Improvements in and in the Method of Manufacturing Taps for Tapping or Forming Screw-threads in Metal or other Substances.
Year: 1890

page_text: Date of Application, 2nd Dec., 1890
Complete Specification Left, 2nd Sept., 1891-Accepted, 24th Oct., 1891
PROVISIONAL SPECIFICATION.
Improvements in and in the Method of Manufacturing Taps for
Tapping or Forming Screw-threads in Metal or other Substances.
We, FRANCIS BUTTERFIELD of the firm of F. and J. Butterfield and Company
Limited, of Keighley in the County of York, Machine Tool Makers and Engineers,
and JAMES DAVIDSON of 10 Vicarage Park, Plumstead in the County of Kent,
Engineer, do hereby declare the nature of this invention to be as follows, that is
to say:
It relates to improvements in taps for tapping or for forming. screw-threads in
openings made in metal or other substances and consists of so forming or arranging
the cutting edges of these taps that they are enabled to cut deeper, clearer and
better threads, and that with fewer operations and less power, than can be cut with
taps as heretoforé constructed, and our invention further relates to the method of
manufacturing our said improved taps, the means employed being hereinafter
described.
As is well known the taps employed for the purpose above described have
heretofore been formed by the cutting edges on the helical ridges, following each
other in succession or in other words so following each other that if these ridges
were not interfered with by the flutings of the tap they would form a perfectly
continuous spiral-thread throughout the entire length of the tap, however in
accordance with our invention we remove, as by cutting away, each alternate
helical ridge in each series of ridges which are formed by the flutings so that' as the
tap thus formed is rotated each cutting edge is followed and preceded by a blank
part in the other or adjoining series of ridges, by which means more freedom of
action is allowed to each successive cutter with the result that a deeper cut may be
made at each operation without the possibility of undue friction being caused or
of the cutters being obstructed by the refuse and so endangering the stripping of
the thread as has heretofore been the case, in this manner the object desired is
attained.
The means employed in accordance with our said invention for removing or
cutting away the alternate ridges of the taps as above described, consist of a
milling-cutter formed with sufficient cutting-edges to take away all the helical
ridges, that are desired to be removed from each series, at one operation, and the
mechanism which is attached to the milling-machine for the purpose of carrying
or holding the tap thus to be operated upon, is arranged, by suitable wheel and
cam attachınents to be rotated at the proper rate of speed to hold said tap while
said operation is being performed after which it is arranged to cause said tap to
move laterally to bring the alternate ridges in the next series into position for
being operated upon.
Dated this 1st day of December 1890.

page_text: COMPLETE SPECIFICATION.
Improvements in and in the Method of Manufacturing Taps for
Tapping or Forming Screw-threads in Metal or other Substances.
We FRANCIS BUTTERFIELD of the firm of F. and J. Butterfield and Company
Limited of Keighley in the County of York, Machine Tool Makers and
Engineers, and JAMES DAVIDSON of 10 Vicarage Park, Plumstead in the County
of Kent Engineer 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, that is to say:-
It relates to improvements in taps for tapping or for forming screw-threads in
openings made in metal or other substances and consists of so forming or arranging
the cutting edges of these taps that they are enabled to cut deeper, clearer and
better threads and that with fewer operations and less power, than can be cut with
taps as heretofore constructed, and our invention further relates to the method of
manufacturing our said improved taps the means employed being hereinafter
described.
In the accompanying sheets of drawings
Fig. 1 is a side view and Fig. 2 a sectional end view of a tap made in accordance
with our invention.
Figs. 3 and 4 are part sectional end elevation and top views of mechanism
applicable for use in the manufacture of said taps, Fig. 5 being a drawing, in
detail, illustrative of a certain part of said mechanism.
Figs. 6, 7 and 8 are side, end and sectional end views respectively of a modified
form of mechanism which may be made use of instead of that shewn by Figs. 3
..and 4.
Fig. 9 is top view of a portion of the mechanism shewn by Figs. 6, 7 and 8.
Fig. 10 illustrates a device used in connection with the mechanism shewn by
Figs. 6, 7 and 8 as will hereinafter be described.
Similar letters and figures of reference indicate similar parts throughout the
several views.
As is well known the taps employed for the purpose of tapping or cutting screw-
threads. as above described, have heretofore been formed by the cutting edges a¹
on the helical ridges a following each other in succession or in other words so
following each other that if these ridges a were not interfered with by the
flutings they would form a perfectly continuous spiral-thread throughout the
entire length from the part c to the outer end of the tap, however in accordance
with our invention we remove, as by cutting away each alternate ridge in each
series of ridges a thus leaving between each of the remaining ridges a blank part d,
so that as the tap thus formed is rotated each cutting edge a¹ in each series of
ridges is followed and preceded by a blank part in the other or adjoining series
of ridges by which means more freedom of action is allowed to each successive
cutting edge with the result that a deeper cut may be made at each operation
without the possibility of undue friction being caused or of the cutters being
obstructed by the refuse and so endangering the stripping of the threads as
has heretofore been the case thus the object desired is attained.
The means employed in accordance with our said invention for removing or
cutting away the alternate ridges of the taps as above described consist of a
milling cutter e (which has continuous rotary motion imparted to it in the well
known manner) formed with sufficient cutting-edges to take away all the helical
ridges a that are desired to be removed from each series, at one operation and the
rotary spindle mounted upon the supports g for carrying or holding the tap a² in
position to be operated upon by the cutter e, is arranged to be rotated by the hand-
wheel through the medium of the worm h and wheel kits lateral motion (corre-
sponding in degree to the lateral distance traversed by each helical ridge of the

page_text: tap a² operated upon) being effected by the gearing wheels m n¹ and n imparting
motion to the screw o that causes the whole of the supports g and the parts
carried by same to slide upon the bed-piece p.
When the cutting operations on one series of helical ridges as above described
are completed, by the continued motion of the hand-wheel the spindle is further
rotated carrying in its said rotations an armr which is rigidly mounted upon it.
On this arm is mounted a ratchet which is sufficiently broad to enable it to
operate upon both the periphery of the cam plate t and the ratchet wheel u when
by an appropriately formed indent in said cam-plate t it is allowed to fall
into contact with said wheel u, so that at such times as said wheel u is thus
permitted thereby to be rotated (and which times are arranged to be on the
completion of the cutting operations as above described) by said wheel w being
attached to the wheel which gears with the wheel w mounted upon a supple-
mentary hollow screw so mounted as to enable it to impart extra sliding motion
to the supports 9 and parts carried by same the tap a² is moved to present its next
series of ridges to be operated upon by the cutter e.
Instead of the cutter e having a number of cutting edges as above described only
one cutting edge for removing each of the ridges singly, need be employed, however
this will require a sufficient number of repetitions of the movements above described
in order to enable it to complete the removal of all the ridges desired to be cut
away as will be readily understood.
7.
Again instead of the continuously rotating milling cutter e being employed, the
tap may be arranged to be thus continuously rotated, as by being mounted between
the rotary spindle 1 and the stationary spindle 2 of the lathe shewn by Figs. 6, 7
and 8, and the cutting tool 3 may be fixed upon and carried by the rest 4 in order
to remove the alternate ridges of the tap as is herein before stated.
To effect the necessary movements of the rest 4, which must be in perfect unison
with the rotary motion of the tap to be operated upon, and which must correspond
also to the pitch of thread on the said tap, the mechanism, hereinafter described,
is employed.
:
Rotary motion at the desired rate of speed is continuously imparted from the
spindle 1, by the gearing wheels 5, 6, 7 (this wheel 7 being rigidly mounted upon
the boss of the wheel 6 so that it may rotate with it) 8 and 9, to the screw 10 which
by the clutch, nut 11 (which may be moved into or out of gear with said screw 10
by the lever 12 operated by the handle 13, as and whenever the operative may
desire) imparts the sliding motion to the rest 4, by which means as the tap is
rotated the tool carried by the rest 4 may be moved a distance corresponding with
the pitch of the thread on said tap and at a rate of speed in unison with its
rotary motion.
To give extra lateral movement to the tool carried by the rest 4 and at the
proper time so that on the completion of the cutting operation for removing one of
the ridges, it (said tool) may be moved into the path of motion of the next ridge
to be thus operated..upon, the movements of the longitudinally sliding rest 4a
(upon which the cutting tool is actually mounted) is effected independently of the
movements imparted thereto by the screw 10. This independent or extra move-
ment is obtained by the screw 14 being operated through the gearing wheels 15, 16
16a and 17 by the ratchet wheel 18 which is rotated by the pawl 19 being mounted
upon its lever 20 which receives its reciprocatory motion from the crank wheel 21
through the medium of the rod 22. The rotary motion of this wheel 21 is obtained
from the spindle 1 (in order that it may be in certain uniformity therewith) by
means of the gearing wheels 5, 6, 23, 24, 25 and 26, rotary shaft 27 and gearing
wheel 28 (the wheels 21 and 28 are of the irregular shape shewn in order that quick
and slow motions may be imparted to the rod 22 so that when the rest 4a is to be
moved on the completion of a cutting operation as above described it may be thus
moved quickly). On the opposite end of the shaft 29 to that upon which the
wheel 21 is rigidly mounted, we mount a crank-plate 30 which by the rod 31
imparts a slightly advancing and receding motion to the rest 4 as also to the one 4a

page_text: and consequently to the cutting tool, by which means the body part of the tap a³
may be cut away or backed off nearer to the centre of said tap a² towards the
completion of each cutting operation than it is at the commencement thereof with
the result that same is not cut in a cylindrical but in an elliptical form, the
difference between the two being shewn in broken lines (which are cylindrical)
and full lines (which are elliptical) in Fig. 2, this formation of the tap a² enabling
it to perform its functions with less risk of being clogged by the refuse than would
be the case had it not to be thus cut away.
In order to ensure the rotary motion. of the tap a² being about its own axial
centre, it is mounted between the pointed ends of the spindles 1 and 2 and on the
spindle 1 is mounted so as to revolve therewith, the face plate 32, which has
jaws 33 arranged somewhat as has an ordinary chuck to lay loosely hold of the
squared end of said tap a² so that it is thereby caused to revolve while it is yet free
enough to be centred between and in line with the axial centres of the spindles 1
and 2.
The mechanism for imparting extra sliding motion to the rests 4 and 4a may be
dispensed with by substituting plane circular wheels for the elliptical wheels 21
and 28, and mounting a cam upon the plate 30. This cam being for operating the
rests 4 and 4a by the rod 31 being rigidly attached and not hinged thereto, by
which means on the completion of the operation of cutting one ridge the rest is
moved to carry its cutting tool entirely clear of the tap being cut until said tap has
revolved to carry its next ridge past said tool which is then advanced by the
actions of the cam and caused to remove the next ridge, a repetition of these
operations effecting the object desired, that is the removal of each alternate ridge.
When this last described mechanism is substituted for that shewn in the drawings,
the gearing wheels from the spindle 1 to the shaft 27 also require alteration in
order that said shaft 27 may impart motion to the rest 4a at the proper rate of
speed to suit its altered actions.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is
1. The formation or construction of a tap, for tapping metal or the like, by
removing or cutting away each alternate cutting ridge substantially as shewn and
for the purpose described.
2. The mechanism formed and arranged substantially as herein specified for
removing the alternate ridges of taps as set forth.
Dated this 1st day of September 1891.
FRANCIS BUTTERFIELD.
"JAMES DAVIDSON.
Per Samuel Hey,
Agent.