Note: Descriptions are shown in the official language in which they were submitted.
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DRILLING TOOL FOR METALLIC MATERIALS
The ~nvent~on relates to a drllling tool for metall~c
materials, compr~s~ng a holder hav;ng an ax~al clamping slot ~n
which a plate-shaped drilling blade is ~nserted to bear against the
base surface of the clamp~ng slot and is clamped against a limb of
5 the clamping slot by means of at least one threaded pin, which is
provided with a head and which engages ~n a bore in the drilling
blade and in a bore in said limb of the clamping slot, wherein the
center axis of the bore in said limb of the clamping slot is offset
relative to the center axis of the bore of the drilling blade and at
10 least one of two mutually facing c~rcumferential edges of the
threaded pin and the bore of the drilling blade is bevelled, and
further comprising a centering p~n which is inserted in the holder
and engages in a centering slot in the s~de of the drilling blade
adjacent to the base surface of the clamping slot so as to center
15 tl~e drilling blade with respect to the rotational axis of the
hol der .
In the case of this known drilling tool (German patent
specification 32 04 210 C2) the tolerance range of the nominal width
of the centering slot must be so selected that the centering slot
~0 exhibits an excess dimension relative to ~he nominal diameter of the
centering pin so as to be able to guide the centering pin into the
centering slot. This has the consequence that the drilling blade
cannot be precisely centered relative to the rotational axis of the
holder or drilling tool. The result is an inexact rotational course
25 of tlle drilling blade, particularly of its tip.
Tlle invention has as its object the provision of a drilling
tool of the kind stated in the preamble in which a precise centering
of the drilling blade is poss~ble.
According to t~le invention this object is attained in the case
30 of a drilling tool of the k~nd stated in the preamble in that the
nominal width of the centering slot is selected to be greater than
that of the portion of the centering pin engag~ng in the centering
slot and that the direction and amount of the offset of the center
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axes of the bore of the drilling blade and bore of the limb of the
clamping slot are so selected that in the tightened state of the
threaded pin only one side face of the centering slot bears on one
side of the centering p~n ~n the centered pos~tion of the drilling
5 blade.
In this construction the tolerance range of the position of
the s~de face of the centering slot bear~ng against the centering
pin can be selected to be as small as desired, so that a very
prec~se centering of the drilling blade and thus an improved
10 rotational course, particularly of the drilling blade tip, is
poss~ble. This gives a longer edge life of the drilling blade.
Preferably it is ensured that the centering slot extends in
the direction of or obliquely relative to the rotational axis of the
holder and the direction of the offset is so selected that the
15 drilling blade in the tightened state of the threaded pin is pressed
against the base surface of the clamping slot by a first clamping
force component and, at sa~d one side face of the centering slot,
against said one s~de of the centering pin by a second clamping
force component. This construction guarantees that the drilling
20 blade bears not only in a radially firm manner aga~nst the centering
pin, but also in an axially firm manner against the base of the
clamping slot, so that vibrations of the drilling blade or drilling
tool during drilling are largely avoided.
It is particularly advantageous if the mutually adjacent side
25 faces of the centering slot and centering pin are flat. The
contacting faces are thereby subjected to a lower contact pressure
and accordingly to a lesser deformation than in the case of a line
contact, which in turn increase the accuracy of the centering.
It can be ensured that the centering pin passes throug~l t~le
30 clamping slot and the centering slot and engages at both ends in
bores of the limb of the clamping slot. In this construction the
centering pin is radially supported at its two ends. It can
therefore bend less easily by comparison w~th mounting at one end.
This also contributes to increasing the accuracy of the centering.
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The invention and developments thereof are descrlbed in more
detail in the following by way of embodiments wlth reference to the
drawing, in which
Fig. 1 is an exploded view of one end portion of a
drilling tool according to the invention;
Fig. 2 is a plan view of said one end portion of the
drilling tool according to claim 1, in assembled
and partly broken-away state;
Fig. 3 is a part of the section III-III of Fig. 2;
Fig. 4 is the section IU-IV of Fig. 2;
Fig. 5 is an exploded view of one end portion of a
second embodiment of a drilling tool according
to the invention;
Fig. 6 is a plan view of the end portion according to
Fig. 5, in assembled and partly broken-away
state;
Fig. 7 is a part of the section VII-VII of Fig. 6;
Fig. 8 is the section VIII-VIII of Fig. 6;
Fig. 9 is a side view of the end portion according to
Fig. 6;
Fig. 10 is an exploded view of one end portion of a
third embodiment of a drilling tool according to
the invention;
Fig. 11 is a plan view of the end portion according to
~ ~ Fig. 10, in assembled and partly broken-away
state;
Fig. 12 is a par~ of the section XII-XII of Fig. 11;
Fig. 13 is the section XIII-XIII of Fig. 11;
Fig. 14 is an exploded view of one end portion of a
fourth embodiment of a drill ing tool according
to th e i nvent i on;
Fig. 15 is a plan view of the end portion according to
Fig. 14, in assembled and partly broken-away
state;
Fig. 16 is a part of the section XVI-XVI of Fig. 15;
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Fig. 17 is the section XVII-XVII of Fig. 15;
Fig, 18 is a side view of the end portion according to
Fig. 15;
Fig. 19 is an exploded view of one end portion of a fifth
embodiment of a drilling tool according to the
i nventi on;
Fig. 20 is a plan view of the end portion according to
Fig. 19, in assembled and partly broken-away
s tate;
Fig. 21 is a part of the section XXI-XXI of Fig. 20;
Fig. 22 is the section XXII-XXII of Fig. 20;
Fig. 23 is a side view of the end oortion according to
Fig. 20;
Fig. 24 is an exploded view of one end part of a sixth
embodiment of a drilling tool according to the
invention;
Fig. 25 is a plan view of the end portion according to
Fig. 24, in assembled and partly broken-away
state;
Fig. 26 is the section XXVI-XXVI of Fig. 25; and
Fig. 2~ is a side view of the end portion according to
Fig. 25.
The drilling tool according to Figs. 1 to 4 comprises a holder
1, a drilling blade 2 and two threaded pins 3 in the form of
25 setscrews.
The end portion of the holder 1 t~lat is not illustrated is
clamped in a drilling machine. The end portion that is illustrated
has a clamping slot 4 in the free end and two swarf discharge
grooves 5, which are diametrically opposite one another with respect
30 to the rotational axis 6 of the holder 1 or drilling tool.
The clamping slot 4 is bounded by clamping surfaces 7 of the
clamping slot limbs 8. The base surface 9 of the clamping slot 4 is
disposed at a right angle to the rotational axis 6 and the clamping
surfaces ;'. A cylindrical centering pin 11 is inserted, by a p~ess
35 fit, into a bore 10 in the base surface 9 of the clamping slot 4,
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the bore be1ng coaxial with the rotational axis 6. Each clamping
slot limb 8 is provided w~th a threaded bore 12, the center ax~s 13
of which is disposed perpendicularly to the clamping surfaces 7, and
at a spac~ng laterally from the rotational axis 6 lies In a
S respective one of the regions of the holder 1 left untouched by the
swarf discharge grooves S.
The drilling blade 2 has a drilling tip, which in the
assembled state of the drilling tool projects beyond the free end of
the holder 1, with cutter sections'14, which include an obtuse
angle. A respective bore 15, one circumferential edge 16 of which
is conically bevelled, is formed in the drilling blade 2 on each
side of the rotational axis 6.
The surface 17 of the drilling blade 2 facing away from the
drilling knife tip is disposed perpendicularly to the plane of the
drilling blade 2 or to the rotational axis 6 and serves for abutment
of the drilling blade 2 with the base surface 9 of the clamp~ng slot
4. Formed in this surface 17 is a centering slot 18, which is
right-angled in the plan view according to Fig. 2 and the nominal
width of which is selected to be greater than that of the portion of
tlle centering pin 11 engaging in the centering slot. The centering
slot 18 lies, in the plan view according to Fig. 2, eccentrically of
the rotational axis 6, wherein 1ts slde faces 19 and 20 are disposed
at both sides of the rotational axis. The centering slot 18 serves
for reception of the centering pin 11, so as to center the drilling
blade 2 in the holder 1.
Each threaded pin 3 has a head 21 with a circumferential edge
22, which is conically bevelled at the same angle as the
circumferential edge 16 of the bores 15, and an externally threaded
shank 23, which fits in a respective one o'F the threaded bores 12.
The center ax~s 24 of the bore 15 at the right in Fig. 2 or of the
circumferential edge 16 thereof and the center axis 13 of the
assoc~ated bore 12 of the clamping slot limb lie in a transverse
plane of the holder 1, which coincides with the plane of the section
III-III and includes an acute angle with the rotational axis on the
side of the tip of the drilling blade 2, wherein the center axes 13
and 24 are offset relative to one another in the mentioned
transverse pl ane so that the center axi s 24 of the bore 15 of the
. , .. _ ...... . .
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drilling blade 2 or the circumferential edge 16 thereof has a
somewhat greater spacing from the base surface 9 of the clamping
slot 4 and from the rotational axis 6 than the center axis 13 of the
threaded bore 12 formed in the clamping slot limb 8 which is at the
5 right in Fig. 2.
The center axes of the bores 12 and 15 at the left in Figs. 1
and 2 thereagainst lie in a plane parallel to the plane of the
section III-III, wherein their spac~ngs relative to the base surface
9 and rotational axis 6 are the reverse of those in the case of the
center axes 13 and 24, illustrated in Fig. 3, of the bores 12 and 15
at the right in Figs. 1 and 2. The direction and amount of the
offset of the center axes 13 and 24 are in that case so selected
that in the untightened state of the threaded pins 3 only the one
side face 20 of the centering slot 18 bears against the one side of
the centering pin 11 in the centered positlon of the drilling blade
2, as is illustrated in Fig. 2. This construction has the advantage
that the position of the side face 20 of the centering slo~ 18
coming into contact with the centering pin 11 on tightening of the
threaded pin 3 can have a very closely dimensioned tolerance, so
that the drilling blade is centered as precisely as possible, which
improves the rotational course of the drilling blade 2, particularly
of its tip, and prolongs the edge life of the drilling blade 2. At
t~le same time the threaded pin 3 exerts, by its head 21, a first
clamping force component against the base surface 9 of the clamping
slot 4 and, by the one side face 20 of the centering slot 18, a
second clamping force component against the one side of the
centering pin 11. The drilling blade 2 is therefore pressed axially
firmly against the base surface 9 of the clamping slot 4 and
radially against the centering pin 11. The drilling blade 2 is thus
secured against vibrations during drilling to a particularly high
degree .
The second embodiment according to Figs. 5 to 9 differs from
tlle first embodiment according to Figs. 1 to 4 merely in that the
portion of the centering pin 11a engaging in the centering slot 18
is formed as a square (see Figs. 5 and 8 in particular), so that the
mutually adjacent side surfaces 2P and 25 of centering slot 18 and
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centering pin 11a are flat and thus bear aagainst one another over a
large area and are subjected to a smaller deformation than in the
case of the line contact in the first embodiment. This contributes
to further Increase ~n centerlng accuracy.
S The third embodiment according to Figs. 10 to 13 differs from
the first embodiment only in that the bore 10 is not coaxial with
the rotational axis 6, but laterally displaced relative to this so
far that its center ax~s 26 intersects the center axis 13 of the one
(at the r1ght in Figs. 1û and 11) threaded bore 12 and the center;ng
1û slot 18 is formed to be continuous to the one (at the right in Figs.
10 and 11) bore 15 of the drilling blade 2, wherein the centering
slot 18 is not only wider than the center~ng pin 11, but also
somewhat wider than the diameter of the threaded shank 23 of the
threaded pin 3. This construction has the advantage that the one
(at the right in Figs. 10 and 11) threaded pin 3 does not have to be
completely unscrewed from its clamping slot limb 8 for exchange of
the dri l l ing bl ade .
The fourth embodiment according to Figs. 14 to 18 differs from
the third embodiment according to Figs. 10 to 13 substantially only
in that the drilling blade 2 has only one bore 15 and also only the
one clamping slot limb 8 is provided w~th a threaded bore 12.
Correspondingly, also only one threaded pin 3 is provided.
Moreover, the bore 10 for reception of the centering pin 11 extends
perpendicularly to the clamping surface 7 of the one clamping slot
limb 8 and through this clamping slot limb 8. The bore 10 also in
part penetrates the one swarf discharge groove 5. rhe centering
slot 18 then extends obliquely to the rotational axls 6, wherein ~t
includes an acute angle with the rotational axis 6 on the side of
the drilling blade tip. In this embodiment, too, the drilling blade
in the tightened state of the threaded pin 3 is pressed by a first
clamping force component against the base surface 9 of the clamping
slot 4 and by a second clamping force component, at the one side
face 20 of the centering slot 18, against the one side of the
centering p~n 11. Due to the inclined course of the centering slot
18 in conjunction with the arrangement of the center~ng p~n 11
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perpendicular to the clamping surface 7 and the cylindrical form of
the pin an additional axial clamping force component is exerted on
the drilling blade 2 in the direction of the base surface 17 when
the threaded pin 3 is tightened. In addition, the side face 20
5 engages slightly behind the centering pin 11, so that the centering
pin 11 also offers an additional axial support for the drilling
blade 2 against axial withdrawal from the clamping slot 4. The
threaded pin 3 then does not need to.be completely unscrewed from
the threaded bore 12 for exchange of the drilling blade 2. Also,
10 the clamping by a second threaded pin 3 and the formation of a
second threaded bore 12 are superfluous.
The fifth embodiment according to Figs. 19 to 23 differs from
the fourth embodiment according to Figs. 14 to 18 only in that the
bore 10 serving for reception of the centering pin 11 extends at the
15 same angle obliquely relative to the rotational axis as the
centering slot 18. The manner of effect is therefore practically
the same as the fourth embodiment.
The sixth embodiment according to Figs, 24 to 27 differs from
the fifth embodiment according to Figs. 19 to 23 for one thing in
20 that the centering pin 11 penetrates the clamping slot 4 and the
centering slot 18 and engages at both ends in bores 10 of the
clamping slot limb 8. Here, too, the centering slot 18 includes an
acute angle with the rotational axis 6 on the side facing the
cutting blade tip. Thereagainst, the side of the centering pin 11
25 adjacent to the side face 20 of the centering slot 18 faces away
from the threaded pin 3 and the offset of the center axes 13 and 24
is selected to be in the opposite direction to the offset in the
case of the fifth embodiment. In this sixth embodiment, too, by
virtue of the inclined course of ~he clamping slot 18 and the side
30 face 20, which co-operates with the side of the centering pin 11
facing away froln the threaded pin 3, of the clamping slot 18, the
drilling blade 2 in the tightened state of the threaded pin 3 is
pressed by a first clamping force component against t~e base surface
9 of the clamping slot 4 and by a second clamping force compol~ent,
35 at the one side face 20 of the centering slot 18, against the one
side of the centering pin 11.
