EP3150347B1 - Driller - Google Patents

Description

The invention relates to a drill, according to the preamble of claim 1.

There are long known drills in which a carbide body is inserted in the drill head. Such drills are particularly suitable for rocks and masonry. The carbide body is typically inserted in a groove of the drill head, usually soldered, which groove is open to the drill tip.

Such drills have a significantly higher service life when drilling stone or concrete compared to pure steel drills and are therefore used on a large scale. The drilling dust removal is typically done by drill bits, but sometimes is not sufficient.

Therefore, so-called suction drills have become known which have a central suction hole, which is connected to a vacuum source. The resulting drilling dust should be removed through these drill bits through the drill.

Also of these drills numerous embodiments have become known; as an example be the DE 29 48 665 A1 mentioned. Such suction drills offer a better drilling dust delivery rate than drills without a central suction hole. Surprisingly, however, the service life is usually lower, and apparently regardless of how the hard metal plate is selected. Another example can EP 0987398 A1 be removed

Therefore, the invention has for its object to provide a drill according to the preamble of claim 1, which is improved in terms of life.

This object is achieved by claim 1. Advantageous developments emerge from the subclaims.

Surprisingly, the solution according to the invention results in a significantly improved service life. While the suction compared to known suction drills is the same size or may be improved according to design, according to the invention by the support element apparently vibrations and resonant vibrations in the hard metal body prevented, so that this typically fairly brittle body is much less prone to fractures, which significantly improves the life.

The support element according to the invention supports, as it were in the manner of a bridge, the cemented carbide body centrally, that is to say at the point at which the extraction bore exists. Even if the support element itself is made of steel and thus has a lower hardness than the hard metal body, it fulfills the support function, in particular if there is an additional solder joint between the support element and the Häusallkörper.

This solder joint centrally receives the central shocks exerted by the impact of the drill on the central tip and the main cutting edge of the cemented carbide body, and passes them to the support element. The support element itself is thus particularly stressed centrally, but can absorb and distribute this load well by the two-sided support.

In this respect, the lower hardness and greater forgiveness of the support element in comparison with the Hartmentallkörper even of particular advantage, since the support element does not even tend to fractures.

Due to the different material properties between the support element and hard metal body resonances are reduced, and the intermediate solder acts so far dampening.

According to the invention, in particular bending vibrations of the cemented carbide body in the axial direction are thereby prevented with the support element. It is favorable in that the daughter holes, in which the suction hole opens, unobstructed by the support member at the customer's discretion in the face of the drill or can also extend laterally. In an advantageous embodiment, it is provided insofar that the support element is adapted to the hard metal body in terms of its radial thickness and in particular is approximately equal.

In a further preferred embodiment, it is provided that the support element is received in a precision bore, by press-fitting. The applied pressing force can be 1000 Newton, but for example 20 kilonewton. Even with a press fit, the solder used for soldering the cemented carbide body flows into the interface between the support element and the drill head, resulting in better reception and support.

The solution according to the invention is not limited to a drill with only one cemented carbide body which extends across the drill head, a so-called double cutter. Much more, the solution according to the invention can also be used in a so-called multi-cutter, for example, a three-cutter, which has a star-shaped cemented carbide body, or in a multi-cutter with a cross-shaped cemented carbide body. Here, then, the support element according to the shape of the hard metal body from the perspective of the drill bit viewed below the carbide body and always always above the central suction hole. Conveniently, the invention can also be used in a multi-cutter with main cutting and transverse thereto extending cutting inserts, in which case the support member extends below the main cutting plate.

The support element may preferably extend transversely across it, ie from one side of the drill head to the other side, in a groove of the drill head that is open in the forward direction. This groove can be dimensioned so that extends in it at the same time above the support member of the hard metal body. Alternatively, the support element itself may have a groove which receives the cemented carbide body.

In any case, the rearward support of the cemented carbide body in the central region and the design of the support element as a bridge are essential.

Preferably, the support element has a constant configuration, viewed from the cross-sectional area over its course across the drill head away. However, it is also possible to provide a central bulge toward the suction hole in the manner of a beam of a bridge in order to reduce the material stress even further.

In a preferred embodiment, the daughter holes extend in a multiple arrangement laterally adjacent to the support element, preferably towards the end face of the drill head. For example, two or four subsidiary bores with an accumulated cross section may be provided, which essentially corresponds to the cross section of the suction bore. The daughter holes then preferably end at different axial locations. This reduces the notch effect of the daughter holes at their end. In addition, will be reduces the swirling of the air flow, the air flow becomes more laminar. Such subsidiary suction holes can be realized for example by spark erosion without further notice.

The arrangement and configuration of the daughter holes is not limited to the coaxial alignment. For example, the daughter holes may also diverge from one another; In this case, it is preferred that their skew angles are different from each other so that they terminate at the same radial location in the end face of the drill head at different axial height in the suction hole even at the mouth.

In a particularly preferred embodiment, it is provided to provide supply air ducts on the lateral surface of the drill. The Zuluftkanäle extend with hollow-section preferably axially parallel, or spirally. They reduce the flow resistance in the borehole, since the supply of supply air is facilitated, so that the overall flow efficiency is improved. The supply air ducts preferably also end in the end face, at a location that is spaced from the mouth of the daughter holes such that the extraction of cuttings and drilling debris is optimized.

In the manufacture of the drill of the present invention, it is preferred to operate in a "bottom up" process. Preferably, the central slot is first drilled. If necessary, an additional precision bore can be made for receiving the support element according to the invention; however, this is optional. The support element is then pressed cold thereafter, after the receiving area for the support element is created. When the support element merely supports the hard metal plate, it is subsequently inserted thereon; if a U-shaped receptacle of the Hartmentallplattenkörpers is provided, the corresponding groove is now milled, and in any case subsequently used the carbide body.

Following this, the hard metal plate is soldered, the solder also runs in the press nip for the support element.

According to an advantageous embodiment of the invention, it is provided that the drill is a double-cutter or multi-cutter and the hard metal body forms a main cutting edge of the drill, optionally further carbide body extending to form side cutting transverse to the main cutting hard metal body.

According to a further advantageous embodiment of the invention, it is provided that at least one subsidiary bore opens at least partially in an end face of the drill.

According to a further advantageous embodiment of the invention, it is provided that the support element supports the hard metal body on its side opposite the drill bit, over the entire extension of the cemented carbide body through the drill head.

According to a further advantageous embodiment of the invention, it is provided that the support element receives the cemented carbide body. The recording can take place in any suitable manner, in particular in a substantially U-shaped groove.

According to the invention, it is particularly favorable that the support element is held by the exerted pressing forces and / or the soldering and in turn supports the cemented carbide body. The pressing force is due to the fact that the support element is introduced into a corresponding and suitably shaped recess in the drill head. If the recess is a groove, it is advantageous to design these with inner radii in order to achieve the lowest possible notch effect.

Furthermore, it is favorable that the cemented carbide body has to be soldered into the drill head anyway. For this purpose, solder is needed, and due to the capillary action, the solder runs as it were automatically into the boundary layer between the recess and the support element, so that in this respect results in a secure anchoring.

In an advantageous embodiment, the length of the support element, which is insofar then pin-shaped, the same size as the diameter of the drill head, or smaller than this.

In a further advantageous embodiment, it is provided that the support element is designed as a pin, which fits into the suction hole. The pin is pressed in and soldered there and supports the carbide body just at the point where he needs the most support, namely in the middle.

This does not preclude that the suction hole can develop their suction, since the branches are then provided to the daughter holes then preferably further back, so seen from the support element in the direction of drill shank.

In a further advantageous embodiment, it is provided to provide the support element with at least one shoulder which is positively against a corresponding shoulder in the drill head at the point in or on which the support element is received. This solution is favorable for supporting the axial forces which are introduced during the impact drilling on the support element via the hard metal body.

The paragraph corresponds in shape preferably a paragraph in the drill head and is intended for investment in this. The shoulder also preferably extends at an angle to the drilling axis which is between 0 and 90 degrees and in particular is smaller than 0 and greater than 90 degrees.

A corresponding shoulder may also be an inclined surface, at any suitable angle to the drill axis, for example at an angle of 45 degrees. It can also be provided several paragraphs, paragraphs with different angles.

In a further advantageous embodiment, it is provided to provide the support element with a rear groove. The supportability of the support element is thereby not diminished, especially when the support element is mainly connected by the pressing force and / or the solder joint with the drill head and is mainly in the suction hole.

Also, if the support member has a larger extent and / or a larger diameter than the suction hole, a rear recess in the support member may be beneficial. The recess in this case preferably has the diameter of the suction hole and ends in a concave end face.

In both cases, the weight of the drill is reduced overall, which benefits the increase in impact energy.

In a further advantageous embodiment, it is provided to choose the skew angle of the daughter holes, ie the angle at which the daughter holes extend to the drilling axis, constant. Nevertheless, in order to produce a different point of impact between the drill axis and daughter axis, there is a radial offset of the daughter holes. In this respect, then extends a subsidiary bore radially slightly further outward than another subsidiary bore. This leads to a distance between the intersections of the axes, which is favorable for the prevention and reduction of notch effects.

According to an advantageous embodiment of the invention, it is provided that at least one channel is provided on a lateral surface of the drill, which extends to the drill head and in particular opens into the end face of the drill and is designed as a supply air duct.

Further advantages, details and features will become apparent from the following description of several embodiments of the invention with reference to the drawings.

Fig. 1

eine schematische Schnittansicht eines Teils eines erfindungsgemäßen Bohrers in einer Ausführungsform;

Fig. 2

die Ausführungsform gemäß Fig. 1, jedoch in einer Seitenansicht des Bohrkopfs und um 90° versetzt;

Fig. 3

eine Stirnansicht der Ausführungsform gemäß Fig.1 und Fig. 2;

Fig. 4

eine Schnittansicht entsprechend Fig. 1, jedoch in einer modifizierten Ausführungsform;

Fig. 5

eine Seitenansicht der Ausführungsform gemäß Fig. 4, in der Darstellung gemäß Fig. 2;

Fig. 6

eine Stirnansicht der Ausführungsform gemäß Fig. 4 und Fig. 5; und

Fig. 7

eine weitere Ausführungsform des erfindungsgemäßen Bohrers, ebenfalls in einer schematischen Schnittansicht;

Fig. 7A

eine schematische Stirnansicht der Ausführungsform gemäß Fig. 7;

Fig. 8

eine weitere Ausführungsform des erfindungsgemäßen Bohrers, ebenfalls in einer schematischen Schnittansicht;

Fig. 8A

eine Stirnansicht der Ausführungsform gemäß Fig. 8;

Fig. 9

eine weitere Ausführungsform des erfindungsgemäßen Bohrers, ebenfalls in einer schematischen Schnittansicht;

Fig. 9A

eine schematische Stirnansicht der Ausführungsform gemäß Fig. 9;

Fig. 10

eine weitere Ausführungsform des erfindungsgemäßen Bohrers, ebenfalls in einer schematischen Schnittansicht;

Fig. 11

eine weitere Ausführungsform des erfindungsgemäßen Bohrers, ebenfalls in einer schematischen Schnittansicht;

Fig. 12

eine Schnittansicht durch eine dritte Ausführungsform des erfindungsgemäßen Bohrers, unter Darstellung der Tochter-Absaugkanäle; und

Fig. 13

eine weitere Ausführungsform des erfindungsgemäßen Bohrers, ebenfalls in einer schematischen Schnittansicht.

Show it:

Fig. 1

a schematic sectional view of a portion of a drill according to the invention in one embodiment;

Fig. 2

the embodiment according to Fig. 1 but in a side view of the drill head and offset by 90 °;

Fig. 3

an end view of the embodiment according to Fig.1 and Fig. 2 ;

Fig. 4

a sectional view accordingly Fig. 1 but in a modified embodiment;

Fig. 5

a side view of the embodiment according to Fig. 4 , in the representation according to Fig. 2 ;

Fig. 6

an end view of the embodiment according to Fig. 4 and Fig. 5 ; and

Fig. 7

a further embodiment of the drill according to the invention, also in a schematic sectional view;

Fig. 7A

a schematic end view of the embodiment according to Fig. 7 ;

Fig. 8

a further embodiment of the drill according to the invention, also in a schematic sectional view;

Fig. 8A

an end view of the embodiment according to Fig. 8 ;

Fig. 9

a further embodiment of the drill according to the invention, also in a schematic sectional view;

Fig. 9A

a schematic end view of the embodiment according to Fig. 9 ;

Fig. 10

a further embodiment of the drill according to the invention, also in a schematic sectional view;

Fig. 11

a further embodiment of the drill according to the invention, also in a schematic sectional view;

Fig. 12

a sectional view through a third embodiment of the drill according to the invention, showing the daughter exhaust ducts; and

Fig. 13

a further embodiment of the drill according to the invention, also in a schematic sectional view.

In the Fig. 1 illustrated embodiment of a drill 10 shows a drill head 12 with a hard metal body 14 which extends in the manner of a double cutter across the drill head and projects in a conventional manner this.

It is provided a central suction hole 16 which is connected to a vacuum source, in the region of the shaft of the drill 10, which is not shown here and can be carried out in any known manner.

The suction hole 16 opens into subsidiary suction holes, of which a daughter suction hole 18 in Fig. 1 is shown.

By the realization of the suction hole 16 of the drill 10 is hollow inside.

According to the invention, a support element 20 extends in the manner of a bridge across the drill 10, or more precisely, over the drill head 12 of time. On the support member 20 of the hard metal body 14 is flat, in such a way that it is supported over its entire rear surface 22 on the support member 20. It completely covers the central suction hole in the thickness of the cemented carbide body 14, but the suction hole 16 has a larger diameter than the thickness or thickness of the cemented carbide body 14 and the support member 20, so that attachment of daughter holes 18 is possible.

The support member 20 is radially outwardly, ie radially outside of the suction hole 16, supported on the drill head 12 surface. This embodiment allows maximum area utilization, so that the surface pressure is as low as possible by the initiated shocks, which is derived via the support member 20 to the "meat" of the drill head 12.

Out Fig. 2 It can be seen in which way the support element 20 extends below the hard metal body 14. The groove 24 for receiving the hard metal body 14 and the support member 20 is completely filled by these two. At the bottom of the groove 26, first the support element 20 extends, and on this the hard metal body 14th

From Fig. 2 apparent thickness or thickness of hard metal body 14 and support member 20 are the same, and the support member 20 is formed in this embodiment as a cuboid.

In this embodiment, secondary cutting plates 30 and 32 radially offset on the outside of an end face 34, but offset relative to the hard metal body 14 by 90 °, arranged and received in correspondingly shaped grooves of the drill head 12 in a conventional manner.

Out Fig. 3 can be seen as the end face 34 of the drill 10 according to Fig. 1 and Fig. 2 looks. Like reference numerals indicate similar parts here as well as in the other figures. Radially outside the suction hole 16, the daughter hole 18 is realized, which opens into the end face 34. Although here the central suction hole 16 is also shown opening into the end face 34, it is understood that instead only the daughter holes 18 can end there. Even if only one daughter bore 18 is shown here, it will be understood that instead of this any number of, for example, four daughter holes can be realized.

Out Fig. 4 and Fig. 5 it can be seen in which way the support element 20 can also be realized. In this embodiment, it is realized as a pin with a circular cross-section. Such a solution reduces the notch effect, as they arise in a rectangular groove in the groove corners, but the surface pressure is somewhat increased. Again, that the Harmetallkörper 14 is supported in particular in the central region of the support member 20.

Out Fig. 6 It can be seen that the support member 20 extends slightly through the drill bit 12, but ends before the radial end of the hard metal body. The support element 20 is pressed into the drill head, in such a way that it is mounted symmetrically to the drill head.

Fig. 7 shows a further embodiment of a drill according to the invention. Here, as in the other figures, the same parts correspond to the same reference numerals and therefore require no further explanation. In this solution, the support member 20 in the suction hole 16, which can also be regarded as a suction, added. The support member is cylindrical and in this embodiment has a height corresponding to about two thirds of the maximum height of the capital body 14. However, the support element 20 can also be shorter, for example half as long as the height of the hard metal body 14, or even longer, for example two or three times as long as the height of the hard metal body 14.

The support member 20 is pressed in this embodiment with a considerable pressing force, the pressing force can be equal to or higher than the pressing force with which the hard metal plate is introduced. It is also possible, the hard metal body 14 which can also be referred to as a hard metal plate, use only loosely, ie without pressing force, in which case the diameter of the support member may be slightly larger, for example by 0.2 mm, than the diameter of the hard metal body 14.

In addition, the support member 20 is preferably at least partially provided with solder, which establishes a secure connection between the side wall of the suction hole 16 and the support member 20.

In this embodiment, the support member has so far no radial support, but a support on flanks of the suction hole 16. The suction hole 16 is insofar regarded as a groove, which causes the support of the support member 20 at their flanks.

The hard metal body is also supported in this solution at its groove bottom, which extends outside of the suction hole 16. The support is either direct or indirect; indirectly when the solder also extends between the rear surface of the hard metal body 14 there and the groove bottom.

Fig. 7A shows an end view of the drill bit of the embodiment according to Fig. 7 , For reasons of simple illustration, the mouths of the daughter channels of the suction hole 16 are not shown.

Another embodiment of the invention is made Fig. 8 seen. In this solution, the hard metal body 14 is received in an additional groove 42 in the support member 20. The support member has the same diameter as the suction hole and a slot with dimensions corresponding to the dimensions of the cemented carbide body also in this solution. In this solution, the hard metal body is smaller in thickness than the diameter of the suction hole or the suction channel 16, and the support member 20 is in turn as in the embodiment according to Fig. 7 pressed into the suction hole and preferably soldered there.

The embodiment according to Fig. 8A , corresponds in this respect to the embodiment according to Fig. 8 , It can be seen that the support element 20 reaches the end face 48 and is visible on this.

Another embodiment, the embodiment according to Fig. 8 , is out Fig. 9 seen. Again, the support member 20 has an additional groove 42 which extends through its entire diameter. The hard metal body 14 is in turn received in this additional groove 42 and supported there both rearward and laterally. In this embodiment, the diameter of the support element 30 is greater than the diameter of the suction channel 16.

The support element 20 is received in the drill head 12 in such a way that increases over paragraphs 44 and 46, the diameter of the support member 20 from back to front. In the illustrated embodiment, the support member extends at the height of the hard metal body 14 to the minor cutting plates 30 and 32. It is understood that in a modified embodiment, the support member may also extend with a slightly smaller diameter and 30 and 32 ends before the secondary cutting plates ,

The support member 20 is also in this embodiment substantially cylindrical, but with inclined surfaces. An end face 48 of the drill is largely occupied by the support member 20 and is conical in a conventional manner.

As is usual with suction drills, it is provided in the drill 10 according to the invention to manage without drill-dust removal grooves on the outside of the drill. Rather, the drilling dust is discharged internally through the auger through the suction bore 16. The supply air to the drill head 12 is via the gap that results between the borehole of the drill and the outer diameter 50 of the drill; in a manner known per se, this is less than the length of the hard metal body 14 transversely through the drill, which produces the borehole.

How out Fig. 9 it can be seen that paragraphs 44 and 46 are each oblique. In the illustrated embodiment, the heel 46, which is the rear heel, has a surface normal 52 extending at an angle of 45 degrees to the bore 54. The angle of the corresponding surface normals of paragraph 44 is greater, in the example case 55 degrees.

It is understood that both the radial extent of the paragraphs 44 and 46 and their angle in wide ranges to the requirements is adaptable. In the illustrated embodiment, the radial extent of the shoulder 46 is greater than the radial extent of the shoulder 44 and is about half the diameter of the suction hole, while the radial extent of the further forward paragraph 44 is about one fifth of the radial diameter of the suction hole 16.

In the embodiment according to Fig. 9A according to the embodiment according to Fig. 9 Both the support member 20 and the hard metal body 14 can be seen, and it can also be seen that the hard metal body 14 is received in a groove in the support member 20.

Out Fig. 10 is a further embodiment of the support member 20 can be seen. The diameter of the support member 20 is again the same as the diameter of the suction hole 16, according to the embodiments of the Fig. 7 and 8th , The support member 20 is pressed and optionally additionally soldered. The support element 20 supports the middle region of the hard metal body 14 and ends for this purpose on the rear surface 22 of the support element 14.

The support member 20 has a concave back surface 56 in this embodiment. This extends dome-shaped over the entire diameter of the rest of the cylindrical support member body and thus forms a concave end face of the suction hole sixteenth

In the embodiment according to Fig. 10 the hard metal body 14 is otherwise butt-welded on the drill 10. The hard metal body 14 is preferably a solid carbide head, which can be designed in a manner known per se, for example as a three-knife trimmer or as a four-cutter, and has correspondingly shaped cutting edges.

Also, the embodiment according to Fig. 11 shows a butt-welded hard metal body 14 on the drill 10 in the rest. In this embodiment, the diameter of the substantially cylindrical support member 20 is greater than the diameter of the suction hole 16. Again, the suction hole 16 terminates in a dome-shaped rear surface 56 of the support member 20. The outer diameter of the dome-shaped end face 56 corresponds to the inner diameter of the suction hole 16. The dome-shaped Rear surface 56 is displaced forward relative to the shoulder 46, on which the support element 20 terminates, ie towards the drill tip. Accordingly, a rear recess 58 is provided in the support member 20, the diameter also corresponds to the diameter of the suction channel 16. Alternatively, the hard metal body may also be soldered.

It is understood that the exact configuration of the support element can be adapted in any way to the requirements.

An embodiment of two daughter holes 18 and 19 is made Fig. 12 seen. The daughter bores 18 and 19 terminate at different axial locations, corresponding to the distance a, in the central suction bore 16. In this way and by the round configuration of the end of the daughter bores 18 and 19, the notch effect is significantly reduced at this point. As can be seen, they extend without affecting them on the support member 20 and the hard metal body 14 along; and
Out Fig. 13 a further embodiment of the drill 10 according to the invention can be seen. The daughter bores 18 and 19 also extend obliquely to the drill axis 54 in this embodiment. The angle of the axes 60 and 62 to the axis 54 of the drill 10 is always the same. In order nevertheless to achieve an axial offset or distance a between the points of intersection of the axes with the drill axis 54, the daughter bore 18 is slightly offset radially inwardly with its mouth opposite the mouth of the daughter bore 19 at the drill bit. By this offset, the daughter hole 19 extends slightly longer and in so far moved backwards relative to the daughter bore 18th

The transition of the daughter hole 18 to the suction hole 16 is chosen so that the support member 20 in any case does not protrude into the daughter hole 18; In this respect, the support element is not a flow obstacle. This of course applies in the same way for the daughter hole 19, the transition to the suction hole 16 is offset from the opposite to the rear.

The design of the support element 20 corresponds essentially to the embodiment according to the embodiment Fig. 8 , Again, an additional groove 42 is provided in which the hard metal body 14 extends and which carbide body 14 at the same time fills the additional groove 42.

Claims (10)

1. A drill, having a cemented carbide body, which is inserted in at least one groove of a drill head, which groove is open towards the drill tip, which groove Is filled by at least one part of the cemented carbide body and in particular guides the cemented carbide body via a solder connection, the cemented carbide body optionally being supported via solder at least indirectly at the bottom of the groove, characterized in that the cemented carbide body has an aspiration bore (16) and In that a supporting member (20) for the cemented carbide body (14) extends across the aspiration bore (16), especially passes through the drill head (12), thereby bridging said drill head, via which supporting member (20) the cemented carbide body(14) is supported, in particular at the groove bottom (26), and/or at the groove flanks, the supporting member(20) and the cemented carbide body(14) being composed of different materials.
2. The drill according to claim 1, characterized in that the supporting member (20) extends from one side of the drill head and passes therethrough to the other side of the drill head, and thus penetrates through the drill head.
3. The drill according to one of the preceding claims, characterized in that the supporting member (20) has a geometric profile of predetermined cross-section, for example a rectangular cross-section, a circular cross-section, an oval cross-section or a trapezoidal cross-section.
4. The drill according to one of the preceding claims, characterized in that the supporting member (20) has substantially constant deviations throughout Its extent, In particular having a maximum deviation of 20% of the cross-sectional area, preferably less than 2% of the cross-sectional area.
5. The drill according to one of the preceding claims, characterized in that the supporting member (20) is inserted into the groove (24) in a substantially clearance-free fit, in particular with a press fit.
6. The drill according to one of the preceding claims, characterized In that the supporting member (20) is soldered Into the drill head (12), in particular using the same solder with which the cemented carbide body (14) is soldered.
7. The drill according to one of the preceding claims, characterized in that the central aspiration bore (16) enters into at least one subsidiary bore (18, 19) which extends at least in part laterally adjacent to the supporting member (20) or extends through the supporting member.
8. The drill according to one of the preceding claims, characterized in that the supporting member (20) receives (24) the cemented carbide body (14) In a groove.
9. The drill according to one of the preceding claims, characterized in that at least two subsidiary bores (18, 19) are provided, which enter into the central aspiration bore (16) and in particular having different lengths so that they enter at different axial positions of the aspiration bore (16).
10. The drill according to one of the preceding claims, characterised in that, the supporting member (20) has at least one shoulder (44, 46).

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