Improvements in Grinding Machines for Precious Stones.
Year: 1892

page_text: Date of Application, 16th Aug., 1892-Accepted, 5th Nov., 1892
COMPLETE SPECIFICATION.
Improvements in Grinding Machines for Precious Stones.
I WILLIAM JOSEPH KNOWLTON of 168 Tremont Street, Boston in the County
of Suffolk, State of Massachusetts, United States of America do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
My invention consists of an improved apparatus for presenting a gem to a lap
wheel, and holding it steadily thereon at any desired angle of inclination, said angle
of inclination being capable of the most minute adjustment. The machine has,
furthermore, certain appliances whereby the gem may be readily and quickly turned
step by step on its axis through a distance equal to any desired fractional portion
of its circumference and set in each position while a facet is being cut, in such a
manner that any desired number of facets may be cut thereon with great precision
and nicety, at any given angle of inclination.
By means of these two sets of graduated adjusting devices in two different planes,
the one governing the angle of inclination at which the stone is presented to the
wheel, and the other the step by step motion of the stone around its axis, the stone
may be cut with regularly formed facets at any number of angles with mathematical
accuracy and with comparatively little skill on the part of the operator, a result
hitherto impossible with appliances in use for this work.
My improved machine not only enables the lapidary to cut an endless number of
new and beautiful designs, but it also renders it an easy matter to reproduce with
great accuracy any particular pattern or design, and to cut any number of stones in
the same pattern.
Referring to the accompanying drawings:-
Fig. 1 shows in elevation my improved machine.
Fig. 2 shows in plan view the clamping sleeve on which rest the working parts
of the machine, said sleeve being shown in place on the upright post, the said
working parts being removed.
Fig. 3 is a sectional view through the center of the device which holds the stone
upon the lap wheel.
Fig. 4 shows on a larger scale the method of fastening into the socket the stick
which holds the stone.
Fig. 5 is a plan view of the machine, and
Fig. 6 is a sectional view through the center of the lateral arm and its bearings.
P is the lap wheel mounted in the usual manner on the vertical spindle P' and
capable of a very high speed of revolution. The working parts of the apparatus
for holding and presenting the stone to the wheel are supported directly by the
upright post B which is firmly set in the base A, near one end thereof. Near the
other end of the base A. is firmly fixed the downwardly extending supporting rod A'
which has its bearing in a suitable box A' screwed or bolted to the bench A³. The
base A and with it the entire apparatus may be set at any height above the wheel
and at any position over the same by means of the set screw a.
The stone to be cut or polished is cemented or otherwise affixed to the end of
a stick H, preferably within a recess cut in the bottom thereof, in such a manner
as to expose a portion of the stone beneath the stick to the surface of the lap wheel
when held thereon. The stick H is held within a suitable revoluble holder K more
fully hereinafter described which has its bearings in the ends of the two branches L²
of the lateral arm L¹. This arm is in turn held within a horizontal sleeve C² which
is rigidly connected with the vertical sleeve C mounted loosely on the upright
post B, the lateral arm L' being capable of rotation within the sleeve C. The
sleeves C C together form what I term the bearing piece for the arm. By the

page_text: rotation of the lateral arm within the sleeve C2 the angle of inclination of the frame
formed by the two branches L2 of the arm and with it the angle of inclination of
the stick H held in said frame is varied at will with reference to the surface of the
lap wheel, and by the rotation of the holder K within its bearings any number of
facets may be cut on the stone at each angle of inclination, both movements being
capable of minute regulation in the manner hereinafter detailed.
D is a sleeve or collar on the upright post B, adapted to be clamped thereon at
any height. For this reason the sleeve is cut through vertically on one side as
shown in Fig. 2 having the two branches or lugs bb through which passes the
screw d. By means of the clamping handle D' which engages with the end of the
screw d the sleeve D may be clamped readily at any height on the upright post B
in a manner obvious without further description. The flanged top of the sleeve D.
is cut away as at d³ and in this recess is held a cam D secured to a spindle d
mounted in suitable bearings d' secured to the side of the sleeve and tightened or
loosened by the screw d' as shown in Figs. 1 and 2. D is a handle fixed to the
end of the cam spindle by means of which the cam is operated.
The vertical sleeve C on the post B either rests directly upon the cam D³ or has
a thin intervening strip C₁ (Fig. 1) on the flanged bottom of said sleeve. By
turning the handle D the cam D raises and lowers the sleeve C. The cam
spindle works quite tight in its bearings in such a manner that the cam when set
in a given position will not change except by turning the handle D³.
The horizontal sleeve C' which is preferably integral with the vertical sleeve C
is conical on the inside to form a bearing for the lateral arm L' (see Fig. 6) which
it accurately fits. L is a collar which fits over the outer end of the arm L' against
the end of the sleeve C³, I being a cap which covers the end of the collar 1. all
parts being held in place by means of the screw 1. The collar L is made to turn
with the arm L by means of the set screw 1, Fig. 1, which passes through said
collar and enters a longitudinal.groove in the arm L.
E is a plate screwed or otherwise secured to a faced off shoulder on the sleeve C,
said plate having thereon the graduated scale E¹ the top of which is curved in the
arc of a circle struck from the centre of the collar L. The scale E' has a series of
indentations e arranged in a circular arc at regular intervals apart.
F is a clamping piece having two arms passing one on each side of the collar L
being pivotally secured to the collar by means of screws f. The piece F has set
therein the pin or pointer F in such a position as to traverse the scale E' directly
in front of the indentations e.
F is a block having the lip f* which fits behind the plate E. F' is a screw
secured to said block F and passing through the clamping piece F. F' is a thumb
nut engaging with the screw, the arrangement and construction being such that
when the thumb nut F¹ is loosened, the arm L' may be casily turned in its bearings
and at the same time the pin F traverses the circular arc of indentations e. The
arm L may thus be set in any position with the stick H which holds the stone at
any desired angle of inclination by screwing up the thumb nut F' with the point f*
of the pin F in engagement with one of the indentations e on the scale E'.
the same.
The ends of the two branches L of the forked frame at the end of the arm L¹
are provided with conical bearings for the enlarged conical portions of the
stick holder K. The portion of the stick holder above the upper bearing projects
upward for some distance and is screw threaded as at *. The nuts I' I' serve to
keep the holder K firm in its bearings but at the same time allow easy rotation of
The stem of the stick H is of a size to fit easily within the holder K but
is enlarged at the bottom as at h to fit against the beveled under side of the holder
as shown in Fig. 3. The upper portion of the stick H is reduced in diameter above
a shoulder the stick being provided near its top with a pin 4' which passes
through the same and projects out on either side. G¹ is a hollow socket which is
of such a size as to fit easily over the diminished top of the stick H and within
the top of the holder K, the socket being provided with bayonet slots g', on
opposite sides to fit over the projecting ends of the pin h¹.

page_text: The socket Ghas the enlarged top G.
I is a thumb nut on the screw portion of the holder K above the nuts I¹ I³.
The stem of the stick H is passed up from beneath through the holder K and the
socket G passed down from above into said holder and over the top of the stem
with the projecting ends of the pin ¹ in the top of the bayonet slots g', the thumb
nut I being first screwed down upon the nut I'. The socket G'is then given a turn
by means of the milled head G so as to bring the ends of the pin ' in the clamping
portion of the bayonet slot g' (as shown in Fig. 4) and the thumb nut I is then
screwed up against the under side of the enlarged head G of the socket G¹ which
by tension holds the stick firmly in place within the holder K, so that it will turn
therewith.
M is a regulating drum on the holder K. This is centrally bored out to fit the
holder and in circles around the surface of the drum are several series of indenta-
tions m m', the indentations in each series being evenly spaced off, the distance
between them being preferably equal to some regular fractional portion of its
circumference as 1, 3, &c. Any number of series of variously spaced indenta-
tions may be provided on the drum.
N is a handle lever pivoted at n between lugs n¹ on the piece L¹ L³, the outer
end of said lever having fixed therein the pin n of a size to engage with the
indentations on the drum M one at a time. The holder K is provided with the
longitudinal groove m² into which projects the end of the set screw M' (see Fig. 3)
mounted in the under portion of the drum M. The drum may thus be slid up and
down on the holder K and clamped at any desired height thereon to turn therewith,
the object of this adjustability being to bring any desired series of indentations m m¹
on the drum, opposite the pin n on the lever N. N¹ is a spring fixed to the under
side of the handle of the lever and bearing against the arm L'in such a manner as
to press and hold the pin n in one of the indentations m m¹ when opposite the
same.
The operator by pressing down on the handle of the lever N and turning the
holder K by means of the milled nut I may thus move the stick with the stone O
therein step by step through an angle equal to that between any two indentations m,
letting the pin n engage successively with each indentation of the series.
The angle of inclination of the stick and with it the angle at which the facets are
to be cut on the stone O is thus determined by the indentation e on the scale. E¹
with which the pin F* is in engagement.
When once the stick is set at the required angle the drum M is adjusted in
position on the holder K to bring the required series of indentations m m' opposite
the pin n according to the number of facets which it is desired to cut on the
stone at the given angle of inclination.
By loosening the set screw a the stick H set at a given angle of inclination may
be moved so as to bring the stone above any portion of the lap wheel P, the
base: A moving about the rod A' as a pivot. When placed in its desired position
the base A is clamped by tightening the screw a. The size of the facet cut on
the stone, or in other words, the pressure of the stone upon the lap depends on the
height of the sleeve C on the post B. This is, therefore, roughly adjusted by
the clamping sleeve D, all fine adjustments being done by means of the cam D*
moved by the handle D..
The facet is cut by pressing down the sleeve C as far as it will go on the post
till it rests upon the cam D2 thus bringing the stone into contact with the
wheel, the clamping sleeve D and the cam D2 having previously been set in proper
position to act as a stop. When the facet is cut the operator lifts up the sleeve C,
turns the drum M through the required angle by means of the regulating device
already described and presses down the sleeve C bringing a fresh portion of the
stone into contact with the wheel and so on. The sleeve C has free motion about
the post B being loose thereon so that the gem may readily be applied to the lap
wheel at any point between the rim and the center.
The polishing of a cut stone is equally simple, it being necessary only to set the

page_text: stone at the proper angle of inclination, and to make the proper adjustments of the
regulating drum M, the sleeve D, and the cam D' at the beginning.
It is frequently useful in polishing gems to employ a lap wheel, the upper surface
of which has two grades of diamond dust arranged with the coarser near the rim of
the wheel and the finer near the center, the dotted circle y y in Fig. 5 representing
for instance the limits of each, the surface outside the dotted circle being sup-
posed to be covered with the coarser and that within the circle with the finer
diamond dust.
In polishing a stone on such a wheel the stone is first applied to the coarser or
outer portion of the wheel surface, and then to the finer or inner part. After the
gem leaves the coarser part, it has certain minute scratches left on its facets which
are removed in the final polishing on the finer portion of the wheel. It is obvious
therefore, that when the stone is applied to the inner or finer portion of the wheel
surface, it must be lowered slightly in order to efface the scratches. I provide as a
simple means for accomplishing this the before-mentioned strip C¹ on the bottom of
the sleeve C which intervenes between the sleeve C and the top of the cam D³.
This strip is in itself virtually a wedge being so arranged that when the stone is
applied to the lap wheel near the rim of said wheel, or on the part outside the
circle y y in undergoing the coarser polishing, the thickest part of the wedge
strip intervenes between the sleeve C and the cam D³, but when the sleeve C
turns on its post B to bring the stone on to the finer portion of the wheel within
the circle yy to undergo the final polishing, the tapering wedge strip C' lowers the
sleeve C and thus the stone O slightly, but sufficiently to efface the scratches left
by the rough polishing.
The hole through the sleeve C does not perfectly conform to the post Bas
shown in Fig. 5 at being slightly irregular. This is to give a very slight play to
the sleeve in one direction so that the stick with the gem therein is not held
perfectly rigid up and down for the reason that when slight inaccuracies on the
surface of the lap wheel are encountered in polishing, the gem would be marred
thereby if rigidly held.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1. In a stone grinding machine, an upright post in combination with a bearing piece
mounted on said post to slide and turn thereon, said bearing piece being provided
with a graduated scale, an angularly adjustable frame mounted in said bearing
piece, a pointer and clamping device engaging with said scale and mounted on a
connection of said frame to turn therewith, and a revoluble stone-holding stick
suitably mounted in said frame, substantially as described.
2. In a stone grinding machine, a suitably mounted angularly adjustable frame
in combination with a revoluble stick bolder having bearings in said frame and pro-
vided with a graduated regulating drum mounted thereon, a stone-holding stick
fixed in said holder to turn therewith and a spring lever pivoted to a connection of
the frame, said lever having a pin engaging with said graduated drum, substantially
as and for the purposes described.
3. In a stone grinding machine, a suitably supported bearing piece provided with
a graduated scale, in combination with an angularly adjustable frame mounted in
said bearing piece, a clamping device and pointer engaging with said scale and
mounted on a connection of said frame whereby the frame may be set at any
desired angle of inclination, a revoluble stick holder having bearings in said frame
and provided with a graduated regulating drum, a stone-holding stick fixed in said
holder to turn therewith and a spring lever pivoted to a connection of the frame,
said lever having a pin engaging with said drum all constructed and arranged
substantially as and for the purposes described.
4. In a stone grinding machine, an upright post B in combination with a bearing
piece C C mounted on said post to slide and turn thereon, a lateral arm L

page_text: mounted in said bearing piece to turn therein, a frame L' L' carried at the end of
said arm, and a revoluble stone-holding stick H suitably held in said frame,
substantially as described.
5. In a stone grinding machine, a frame L' L' in combination with a revoluble
stick holder K having bearings in said frame, and having the screw threaded
portion, a stone-holding stick H having the enlarged end and provided with
the pin H¹, a socket G engaging with the stem of said stick, having bayonet
slots g engaging with said pin and provided with an enlarged head C and a thumb
nut I mounted on said screw threaded portion of the holder, all constructed and
arranged and operating substantially as described.
6. In a stone grinding machine, the combination with an upright post B of a
bearing piece CC supporting a suitably mounted angularly adjustable revoluble
stone-holding stick, a clamping sleeve D having a fastening device whereby the said
sleeve may be clamped at any desired beight on said post, a cam D' fixed to a
spindle mounted in a connection of the sleeve D and a cam operating handle D³,
the said cam being arranged to support the bearing piece and to adjust the working
position of the bearing piece on the post, substantially as described.
7. In a stone grinding machine, the combination with an upright post B of a
bearing piece CC supporting a suitably mounted angularly adjustable stone-
holding stick and a wedge-shaped piece C₁ on the bottom of said bearing piece, a
clamping sleeve D provided with a handle operated cam D' engaging with said
piece, substantially as and for the purposes described.
8. In a stone grinding machine, the combination with an upright post B of a
bearing piece. CC supporting a suitably mounted angularly adjustable stone-
holding stick, said piece C C being loosely mounted on said post to slide and turn
thereon and having also a lateral play on said post, substantially as and for the
purposes described.
Dated this 16th day of August 1892.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.