. A small disc of jewel upon which a watch pivot rests; particularly
for the balance staff pivot. It is generally fixed to the balance cock by means of screws. In continental watches, the
end-plate was a polished steel plate screwed to the balance cock. It is called a 'coqueret' (q.v.). Endstones are also
referred to as 'cap jewels.'
ENDLESS SCREW. Also called a 'worm' or tangent screw.
ENGINE TURNING. Decoration performed by an engine-turning lathe, producing a variety of patterns on a
metal surface. It is also known as 'guilloché'It was a very popular method of decorating watch cases from about
1770, often being overlaid with transparent or translucent enamel.
ENGLISH LEVER ESCAPEMENT. A lever escapement in which the escape wheel teeth are pointed, the
impulse being taken entirely by the pallet-stones; the lift is entirely on the pallets. See also LEVER
ESCAPEMENT.
ENTRY PALLET. The receiving pallet, which receives impulses from the escape wheel teeth as they enter. The
exit pallet, or discharging pallet, receives impulse as the teeth leave.
EQUATION OF TIME. Adding to or subtracting from true solar (sun) time the amount necessary to obtain
mean time, mean time being the average length of all the solar days in the year, which is therefore a mathematical
division. The 'equation' was worked out by John Flamsteed in about 1670. He tabulated the difference between
noon mean time and true solar noon. The tables were used to check a watch against a sun dial. A few watches
have been made to show the equation on a subsidiary dial. Watch papers were sometimes printed giving the
equation.
ESCAPEMENT. That part of the movement which controls the release of the motive power. The escapement
both controls the release of the driving force and also imparts energy (impulses) to the balance to maintain it in
oscillation. The regularity with which this dual action takes place is controlled by the balance and its spring. The
timekeeping properties of an escapement, therefore, depend essentially upon the balance and spring.
Escapements may be classified as:
(1) Frictional rest, in which the balance is constantly in contact with a part of the escapement - e.g. (a) recoil escapements in which the locking faces are eccentric, causing a recoil of the escape wheel. (b) dead-beat escapements, with concentric locking faces, which give no recoil.
(2) Detached escapement, in which the balance is detached from the escapement except at the time of locking and receiving impulse. The verge escapement is an example of 1(a). The cylinder is an example of 1(b) and the lever an example of 2. A single beat escapement gives a single impulse for each double swing of the balance. The duplex and the chronometer detent escapement are examples. A constant-force escapement employs an intermediate spring, a 'remontoire', wound periodically by the train, which spring impulses the balance.
See PICS:
ESCAPE WHEEL. The last wheel in the going train, which permits 'escape' of the motive power, giving impulse to the balance. It is alternately locked and released.
EXIT PALLET. See ENTRY PALLET