EP0595214A2 - Rock drill - Google Patents

Abstract

A drilling tool and in particular a rock drill for making apertures in concrete or masonry for the use of drilling hammers is proposed which is designed as a cross bit with four cutting lobes. In order to optimise the drilling capacity, the drilling tool is provided with a cross-bit head which merges in one piece into a conveying helix adapted to the drill head. A specific complement of cutting elements serves to optimise the drilling capacity. <IMAGE>

Description

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

State of the art:

Drilling tools for the production of breakthroughs have become known from EP-0 347 601 A1 (Hawera) with the references cited therein.

In particular from DE-27 56 990 C2 (Krupp) and DE-28 56 205 A1 (HILTI) drilling tools for stone processing have become known, in which the radially arranged cutting blades have axially extending outer cutting blade edges which are equipped with hard metal pins, whereby between the radially outer cutting blade edges and the central centering point, flat depressions are provided, which are also equipped with hard metal pins. In contrast, the drilling tools according to EP 0 347 601 A1 mentioned at the outset and the German utility model GM-81 04 116 (Bosch, FIG. 5) are designed with largely flat cutting blades on their end face.

The well-known drilling tools, in particular for making breakthroughs in concrete or masonry, which are also referred to as breakthrough drills, are based on the principle that the rock material is shattered by the impact of a heavy hammer drill, whereby the hard metal cutting edges, like pointed chisels, cause an explosive effect in the brittle material . If only the radially outer, axially protruding edge area of the drilling tool according to DE-27 56 990 (Krupp) or DE-28 56 205 (HILTI) acts, the stone material is removed in a pot-shaped manner, the radially inner area also being removed due to the brittleness of the material breaks away. The axially protruding wall areas lead to an increased pointed chisel effect and thus to an increased removal. The axially recessed, inner area of the cutting blades is also covered with hard metal pins in the known drilling tools. However, these do not primarily serve to remove material, but to shred the material that has already broken away.

A cup-shaped design of the drill bit with axially protruding edges does have the advantage of increased surface pressure and thus increased drilling performance, since the axially recessed recesses do not or only insignificantly contribute to the removal of the rock. Here, however, the circumstance arises that the drilling dust removed from the axially projecting ring segments and partially crushed comes to rest on the end face of the cutting blades before it is discharged through the discharge openings provided between the cutting blades into the drilling dust grooves or into the conveying helix. This can lead to the drilling tool practically on a drilling dust cushion in these largely flat end regions of the cutting blades is seated, which leads to a certain damping of the impact and thus to a reduction in drilling progress. This applies in particular to a larger front set-back area, as is shown in the literature mentioned at the beginning.

The known tools generally have a boring head, which is not followed by a conveyor spiral connected in one piece. Rather, according to the representation in EP 0 347 601 A1 (Hawera), additional conveying coils that can be placed on the smooth drill shaft are used for the transport of drilling dust. These additional conveying spirals, in particular made of plastic, are subject to increased wear and, in particular, cannot contribute to the solidification of the drilling tool as a whole.

A drilling tool has become known from the Westa company, the drilling head of which has four cross-shaped, radially running cutting blades which are covered with hard metal plates. This drill bit is connected in one piece to a double-start conveyor helix, the ends of which on the drill head end in an axially parallel surface of the two opposing cutting blades, so that these two cutting blades are very bulky, while the two further cutting blades arranged at right angles to them are severely undercut by the respective conveyor helix.

Furthermore, from the generic DE-U 90 02 460 (Fa. Drebo) a "crown drill" has become known which has a drill head with two cutting blades with intermediate drillings outlets to form a double conveyor helix connected in one piece with it. The respective spiral feed end ends in the entire radial width of the respective cutting blade, so that the drill head is very asymmetrical and bulky and the cutting blades have a very different material support from the conveyor helix.

Advantages of the invention:

The rock drill according to the invention with the characterizing features of claim 1 has the advantage that a drilling tool is created which has been optimized and improved in several respects compared to the known drilling tools. In particular, a low weight that is acceptable for a one-piece tool is achieved despite the one-piece construction, and a robust tool with simple handling. Due to the special shape of the drill head in connection with a conveyor helix that runs in one piece, high drilling capacities are achieved both in new and used condition and thus a long service life.

The invention is based on the core idea that the advantageous properties of a drilling tool of the type described in the introduction, ie a drill bit such as is shown in DE-28 56 205 A1 of DE 27 56 990 C2 or DE-U 90 02 460, for example improve, an increased drilling performance can be achieved. The invention is initially based on a tool in which the feed spiral is connected in one piece to the drill head. This reduces the wear on the drill helix and thus significantly improves the service life. However, a drilling head with a conveyor helix connected in one piece herewith initially has the serious disadvantage that a very bulky tool is formed in the region of the drilling head due to the outlet of the conveyor helix into the drilling head. If the design of the individual cutting blades is very different due to this one-piece construction, that is to say very asymmetrical, very different tension conditions arise in the individual cutting blades, which often increase cause the cutting blades to break prematurely. For example, a cutting blade supported by a feed spiral behaves completely differently in terms of its vibration behavior than a cutting blade which projects freely over a feed spiral groove. A symmetrical arrangement of the drill head, as shown, for example, in DE-28 56 205, is not known with a conveyor helix connected in one piece to the drill head.

Here, the invention is used in such a way that a drilling tool with a drilling head is created, in which the drilling head maintains a symmetrical and, for example, bell-shaped outer contour, despite a one-piece connection to a conveying helix, as is the case in principle in the cited prior art (HILTI), however, without a conveying helix is shown. This can be achieved in connection with a one-piece integrated feed helix in that the outlet area at the end of the feed helix on the drill head side and in particular the subsequent wall section on the drill head is shaped in such a way that not only a cylindrical outer contour with an outer helix of this feed head section but a harmonious transition from the helix is achieved in the drill head. This is achieved by constricting or tapering the area of the drill head that adjoins the outlet of the conveying helix. The drill head is therefore largely symmetrically rounded in its outer contour or lateral surface and in particular constructed bell-shaped, the outlet of the feed spiral being integrated into these areas.

This results in an extremely symmetrical construction of the drill head with its wings, which leads to almost the same vibration behavior of each individual wing. Experiments have shown that the service life of such a drilling tool, even under increased load, is considerably greater than that of a drill head, the wing of which is due to the The outlet of a drill helix are very differently material-supported. The vibration behavior of the entire drilling tool is therefore decisively improved, which reduces the susceptibility to wear. The aim of the drilling tool according to the invention is therefore to create a drilling head that is as symmetrical and, in particular, bell-shaped as possible, in which the transition from the feed spiral into the drilling head is carried out in such a way that an approximately bell-shaped outer contour of the drilling head is largely retained. This is achieved by means of a corresponding waist or concave design of the drill head area following the feed spiral outlet. Through these measures, a drilling tool is created which meets the highest demands without stress peaks and thus a risk of breakage in the drilling head. At the same time, the conveyor helix contributes to high drilling performance and long service life with its guidance.

The goal of a construction of the drill head that is as symmetrical as possible with a harmonious transition of the double conveyor helix has the consequence in the drilling tool according to the invention that optimal vibration conditions are created in the drilling tool.

According to an advantageous development of the invention, it is provided that the transition from the conveying helix into the shaft region again takes place harmoniously without any significant cross-sectional jumps by providing an arcuate transition of the outlet of the conveying helix into the drill shaft. Large radii at the transition of the drill shank into the inlet area of the feed spiral prevent stress peaks in these areas as far as possible.

In a consequent development of the invention, it is provided that the entire drill shank has as few cross-sectional jumps as possible which lead to voltage peaks. Especially with larger drilling tools Drill diameters of 65 or 80 mm, for example, the drill shank in the area of the helical inlet is much stronger than at its clamping end. In the tool according to the invention, this diameter transition is carried out by conical shank areas, wherein according to the invention cylindrical areas are provided between the conical areas, on which the drill shank can be easily clamped in a jaw chuck for machining. As a result, a long drill shaft, the length of which can be 300 mm or more, can be connected to the feed spiral by means of a friction welding process or the like. The shaft can be aligned by clamping the partly conical shaft on the cylindrical shaft sections.

Further advantageous refinements are specified in the further subclaims.

The formation of the rock drill is particularly advantageous in that the drill head has four ring segments interrupted by breakthroughs or grooves, as is known in principle from DE 28 56 205 with three ring segments.

However, according to the invention, the ring segments are roof-shaped or V-shaped in their end region, so that the cutting pin set, which is set obliquely with respect to the longitudinal axis of the drill bit, can be placed on the two flanks of the roof-shaped configuration. This results in an optimal application of force to the stone material on the face side.

It is also advantageous that weight is also saved due to the waisted design of the drill head in the area of the feed spiral outlet, which increases the safety against breakage due to the avoidance of voltage peaks.

The outside diameter of the drill head is expediently chosen to be larger than the outside diameter of the conveying helix in order to avoid tilting of the tool, while still maintaining an optimal longitudinal guidance.

The helix is expediently only made as long as is absolutely necessary for the removal of drilling dust. The length of the conveying helix is expediently chosen to be at least twice the diameter of the drill head in order to achieve adequate support of the drill head and removal of drill dust.

The cup-shaped drill head has a cutting blade base, which in cross-section is designed in the shape of an arc or a circle between the radially outer edge segment and the centrally arranged centering tip. This has the advantage that there is no high surface pressure on flat surfaces at any point.

The arc-shaped or circular base of the cutting blades also has a cutting pin attachment known per se, which, however, is arranged on the one hand directly next to a radial groove, and on the other hand centrally on a cutting blade. Due to the radial offset of these cutting pins and the arrangement on the floor which is circular in cross section, an optimal discharge of drilling material results from this recessed arcuate part of the cutting blades. The recesses or grooves between the ring segments protrude as far as possible into the center of the drill head in order to remove the drilling dust that is collected there as easily as possible into the drilling dust grooves of the production helix. For this purpose, the groove is arranged obliquely in the area of the outlet of the conveyor spiral in order to lead into the conveyor spiral located radially there.

Fig. 1

eine Seitenansicht des Bohrwerkzeugs mit einteiliger Doppelförderwendel,

Fig. 1a

eine Seitenansicht (Drehung um 90°) des Bohrwerkzeugs nach Fig. 1 mit einem Teilschnitt durch den Bohrkopf,

Fig. 1b

eine Draufsicht auf das Bohrwerkzeug gemäß Fig. 1

Fig. 2a bis 2c

eine vergrößerte Darstellung des Bohrkopfes mit Teilschnitten,

Fig. 3a, 3b

eine Ansicht des Bohrwerkzeuges nach Fig. 1 (Fig. 3a) mit einer Ansicht des Förderwendeleinlaufes (Fig. 3b),

Fig. 4

ein Bohrwerkzeug mit konisch/zylindrischem Schaft und

Fig. 4a

eine nähere Darstellung des Schaftes nach Fig. 4.

Further details of the invention are shown in the drawings and are explained in more detail in the following description with further advantages. Show it

Fig. 1

a side view of the drilling tool with one-piece double conveyor helix,

Fig. 1a

2 shows a side view (rotation through 90 °) of the drilling tool according to FIG. 1 with a partial section through the drilling head,

Fig. 1b

2 shows a plan view of the drilling tool according to FIG. 1

2a to 2c

an enlarged view of the drill head with partial sections,

3a, 3b

1 shows a view of the drilling tool according to FIG. 1 (FIG. 3a) with a view of the feed spiral inlet (FIG. 3b),

Fig. 4

a drilling tool with conical / cylindrical shank and

Fig. 4a

4 shows a detailed illustration of the shaft according to FIG. 4.

Description of an embodiment:

The basic structure of a drilling tool of the generic type, ie a drill bit for producing breakthroughs in concrete or masonry, is explained in more detail in the literature references mentioned at the beginning. In this regard, reference is made in particular to the content of DE 28 56 205 (HILTI).

The drilling tool 1 shown in FIGS. 1, 1a in two side views and in a top view in FIG. 1b consists of a drill shank 2 and a drill head 3, which is also referred to below as a "cross-drill head". Between the drill head 3 and the drill shaft 2 there is a conveyor helix 4 which is connected in one piece to it and which is designed as a double helix or two-start helix with the helices 4 ', 4' '.

The drill head 3 of the drilling tool has a central drill head tip 5, which is equipped with a roof-shaped hard metal cutting element 6. 1b, the rock drill 1 has radially extending cutting blades 7 to 10 to form a drill bit 4, which are separated or interrupted by cutouts or grooves 11, 11 'or 12, 12'.

The representation according to FIG. 1a results from the side view of FIGS. 1 and 1b from the direction of the arrow 13 in FIG. 1b.

1, 1b, the first conveyor helix 4 'of a double conveyor helix 4', 4 '' ends in the region of the recess 11 along the edge 17, the region 14 following the conveyor helix 4 'supporting the cutting blade 9 above it in terms of material, whereby this is reinforced to a certain extent. In contrast, the left-hand cutting blade 10 shown in FIGS. 1, 1b is not supported in terms of material due to the conveying helix 4 ′ underneath, so that the outer contour of the drill head in this area is V-shaped or bell-shaped. The blade 10, which is slender in its longitudinal cross section, would consequently be followed by a cutting blade 9 which is made of material. The same conditions exist for the two other cutting blades 7, 8.

In order to give the drill head a symmetrical and uniform structure overall, and thus to give the individual cutting blades 7 to 10 a longitudinal cross-section that is as uniform as possible and with the same wall thicknesses as possible, the cutting blades 9 and 7 following the respective drill helix outlet are subjected to additional machining treatment in such a way that the helical outlet (Edge 17) subsequent area 14 receives a concave constriction or waist 15, which extends over the entire outer surface of the respective cutting wing 9, 7. As a result, the region 14, which is initially thick in material, receives a material removal which rounds the outer contour of the drill head in a bell-shaped manner, as is shown in principle in the drilling tool according to DE 28 56 205 (HILTI), however, without a conveying helix. This waist of the area following the respective conveyor helix achieves a harmoniously rounded transition to the next successive wing or the next successive recess between the wings. As a result, the drill head can be made narrow and delicate even with large tools.

These characteristic cross-sectional relationships of the individual wings are shown again in FIGS. 2b and 2c. Fig. 2b shows a longitudinal section through the wings 7, 9 with the material support of the conveyor 4 ', 4''in the subsequent area 14, the concave constriction 15 leads to a material cross-section 38 which is approximately the same in its wall thickness s₁ as the wall thickness s₂ of the cross-section 39 of the two wings 8, 10, which lie above the respective helical feed groove 4 ', 4'', ie are not material-supported. This means that all cutting blades 7 to 10 have approximately the same cross-sectional structure, and thus effect the overall symmetrical structure of the drill head.

The recesses 11, 11 'in the area of the outlet 17 of the respective feed helix 4', 4 '' lie on a larger drill core diameter d 1 since this area is considerably larger than the core diameter d 2 in the area of the recesses 12, 12 '. Accordingly, the recesses 11, 11 'must be guided in an approximately 45 ° bevel 16 into the outlet of the respective conveyor helix 4', 4 '' (outlet edge 17). In contrast, the recesses 12, 12 'can be guided almost vertically in the respective lower sections of the conveyor helix 4', 4 ''. The associated outlet slope 18 can therefore be kept very steep (see Fig. 1b).

The exact structure of the drill head 3 according to the invention with regard to the cutting stock can be seen from FIGS. 1a, 1b and in particular from FIG. 2a. First, each cutting blade 7 to 10 each has a ring segment 19, which is formed in its front area as a roof-shaped configuration with a first outwardly facing slope 21 and a second inwardly facing slope 22. As can be seen from FIG. 1b, each ring segment 19 has at least one cutting element 23, 23 'or 24, 24', at least on its outer bevel 21. In addition, the two ring segments 19 of the cutting blades 7, 9 have a further cutting element 25, 25 'on the inward slope 22. Accordingly, the two cutting blades 7, 9 each have on their roof-shaped bevels 20 two cutting elements 24, 25 and 24 ', 25', respectively, which are arranged asymmetrically with the angle indications β shown in FIG. 1b, the angle β at 0 designated lower position in Fig. 1b begins. Likewise, the cutting blades 8, 10 each have a cutting element 23, 23 'only on their outer bevels 21, which are arranged symmetrically on the respective cutting blade. The specified angles β₁ to β₆ for the arrangement of the respective cutting elements follow in steps β₁ = 35 ° for that Cutting element 25, β₂ = 55 ° for cutting element 24, β₃ = 135 ° (cutting element 23), β₄ = 215 ° (cutting element 25 '), β₅ = 235 ° (cutting element 24'), β₆ = 315 ° (cutting element 23 ') .

As shown in FIG. 2a, the cup-shaped design of the drill head 3 to the side of the drill head tip 5 each has an arcuate or semicircular course, which is referred to as a circumferential, arcuate base 28. This bottom has a radius of curvature R₁, which is in the order of R₁ ≈ 8 to 10 mm in a drilling tool with a drill head diameter D₁ = 65 mm. In contrast to the known drill bits, the circumferential bottom 28 of the cutting blades is therefore strongly arched, so that this always results in an axial thrust on the drilling dust collected therein in order to feed it into the recesses 11, 12.

As can be seen from Fig. 1b in connection with Fig. 2a, the arcuate bottom 28 has, for example in the cutting blade 7 or 10, a further cutting element 26 which is inclined at an angle α₂ ≈ 30 ° with respect to an axis-parallel vertical 40 inwards towards the drill axis 30 is. The central axis 29 of the cutting element 26 forms the surface normal to the arcuate surface 28. The arrangement of the cutting element 26 is at the same angular distance β₆ as the arrangement of the cutting element 23 'on the slope 21.

In addition to the cutting element 26, the arcuate bottom 28 has a further cutting element 27, which is also inclined by an angle α₃ ≈ 30 ° with respect to an axis parallel 40 to the outside. According to the additional illustration in FIG. 1 b, this cutting element 27 is arranged radially further inwards than the cutting element 26.

It is preferably located behind the recess 12, at an angular distance β₇ = 90 °. The central axis 29 in turn forms the surface normal to the arcuate base surface 28 of the drill head.

The two cutting elements 24, 24 'with the central axis 29 and the two cutting elements 25, 25' with the central axis 29 'are also inclined at an angle α 1 ≈ 30 ° to a vertical 40. Likewise, these central axes 29, 29 'form the surface normals on the surfaces 21, 22 of the roof-shaped slope 20.

From Fig. 2a it can also be seen that the curved bottom 28 can be trough-shaped in the lower section in drilling tools with larger drilling diameter D 1, i.e. the centers 41, 41 'of the radii R₁ are laterally apart by an amount S₃, so that there is a corresponding flat bottom area 42 with the same width S₃.

In Fig. 1a, the angle δ ≈ 120 to 130 ° for the roof-shaped slope of the hard metal cutting element 6 is additionally shown. The diameter D₂ of the drill head tip 5 is D₂ ≈ 12 mm with a drilling tool of D₁ ≈ 65 mm.

.The length l₁ of the conveyor spiral 4 is such that it is at least twice as large as the diameter D₁, ie $\text{l₁ ≧ 2 x D₁}$

.

3a again shows the view of the drilling tool according to FIG. 1, FIG. 3b shows the lower inlet area 36, 36 'of the respective conveyor helix 4', 4 ''. This transition or inlet area of the conveyor helix 4 ', 4'' is formed from the drill shaft 2 into the helical region such that the radially outer end 43, 43 'leads tangentially to the outer diameter D₄ of the drill shaft 2 via an arcuate curve 37, 37'. This arcuate or spiral inlet of the respective conveyor helix is shown in FIG. 3b with the arrows 44. The curve 45, 45 ', which is also shown in FIG. 3b, results from the rounded transition of the respective adjacent conveyor helix 4', 4 ''. The area between the curves 37, 45 and 37 ', 45' lies with the large radius of curvature R₂ in the drill shank 2 (Fig. 3a), so that voltage peaks are avoided. The greatly rounded outlet 37, 37 'of the respective feed helix 4', 4 '' in the drill shaft 2 further prevents jamming of the feed helix ends in a bore wall.

FIG. 4 shows the complete drilling tool with attached drill shank 2, which is shown again in isolation in FIG. 4a.

The drill shaft 2 has a total length l₃, which is generally more than 300 mm. The drill shank 2 is generally connected to the cylindrical end 46 below the feed helix 4 via a friction weld connection 31. The diameter D₄ at this interface 31 is larger than the diameter D₅ of the lower clamping part 33, so that the drill shaft tapers l₃ over its length.

With known drilling tools, this tapering can be carried out by a one-piece conical component or by cylindrical shoulders with cross-sectional jumps. Cylindrical shoulders for tapering the diameter of the drill shank have the disadvantage compared to a conical design that stress peaks occur at each jump in diameter due to the striking stress on the drilling tool, which lead to an increased load on the drilling tool. Shock wave reflections continue to occur on the individual paragraphs due to the impact impulses, which have a disadvantageous effect on the tool and in particular the strength of the tool. Furthermore, the vibration behavior of such a tool is negatively influenced due to the cross-sectional jumps. These criteria increasingly apply to a drilling tool with a one-piece conveying helix, since the weight and the vibration behavior of the conveying helix also affect the subsequent drill shaft.

With a conical design of the drill shaft 2, these disadvantages are not present to this extent. Such a drill shank can therefore transmit higher drilling performance of the tools. A disadvantage of a conical design of the drill shaft, however, is the unfavorable absorption and clamping possibility when friction welding and when straightening the drill shaft. In particular, with different lengths of the drill shank, very different cone angles result, which require special clamping jaws or special collets for clamping such a conical shank.

Accordingly, the invention provides that the drill shank 2 is designed in steps from the lower insertion end or clamping part 33 to the upper drill head connection, the transitions of the steps each being conical. This design achieves the advantage of increased performance, ie better passage of the impact impulses and the avoidance of reflections on the heels. The batch-wise cylindrical design also enables problem-free picking up and clamping of the drill shaft both in the production of the friction weld connection 31 and in the straightening of such a tool. With different lengths of the drill shank, the design each area optimally. Measurements have shown that significant improvements in performance can be achieved through these measures. In the exemplary embodiment of such a drill shaft according to FIG. 4, the drill shaft 2 is connected to the feed helix 4 via the friction weld connection 31, at least the uppermost part 32 with the length l₄ being designed as a cylindrical shaft part 32 and between this cylindrical shaft part 32 and the lower clamping part 33 for the drive machine in particular two conical shaft sections 34, 35 with a length l₅ and l₇ are provided.

The drill shaft 2 accordingly consists of sections of an upper cylindrical section 32 with the length l₄, a subsequent conical section 34 with the length l₅, a further cylindrical shaft section 47 with the length l₆ and a further conical shaft section 35 with the length l₇, which is the Clamping part 33 with the length l₈ connects. The lengths l₄, l₆ of the cylindrical shaft sections 32, 47 have an axial length which preferably corresponds to two to four times the upper shaft diameter D₄ in order to obtain a sufficient length for clamping this shaft part.

These measures make it possible to increase the drilling performance by better transmission of the impact energy from the insertion end 33 to the drilling head, since in particular there are no reflections of the impact pulse on changes in diameter. Nevertheless, the drill shank can be used on its cylindrical parts without any problems in a conventional chuck or jaw chuck or in other usual clamping devices.

The invention is not restricted to the exemplary embodiment shown and described. Rather, it also includes all professional developments and refinements within the scope of the inventive idea.

Claims (17)

Drilling tool, in particular rock drill for the production of breakthroughs in concrete or masonry or the like., With a drill shank and with a carbide-tipped drill head, which comprises radially extending cutting blades, the drill head being associated with a conveyor helix connected in one piece with this and a recess in the drill head opens as a drill meal outlet in the helix, characterized in that the transition between the drill head (3) and the helix (4) has a circumferential constriction or waist (15) in such a way that all cutting blades (7 to 10) have a largely identical longitudinal cross section, so that the drill head (3) with the spiral feed outlet has a largely symmetrical structure. Drill according to claim 1, characterized in that the four cutting blades (7-10) interrupted by recesses (11, 11 ') or (12, 12') with radially outer, axially extending ring segments (19) have two opposite recesses or grooves (11, 11 ') are assigned, each of which has an inclined outlet (16) directed towards the longitudinal axis (30) of the axis of approximately 45 ° with respect to an axis parallel to the longitudinal axis (30) of the drill hole in the outlet (17) double-start conveyor coils (4 ', 4'') open, and that two further recesses (12, 12') have a largely axially parallel outlet with a steep slope (18) to the conveyor coils (4 ', 4'') underneath. Drill according to one of the preceding claims, characterized in that the outer diameter (D₁) of the drill head is approximately 10% larger than the outer diameter (D₃) of the conveying helix (4). Drill according to one of the preceding claims, characterized in that the axial length (l₁) of the conveyor helix (4) is at least twice as large as the outer diameter (D₁) of the drill head (3). Drill according to one of the preceding claims, characterized in that the pot-shaped drill head (3) has a circumferential base (28) which is curved in a semicircle towards the centering tip. Drill according to one of the preceding claims, characterized in that the end face of the ring segments (19) of the cutting blades (7 to 10) has a roof-shaped or V-shaped cross section (20), and that at least the radially outer bevels (21) of the roof-shaped Surface (20) have a hard metal cutting pin (23, 23 ') or (24, 24'). Drill according to one of the preceding claims, characterized in that the radially inner inclined surface (22) of the roof-shaped end face (20) of each ring segment (19) has a hard metal cutting pin (25, 25 ') at least in the case of two opposite cutting blades (7, 9). having. Drill according to one of the preceding claims, characterized in that at least some of the hard metal cutting pins (24, 24 ', 25, 25') are arranged asymmetrically on the roof-shaped end face (20) of the cutting blades (8, 10). Drill according to one of the preceding claims, characterized in that the arcuate bottom (28) of the pot-shaped drill head (3) has at least two cutting pins (26, 27) arranged, preferably asymmetrically and at different radial distances from the longitudinal axis of the drill (30). Drill according to one of the preceding claims, characterized in that the radially outer hard metal cutting pin (26) in the arcuate base (28) in the wall section (14) (waist region (reinforced area) after the outlet (17) of the conveying helix (4, 4 ') 15)) is arranged. Drill according to one of the preceding claims, characterized in that the central axes (19, 29 ') of all hard metal pins form an angle $\text{α₁ = α₂ ≈ 30 °}$

with respect to an axis-parallel vertical (40) and that in particular the central axes (29, 29 ') each form the surface normals on the insert surfaces (20, 28) of the hard metal pins. Drill according to one of the preceding claims, characterized in that at least one radially inner cutting element (27) is arranged in the arcuate base (28) in the region of the inclined outlet (11, 12). Drill according to one of the preceding claims, characterized in that the back of the conveying helix (49) of the conveying helix (4 ', 4'') in the area of the helical feeder inlet (48) on the drill shaft (2), starting from the outer diameter (D₃), curves or spirally to the Shaft diameter (2) approximates and merges tangentially, the feed spiral inlet (48) largely starting at the surface of the drill shaft. Drilling tool according to claim 1, characterized in that the drill shaft (2) is connected to the feed helix (4) via a friction weld connection (31) or the like, at least the part (32) facing the feed helix (4) as a cylindrical shank part (32) is formed and that between this cylindrical shaft part (32) and a cylindrical clamping part (33) for the drive machine at least one and in particular two conical shaft part sections (34, 35) are provided. Drilling tool according to claim 14, characterized in that the drill shank (2) is formed in sections from an upper cylindrical shank section (32), a subsequent conical shank section (34), a further cylindrical shank section (47) and a further conical shank section (35), which is followed by the cylindrical clamping part (33). Drilling tool according to claim 14 or claim 15, characterized in that the cylindrical shank sections (32, 47) have an axial length (l₄, l₆) which corresponds to at least two to four times the upper shank diameter (D₄). Drilling tool according to claim 1, characterized in that the lateral surface (14) of the drilling head (3) adjoining the outlet of the conveying helix (4) has such a constriction or waist (15) that the drilling head (3) has a symmetrical, bell-shaped structure .

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