Improvements in Machines for Cold-rolling Screw Threads Cut on Metal Bars or Rods.
Year: 1899

page_text: Date of Application, 15th Aug., 1893-Accepted, 27th Jan., 1900
COMPLETE SPECIFICATION.
Improvements in Machines for Cold-rolling Screw Threads Cut on
Metal Bars or Rods.
I, FRANK GLENN ECHOLS, of No. 57, Imlay Street, in the City of Hartford,
County of Hartford, and State of Connecticut, United States of America,
Machinist, 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 relates to machines for cold-rolling, to a precisionized form, threads
cut in the surface of a blank, and the object thereof is to produce a substantially
perfect thread the metal of which is densified or compacted as hereinafter
described.
In the embodiment of the invention illustrated, a machine is shown for cold-
rolling the cut-threads of a blank to be employed in the manufacture of screw-
cutting taps, but the machine is not limited to this use, as it may be employed
for cold-rolling or forming other kinds of thread.
In the usual practice of cold-rolling a screw-thread directly upon a bar of metal,
what is termed the "skin" of the material is not removed, and said "skin,"
which is quite thin, is so effected by the cold-rolling operation that the thread will
become warped or distorted during the process of tempering, thereby seriously
weakening the surface or cutting edge of the article and also materially impair-
ing its quality of precision.
In my improved process, however, the primary cutting of the thread or surface
of the metal removes this weak skin, and the blank is therefore in better
condition for the subsequent rolling operation by which the molecules of metal
are compacted into a solid and dense mass, the result being that the working
surface of an article produced in this manner will not become distorted or warped
while being tempered, and that the finished article will be in as nearly a pre-
cisionized form as can be secured mechanically.
•
My improved machine comprises one or more thread-forming rolls, which are
preferably rotatably supported, and in the present case two rolls are represented,
mechanical means being employed for sustaining the blank while it is being
subjected to the rolling operation. These rolls are duplicates, and they should
be of substantially the same diameter, so that they will uniformly rotate, and said
rolls are preferably mounted for yielding movement longitudinally, whereby the
threads upon the periphery thereof may automatically find or seat themselves in
the grooves between the threads of the blank.
In the drawings accompanying and forming part of this specification, Figure 1
is a plan view of my invention, shown as applied to an ordinary turning-lathe.
Fig. 2 is a horizontal plan view, partly in section, showing the rolls in operation
upon a blank with cut-threads thereon. Fig. 3 is a side view showing a blank
supported between the centers of the lathe, and illustrating an attachment by
which the position of the rolls with relation to said blank may be accurately
determined. Fig. 4 is a vertical section, taken in liner of Fig. 2. Fig. 5 is a
view of the blank with a cut-thread before it has been cold-rolled. Fig. 6 is a

page_text: view of the finished blank, having a cut-thread cold-rolled.
Fig. 7 is a detail
view in section, showing the action of one of the rolls upon the blank. Fig. 8
is a diagrammatic view on an enlarged scale; showing the same action; and Fig. 9
is a diagrammatic view, showing by dotted lines the original form of the thread,
and by stippling the changes in form and in the densification of the metal during
the cold-rolling operation.
Similar characters designate like parts in all the figures of the drawings.
For convenience in demonstrating the nature of my invention, I have illustrated
the same applied to a metal turning lathe of ordinary construction, in which case
the blank to be operated upon is mounted between the head and tail centers
of said lathe, although it is obvious that the invention is not limited to the
character of means shown for supporting the same, it being adapted for use with
various classes of machines.
The lathe includes the usual live and dead centers 2 and 3, between which the
blank, as B, is supported, and as I prefer to rotate said blank while cold-rolling
the same, the necessary motion is transmitted thereto from the live-spindle or
center 2, through the face-plate 4 and dog 5. It is evident that the blank B,
which is illustrated as a tap-blank, may be otherwise supported by the lathe and
also differently rotated, and also that the blank may be held stationary and the
rolls be caused to revolve around and travel along the same if deemed desirable.
The driving mechanism for the live-center is designated in a general way by D.
As herein before set forth, my improved machine includes means for cold-rolling
the surface of a previously-cut blank, said blank being shown as a threaded one,
and to accomplish this purpose two rolls are illustrated, they being designated
by R and R', and conveniently carried by section 41 of the slide S, which travels
along said slide as the rolling operation progresses, the blank being rotated
and its thread serving by its engagement with the threads of the rolls to advance
said slide-section 41 longitudinally of the blank.
I have found, in practice, that by my improved mode of operation a tap is
produced the thread of which is of precisionized form and the molecules of metal
constituting said thread are wrought together or swaged into a compact condition,
the result being a finished article having a uniform and perfect thread, which has
long been a great desideratum.
After the blank with a cut-thread has been operated upon by the rolls, it is to
be grooved or fluted and then tempered, and in virtue of the cold-rolling operation
the metal near the periphery of the blank is so dense and compact that it will
not become materially warped or distorted when the tap is subjected to the
hardening process.
in
The rolls R and R¹ have surfaces adapted for cold-rolling the truncated cut-
thread of the blank and for finishing the same, and said rolls are ground with great
accuracy, whereby the reproduction of the form of the thread thereof on the
tap-surface is as near precision as can be obtained. The rolls are rotatively
mounted in the blocks 12 and 13 supported for sliding movement
the transverse bore or passage 14 in the section 41 of slide S, and,
therefore, may be moved toward or from each other, said rolls being shown 4
journaled on the shafts 15 and 16, fixed in bearings in the two blocks. In working
upon blanks of a uniform size, the roll R¹ is usually held in fixed relation,
while the companion roll R is moved toward or from the same, either to act upon
the blank or permit the removal of the same.
To produce work of differing diameters, the block 13 carrying roll R₁ may 6
be moved inward or outward, as the case may be, to accomodate the size of
blank to be rolled. The roll-carrying blocks 12 and 13 are slid back and forth in
the bore 14 by the screws 20 and 21, which pass through the fixed nuts 22; fitted
in the opposite ends of said bore. As before stated, the block 13 is normally.
maintained in fixed relation to the complemental block, and for thus holding 5
the same a check-nut 23 in threaded engagement with the screw 21 and abutting
against the fixed nut 22 is employed.

page_text: The screw 20 is equipped with a crank 24, by which it may be turned to
adjust the block 12, and hence the roll R, toward or from the blank.
To enable the roll R to be accurately re-set after a finished blank has been
removed and an unfinished one placed in position, there is employed in connection
with said roll an index or gage which is preferably carried by the screw 20, and
which consists in the present instance of a disk graduated in thousandths of an
inch, whereby accuracy in the readjustment of said roll is insured. This index is
illustrated as a disk G, which is fixed to screw 20, said disk being graduated, as at
30, and the graduations being adapted to co-operate with the gage or index-
mark 31 upon the outer surface of the slide-section 41 in proximity to the
periphery of the disk.
In Fig. 2 the rolls R and R¹ are shown operating upon the blank B, and in
Fig. 3 the parts are represented occupying a corresponding position, the index-
mark zero being opposite the mark 31 upon said slide-section. When the rolling
operation is completed the crank 24 is turned thereby causing the screw 20 to
move the block 12, and consequently the roll R, away from the work, so that the
latter can be removed from the machine; and when a new blank of the same
diameter is placed in position the crank is turned in a reverse direction until
the zero-mark is brought opposite or in line with said mark 31, thereby indicating
that the block 13 is in correct position-i.e., the one it before occupied. In
adjusting the roll R to a blank of a different diameter, the zero-mark, will, of
course, be opposite another index; the relation shown being merely to illustrate
the nature of the gage.
In Fig. 5 I have illustrated a blank 131 having threads cut thereon in the usual
manner; while the blank with the finished and precisionized cold-rolled thread
is designated by B in Fig. 6. To cold-roll the blank 13¹ it is first mounted between
the centers 2 and 3 of the lathe, the slide S being in such a position that the
normally stationary roll R' is clear of and is opposite an extreme end of said
blank, the roll R being also out of contact with the blank and opposite said
roll R. The slide S is then moved crosswise of the bed until the thread of the
roll R is opposite the cut-thread of the blank, after which the crank 24 is
manipulated to cause the thread of said roll R to enter the grooves between the
convolutions of the thread of the blank at a point directly opposite the roll R',
this relation of the parts being represented in Fig. 4.
It will be apparent that this means for rolling the thread of the blank is
self-centering and that if the roll R¹ is not quite up to the work it will be drawn
up by the crosswise movement of the slide S, which, in such a case, will begin
to draw the roll R¹ toward the blank as soon as the roll R is in engagement with
the latter, it being understood that as the turning of the crank 24 is continued,
the fixed nut 22, the section 41, and the slide S will move freely crosswise of the
bed toward the right, as seen in Figure 4, and will carry with them the roll R'.
The spindle 2 is then set in motion, and as the blank turns, the threads thereof
will rotate the rolls R and R¹, and as these rolls rotate, the upper section 41 of
the slide will, of course, be moved toward the shank 42 of the blank, the said
rolls, as they turn, cold-rolling the cut-thread to finish and precisionize the same.
When the blank has been cold-rolled, it is in the condition illustrated in Fig. 6;
and to remove the same from between the two centers, the crank 24 is first turned
to carry the roll R away from said blank, and subsequently the slide S is shifted
crosswise of the machine to the left, as seen in Fig. 4 to carry the threads of the
roll R¹ beyond the periphery of the rolled blank. The two rolls R and R' are of
substantially the same size, and their outside diameters are the same throughout the
length thereof, and the bottoms or bases of the threads of said rolls are of the
same width, but the widths of the tops or apexes of said threads gradually increase
from a V shape in the first convolution to a truncated form, the several threads
(see Fig. 7) being designated, respectively, by a, b, c, d, and e, and the two first-
mentioned ones being angular, while the three succeeding threads are of progres-
sively-increased widths at their truncated portions.

page_text: The blank B has comparatively wide truncated cut-threads, said threads being
reduced to the desired standard, and the diameter of the blank being increased
slightly, by the cold-rolling operation.
Un inspection of Figs. 7 and 8, it will be observed that the first convolution a of
the roll-thread displaces the adjacent convolution of the cut-thread of the blank
toward the longitudinal axis thereof and at the same time radially outward, and
that the next convolution b reduces the thread of the blank to
a' still
greater degree, this operation continuing until the thread has reached the requisite
standard at the time it leaves the last convolution e-of the roll. The apexes of the
several convolutions of the thread of the blank are at first caused to assume a
slightly concave form by the rolling operation, but this is wholly eliminated
by the contact of said convolutions with the bottoms of the grooves of the finishing-
threads of the rolls, as shown in Figs. 7 and 8. The rolling operation successively
densifies or compacts the metal and forces the same radially outward, the stippling
in Fig. 7 of the successive convolutions of the blank B showing the manner in
which the molecules of the metal are compressed. This peculiarity is also illustrated
in Fig. 9, the dotted line a indicating a convolution of the cut-thread before it
reaches the rolls R, R', and the lines b' c, d, and e' indicating the respective
compressions of the molecules of the metal by the rolls, and the blank-space
between the lines d' and e¹ indicating the condition of the metal at the last step
of the operation.
For the purpose of seating the threads of the rolls R and R' without the necessity
of adjusting the slide S or the blank with relation to said rolls, I prefer to make
one or both of the latter yielding in a longitudinal direction.
The shafts or pins 15 and 16 are mounted in the present case for slight move-
ment in the direction of their axes in their bearings in the blocks 12 and 13, and
said shafts 15 and 16 are encircled near their opposite ends (that is, between
the rollers and their bearings) by springs, as 45, (see Figs. 2 and 4,) which bear
against the blocks and the rolls, respectively, to hold the latter substantially
midway between the branches of said bearings.
In positioning the roll R with respect to the work, the thread of said roll may
squarely strike the thread of the blank, and as said roll is advanced the beveled
surface of the cut-thread of the blank acting against the corresponding surface
of the roll-thread, acts as a wedge and moves the roll in the direction of its length,
so that the thread of the roll can be accurately seated in the grooves of the blank,
the roll R being capable of the same operation. It will be observed that the
axes of the rolls are parallel with that of the blank, and for the purpose of adjust-
ing the rolls to enable them to operate on threads of varying inclinations they are
mounted for shifting movement relatively to the blank and independently of the
rotative and longitudinal movements hereinbefore mentioned. This adjustment
for effecting different degrees of angularity may be obtained by supporting the
rolls for bodily shifting movement in a plane transverse to the plane of the axis
of the blank, and is carried out as follows. The blocks 12 and 13, which constitute
convenient carriers for the two rolls, are preferably made cylindrical to conform
to and turn in the bore or passage 14 in the slide. Should a blank having threads
of different inclination from that represented in Fig. 5 be inserted between the
lathe centers, the rolls will automatically adjust themselves to said thread, the two
blocks rotating in their seats and the threads of the rolls instantly seating them-
selves in the grooves of the blank. The two blocks 12 and 13 are connected with
the screws 20 and 21, respectively, by couplings which permit the rotative move-
ment of said blocks around the screws, the latter terminating at their inner ends
in enlarged heads 50 and 51, fitting against plugs 52 and 53, respectively, which
are seated in the outer faces of said blocks. Flanged caps, as 54 and 55, secured
by screws or other suitable means to the blocks, hold the heads 50 and 51 in
place. By the connections described between the feed-screws and the blocks said
screws may be rotated to move the blocks in opposite directions, and the blocks

page_text: may also rotate independently of the screws to adapt the rolls to threads of different
inclinations.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. In a metal-working machine, the combination, with means for supporting
a blank having a cut-thread thereon, of means for cold-rolling said thread.
2. In a metal-working machine, the combination, with means for supporting
a blank having a cut-thread thereon, of rolls having accurate threaded surfaces
for cold-rolling said cut-thread to a precisionized form of standard size and gage.
3. In a metal-working machine, the combination, with means for supporting
a blank, of a threaded roll for rolling a thread previously formed on said blank,
said roll being shiftably supported automatically to adapt itself to threads of
various inclinations.
4. In a machine of the class specified, the combination, with means for support-
ing a blank, of a threaded roll in engagement with one side of a blank: a threaded
surface in engagement with the other side of said blank; a support for said roll
and threaded surface, said support being movable longitudinally of the blank; a
roll-carrier capable of automatic movement in the support to present the roll at
the desired angle to the blank; and means for adjusting the roll toward and
from the blank.
5. The combination, with a set of rolls, of a cylindrical support for each of said
rolls and in which the roll is loosely mounted, and springs bearing against each
side of the roll, the construction being such that the roll is permitted to have
a yielding movement transversely of its support.
DL 1511
L
1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.