Note: Descriptions are shown in the official language in which they were submitted.
~787~
The present invention relates to a helical twist drill havin~
internal cooling channels.
Twist drills of thi~ type, made of high-speed steel, are already
known, and achieve high cutting speeds. In such high-speed steel units, the
shank and the cutter section can be made in one piece, even though this can
re6ult in production difficulties since the shanX and the cutter section
require different trsatment. When made from a combined shank and socket, with
a hard-metal cutter tip attached to the socket, there can be difficulties in
connecting the cooling channels formed within the carrier tip to the shank or
socket section. In this latter structure, the possibilities for reBrinding
are greatly restricted.
It is an object of the present invention to produce high-performance
twist drills which can be made very simply but nevertheless deliver greatly
increased cutting performance.
The concept of a twist drill embodying the present invention permits
its production from two separately manufactured parts, namely, a cutter
section having uninterrupted flutes extending its entire length, and the
shank. A cylindrical section of material of any length can thus be fluted, so
that, either subsequently or even during the fluting process, it can be
divided into smaller sections of desired length. When the shank and the
cutter section are assembled it is possible to achieve reliable sealing of the
cooling channels agalnst leakage into the chip space by comparatively simple
means at the matching surfaces between the cutter section and the shank.
Since the transmission of torque from the ghank to the cutter section can take
place in such a twlst drill where the receg~ in the ghank matches the outer
surface of the cutter section preferably throu~h the outer surfaces of the
drill lands, which are soldered to the inner surfaces of the shank, there is
no significant extra expenditure involved in production. In ad~ition, during
soldering to the ed8es of the drill lands, a resultant bead of soldering
material pro~ects sli8htly into the grooves, and further improves the torque
transmission. At the end of the service life of the cutter section, it can
simply be removed from the shank at minimum expense, and the shank can be
reused. Longer overall service life of the twist drill results from the fact
that, the cutter section can be repeatedly reground right up to the place
where it enters the shank.
PAT 10757~
1'~787~0
Assembly and dismantling of the twist drill are greatly simplified
with the sbank being cylindrical and conforming to the outside diameter of the
cutter section. It has been shown that soldering at the outer surfaces of the
drill lands is quite sufficient to transmit even the highest torques
encountered, provided that the dimensions of the matching surfaces are
properly selected.
A Dy a ~ 6 the coolant channel in the shank to the channels in the
cutter section with direct face contact at the bottom of the recess prevents
leakage into the spaces formed by the flutes.
When the contact surface between cutter section and shank ls formed
by the bottom of the recess, it is simpler to connect the cooling channels in
the cutter section with that in the shank.
The arrangement of a cooling channel transition element, between the
shank and the cutter section makes it possible to dispense with any special
measures in the shank or cutter section, it being possible to configure the
cooling channels formed in the individual parts independently of each other.
The face surfaces of the cutter section arranged in the recess can be
provided with a radial transverse channel which connects the opening surfaces
of the cooling channel w~th each other to simplify connection of the cooling
channels in the cutter sectlon wlth those of the coollng channel transltion
element of the shank, respectlvely.
As an alternat~ve to this, it can be expedlent to slot the channel
transition element, and use it for purposes of sealing and force transmlsslon.
The installation of adhesive between the shank and the cutter
6ection, in the area of the opening of the recegs, increase~ the bond between
the cutter section snd the shank, and prevents any chips enterin8 the recess.
When the recess 18 conflgured witb a helical internal thread section
a substantially continuous, even flow of the load from the shank into the
cutter sectlon is possible. ~his effect i8 enhanced if the thread extends
axially the whole length of the recess.
A shaped plate closing off the opening to the recess permits the
transmission of force by form fit, without the need for any special shaping of
the recess in the shank. Depending on the type and manner of production, the
plate can be produced in one piece with the shank, or can be produced
separately and fixed rigidly to the shank.
PA~ 10757-1
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1',~787~0
A configuration where the peripheries of the cutter section and shank
are shape locking, permits a considerable reduction in the surface required
for the transmission of torque, this surface being enlarged only slightly by
the configuration of the slot recess or the connector channel sections to
connect the cooling channels in the cutter section to the shank, respectively.
Where the shank or its section forming the recess is cast, the recess
and in particular the elements within it effecting the transmission of forces,
can be produced simply and with a high degree of precision.
More particularly in accordance with the invention there is provided,
a twist drill having internal cooling channels, comprising a shank and a
cutter section, and having at least two helical flutes forming a chip space,
characterized in that the cutter section is entirely of hard metal, has flutes
which extend its whole length, and is connected with its end section remote
from the tip of the drill to the shank by face surfaces formed on it and on
the forward end section of the shank, said end section being inserted into a
matching recess in the shank: and, the cooling channels being sealed off from
the chip space by means of soldered matching surfaces between the cutter
section and the shank.
Specific embodiments of the invention will now be described with
reference to the accompanying drawings in which:
Figure 1 is a plan view of a twist drill when assembled;
Figure 2 shows the cutter section of the twist drill in side view;
Figure 3 shows the cutter section in cross-section;
Figure 4 is the shank in side axial section:
Figure 5 is a section on line V-V of Figure l;
Figure 6 is an exploded view of a second embodiment of the twist
drill:
Figure 7 i9 an axial section oE an embodiment of the shank of the
second embodiment of the twist drill;
3Q Figure 8 is an axial section of a further embodiment of the shank of
the second embodiment of the twist drill:
Figure 9 is an axial section through the shank, helically grooved,
accommodating the adjacent end section of the cutter section:
Figure 10 is a partly sectional view of the connection between the
shank and the cutter section of the twist drill
Figure 11 is a front view of the cooling channel transition element
12q87~0
shown in Figure 10;
Figure 12 i9 a partly sectional view of another connection similar to
that shown in Figure 10;
Figure 13 is a front view of the cooling channel transition element
shown in FigurQ 12,
Figure 14 is a partly sectional view of yet another connection,
similar to that shown in Figure 10;
Figure 15 is a front view, of the cooling channel transition element
shown in Figure 14;
Figure 16 is a front view of a radial transverse channel connection
in the cutter section;
Figure 17 is a front view of a transverse channel connection in the
cutter section confi~ured differently;
Pigure 18 is a partly sectional view of a connection between the
cutter section and the shank, both bein8 of the same diameter;
Figure 19 i8 a front view of the shank of a fourth embodlment of the
twist drill;
Figure 20 is a section along line A-A of Figure 19, showing in
addition the ad~acent end of the cutter section;
Flgure 21 is a section along line B-B of Fl~ure 20;
Figure 22 is a front view of the shank portion of a fifth embodiment
of the twist drlll;
Figure 23 i0 a sectlon along line A~A of Pigure 22, additionslly
showing the ad~acent end of the cutter section;
Fi~ure 24 is an exploded view Oe the transitlon zone of the twist
drill of Figures 22 and 23;
Figure 25 i8 an exploded vlew of the transition zone of the twist
drill, in which two connector channel ~ections sre provided.
The twist drill 10 shown in Pigures 1 to 4 is divided essentially
~0 into two sections, the cutter section 12 and the shank 14.
The cutter section 12 is entirely of hard metal and, in the
embodiment ~hown, has two flutes 16, 18 on the outside surface of the cutter
section 12 staggered by 180 degrees relative to one another and which
constitute a chip space through which the shavings are removed from the bottom
of the drilled hole.
PAT 10757-1
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78~7~LO
The flute~ 16, 18 are definea by two drill webs 20, 22 within each of
which there i8 a cooling channel 38, 40 set radially outwards from the axis of
the bit. The outer surfaces of the drill webs 20, 22 have lands, by which the
cutter section 12 of the twist drill 10 is guided or centered, within a
drilled hole. The shank 14 serves to transmit the forces to the cutter
section 12 being connected by a slip-free coupling to the output shaft of the
drill motor.
To connect to the cutter section 12, the shank 14 is provided, as
~hown in Figure 4, with a recess 24, the inside diameter of which is
approximately the ssme as the outside diameter of the cutter section 12.
Within the area of the opening surface of the recess 24 the outside surface of
the cutter section 12 is connected to the inner wall of the recess 24 within
the shank 14, as is shown in Figure S. The lands are soldered to the inner
wall of the recess 24 and adhesive 19 is placed in the flutes close to the
opening surface. The adhesive bond formed is intended to last throughout the
service life of the twist drill 10 and serves to fill the cavity formed by the
flutes 16, 18 in the area of the opening surface, to prevent the ingress of
chips into recess 24 within shank 14.
In a further embodiment, shown in Fi~ure 6, the outer end of the
reces6 24 is closed by a plate 26. The plate 26 forms an opening, whose
cross-section matches that of the cutter section 12. The end of the cutter
section 12 remote from the tip of the drill ia slid axially through the plate
opening 26 and lnto the reces~ 24, by giving it a rotary motion requlred by
the form fit, until lts tip reqts against the bottom of the recess 24. In
this embodiment, torque for th0 drill is tran~mltted essentially from the
shanX 14 by m0ans of the shape and force lockin6 fit betwe0n the plate 26
~connectQd rigidly with the ~hank 14) and the cutter s~ction 12. The soldered
joint between the correspondlng mstching surfaces in the bottom of the recess
24 which have atill to be described, prevents cooling medium escaping into the
chip space. The chemical resistance of this goldered connection must be
sufficient to prevent corrosive action by the cooling medium throughout the
service life of the cutter section 12.
Instead of the arrangement shown in Figure 7, in which the plate 26
is shown as a separate element fixed rigidly to it, the shank 14 can be formed
in one piece with an annular projection 28, the cross~section of which matches
PAT 10757-1
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lZ787~0
the plate 26 overall and which projects radially inwards, as is shown in
longitudinal section in Figure 8.
Figure 9 shows the shank 14 of the twist drill 10, which has an
internally threaded section 15 configured to correspond to the shape of the
cutter section, the overall axial overlapping length between the cutter
section 12 and the shanX 14 being usable for transmission of working loads.
Figureæ 10 to lS show embodiments of the connection between the
cooling channels 38, 40 of the cutter section 12 to the cooling channel 44 of
the shank 14 and for sealing the connection. Between the face side of the
cutter section remote from the drill tip and the bottom of the recess 24 in
the shank 14 there is in each instance a cooling channel transition element
28, 30, 32. This element is connected to both the shank 14 and to the cutter
section 12 80 as to be leakproof. There is thus no need for additional
measures to ensure a seal between the cooling channels and the chip space.
Since the connecting surfaces between the shank 14 and the cutter section 12,
which serve to transmit the forces encountered, are not exposed to the cooling
medium, they can be made more cheaply, or in certain circumstances, be
dispensed with when torque being transmitted by shape or force locking.
The coolin~ channel transltion element 28 shown in Figures 10 and 11
Z0 has two separate cooling channel sectlons 34, 36; these are parallel and
extend in the axial direction of the drill 10, thereby connecting the cooling
channels 38, 40 of the cutter sectlon 12 separately, with a wider sectlon 42
of the end of the cooling channel 44 in the shank 14.
The cooling chsnnel transition element 30 ~hown in Figures 12 and 13
has two mutually inclined cooling channel gectlong 46 and 48; each runs from a
common connectlon 50 in the cooling channel 44 of the shank 14 to a respectlve
end opening of the cooling channels 38, 40 o the cutter sectlon 12.
Fi~ures 14 and lS show a cooling channel transitlon element 32 w~th a
slot 49, through which the whole centre section of the face end of the cutter
section 12 located within the recess 24, and thus the two open end surface of
the cooling channels 38, 40 of the cutter section 12 are connected to the
cooling channel 44 in the shank 14.
Where the cooling channel transition element has only one opening,
which does not cover both the openings of the cooling channels 38, 40 formed
in the cutter section 12, a groove-like depression 52 is formed in the
PAT 10757-1
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~'~7B7~0
corresponding face surface 13 of the cutter section 12 as a transverse channel
connection extending across the total diameter of the cutter section 12 or, as
in Figure 17, only across its mid-section.
With a cutter section diameter approximately the same as that of the
shanX 14, an assembly section 56 is formed in the end section of the cutter
section remote from the cutting tip by a radial step or necked-down section,
used to join both parts. The outside diameter of this assembly section 56
corresponds to the inside diameter of the recess 24 formed in the shank 14
An embodiment is shown in Figure 18.
The shank 14 shown in Figures 19 to 21 has a face side 13a in the
transition section, and this is formed by a hollow-edge recess 14b. The two
flat surfaces forming the recess 14b intersect in the middle of a slot 14a
which connects the openings forming the cooling channels 38, 40 in the face
side 13 of the cutter section 12, with the central cooling channel 44 in the
shank 14. The faces 13 and 13a are soldered to one another, which prevents
leakage of coolant into the chip space formed by the flutes 16, 18. Effective
transmission of the torque is ensured by the ghape locking fit particularly at
the periphery of the twist drill where the prism-shaped tip of the end of the
cuttsr sectlon 12 enga8es in the reces~ 14b in the shank 14.
Figures 22 to 24 show a twist drill similar to the one described
above but, in this instance, the prism-ghaped tip 13 of the cutter section 12
and the hollow wedge recess 14b of the shank 14 are interchanged. The
functlons and the effects correspond to those describQd for the embodiment of
Figures 19 and 20.
Flgure 25 shows an alternative posslbility for the connectlon for the
cooling chsnnels 38, 4Q Oe a twist drill simllar to the one shown in Figures
19 to 24. Here, connecting channel sections 14d and 14e are formed in the
transition zone between the shank 14 and the cutter section 12, in place of
the slot reces~ 14a. These connect each cooling channel 38, 40 individually
with the cooling channel 44 in the shank 14.
PAT 10757-1
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