IMPROVEMENTS IN DRESSING OR PREPARING THE SURFACE OF MILLSTONES
Year: 1861

page_text: LETTERS PATENT to William Spence, of 50, Chancery Lane, in the County
of Middlesex, Patent Agent, for the Invention of "IMPROVEMENTS IN
DRESSING OR PREPARING THE SURFACE OF MILLSTONES."-A communication
from abroad by Louis Wells Broadwell, of the American Legation,
St. Petersburgh.
Sealed the 26th July 1861, and dated the 27th March 1861.
PROVISIONAL SPECIFICATION left by the said William Spence at the
Office of the Commissioners of Patents, with his Petition, on the 27th
March 1861.
I, WILLIAM SPENCE, of 50, Chancery Lane, in the County of Middlesex,.
Patent Agent, do hereby declare the nature of the said Invention for "Iм-
PROVEMENTS IN DRESSING OR PREPARING THE SURFACE OF MILLSTONES," (being a
communication to me from abroad by Louis Wells Broadwell, of the American
Legation, St. Petersburgh,) to be as follows:-
This Invention has for its object the formation on the operating surface of
millstones of curved furrows of such shape and so arranged and combined as
to work in harmony with. the centrifugal and centripetal or natural forces
produced by rotary motion. For this purpose the face of the stone, after
being made level and true, is divided into a number of equal parts, according
to the size of the stone, by diameters, or straight, lines; drawn through the
centre to the circumference. The lines for the curved furrows are marked

page_text: out on this prepared face of the stone by means of a "schablone" or curved
rule, the convex or inner curvature of which is a little less in radius than the
stone, and the concave or outer curvature is a little greater, the mean
curvature being of the radius of the stone. The length of this "schablone" or
curved rule is a little less than the radius of the stone. This "schablone'
or curved rule is then applied to each radial line previously marked on the
stone, the narrow end of the same being next the eye of the stone, and the
wider end touching the circumference thereof. By marking round the inner
and outer curvatures of the "schablone" thus applied to each radial line in
succession, the size, shape, and position of each major furrow will be
indicated on the face of the stone. The lines for the minor or intermediate
furrows are obtained by placing the "schablone" or curved rule with the
narrow end applied to the concave side of each major furrow. The furrows
are cut (according to the lines so obtained) to a depth slightly and gradually
increasing from the eye of the stone to the circumference thereof; they are.
also made slightly inclined on the back or convex side, and brought up on
an inclined plane to a feather edge on the front or concave side. The draught
of the dress or forward inclination of the furrows from a straight line drawn
through the centre of the stone is proportioned to the speed with which the
stone revolves. Both the runner and the bedstone are dressed alike, but
when the former is turned over and placed in the position for grinding, then
its dress assumes a reversed position in relation to that of the bedstone. In
some cases the ordinary surface dress is used, but in other cases the grinding
surfaces are filled with numerous parallel grooves as narrow and close together
as they can be made.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Spence in the Great Seal Patent Office on the
26th September 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME,. I, WILLIAM
SPENCE, of 50, Chancery Lane, in the County of Middlesex, Patent Agent,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-seventh day of March, in the year of our
Lord One thousand eight hundred and sixty-one, in the twenty-fourth year
of Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said William Spence, Her special license that I, the said William

page_text: Spence, my executors, administrators, and assigns, or such others as I, the
said William Spence, my executors, administrators, and assigns, 'should at
any time agree with, and no others, from time to time and at all times
thereafter during the 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 "Iн-
PROVEMENTS IN DRESSING OR PREPARING THE SURFACE OF MILLSTONES," being a
communication from abroad by Louis Wells Broadwell, of the American
Legation, St. Petersburgh, upon the condition (amongst others) that I, the
said William Spence, by an instrument in writing under my hand and seal,
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
immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said William Spence, do hereby declare
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the follow-
ing statement, reference being had to the Drawings hereunto annexed, and to
the letters and figures marked thereon (that is to say) :-
This Invention of "Improvements in Dressing or Preparing the Surface of
Millstones" has for its object the formation on the operating surface of mill-
stones of curved furrows, of such shape and so arranged and combined as
to work in harmony with the centrifugal and centripetal or natural forces
produced by rotary motion.
For this purpose the face of the stone, after being made level and true, is
divided into a number of equal parts, according to the size of the stone, by
diameters or straight lines drawn through the centre to the circumference.
The lines for the curved furrows are marked out on this prepared face of the
stone by means of a "schablone" or curved rule, the convex or inner
curvature of which is a little less in radius than the stone, and the concave or
outer curvature is a little greater, the mean curvature being of the radius of
the stone. The length of this "schablone" or curved rule is a little less than
the radius of the stone. The schablone" or curved rule is then applied to
each radial line previously marked on the stone, the narrow end of the same
being next the eye of the stone, and the wider end touching the circumference
thereof. By marking round the inner and outer curvatures of the "schablone."
thus applied to each radial line in succession, the size, shape, and position of
each major furrow will be indicated on the face of the stone. The lines for
the minor or intermediate furrows are obtained by placing the "schablone."

page_text: or curved rule with the narrow end applied to the concave side of each major
furrow. The furrows are cut (according to the lines so obtained) to a depth
slightly and gradually increasing from the eye of the stone to the circumference
thereof; they are also made slightly inclined on the back or convex side, and
brought up on an inclined plane to a feather edge on the front or concave a
side. The draught of the dress or forward inclination of the furrows from a
straight line drawn through the centre of the stone is proportioned to the
speed with which the stone revolves. Both the runner and the bedstone are
dressed alike, but when the former is turned over and placed in the position
for grinding, then its dress assumes a reversed position in relation to that of
the bedstone. In some cases the ordinary surface dress is used, but in other
cases the grinding surfaces are filled with numerous parallel grooves as narrow
and close together as they can be made.
Having thus stated the nature of the said Invention, I will proceed to
describe more particularly in what manner the same is to be performed by the
aid of the accompanying Drawings.
DESCRIPTION OF THE DRAWINGS.
Figures 1, 2, and 3 represent different modes of forming the furrows on the
face of the stone; and Figures 4, 5, and 6 represent the mode of projecting
the form of the "schablone" or curved rule. After making the surface of the
stone level and true, it is divided into a number of equal parts (more or less
according to the diameter of the stone) by diameters or straight lines drawn
through the centre to the circumference. Stones of three feet diameter should
have their surfaces divided into eight equal parts, those of three and a half
feet into ten equal parts, those of four feet into twelve equal parts, &c.
This is to be the case when the furrows are to be formed in the manner shewn
in Figures 1 and 2, but when they are formed as shewn in Fig. 3, then only
two-thirds as many equal divisions are required. When the prepared surface
of the stone has been thus divided, the "schablone" or curved rule A (the
mode of projecting which is herein-after described) is placed on the stone,
with its point a on its concave side at the narrow end upon one of the radial
lines at the eye of the stone, and its point b on the convex side of the broad
end at the circumference of the stone, and the size and shape of the
"schablone" or curved rule thus placed are marked out on the stone. The
two curved lines thus obtained will indicate the size, shape, and position of a
major furrow B. The operation is repeated on each of the remaining half
diameters, and the positions of all the major furrows B, B, are thereby
determined. The lines for the minor or intermediate furrows C, C, are

page_text: obtained by laying the "schablone" or curved rule A between two major
furrows, with its concave side parallel with the convex side or back of one of
the said major furrows, as shewn in Figures 1 and 2, and marking round the
"schablone" or curved rule while in this position. By this means the lines
for one of the minor or intermediate furrows C, C, will be determined, and by
repeating the process all round the surface of the stone, the size, shape, and
position of the several minor or intermediate furrows will be marked out
provided only two furrows to a division be required, as shown in Figures 1
and 2. But if three furrows in a division are required, as in Fig. 3, then a
second set of minor furrows C, C, are formed in the same manner as the
former set above described, all the furrows in each division being parallel, as
shewn. The size, shape, and positions of all the furrows being thus marked
out, they are cut in the stone at about from one-half to three-quarters of an
inch deep at the eye of the stone, and about from three-quarters to an inch
deep at the circumference thereof, with an uniform and gradual fall from one
depth to the other. They are also made not quite at right angles with the
surface of the stone on the back or convex side, and brought up in an inclined
plane to a feather edge on the front or concave side, as shewn at D in the
section below each of the Figures 1, 2, and 3. The section below Fig. 1
illustrates the minimum of the draught of the dress or forward inclination of
the furrows from a straight line drawn through the centre of the stone used in
connection with this system of dressing, and is suited to any motion over one
hundred and forty revolutions per minute. That below Fig. 2 illustrates a
draught increased three inches over that of Fig. 1, and is suited to a motion
of one hundred and twenty revolutions per minute. The rule for increasing
the draught of this dress is to give one inch and a half increased forward
inclination to the furrows for each decrease of ten revolutions per minute in
the motion of the stones. The dotted lines in the Figures represent the
furrows in the runner, while the full lines represent those of the bedstone.
Both stones are furrowed alike, but when the runner is turned over and
placed in the position required for grinding, the furrows are reversed in relation
to those of the bedstone. The arrows indicate the direction in which the
runner revolves. With stones as shewn at Figures 1 and 2, the ordinary
surface dress is used, but in such as are shown at Fig. 3, the grinding surfaces
are filled with numerous parallel grooves of about one-sixteenth of an inch
deep as narrow as possible without breaking into each other. The usual
"bowl," "bed," or "bason " is entirely omitted in this case.
Figures 4, 5, and 6 represent the mode of projecting the "schablone" or
curved rule adapted for stones of different diameters. Fig. 4 relates to a

page_text: stone of forty-eight inches in diameter; Fig. 5 to one of forty-two inches; and
Fig. 6 to one of thirty-six inches. The mode of proceeding is as follows:-
On a piece of thin planed board (or metal may be used) draw the segment of a
circle a, a, the diameter of which is equal to that of the stone intended to be
furrowed. Draw the lines b, b, c, c, and d, d, from a common centre, so as to
cut the segment at right angles with its tangent at each of the three points
shewn, the lines b, b, and d, d, being distant from each other about the length
of the required "schablone" or curved rule, which should be a little less than
half the diameter of the stone. Now measure on each of these three lines
and on each side of the segmental line a, a, half the width of the "schablone "
or curved rule required at the points shewn by the numbers 10, 15, 20, in the
Diagrams; then through the three inner points draw another segment of a
circle n, n, the diameter of which is a little less than that of the stone; this
will give the inner or concave side of the "schablone" or curved rule, and
through the three outer points draw another segment of a circle o, o, the
diameter of which is a little greater than that of the stone; this will give the
outer or concave side of the "schablone" or curved rule. The curvature of
the stone's circumference being the mean between the inner and outer cur-
vatures of the "schablone" or curved rule.
Having thus described the nature of the said Invention, and in what manner
the same is to be performed, I hereby declare that what I claim as of the
Invention communicated to me as aforesaid is, the formation of curved furrows
on the operating surfaces of millstones in the manner described, such furrows
being so formed, arranged, and combined as to work in harmony with the
centrifugal and centripetal forces produced by rotary motion, as herein-before
described.
In witness whereof, I, the said William Spence, have hereunto set my
hand and seal, the Twenty-fourth day of September, in the year of our
Lord One thousand eight hundred and sixty-one.
Witness,
GEORGE B. COULCHER,
50, Chancery Lane,
Law Stationer.
WILLIAM SPENCE. (L..s.)