An Improved Machine for Milling Twist Drills.
Year: 1888

page_text: An Improved Machine for Milling Twist Drills.
I, AMOS WHITNEY, of No. 231 Lawrence Street, in the City of Hartford; in the
County of Hartford, and State of Connecticut, one of the United States of America,
Superintendent, do hereby declare the nature of my said invention, and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement :—
This improved machine cuts the spiral grooves of twist-drills, to have an increasing
pitch, and of decreasing depth measuring from the point of the drill toward the shank
thereof.
In the drawings accompanying and forming a part of this specification, Fig. 1 is a
plan of, a twist-drill-milling machine embodying my invention. Fig. 2 is a front
elevation of the machine, one of the milling-heads being removed. Fig. 3 is a hori- .
zontal vertical sectional elevation, illustrating more in detail the arrangement of the
several parts. Fig. 4 is an elevation of that end of the machine which is at the right-
band in Figs. 1, 2 and 3. Fig. 5 is a sectional elevation in line a a, Fig. 2. Fig. 6 is
a horizontal section through one of the milling heads. Fig. 7 is a detail drawing, in
two views, of the drill guide.
Similar characters designate like parts in all the figures.
The mechanisms of the machine, are supported on and by some suitable bed, A,
which may be set on pillars, or otherwise sustained in usual manner; they consist of
two milling heads, B 13, oppositely-disposed on one end of the bed; a drill-guide C,
set between said heads B B' the blank-carrying spindle D carried (directly or
indirectly) in bearings; feed-apparatus for simultaneously revolving and sliding said
spindle D; a pattern-apparatus for modifying the movement of said spindle, to
produce the desired increase of twist in the drill grooves; and cams or patterns

page_text: actuated and connected with the milling heads to govern the depth throughout their
length, of the drill grooves.
The bed A is shown to be of the form of a flat table, provided with bearings for the
shafts supported thereon, and fitted to have the several removable parts of the machine
attached thereto. On the front or left-hand end of this bed, the two milling-heads are
set in opposite and corresponding positions. As the said heads are duplicates except
as to arrangement, their several corresponding details are designated by the same
characters in each. A frame F has a base, 2, whereby it is bolted to the bed, A, by
screws 3; and has an upright part, 4, which is fitted to receive the vertically-movable
slide S. This slide is provided with two bearings, 5 being a clamp-bearing, for the
adjustable-bearing of the milling-spindle P, and 6, an ordinary bearing for the
hub 7, of the driving wheel S. In one milling-head, these bearings are below, and in
the other above, the plane of the drill blank. The milling spindle is fitted to carry
the milling cutter T; has collar-nuts 9 for adjusting in usual manner its position in
said slide bearing L; and is splined into the driving wheel, to be driven therefrom
in usual manner. Collar-nuts 10 on wheel-hub 7, serve to hold the wheel 8 in
proper longitudinal position. As shown in the drawing, and preferably, the wheel S
is a gear, driven by the pinion 81 on the hub of pulley N, which is carried on a
stud 8, that is fixed in slide S. The gears 8 8 being bevel gears, permit the pulleys
to be so placed as to be more readily belted to one ordinary driving shaft, which is not
shown.
The vertical adjustment of the milling slides S is effected by means of the
adjusting screw 12, properly squared at 11, which screw turns in the slide S, and is
tapped into the spindle 50; which is fitted to slide in said slide S, and passes down
through the table its lower end 13 resting on certain cams that will be hereinafter
described.
The drill-blank guide (consists of bracket, 16, suitably placed and secured
to the bed A, and a bushing or thimble 15, removably fixed in said bracket, and
perforated at 17 18 for the upper and lower milling cutters, respectively. One of
the bushing 15 is provided for each diameter of drill which is to be grooved by the
machine.
The spindle D is to be fitted with some suitable means, as chuck 19 or other well-
known device, for holding the drill-blank, 20, and is to be supported in axial alignment
with the aforesaid bushing 15 of the drill-guide C. One end of said spindle (the
right-land end in this instance) has a thread, 21, which engages with a corresponding
internal thread in the hub, 23, of the gear 24; which gear is supported by said hub
in the bearing 25 on bed A. The gear 24 is (or may be) a worm-gear, being driven
by the worm 27 on driving-shaft 28, which shaft is carried in bearings 3, and is itself
driven by a pulley 31. A hand-wheel, H, on shaft 28, is provided for operating the
feed-mechanism by hand. By these means, a longitudinal movement is imparted to
said blank-carrying spindle.
The opposite end of spindle D has a spline, 32, and is fitted to slide through (but
not to turn within) the hub 33 of the worm-gear 34; which gear is carried by its
said hub in bearing 35 on beu A. The usual nut or collar 37 is provided to hold said
gear in place in said bearing. A worm, 36, carried by shaft 40, meshes witli said
gear 34, and is driven by means of connecting shafts and gearing from the gear 42
on the aforesaid hub 23, of gear 24. The shaft 40 extends through the hub 41 of the
bevel-gear 43 (carried in bearing 51) and is splined thereto in usual manner. Gear 42
meshes with gear 44 on shaft 45, which is provided at the opposite end with the change-
wheel 46, that is connected by intermediate wheel 47 with the aforesaid driving
gear 42. Shaft, 45 is carried in bearings 48 49, and by means of the change-
gearing 42, 46, 47, may be driven at any required speed relative to the feed-nut (or
hub) 23. The intermediate change-gear, 47, is carried in usual manner by the stud 53,
which is adjustably fixed in the adjustably-fixed arm 34.
For producing the required increase of pitch in the drill grooves, I employ a
can, M, having a pattern groove, 60, formed therein, of suitable character for the
required purpose. Said cam M is carried on the shaft 61, which turns in

page_text: bearings 62 63, on bed A. This shaft 61 is about parallel to shaft 40, and has a
worm-gear. 65, whereby the same is driven from worm 66 on shaft 45; by this
means, cam M has a simultaneous and normally-corresponding rotary movement
relative to spindle D.
The forward end of shaft 40 is carried in a slide, or sliding bearing, 70, (being held
therein by nuts 69,) which is fitted to slide in the bearing 68. Said slide has an
arm 72, which reaches out through the guide slot 71 in said bearing, and enters the
groove 60 in cam M. As the can revolves, the slide is thus moved endwise, carrying
with it the worm 6, which then acts as a rack to revolve spindle D. This auxiliary
movement modifies the normal movement imparted to said spindle by the gearing
hereinbefore described, such modification being governed by the shape of said cam-
groove 60. It is contemplated to use different cams M, as the drills to be grooved
may require.
The vertical adjustment of the cutters T, and the means therefor, have already been
described. But the slides S have, also, a working movement for the purpose of
governing the depth of the drill-groove throughout the different parts of its length.
For this purpose the spindles 50 pass downward and rest on cams 80 80, respectively,
which cams are removably-fixed on a shaft, 82, that is carried in bearings underneath
said slides S. Shaft 82 has a gear, 81, meshing with gear 83, on shaft 84; and this
latter shaft has a spiral-toothed gear 85, meshing with the similar gear 86, on shaft 61.
By this means the cams 80 move in unison with cam M, and spindle D. The slides S
are moved down by stout springs 88, on pull-rods 90, that are attached to said slides.
The cams 80 are made of such external conformation as required for producing the
desired variation in the depth of the cam grooves; and they are set on their shaft one
oppositely to the other, so that when one slide (carrying the cutter above the drill)
goes up, the other slide will go down.
The operation of my machine is as follows: The milling cutters being properly
driven, the drill blank 20 is secured in the chuck of spindle D, which is fed forward
by hand until the point of the blank enters the bushing 15, ready to begin milling.
The shaft 28 is now set rotating in proper direction by a belt on pulley 31, from a
countershaft not shown. This imparts motion to the several shafts and wheels, as
shown by arrows thereon, and gives to spindle D rotating and advancing motions, of
which the former is modified as required by the cam M. At the same time, the
cams 80 separate the cutters, to give the proper variation in the depth of the two
opposite spiral drill-grooves. The drill being milled for a sufficient distance, the
shaft 28 is stopped, and the spindle D then retracted by hand; the drill is removed,
and the several operations repeated as before.
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 1
clain is:
1. The combination of the splined and threaded spindle D, the feed-nut engaging
the thread on said spindle, the worm-gear splined to said spindle, a worm meshing
with said worm-gear, the cam, M, connecting shafts and gearing simultaneously
rotating said worm and the feed-nut and cam M, said cam being operatively
connected to slide said worm during the rotary movement thereof, substantially as
described.
2. The combination of the spindle D, the driving wheel 34 splined thereto,
worm 36 on shaft 40, slide 70, and the cam geared to revolve in unison with shaft 40,
the slide being connected to be actuated from said cam, all substantially as described.
3. The combination in a twist-drill-milling machine, of the spindle D, the increase-
pitch feed-apparatus substantially as described, the oppositely-disposed milling heads,
and lifting cams operating the slides of said heads, said lifting cams being geared
to move in unison with the pattern-cam of said apparatus, all substantially as
described.
4. The combination in a machine of the class specified, of the slide S, cam 80, and

page_text: spindle 50 bearing on said cam, and adjustably-fixed in said slide, all substantially as
shown and described.
5. The combination with spindle D, and with shafts 40 and 61 geared together as
described, of gear 34 splined to said spindle, worm 36 on shaft 40, the pattern-cam,
bearing 68 having slot 71, and slide 70 having arm 72 working in said slot in
engagement with said cam, all arranged and operating substantially as described.
6. The combination in a machine of the class, specified, of the two slides S S, one
carrying a cutter-spindle above, and the other carrying such spindle below, the drill
blank, shaft 82, and cams 80 80, oppositely-placed on said shaft, whereby one slide is
moved up while the other moves down, substantially as described, and for the purpose
specified.