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MACHINERY'S REFERENCE SERIES

EACH NUMBER IS ONE UNIT IN A COMPLETE LIBRARY OF MACHINE DESIGN AND SHOP
PRACTICE REVISED AND REPUBLISHED FROM MACHINERY

NUMBER 21

MEASURING TOOLS

THIRD EDITION



CONTENTS

History and Development of Standard Measurements

Calipers, Dividers, and Surface Gages

Micrometer Measuring Instruments

Miscellaneous Measuring Tools and Gages



Copyright, 1910, The Industrial Press, Publishers of MACHINERY.

49-55 Lafayette Street, New York City

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CHAPTER I

HISTORY AND DEVELOPMENT OF STANDARD MEASUREMENTS[1]

While every mechanic makes use of the standards of length every day, and
uses tools graduated according to accepted standards when performing even
the smallest operation in the shop, there are comparatively few who know
the history of the development of the standard measurements of length, or
are familiar with the methods employed in transferring the measurements
from the reference standard to the working standards. We shall therefore
here give a short review of the history and development of standard
measurements of length, as abstracted from a paper read by Mr. W. A. Viall
before the Providence Association of Mechanical Engineers.

Origin of Standard Measurements

By examining the ruins of the ancients it has been found that they had
standard measurements, not in the sense in which we are now to consider
them, but the ruins show that the buildings were constructed according to
some regular unit. In many, if not all cases, the unit seems to be some
part of the human body. The "foot," it is thought, first appeared in
Greece, and the standard was traditionally said to have been received from
the foot of Hercules, and a later tradition has it that Charlemagne
established the measurement of his own foot as the standard for his
country.

Standards Previous to 1800

In England, prior to the conquest, the yard measured, according to later
investigations, 39.6 inches, but it was reduced by Henry I in 1101, to
compare with the measurement of his own arm. In 1324, under Edward II, it
was enacted that "the inch shall have length of three barley corns, round
and dry, laid end to end; twelve inches shall make one foot, and three feet
one yard." While this standard for measurement was the accepted one,
scientists were at work on a plan to establish a standard for length that
could be recovered if lost, and Huygens, a noted philosopher and scientist
of his day, suggested that the pendulum, which beats according to its
length, should be used to establish the units of measurement. In 1758
Parliament appointed a commission to investigate and compare the various
standards with that furnished by the Royal Society. The commission caused a
copy of this standard to be made, marked it "Standard Yard, 1758," and laid
it before the House of Commons. In 1742, members of the Royal Society of
England and the Royal Academy of Science of Paris agreed to exchange
standards, and two bars 42 inches long, with three feet marked off upon
them, were sent to Paris, and one of these was returned later with "Toise"
marked upon it. In 1760 a yard bar was prepared by Mr. Bird, which was
afterwards adopted as a standard, as we shall see later.

In 1774 the Royal Society offered a reward of a hundred guineas for a
method that would obtain an invariable standard, and Halton proposed a
pendulum with a moving weight upon it, so that by counting the beats when
the weight was in one position and again when in another, and then
measuring the distance between the two positions, a distance could be
defined that could at any time be duplicated. The Society paid 30 guineas
for the suggestion, and later the work was taken up by J. Whitehurst with
the result that the distance between the positions of the weight when
vibrating 42 and 84 times a minute was 59.89358 inches. The method was not
further developed.

How the Length of the Meter was Established

In 1790, Talleyrand, then Bishop of Autun, suggested to the Constituent
Assembly that the king should endeavor to have the king of England request
his parliament to appoint a commission to work in unison with one to be
appointed in France, the same to be composed of members of the Royal
Society and Royal Academy of Science, respectively, to determine the length
of a pendulum beating seconds of time. England did not respond to the
invitation, and the French commission appointed considered first of all
whether the pendulum beating seconds of time, the quadrant of the meridian,
or the quadrant of the equator should be determined as a source of the
standard. It was decided that the quadrant of the meridian should be
adopted and that 0.0000001 of it should be the standard.

The arc of about nine and one-half degrees, extending from Dunkirk on the