IMPROVEMENTS IN THE MANUFACTURE OF WOOD SCREWS AND IN MACHINERY THEREFOR"
Year: 1876

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for the Invention of
IMPROVEMENTS IN THE MANUFACTURE OF WOOD SCREWS AND IN MACHINERY
THEREFOR" A communication from abroad by Charles D. Rogers, of Providence,
Rhode Island, United States of America.
Sealed the 23rd June 1876, and dated the 5th May 1876.
COMPLETE SPECIFICATION filed by the said William Robert Lake at the Office
of the Commissioners of Patents on the 6th May 1876.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN THE MANUFACTURE OF WOOD
SCREWS AND IN MACHINERY THEREFOR” A communication from abroad by
Charles D. Rogers, of Providence, Rhode Island, United States of America.
This Invention relates to the manufacture of that class of wood screws in which
the threads are formed by cutting away the metal between them by a tool or chaser
whose form corresponds with the space left between the threads.
Heretofore in the manufacture of wood screws when the portion immediately
below the neck, which is the part usually termed the cone of the screw, has been
cut by the same tool that has been used to cut the remainder of the body of the
screw, the thread over the cone instead of being brought to an edge has been left
with a flat top, this flat top gradually decreasing in width until at the termination
of the cone it came to an edge, which was continued for the rest of the screw.
It is obvious that in cutting a screw of any given lead by a chaser having its
sides inclined to the axis of the screw the thread can be brought to an edge by
cutting to a sufficient depth; and it is also obvious that a screw cannot be cut from
a cylindrical wire so as to leave a conical body beneath the thread and at the same
time carry the tool everywhere to a uniform depth; consequently with a conical
body the thread has a thick edge and the shallower the cut the thicker the edge.
These screws therefore have been imperfect, for the wide or thick part of the thread
over the cone does not follow the part brought to an edge over the cylindrical
portion of the body as readily as if all parts were brought to the same edge. The
ength of this imperfect part of the thread is generally reduced as much as possible
D

page_text: by quickly bringing the cut to its maximum depth; but this formation does not
wholly remove the evil, and introduces another which it is desirable to avoid; the
screw is most liable to break immediately below the neck or at the part where in
cutting the thread its body is reduced from the full diameter of the blank to the
diameter at the bottom of the cut, and the more sudden this reduction the greater 5
is the liability of the screw to be broken.
Attempts have been made to bring the threads to an edge over the cone by
introducing a second cutting tool for that part of the screw, but this method not
only involves difficulties which enhance the cost of manufacture but necessitates a
different inclination of the sides of this part of the thread, which gives to the screw
an unsymmetrical appearance, prevents the portion of the thread over the cone from
following the lower portion with exactness, and diminishes the holding power.
The object of this Invention is to obviate the difficulty above stated by making
cuts of increased width and diminished depth over the cone in comparison with the
width and depth of the cuts along the cylindrical portion of the body of the screw,
the increase of width and diminution of depth being such that the thread is
everywhere brought to an edge without any difference in the inclination of the
sides, while the full outer periphery of the screw is everywhere maintained. This
object I have accomplished by introducing in an ordinary machine for cutting a
thread on wood screws a contrivance which causes the chaser to increase the width
of its cuts over the cone proportionately, as the depth is less than it is over the
main part of the screw.
In the accompanying Drawings Figure 1 is a view of one of my improved screws;
Figure 2 is a section of the same.
Figure 3 is a plan of a screw cutting machine for making the said screws.
Figure 4 is a front elevation of the said machine; Figure 5 is a rear elevation of
the same.
Figures 6 and 7 are sectional elevations taken on the lines x, x, and y, y, in
Figure 3.
Figure 8 shews one of the cams of the said machine.
A is the frame of said machine; B is the spindle to which the power is applied,
and which for the most part is hollow, carrying within it an ordinary apparatus for
holding the screw blank and presenting it to the chaser. This apparatus consists of
a pair of jaws a which are opened and closed by a rod not shown connected with
them and extending back through the spindle, and having a reciprocating motion
derived from the sleeve C on the spindle, the sleeve and rod being connected by a
pin working in a slot, not shown, and the sleeve having a groove c by means of
which it obtains a longitudinal reciprocating motion at proper times by devices
herein-after described.
D is the tool post, being an upward rigid projection from a rock shaft D' which
has bearings at A, A, in the frame. The chaser is held in a slot at the side of
the tool post by a plate d' secured to the post by a set screw, as shown. The rock
shaft 1) has also a projection d extending downwards, attached to which a spring,
not shown, tends to swing the tool post outwards against a plate S which carries a
former 8 and resists the pressure, as herein-after shown. The rock shaft D' has a
longitudinal movement in its bearings equal in length to that part of the blank to
be threaded, and the spring just referred to also acts to keep the shaft in contact
end to end with a revolving shaft E, which has also a reciprocating longitudinal
notion derived from a worm carried upon it, as shew, and operated by a
corresponding half nut or female screw on a rocking lever F, which is hinged to a
shaft which has one bearing in a projection from and under the inain frame, and
the other bearing in a sleeve E' fixed in the main frame, as shown. Through the
outer end of the sleeve E' and across the end of the shaft F¹ plays a wedge e
forcing the shaft F' at certain times inward longitudinally and carrying with it the
rocking lever F, by means of a collar on the shaft coming against the hinge of the
lever, as shown; a coiled spring on the other end of the shaft F', having one end in
the main frame, keeps the rocking lever F up against the collar aforesaid and forces

page_text: the shaft back longitudinally as the wedge is withdrawn, and this spring is so
connected with the rocking lever as to tend to keep the half nut of the latter out
of gear with the worm of the shaft E.
The shaft E not only revolves but has a longitudinal movement. Near the end
in contact with the tool post shaft D', as aforesaid, it has a bearing in the main
frame at A. The other bearing is in a recess in the end of a revolving shaft G,
which has its bearing within the main frame, principally in a cone-shaped
projection A, the shaft E being feathered to the shaft G.
The shaft at its outer end carries a gear wheel g, which takes into cogs on
the spindle B, as shown. H is a rest or support for the screw blank; it has a slot
(see Figure 7) across the edge to embrace that part of the screw blank which
extends in front of the jaws a, and with the jaws holds the blank firm against the
action of the chaser, the blank revolving in the slot on its own axis. The rest H is
movable, and is so arranged in the machine as to be brought up to the blank at the
moment the jaws a close to grasp the same; this is accomplished by a slide rod h
having a longitudinal movement across aud under the front edge of a plato I, the
rod being supported by cross pieces of the main frame, as shown; a projection h¹
strikes tho rest H and forces it up to the blank. A slot in the rod h embraces the
rear end of a fork ; working in the groove c of the sleeve C; this fork is a rigid
projection from a sleeve J sliding on a rod K attached to a cross piece of the frame,
as shown; the movement of the sleeve J consequently controls both the sleeve C
with the jaws a and the rest H, and the sleeve J is itself controlled by a cam on the
shaft M that revolves between two pins j¹, j, in sleevo J. M is a shaft geared with
the shaft G and extending at the rear of the machine from end to end of the same; it
carries most of the cams of the machine. O is a cam with two lifts rigidly attached
to a sleeve o on the shaft M to operate the worm lever F. Between the cams Land O
is a clutch N keyed to the shaft M and operating the cam L or the cam O, according
to its longitudinal position; and this position is determined by means of a groove n
extending around the clutch, as shewn, in which play two pins p, p, on tho end of
the fork P which loosely embraces the clutch, and which has a pivot in the main
frame on which it swings to the right or left. The fork P has also a projecting arm,
the lower end of which follows a cam slotted wheel Q on a shaft R having bearings
under the frame, as shewn ; at the other end of the shaft R is a star R¹, one point
of which is struck by an arm m³ rigidly connected to the shaft M at each revolution
of shaft M. A spring acting against a slot across the rim of cam L assists in
keeping that cam steady when not in gear with the clutch N.
The aforesaid plate S slides in ways in projections A, Aº, of the frame, and is
rigidly secured to a movable yoke T which is slotted, as shewn in Figure 7, to
permit the slide rod and other parts of the machine to have motions underneath
the plate I in directions at right angles to the motions of the yoke.
The movement of the yoke T in one direction brings the sliding plate $ nearer
to the blank, the chaser d consequently making a deeper cut; and this movement is
accomplished by a slide rod V working longitudinally in the main frame and having
at one end a projection v slightly wedged shaped to force the yoke T back as the
wedge advances through the slot of the yoke.
When the yoke T is released from the wedge of the slide rod V the spring,
before referred to, on the projection d of the tool post shaft carries back the tool
post, the chaser, the plate S, and former 8, and with them draws over the yoke T.
At the other end of the slido rod V is a projection v and a set of teeth v³,
one of which is shown in Figure 5, against which projection and teeth act two
peculiarly shaped arms W and WI, revolving with shaft M, to which they aro rigidly
connected.
✓
The machine is so timed that the slide rod V is drawn back so that the wedge v
does not act upon the yoke T while the jaws a aro dropping the screw and receiving
the blank. To bring the wedge vinto play with the yoke T after the blank has
been grasped projections on arms W and W' successively strike the projection v¹ on
the rod Vand move the rod forward.

page_text: =
After all the teeth have been brought into play the rod V is drawn back by
means of an arm projecting from the rod, the arm being struck by the upper
arin of a bell-crank lever U, which is attached to the main frame and operated by a
cam W upon the same sleeve which carries the cam L. Y is a side cam of two lifts
rigidly attached to the shaft M, and z is a wedge having a movement under the
plate I at right angles to the motions of the yoke T. This wedge has rigidly con-
nected with it a pin which follows the can Y, being forced into contact with it at
its depressions by two short arms ', ', on a sleeve rigidly attached to the shaft M.
The wedge acts against the slide rod V, and through that rod against the yoke T,
drawing back the yoke when either lift of the cam Y (the two lifts being alike)
acts upon the pin, the slide rod V for this purpose being free to move sidewise
and being separated from the wedge by a gib, as shown in Figures 3 and 7. The
cam Y accordingly controls the movement of the plate S, and through it the
movement of the chaser towards the blank. While the pin is in the depressions
of the cam Y it has no effect upon the tool post and chaser, they in fact at that
time being on the way back from the point to the neck of the blank; but the lifts
of the cam at proper times acting through the pin and mechanism, previously
explained, hold the tool up to the blank to make a cut, and each lift of the cam is
so shaped as to pull the tool as it passes from neck to point gradually inward
to gradually increase the depth of the cut till the full depth is reached, which is
maintained for the remainder of the blank. This is independently of the wedge v
before referred to. The operation of the cam Y is illustrated in Figure 8, where
the can is shown as if removed from the side rim of a wheel, the curve of the
wheel being disregarded; as the pin passes from to, the tool gradually
increases the depth of its cut. The pin reaching from that point to the tool
nakes a cut of uniform depth.
While the cam Y has the above described effect upon the bottom cuts of the tool
the cam M, before referred to, performs a similar duty with reference to the side
cuts. This eam M' is a cam of two lifts on shaft M to operate the wedge e¹;
this operation it effects by means of a rocking lever E which is pivoted to the
main frame, as shown in Figure 6, and follows the cam by force of a spring coiled
on the shaft, on the end of which is formed the wedge e'; but the two lifts of the
cam M, as shown in Figure 6, are unequal, and the wedge e' is therefore pushed
further into or drawn back in the slot in the end of the sleeve E, before referred
to, accordingly as the end of the rocking lever E is in contact with the greater
or the lesser lift; and it follows from the effect of the wedge e¹ upon the shaft F,
and mechanism previously described, that when the rocking lever is in contact
with the greater lift of the cam M' one side of the chaser is brought into nction
against the blank, and when the rocking lever is in contact with the lesser lift the
other side of the chaser is brought into action against the blank, the chaser thus
alternately cutting on one side and on the other.
The cam M is further divided, there being a decrease in radius from m' to m of
the greater lift and an increase in the radius of the lesser lift from f to e, while the
remainder of both lifts are respectively of uniform radius. Accordingly when the
rock lever E is in contact with the cam M at m³ the chaser is cutting on the upper
side of the thread and presses with its greatest force or makes its greatest cut
towards the point; and this sidewise pressure gradually diminishes until the lever
reaches m, when the sidewise pressure remains uniform for the rest of the cut. The
next time the chaser goes over the blank at the beginning of the cut the rock lever E*
is in contact with the cam Mat fand the chaser is cutting on the lower side of the
thread and presses with its greatest force towards the neck, and the sidewise
pressure gradually diminishes until the lever reaches c, whence it remains uniform
for the rest of the cut. The cams Y and M' are timed in combination, so that when
the chaser is cutting to the least depth inwards towards the axis of the blank it is
making its greatest sidewise cut towards the point or towards the neck, as the case
may be, and so that where the inward cut is of uniform depth the sidewise cuts are
neither increased or diminished.

page_text: The chaser which I have used has an inclination towards the point of the screw.
This inclination gives to the screw the strongest form of point when the entire
screw is cut with a single tool; but this featuro forms no part of my Invention,
which has reference only to cutting the thread over the cone and cylindrical
portion of the body of the screw where the full outer periphery of the thread is
inaintained.
The dotted lines in Figures 1 and 2 shew the division of the screw into neck,
cone, cylindrical body, and point.
Having thus fully described the said Invention, as communicated to me by my
foreign correspondent, and the manner of performing the same, I wish it understood
that I claim,-
First. In combination with an ordinary screw-cutting machine the mechanism for
accelerating, retarding, and limiting the sidewise cuts of the chaser over the cone
and cylindrical body of the screw, proportionately to the depth of the chaser, or
towards the axis of the screw, to bring the threads to an edge of a uniform angle
over those parts, without changing the outer periphery of the screw, as above
described.
Second. A wood screw having the outer periphery of the thread upon its body
cylindrical, while a portion of the body below the thread and near the neck is
conical, and all the threads are brought to an edge of a constant angle, the path
between the threads at the same time being free from shoulders, as above described.
Third. A pointed wood screw having the threads all brought to an edge with the
sane angle at all parts, but of different depths, and having the bottom of all the
cuts between the threads equally inclined to the axis of the screw, as above
described.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Fourth day of May, in the year of Lord One thousand
▸ Witness,
JA. EDWARDS,
8, Southampton Buildings,
London.
W. ROBT. LAKE, (LS)