An Analysis of the Lever Escapement

H.R. Playtner
Analysis of the Lever
Escapement, by H. R. Playtner

Project Gutenberg's An Analysis of the Lever Escapement, by H. R.
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Title: An Analysis of the Lever Escapement
Author: H. R. Playtner
Release Date: June 30, 2007 [EBook #21978]
Language: English
Character set encoding: ISO-8859-1

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[Illustration: THOMAS MUDGE
The first Horologist who successfully applied the Detached Lever
Escapement to Watches.

Born 1715--Died 1794.]


Before entering upon our subject proper, we think it advisable to
explain a few points, simple though they are, which might cause
confusion to some readers. Our experience has shown us that as soon as
we use the words "millimeter" and "degree," perplexity is the result.
"What is a millimeter?" is propounded to us very often in the course of
a year; nearly every new acquaintance is interested in having the metric
system of measurement, together with the fine gauges used, explained
to him.
The metric system of measurement originated at the time of the French
Revolution, in the latter part of the 18th century; its divisions are
decimal, just the same as the system of currency we use in this country.

A meter is the ten millionth part of an arc of the meridian of Paris,
drawn from the equator to the north pole; as compared with the English
inch there are 39+3708/10000 inches in a meter, and there are
25.4 millimeters in an inch.
The meter is sub-divided into decimeters, centimeters and millimeters;
1,000 millimeters equal one meter; the millimeter is again divided into
10ths and the 10ths into 100ths of a millimeter, which could be
continued indefinitely. The 1/100 millimeter is equal to the 1/2540 of
an inch. These are measurements with which the watchmaker is
concerned. 1/100 millimeter, written .01 mm., is the side shake for a
balance pivot; multiply it by 2¼ and we obtain the thickness for the
spring detent of a pocket chronometer, which is about 1/3 the thickness
of a human hair.
The metric system of measurement is used in all the watch factories of
Switzerland, France, Germany, and the United States, and nearly all the
lathe makers number their chucks by it, and some of them cut the
leading screws on their slide rests to it.
In any modern work on horology of value, the metric system is used.
Skilled horologists use it on account of its convenience. The millimeter
is a unit which can be handled on the small parts of a watch, whereas
the inch must always be divided on anything smaller than the plates.
Equally as fine gauges can be and are made for the inch as for the
metric system, and the inch is decimally divided, but we require
another decimal point to express our measurement.
Metric gauges can now be procured from the material shops; they
consist of tenth measures, verniers and micrometers; the finer ones of
these come from Glashutte, and are the ones mentioned by Grossmann
in his essay on the lever escapement. Any workman who has once used
these instruments could not be persuaded to do without them.
No one can comprehend the geometrical principles employed in
escapements without a knowledge of angles and their measurements,
therefore we deem it of sufficient importance to at least explain what a

degree is, as we know for a fact, that young workmen especially, often
fail to see how to apply it.
Every circle, no matter how large or small it may be, contains 360°; a
degree is therefore the 360th part of a circle; it is divided into minutes,
seconds, thirds, etc.
To measure the value of a degree of any circle, we must multiply the
diameter of it by 3.1416, which gives us the circumference, and then
divide it by 360. It will be seen that it depends on the size of that circle
or its radius, as to the value of a degree in any actual measurement. To
illustrate; a degree on the earth's circumference measures 60
geographical miles, while measured on the circumference of an escape
wheel 7.5 mm. in diameter, or as they would designate it in a material
shop, No. 7½, it would be 7.5 × 3.1416 ÷ 360 = .0655
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