Improvements in Screw Cutting Machines.
Year: 1894

page_text: Date of Application, 7th Apr., 1894
Complete Specification Left, 23rd July, 1891-Accepted, 25th Aug., 1894
PROVISIONAL SPECIFICATION.
Improvements in Screw Cutting Machines.
I, THOMAS BENJAMIN SMITH of 28 Westminster Road, Birchfields, Birmingham
in the County of Warwick, Screw Maker, do hereby declare the nature of my
said invention to be as follows:-
My invention has for its object improvements in screw cutting machines by which
I can cut a screw much more cleaner & quickly than hithertofore.
In carrying my invention into effect I use two, three, four, or more cutters which
I mount in a box which forms part of a face plate or chuck. These cutters which
for the convenience of description I will take as four, are mounted to slide in the
said box to the centre of which they all radiate. Blocks having an incline are
formed upon each cutter a facing being formed upon the plate against which these
blocks slide. Intermediately between each cutter I mount a guard so as to have a
sliding movement each guard being also provided with a similar block to those
formed upon the cutters. Passing through the plate are sliding bars having
inclined ends one bar to each cutter and guard the said bars being slotted for the
cutters and bars to pass through. The bars to the cutters are connected to a rear
plate which is operated in a sliding manner by a wedge, cam, or crank action so that
the wedge ends operate upon the inclines formed on the cutter blocks and thus press
them into the centre for the points to act upon the screw blank which is held in
position, revolved and carried forward in the ordinary manner. The guards are
mounted to support the screw immediately in front of the cutters and these guards
are actuated in a similar manner to the cutters only that the bars or rods for
operating the same are connected to a second rear plate so as to have a movement
independent of the cutters which is most important as in the case of short screws
the guards have to recede from the screw prior to the cutters finishing their work.
The cutters and guards are caused to recede by means of small coil springs between
the blocks and the box and the rear plates are also actuated in an opposite direction
to the action of the wedge by a coiled spring or springs at the rear of the plates.
The box is cut away to allow of the blanks being fed in, and one cutter and one
guard recede doubly the distance of the others to allow the blanks to pass into
position. I may use one rear or operating plate only, and by having my cutter
straight it will be seen that I can have a cutter of any length.
Dated this 6th day of April 1894.
GEORGE BARKER,
77, Colmore Row, Birmingham, Agent for Applicant.
COMPLETE SPECIFICATION.
Improvements in Screw Cutting Machines.
I, THOMAS BENJAMIN SMITH, of 28 Westminster Road, Birchfields, Birmingham,
in the County of Warwick, Engineer, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement :-
My invention relates to that class of wood-screw cutting machines in which
cutting tools are advanced in a radial direction towards a revolving and advancing
screw blank so as to cut the thread thereon.
My improvements have for their object to enable the screws to be cut more
Di

page_text: rapidly and cleaner than heretofore, while the machine is rendered of comparatively
simple and compact construction and of very reliable action by dispensing in great
measure with lever actions and pivotted joints.
According to my invention 1 mount the cutting and guiding tools in blocks
capable of sliding radially to and fro in guides on a face plate, the inward motion
for operating on the screw blauk being effected by forming inclines on the
sliding blocks against which act inclined planes on bars that are caused by a
wedge, cam or lever motion to move in a direction parallel or nearly so with
the axis of the machine, so that by such motion in one direction the inclined
planes force the block with the cutters and guides inwards against the action
of springs, so as to cut the thread on the screw, while when the bars move in
the other direction so as to relieve the cutter blocks of their pressure, the blocks
with the cutters and guides are forced outwards into their original position by
the said springs.
I will describe the construction and action of my improved machine with
reference to the accompanying drawings in which
Fig. 1 shews a front view and Fig. 2 a sectional plan of an arrangement in which
the guides and cutters are each operated by a separate motion, Fig. 3 shews an
enlarged part section of one of the bars with inclines and the cutter blocks.
Figs. 4, 5 and 6 shew respectively a side view, a plan and a back end view of
another arrangement in which the cutters and guides are all operated by one and
the same motion.
Fig. 7 shews a cross section on line X X Figs. 2 and 5; Fig. 8 shews a separate
view of one of the inclined plane bars, Figs. 9 and 10 shews separate views
respectively of the sliding blocks for the guides and the cutters, Fig. 11 shews the
form of the cutter. Fig. 12 the trimmer, and Fig. 13 the guide.
The drawing only shews so much of the complete machine as relates to my
present invention, the other part of the machine, namely that whereby the screw
blanks are fed into the machine, and are held, advanced and rotated while the
cutters cut the thread thereon, and are then withdrawn and removed from the
machine, being of the well known construction heretofore employed in such
machines and requiring no description.
Referring to Figs. 1, 2, 3 and 7 a base A has formed or fixed thereon a face
plate or chuck B, in the front face of which are formed a series of radial grooves b
extending to within a certain distance of the centre, the central portion of B being
made with narrower grooves b¹.
Into the grooves b are fitted sliding blocks C C¹ of which C carry the cutting
and trimming tools D D' which extend into the corresponding smaller grooves b',
while the blocks C₁ carry the guides D which also enter the corresponding smaller
grooves, the cutting and trimming tools and guides being secured in their blocks
by setting screws. The outer fares of the blocks CC¹ are formed with inclines e e¹
and against these bear inclines formed on sliding bars E which slide through
correspondingly formed holes formed in the face plate B, the blocks C C being
kept pressed against the inclines e of the bars E by means of helical springs F
bearing with one end against the blocks and with the other end against the end of
the grooves b'.
The rear ends of the bars E have threaded holes into which are screwed threaded
stems G that are secured by collars g g to a disc H, the stems G being rotatable
in the disc by means of a spanner so as by screwing into or out of the bars E and
by the aid of lock nuts, to adjust these either nearer to or farther from the disc.
The front ends of the bars E have slots e' for the tools D D' and guides D² to
pass through.
The disc H is formed or fixed on a sleeve H¹ that can slide backwards and
forwards upon a fixed tubular axis I which is secured to the face plate B and to a
standard J at back. Part of the sleeve H¹ is cut away to form an inclined face h' 5
against which bear inclines k formed on the forked end of an arm K sliding in a
guide fixed to the back face of the plate B.

page_text: The outer end of the arm has a roller bearing against a cam L' on a shaft L
geared in any suitable manner to the driving shaft of the machine so as to make
one revolution for every feed of a screw blank. The cam L' is so shaped as at
one time to force forward the arm K and thereby to force backward the sleeve H'
disc H and bars E carrying the guides, and at another time to allow the arm to
recede as the sleeve and disc are forced forward again by the action of the
springs acting on the blocks C¹.
The screwed stems G¹ of those bars E that act on the cutter blocks C pass
freely through holes in the disc H and are secured in a similar manner to a second
disc M formed on a second sleeve M' that also slides upon the axis I and is formed
with a neck with which engages the end of a lever N pivotted at N' whose other
end engages with a second cam L2 on the shaft L, so formed as to cause the lever N
at one time to move the disc M and bars E backward and at another time to move
them forward again, such forward motion being assisted by a spring O if necessary.
The cutters, trimmers, and guides are held in their several grooves in the face
plate B by a plate P bolted to the latter.
The action of the above described machine is as follows:-The blocks C C¹ with
the cutters, trimmers and guides being in the retracted or outward position shewn
at Fig. 1 and consequently the discs H, M, and bars E being in the forward
position, a screw blank is introduced laterally into the axial line of the machine,
being held by grippers in the well known manner for this purpose, a chase Q Fig. 1
being cut in the face of the face plate for this purpose, and in order to afford room
for the passage of the blank between the top cutters and trimmers D D' and the
contiguous guide D2 to the right hand at Fig. 1, these have to be retracted to a
greater extent than the other tools, as shewn. In order to effect this the inclined
planes e of the corresponding bars E have to made of greater depth and with a
greater incline than the others, as shown at the enlarged part section at Fig. 3, so
as by their motion to produce a greater travel of the corresponding blocks C
and C¹.
The screw blank being held in the central position by the grippers and advanced
and rotated thereby, the rotation of the cam shaft L causes sliding arm K to force
back the disc H, and the lever N to force back the disc M, thereby retracting the
bars E and forcing the whole of the blocks C C' forward towards the axis of
the machine. By this means the guides D², which are slightly in advance of the
cutters DD, are made to hold the blank accurately in the central position at a
point in advance of the cutters while the cutters D cut the helical thread on the
blank, and the trimmers D¹ following on, trim the roughnesses of the screw thread
produced. The machine shewn at Figures 12 and 5 is more particularly intended
for cutting short screws.
With these, as the screw thread is cut nearly close up to the head, it is necessary
that the guides D2 should be made to recede from the blank when they approach
the head thereof, in order to allow the cutters D D¹ to cut nearly up to the
latter.
To effect this, the cam L' is made of such a shape as to allow the arm K to
recede when the blank has been advanced to the above mentioned point, thus
allowing the springs F to force back the blocks C¹ which in their turn force forward
the bars E and disc H. When the thread has been completely cut on the blank,
the cam L also allows the disc M and bars E to be moved forward by the spring O,
thereby allowing the blocks C and cutters D D' to recede again, whereupon the
screw is retracted by the grippers and is removed laterally through the chase.
Within the tubular axis I is a sliding bar R operated by a cam on the shaft L
(as shewn at Figs. 4, 5 and 6, and having a cutter at its front end, which cuts the
point on the end of the screw while the thread is being cut on it. This cutter is
of known construction and forms no part of my present invention and need therefore
not be farther described.
The construction of the machine shewn at Figs. 4, 5 and 6 is more particularly
adapted for cutting longer screws in which a considerable extent of the blank

page_text: behind the head is left without a thread, so that it is not necessary in this case to
withdraw the guides D² before the cutters are withdrawn.
The second disc M, with its operating cam L' is consequently dispensed with,
and the bars E for operating the guides, cutters and trimmers are all connected to
the disc H which is operated by the arm K and cam L' in the same manner as
above described.
The construction and mode of action of this machine is otherwise precisely the
same as that described with reference to Figs. 1 and 2 and the several parts are
indicated by the same letters of reference and need therefore not be farther
described.
It will be obvious that a greater or less number of guides and cutters than that
shewn may be employed, and also that the arrangement may be variously modified
in detail; thus in the construction at Figs. 1 and 2 the front disc H may be made
to operate the bars E for the cutter blocks, as in Figs. 4 and 5 and the rear disc M
be made to operate the bars for the guide blocks. Also, any other suitable known
mechanisms may be employed for effecting the backward and forward motion of the
discs H and M in the manner described in place of those shewn.
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 screw cutting machine in which a number of cutters or operating tools
are made to advance in a radial direction to operate upon a centrally situated screw
blank, effecting such forward motion of the tools by means of bars sliding in a
direction parallel or nearly so with the axis of the machine and having inclines,
which operate upon corresponding inclines on sliding blocks carrying the said tools
so as to force the same forward, the backward motion of the block and tools after
the completion of the cutting operation being effected by springs substantially as
described.
2. In a screw cutting machine of the kind referred to in the first claim, the
combination of sliding blocks C C¹ carrying the tools and guides, sliding bars E
with inclines e operating on inclined faces on the blocks, and a disc H having the
said bars E adjustably attached thereto and receiving a backward motion for
effecting forward motion of the blocks C C¹ and the tools, either by a wedge, cam
or lever action substantially as described.
3. In a screw cutting machine of the kind referred to in the first claim, the
combination of sliding blocks C carrying cutting tools actuated by sliding
bars E with inclines e and connected to a disc receiving a backward motion by
means of wedge, cam or lever action, and of sliding blocks C' carrying guides for
guiding the screw blank actuated by other bars E with inclines e and connected to
a second disc actuated by a wedge, cam or lever action, in order to enable the
guides to be removed from the screw while the cutters continue in operation
substantially as described with reference to Figs. 1, 2 and 7 of the drawings.
4. In a screw cutting machine, the construction of the thread cutting mechanism
combined and operating as herein described with reference to Figs. 1, 2, 3 and 7 of
the accompanying drawings.
5. In a screw cutting machine the construction of the thread cutting mechanism
combined and operating as herein described with reference to Figs. 4 and 5 of the
accompanying drawings.
Dated this 23rd day of July 1894.
ABEL & IMRAY,
Agents for Applicant.