AN IMPROVED INSTRUMENT FOR "ASCERTAINING CORRECT MEASUREMENTS
Year: 1866

page_text: LETTERS 'PATENT to David Kirkaldy, of Southwark, in the County of
'Surrey, Engineer, for the Invention of "AN IMPROVED INSTRUMENT FOR
"ASCERTAINING CORRECT MEASUREMENTS."
Sealed the 14th May 1867, and dated the 17th November 1866.
PROVISIONAL SPECIFICATION left by the said David Kirkaldy at the
Office of the Commissioners of Patents, with his Petition, on .the
17th November 1866.
I, DAVID KIRKALDY, of Southwark, in the County of Surrey, Engineer, do
hereby declare the nature of the said Invention for "AN IMPROVED INSTRUMENT
FOR ASCERTAINING CORRECT MEASUREMENTS," to be as follows:-
This. Invention relates to an instrument for ascertaining with the greatest
exactitude the most minute differences in measurements or dimensions (whether
internal or external), which is especially applicable for testing and other
scientific experimental purposes, and may also be used in various manufactures
where great accuracy, of measurement is desirable.
In carrying out this Invention I take two rods or bars of metal connected
together, at one end by a strap of metal fixed at right angles to the two rods.
or, bars, which latter are a short distance apart and parallel to each other.
One of the rods, or bars is marked accurately with the main divisions, such as
inches and subdivided into twentieths, and the other is cut with a screw thread
of a certain corresponding pitch (say twenty threads to the inch), the screwed
rod works through a long nut carried by and capable of revolving in a socket

page_text: through a second hole, in which the plain divided rod or bar also slides. A
collar on the nut (say, for instance, of five inches in circumference) works
against the face of the socket, which latter is provided with a "zero" point or
line. The circumference of the collar is divided into (say) fifths, and again
subdivided into (say) fiftieths. Each division on the collar (or fifth of a turn)
will move the slide one-hundredth of an inch, and again each subdivision will
give one-thousandth of an inch. Further subdivisions might of course be
made if desired. The strap which connects the ends of the two parallel rods
or bars is provided with a point or finger (or both), and another point or
finger is attached to the socket by means of a telescopic tube (or otherwise).
Upon applying these points or fingers to the article to be measured, and.
adjusting the point or finger connected to the two rods or bars by turning the
screw nut by means of a milled rim, the main dimensions will be visible on the
divided rod or bar, and the subdivisions (hundredths and thousandths of
an inch) on the collar of the nut. In order to compensate for any wearing of
the thread of the screw or of the other working parts the "zero"-point or line
is not marked upon the collar of the nut itself, but upon a small plate which
is adjustable thereon by means of a slot.
The foregoing are the characteristic features of my Invention, but it will be
evident that the precise form of the instrument will necessarily be varied to
suit the purpose for which it may be intended; for instance, for measuring
long or short articles, diameters of cylinders, or holes, depths of recesses,
and so forth.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed.
by the said David Kirkaldy in the Great Seal Patent Office on the
17th May 1867..
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVID
KIRKALDY, of Southwark, in the County of Surrey, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventeenth day of November, in the year of our Lord
One thousand eight hundred and sixty-six, in the thirtieth year of Her reign,³
did, for Herself, Her heirs and successors, give and grant unto
me, the said
David Kirkaldy, Her special licence that I, the said David Kirkaldy, my
executors, administrators, and assigns, or such others as I, the said David
Kirkaldy, my executors, administrators, and assigns, should at any time agrees
with, and no others, from time to time and at all times thereafter during the

page_text: term therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "AF IMPROVED INSTRUMENT FOR
ASCERTAINING CORRECT, MEASUREMENTS," upon the condition (amongst others).
that I, the said David Kirkaldy, my executors or administrators, by an instru-
ment in writing under my, or their, or one of their hands and seals, should.
particularly describe and ascertain the nature of the said Invention, and in
what manner the same was to be performed, and cause the same to be filed
in the Great Seal Patent Office within six calendar months next and imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said David Kirkaldy, do hereby declare the
nature of my said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement
in writing, and on reference to the accompanying Sheet of Drawings, that is
to say:-
ui
"
This Invention relates to an instrument for ascertaining with the greatest
exactitude the most minute differences in measurements or dimensions
(whether internal or external), which is especially applicable for testing
and other scientific experimental purposes, and may also be used in various
manufactures where great accuracy of measurement is desirable.
"
In carrying out this Invention I take two, rods or bars of metal connected.
together at one end by a strap of metal fixed at right angles to the two rods
or bars, which latter are a short distance apart and parallel to each other.
One of the rods or bars is marked accurately with the main divisions, such
as inches and subdivided into twentieths, and the other is cut with a screw
thread of a certain corresponding pitch (say, twenty threads to the inch), the
screwed rod works through a long nut carried by and capable of revolving in
a socket through a second hole, in which the plain divided rod or bar also"
slides. A collar on the nut (say, for instance, of five inches in circumference)
works against the face of the socket, which latter is provided with a "zero
point. The circumference of the collar is divided into (say) fifths, and again
subdivided into (say) fiftieths. Each division on the collar (or fifth of a turn)
will move the slide one-hundredth of an inch, and again each subdivision will
give one-thousandth of an inch. Further subdivisions might of course be
made if desired. The strap which connects the ends of the two parallel rods
or bars is provided with, a point or finger (or both), and another-point or
finger is attached to the socket-by means of a telescopic tube or otherwise.
Upon applying these points or fingers to the article to be measured, and
adjusting the point or finger connected to the two rods or bars by turning.

page_text: the screw nut by means of a milled rim, the main dimensions will be visible on
the divided rod or bar, and the subdivisions (one-hundredths and one-thousandths'
of an inch) on the collar of the nut. In order to compensate for any wearing
of the thread of the screw or of the other working parts the "zero" point or
line is not marked upon the collar of the nut itself; but upon a small plate
which is adjustable thereon by means of a slot.
The foregoing are the characteristic features of my Invention, but it will
be evident.that the precise form of the details of the instrument will necessarily
be varied to suit the purpose for which it may be intended, for instance, for
measuring long or short articles, diameters of cylinders, or holes, depths of
recesses, and so forth.
Such being the nature and object of my said Invention for "An Improved
Instrument for Ascertaining Correct Measurements," I will now proceed to des-
cribe more in detail the manner in which the same is to be or may be performed
or carried into practical effect, and in order that the same may be distinctly
understood I have annexed hereunto a Sheet of Drawings illustrative' thereof,
and have marked the same with figures and letters of reference corresponding
with those in the following explanation thereof, that is to say :-
In the annexed Drawing, Figure 1 is a side elevation, drawn partly in
section, of one form of my improved measuring instrument shown full size,
and Figures 2
and 8 are elevations of the respective ends opposite to which
they are placed.
:
a, a, and b, b, are two parallel rods of metal connected together at one end
by a strap of metal c, c, fixed at right angles thereto. The rod a, a, is marked
accurately with a scale of the main divisions, such as inches and subdivided
into twentieths; and the rod b, b, is cut with a screw thread of (say) twenty
threads to an inch; this screwed rod b, b, works through a long screwed nut d, d,
carried by, and revolving in a socket e, e, through a second hole in which the
plain divided rod a, a, also slides. The nut d, d, is provided with a collar
ff, which works against the face of the socket e, e, and is divided into (say)
fifths and subdivided again into fiftieths. The face of the socket is provided.
with a "zero point or line at g. To the socket e, e, is fixed a telescopic
tube h, h, inside which slides another tube i, i, the ends of the two tubes being'
split and the outer one h, h, provided with a screw clip k, k. The outer end
of the tube i, i, is furnished with a strap 2, 1, (somewhat similar to the strap c, c,)
fixed at right angles to it, and provided like the strap c, c, with a finger m and
a diamond point n.
Figure 4 is an end view, and Figure 5 a side elevation of the instrument
when adapted for ascertaining the diameter of cylinders, thickness of plates, or

page_text: short lengths. The same description and letters of reference from a to'g will
answer for these Figures; the principal difference being that the socket 'e, is
provided with or forms part of a-bracket h, h, the object of which is 'to-support
the fixed stop piece i, i, between which and the end of the screwed rod b, bi
the article to be measured is placed:
Figures 6 and 7 are side and end views of the same.as arranged for taking
the measurement of the thickness. of plates and the internal diameter. of holes.
In this case the strap c, c, and socket e, e, are. both provided with fingers m, m;
and inasmuch as the dimensions are taken in the one instance by screwing
them in, and in the other by screwing them out, the bar a, a, is provided with
two scales (one on each side), and the collar f.f, with two circles of divisions
and subdivisions commencing at opposite. points.. The "zero."". point instead
of being engraved upon the socket itself is engraved on a plate 9, 9, which is
adjustable in order to compensate for the wearing of the thread of the screw
or any other working parts of the instrument.
Figures 8 and 9 represent end and side elevations of, the instrument as
arranged for taking shorter dimensions. This modification is similar to that
shewn in Figures 1, 2, and 3, excepting that the telescopic tube i, i, is dispensed
with and the strap 7, 1, is fixed on the end of the tube h, h.
Figures 10 and 11 show the same as arranged for measuring the depth of
recesses or the height of elevations. This is similar to the arrangement shown
in Figures 4 and 5, with the exception that the form of the bracket h, h, is
altered so that its ends may rest upon the plane surface, whilst the amount of
elevation or depression is gauged by the point of the screwed rod 6, 6; and a
double set of scales is provided, as explained with reference to Figures 6 and 7,
in order to take dimensions in either direction; but in this instance the figures
upon the circumference of the collar read off in opposite directions; the
"zero" point g is also adjustable.
Figures 12 and 13 represent in elevation a standard and clip which may be
employed for supporting either of the instruments shown at Figures 1 and 9,
the standard (Figure 12) being drawn only half. size, whilst the clip (Figure
13) is drawn full size. Figure 14 is a plan view of Figure 18.*
The standard consists of a base a, a, and a vertical rod b, b, on which the
ere c, c, of the bracket fits, and is capable of sliding up or down, being fixed-
when adjusted by means of the set screw d, d. At the other end of the bracket
is à clip e, e, for holding the body h, h, of the instrument, and which may be
tightened or slackened by means of the screws f,f.
Having now described the nature and object of my said Invention for " An
Improved Instrument for Ascertaining Correct Measurements," together with

page_text: the manner in which the same is to be or may be performed or carried into
practical effect, I would remark in conclusion that I claim as my Invention
the improved instrument, constructed substantially as herein-before described
and represented in the Drawing annexed, or any mere modification or imitation
thereof, constructed and operating in the same or a similar manner.
In witness whereof, I, the said David Kirkaldy, have, hereunto set my
'hand and seal, this Sixteenth day of May, in the year of our Lord One
⚫ thousand eight hundred and sixty-seven.
DAVID KIRKALDY. (L.s.)
Witness,
BRISTOW HUNT,
Solicitor and Patent Agent,
1, Serle Street, Lincoln's Inn.