EP0730082A2 - Drill bit for percussive drilling - Google Patents

Abstract

This core bit is esp. suitable for rotary impact drilling of e.g. stone, concrete or similar materials. The thin-walled cylindrical cup bit (106) is open-ended towards the cutting end, and has a radial base (20) extending to the axial shaft (101), where it is attached. The principal original feature is in the unusual profiling of the base. Its radial outer contour follows a curved path, with at least one point of inflection.

Description

The invention relates to a drill bit for rotary drilling of preferably rock, concrete or the like according to the preamble of claim 1.

State of the art:

Drill bits of the type listed above have already become known, in which the bottom of the drill bit extends essentially radially outward in a straight line perpendicular to the axis of rotation or also slightly inclined to the drill side. In these embodiments, the outer contour of the drill bit base generally follows the contour of the inside of the drill bit base in substantial sections.

In operation, a percussion movement stimulated by a boring machine should be passed on in the best possible way via the drill bit shank, the drill bit base, to the open end-side drill side of the cylindrical drill body. In the known embodiments mentioned above, however, the transport of Impact movement to record large damping losses, which significantly reduce the drilling performance.

In addition, when the thin-walled cylindrical drill body penetrates the material to be drilled in a rotational manner, a further disadvantage generally arises in the described embodiments. Shortly before reaching a drilling depth, which is generally determined by the length of the cylindrical drill body, drilling material that has already been loosened, such as rock, can jam between the largely flat drill bit base and the material that is still to be drilled and further penetration of the drilling body up to prevent its full length.

The present invention is therefore based on the problem of optimizing a drill bit, in particular in rotary drilling. Essentially, the impact energy applied to the shank should, as already mentioned, be implemented with the highest possible efficiency, ie low losses for the destruction of the rock. The problem of implementing the impact energy is discussed, for example, in the applicant's patent DE 30 49 135 C2. In general, the development of drill bits is that the inertial mass is to be reduced overall in order to convert the striking energy into drilling work with as little loss as possible. As a result, the drill bit base, the insertion shank and in particular also the wall sections of the crown part are always made with less mass, ie thinner, in order to generate low counter-inertia forces. However, thinner wall sections, in particular in the bottom of the drill bit, also result in vibrations which, however, should not have a negative effect on the drilling performance. In particular, no vibrations should arise, the standing waves lead within the drilling tool and thus consume energy through appropriate sound radiation or heating. An overall thin-walled drill bit must therefore also be optimized in terms of vibration technology, provided that it is exposed to high impact loads.

Usual or conventional thin-walled drill bits generally have no conveying helix on the outer contour of the crown part. In particular with thin-walled drill bits with a wall thickness of the crown part of the order of magnitude of approx. 5 mm, normal grooves for drilling dust cannot be made, since this would lead to a strong weakening of the wall thickness. DE-OS 27 35 368 of the applicant shows a rock drill bit with an external production helix in the region of the crown part, which is used to remove the cuttings. Also from this prior art it can be seen that the depth of the drilling dust groove can only be made small in the case of drill bits in order not to bring about an excessive weakening of the wall thickness. The subject of this publication also deals with the question of the longitudinal vibrations of the drilling tool occurring during the drilling process, which should be kept as low as possible. This should also keep the noise emissions low.

Small, that is to say only shallow, feed spiral grooves have the disadvantage that only a small amount of drilling dust can be transported. Accordingly, the present invention provides a further development of the conveying helix arrangement on a drill bit in such a way that both the vibration behavior and thus an optimal power transmission as well as the drilling dust transport and the thereby improved mode of operation is improved, in particular in the case of thin-walled drill bits.

Object and advantages of the invention:

The invention has for its object to eliminate the disadvantages of known drill bits and in particular to improve the efficiency or the drilling properties of a drill bit under the aspect of vibration control. This object is achieved by the features of claim 1 and independent independent claims 8, 15 and 21, respectively.

Advantageous and expedient developments of the drill bit according to the invention are specified in the subclaims.

The essence of the invention is that a drill bit, which is used in particular for rotary impact drilling of preferably rock, concrete or the like and essentially consists of a thin-walled cylindrical drill body open to the drill side and a substantially radially extending drill bit base with an axially arranged drill bit shaft for fastening the drill bit exists, is provided with a drill bit base which has an outer contour in the radial direction which follows a curve which has at least one turning point. Such a shape of the drill bit base transmits a striking movement excited by the boring machine to the cylindrical drill body with particularly little losses. From a physical point of view, the drill bit base according to the invention has a lower damping than a conventional bit bit base. On the one hand, this can be attributed to the predominantly elastic vibration properties of the drill bit base according to the invention. On the other hand, in the drill bit according to the invention, a more balanced mass progression in the axial direction can be seen in comparison with conventional embodiments. This applies in particular to designs in which a predominantly on the drill bit shaft horizontal drill bit bottom follows. As a result, there is a cross-sectional jump by a factor of 10, for example, at the intersection of the drill bit shank and the bit bit base, and thus, when considering small disk elements perpendicular to the axis of rotation, a corresponding jump in mass. As a result, in conventional designs, a starting impact pulse is partially reflected or partially damped at this point, so that there is a considerable loss of transmission of the impact movement up to the drill body. In an embodiment of the drill bit base according to the invention, such a cross-sectional jump with the associated jump in mass is not present at the transition from the drill bit shaft to the drill bit base. Due to the more uniform mass distribution in the transition area between the shaft and the cylindrical drill body of the drill bit according to the invention and the possibility that the drill bit shaft can carry out oscillating movements relative to the drill body due to the drill bit base according to the invention, there is an improvement in drilling performance of up to 50% compared to the previously known designs.

It is particularly advantageous if the course of the curve, which determines the outer contour of the bottom of the drill bit, is a continuously differentiable function. By avoiding shoulders and edges, the service life of the drill bit can be increased and, in addition, a uniform, continuously differentiable curve can be easily produced with a CNC lathe.

It is particularly preferred if the course of the curve, which determines the outer contour of the drill bit base, is an attenuated decaying vibration over the radius of the drill bit shaft. In this way, a particularly uniform mass distribution of the drill bit shank is achieved Drill bit bottom reached to the drill body, with particularly low damping losses occurring during the transmission of impact impulses from a boring machine.

Furthermore, it is very favorable if the contour of the inside of the drill bit base follows a curve which has at least one turning point. A curve shape similar to that on the outside of the bottom of the drill bit is thus achieved, it being advantageous if the contour follows the inside of the outside contour in substantial radial sections. In this way, manufacturing material can be saved.

In addition, it is advantageous if the wall thickness of the bottom of the drill bit is at least in the radially outer section in the region of the wall thickness of the cylindrical drill body. By designing the bottom of the drill bit with the wall thickness of the cylindrical drill body, up to 30% material can be saved and, in addition, a particularly uniform mass distribution in the drill bit, which results in a correspondingly good drilling performance, can be achieved.

It can also be advantageous if the curve shape that determines the outer contour and / or inner contour of the drill bit base is realized by linear sections in each case.

To achieve the object, it is particularly advantageous as a further essential idea if the drill bit base has an outer contour that runs through a minimum in the radial direction, the drill bit base being connected to the cylindrical drill body in the increasing radially outer curve section of its contour. This is particularly advantageous when drilling bits with a relatively small diameter are made. In this case, the outer contour of the drill bit base cannot be complete Execute curve shape, corresponding to that described in claim 1, but passes before reaching the turning point in the cylindrical drill body. For this curve of the contour of the bottom of the drill bit, too, there is a significant improvement in the drilling performance for the same reasons mentioned above.

The advantages of the dependent claims 9 to 13 are in agreement with the already discussed claims 2 and 3 and 5 to 7.

It is also particularly advantageous to achieve the object as a main feature if at least one elevation protruding from the contour of the inside is provided on the inside of the bottom of the drill bit to destroy the material to be drilled. When the drill body penetrates the material to be drilled, rocks can be broken shortly before the maximum drilling depth is reached by at least one protruding elevation on the inside of the drill bit bottom, so that the further drilling process is not blocked and the drill bit reaches its maximum drilling depth.

It is also advantageous if the elevation protruding from the contour of the inside of the drill bit base is an annular bead. This annular bead can already result in a simple manner when the drill bit base is designed in accordance with claim 1 or independent independent claim 8, in particular when the contour of the inside of the drill bit base follows the outer contour in substantially radial sections. Likewise, of course, an annular bead or oval bead or multiple interrupted bead can also be attached to the inside of the drill bit base.

It is particularly preferred if the contour of the inside of the drill bit base in the radially inner region extends obliquely upwards in the direction of the drill bit shaft to form a conical cavity up to the receiving point, for example a center drill. Drilling cuttings can escape into the conical cavity, which is created when small pieces of rock are pre-crushed shortly before reaching the greatest drilling depth by at least one elevation protruding from the contour of the inside of the drill bit base. This means that the drill bit can not only penetrate to the full drilling depth, but also deflagration of drilling dust at greater drilling depths is prevented.

Furthermore, the inventive design of the conveyor helix arrangement according to the features of the associated claims has the advantage that the efficiency of such a drill bit can be further improved. This further development according to the invention is based on the core idea that the conveying helix arrangement is improved in terms of vibration technology and in terms of the volume conveyance of the drilling dust per unit of time.

From the older patent of the applicant EP 0 126 409, the basic problem of cross-sectional jumps in conveying coils and the associated vibrations has become known for a normal rock drilling tool. In the case of such a drilling tool, it has been proposed in particular to vary the groove pitch over the length of the conveying helix in order to avoid equidistant cross-sectional jumps between the groove base and the webs of the conveying helix. However, this is a drill geometry and in particular a feed helix geometry that differs fundamentally from that in the case of flat helical drill bits.

According to the present invention, a conveyor helix construction is now to be realized in a drill bit, in which the external conveyor helix has a drilling dust removal groove which, on the one hand, has an increasing gradient towards the end of the shaft. This should result in a constant increase in the width of the drilling groove starting from the end face of the drilling tool. On the other hand, the back width of the conveyor spiral webs should be as small or narrow as possible, with a largely constant width.

Because the depth of the drilling dust grooves in the drill bit according to the invention is only small, possibly variable, in the order of magnitude of, for example, 1 to 1.5 mm, the groove width is widened continuously or discontinuously due to an increasing slope, the volume of the drilling dust groove also increasing. At the same time, however, the back width of the broad webs of the feed spiral of the drill bit, which are relative to a normal drilling tool, should remain approximately constant over a wide range.

These measures prevent equidistant cross-sectional jumps in the conveyor spiral, so that, among other things, no standing waves with a corresponding energy absorption are formed. This also reduced noise emissions. Furthermore, due to the continuously, in particular continuously increasing, gradient of the drilling dust groove and the constantly increasing volume of drilling dust groove, a rapid removal of the cuttings is effected. An optimization of the vibration properties through these measures makes it possible to choose relatively thin wall thicknesses both in the crown base and in the lateral wall area, which leads overall to low masses. The optimization of the vibration properties allows such a reduction in mass the drill bit overall, with improved transport properties of the drilling dust. A variation of the groove depth with a larger groove depth on the tool head in the cutting area and a possibly continuously removable groove depth in the direction of the clamping shank also results in an increase in the groove volume in the area of a small groove pitch and a solidification of the drill bit in the area towards the shank end due to increasing wall thickness.

Drawings:

Fig. 1

ein Diagramm mit mehreren Kurvenverläufen nach denen der Bohrkronenboden einer Bohrkrone ausgebildet werden kann;

Fig. 2

einen axialen Querschnitt einer erfindungsgemäßen Bohrkrone, wobei der Kurvenverlauf des Bohrkronenbodens in radialer Richtung zwei Wendepunkte besitzt;

Fig. 3

ein axialer Querschnitt einer erfindungsgemäßen Bohrkrone, deren Bohrkronenboden in radialer Richtung ein Minimum durchläuft;

Fig. 4

eine teilweise geschnittene Ansicht einer erfindungsgemäßen Bohrkrone mit variabler Wendel; und

Fig. 5

die ungeschnittene Seitenansicht der erfindungsgemäßen Bohrkrone aus Fig. 4.

Three exemplary embodiments of the invention and a mathematical function for a better understanding of the invention are shown in the drawings and explained in more detail in the following description with further advantages and details. Show it

Fig. 1

a diagram with several curves according to which the drill bit bottom of a drill bit can be formed;

Fig. 2

an axial cross section of a drill bit according to the invention, wherein the curve of the drill bit base has two turning points in the radial direction;

Fig. 3

an axial cross section of a drill bit according to the invention, the bottom of the drill bit passes through a minimum in the radial direction;

Fig. 4

a partially sectioned view of a drill bit according to the invention with variable helix; and

Fig. 5

the uncut side view of the drill bit according to the invention from Fig. 4th

Description of the embodiments:

1 shows a diagram with three different curves, which for example determine the outer contour of a drill bit base for three different diameters. In the diagram, the horizontal x-axis describes the radial and the vertical y-axis the axial curve. The curves can be represented analytically by the mathematical function 1. The curve profile 2 can be used, for example, for the radial profile of the outer contour of a drill bit base of a drill bit with a diameter of 80 mm, the curve profile 3 for a drill bit with a diameter of 90 mm and the curve profile 4 for a drill bit with a diameter of 100 mm. The table b also contains the corresponding parameters b2, b3 and c3 of function 1 in order to obtain the respective curve shape. The three curves are a dampened decaying vibration. The curve shape 2 has a turning point and the curve shapes 3 and 4 have two turning points due to the adaptation to a larger drill bit diameter.

2 shows a first exemplary embodiment of a drill bit according to the invention in cross section through the axis of rotation. The drill bit consists of a drill bit shank 6, a bore 7 for receiving a centering drill, a drill bit base 8, the outer and inner contours of which have a curve corresponding to a damping decaying vibration and the cylindrical, thin-walled drill body 9 which is open to the drill side. The wall thickness of the drill bit base 8 lies in substantial radial sections in the area of the wall thickness of the drill body 9. The drill bit is made in one piece, but in other embodiments can also be in several pieces.

To destroy the material to be drilled shortly before reaching the maximum drilling depth, the inner contour of the drill bit base 8 has an annular bead 10 protruding from the inner side contour. The annular bead is largely determined by the curve shape of the inner or outer contour of the drill bit base. For receiving drilling dust, the contour of the inside of the drill bit base 8 extends obliquely upward in the radially inner region 11 to form a conical cavity 12 up to the receiving point of the center drill 7.

A second exemplary embodiment according to the invention is shown in FIG. 3 as representative of the small diameter of a drill bit. The exemplary embodiment also has a drill bit shaft 13, a bore for receiving a centering drill 14, a drill bit base 15, which, however, in contrast to the first exemplary embodiment, has an outer contour which consists of a broken, damped, decaying vibration and thus has no turning point, but in the radial direction Passes through minimum, wherein the bottom of the drill bit is connected to the cylindrical drill body 16 in the rising curve portion of its outer contour. The second exemplary embodiment likewise has a conical cavity 17 and an annular bead 18.

A third exemplary embodiment according to the invention for average drill bit diameters of approximately 80 mm is shown in FIG. 4. In the partially sectioned side view, the annular bead 19 and the curve of the outer contour of the drill bit base 20 are particularly clearly visible with a turning point. With rotary impact drilling, axial impacts are exerted on the drill bit during turning. A striking movement excited by a boring machine is applied to the drill body 9, 16, 106 via the drill bit shank 6, 13, 101, the drill bit base 8, 15, 20 transfer. The design of the drill bit base according to the invention enables the drill body 9, 16, 106 to oscillate relative to the drill bit shaft 6, 13, 101. As a result, an incoming shock wave is damped particularly little. If the drill body 9, 16, 106 penetrates further and further into the material to be drilled, pieces of rock that have already been loosened are finally pre-shattered by the annular bead 10, 18, 19 and displaced into the conical cavity 12, 17. As a result, the drill bit according to the invention can penetrate into the material to be drilled to its full drilling depth.

The drill bit 100 shown in FIGS. 4 and 5 has a coaxial insertion shaft 101, a pot-like drilling body or a pot-like crown part 102, the end 103 of which on the end face or opposite the insertion shaft has only indicated cutting edges 104 in a known manner for workpiece machining. The coaxial insertion shaft 101 merges via a previously described thin-walled drill bit base 20 into a thin-walled cylindrical wall part 106 which has a conveying helix 108 on its outer contour 107. The preferably single-start conveyor spiral 108 consists of a spiral drilling groove 109 with a groove width n1 to n4 with a core diameter D ₂ and axially adjoining conveyor spiral webs 110 with a web back width r1 to r4 and an outer diameter D ₁ .

The outer diameter or nominal diameter D _{N of} the drill bit is determined by the arrangement of the cutting teeth 104 in the end region of the wall part 106. This outer diameter D _N is somewhat larger than the outer diameter D1 of the conveying spiral 108, which is formed by the outer diameter of the conveying spiral webs 110. Accordingly, in the figure the outer diameter of the drilling dust groove 109 is denoted by D ₂ , the groove depth t resulting from the difference between these diameters or radii. The groove depth t of the drilling dust groove 109 is in the range t ≈ 1 to 1.5 mm. The wall thickness s of the cylindrical wall part 106 is of the order of magnitude s ≈ 5 mm. This applies to a drill bit with a nominal diameter of D _N ≈ 80 mm.

The groove depth t can be constant or variable. In the latter case, a larger groove depth t _{1 is selected} in the area of the drill head 103 to increase the groove volume. This groove depth then decreases continuously in the direction of the shaft end to a value t ₂ , with a simultaneous increase in the wall thickness s, ie a core reinforcement of the helix. This results in an overall solidification of the drill bit. The values t ₁ 1.5 mm and t ₂ ≈ 1 mm can of course be optimized in another order of magnitude depending on the embodiment.

As can also be seen from the figures, the drilling dust groove 109 has a changing slope α 1 to α 4, where α 1 ≈ 1 to 3 °. The slope then increases to the bottom of the drill bit to a value of α 5 ≈ 10 to 15 °. The start of the feed spiral groove is shown with reference number 111. This feed helix groove 111 lies only slightly axially above the symbolically illustrated arrangement of a cutting tooth 104, so that there is a large free cut in the front area of the drill bit. The front wall section 112 lying in front of the foremost conveying spiral groove 109 'has an outer diameter D ₁ which corresponds to the outer diameter of the conveying spiral webs 110. This enlarged diameter area results in an increased wall thickness for receiving the cutting teeth 104 and thus an increased strength of this area.

Due to the very flat pitch angle α 1 of the feed helical groove 109 'in the area of the drill head, there is only a very small web width r1 for the lowest helical feed web 110' in the figure, which, however, quickly increases to a larger value r2 or r3. The web width r of the conveyor spiral webs 110 should overall be kept as small as possible, so that - apart from the beginning of the conveyor spiral - only a slight or no further increase in the back width r ₂ to r _{5 of} the conveyor spiral webs 110 to the values r2 to r5 ≈ is constantly sought. In contrast, the width n1 to n4 of the drill dust groove 109 should preferably increase continuously, so that the volume of the respective drill dust groove increases continuously. In this way, enough drilling dust can be absorbed, which is quickly removed due to the increasing drilling dust pitch. In spite of only a small depth t of the drilling dust grooves, which are essentially rectangular in cross section, there is no drilling dust backlog.

In the exemplary embodiment according to FIG. 4, the following technical data are realized in a preferred exemplary embodiment:
The nominal diameter of the drill bit depends on the lateral projection of the cutting teeth 104 and is D _N ≈ 80 mm. The outer diameter of the spiral conveyor webs is D1 ≈ 78 mm, the core diameter of the drilling dust grooves 109 is D ₂ ≈ 76 mm. These dimensions are matched to one another in such a way that the groove depth t is set to approximately 1 to 1.5 mm. The groove depth can also be variable.

The inner diameter of the pot-like crown part 110 is D ₃ ≈ 68 mm, which leads to a constant or variable wall thickness s ≈ 3.5 to 5 mm, measured between Inner wall 113 and outer diameter D _{1 of} the conveyor spiral web 110.

The start of the groove 111 is approximately at a height h ₃ ≈ 5 mm above the lower edge 114 of the drill bit. The groove width n1 in the front area of the drill bit begins with a dimension n1 ≈ 4 to 6 mm and increases continuously to a dimension n4 ≈ 10 to 15 mm. The web width r2 to r5 ≈ 5 mm = constant.

The height h1 of the drill bit from the end face to the crown base 20 is h1 ≈ 75 mm, the inner height from the end face 114 to the inner crown base h2 ≈ 68 mm.

The upper flank 115 of each drill dust groove 109 shown in FIG. 4 has a bevel with an angle β ≈ 20 °. The lower edge 116 is relatively sharp, i.e. radially directed or perpendicular to the surface.

Claims (24)

Drill bit in particular for rotary drilling of preferably rock, concrete or the like, which essentially consists of a thin-walled, cylindrical drill body (9, 16, 106) open to the drill side and an essentially radially extending drill bit base (8, 15, 20) with axial arranged drill bit shaft (6, 13, 101) for fastening the drill bit, characterized in that the drill bit base has an outer contour in the radial direction which follows a curve (2, 3, 4) which has at least one turning point. Drill bit according to claim 1, characterized in that the curve (2, 3, 4) which determines the outer contour of the drill bit base (8, 15, 20) is a continuously differentiable function (1). Drill bit according to one of the preceding claims, characterized in that the course of the curve (2, 3, 4), which determines the outer contour of the drill bit base, is a damped decaying vibration (1) over the radius from the drill bit shaft to the outside. Drill bit according to one of the preceding claims, characterized in that the contour of the inside of the drill bit base (8, 15, 20) follows a curve (2, 3, 4) which has at least one turning point. Drill bit according to one of the preceding claims, characterized in that the contour of the inside of the drill bit base (8, 15, 20) follows the outer contour in essentially radial sections. Drill bit according to one of the preceding claims, characterized in that the wall thickness of the drill bit base is at least in the radially outer section in the region of the wall thickness of the cylindrical drill body. Drill bit according to one of the preceding claims, characterized in that the curve shape which determines the outer contour and / or inner contour of the drill bit base is realized by linear sections in each case. Drill bit in particular for rotary drilling of preferably rock, concrete or the like, which essentially consists of a thin-walled cylindrical drill body open to the drill side and an essentially radially extending drill bit base (8, 15, 20) with an axially arranged drill bit shaft (6, 13, 101 ) for fastening the drill bit, characterized in that the drill bit base has an outer contour which runs through a minimum in the radial direction, the drill bit base (15) being connected to the cylindrical drill body (16) in the increasing radially outer curve section of its outer contour. Drill bit according to claim 8, characterized in that the course of the curve, which determines the outer contour of the drill bit base (15), is a continuously differentiable function. Drill bit according to one of claims 1, 4, 8 or 9, characterized in that the drill bit base has an inner contour which runs through a minimum in the radial direction. Drill bit according to one of claims 8 to 10, characterized in that the contour of the inside of the Drill bit bottom (15) follows the outer contour in substantial radial sections. Drill bit according to one of claims 8 to 11, characterized in that the wall thickness of the drill bit base (15) is at least in the radially outer section in the region of the wall thickness of the cylindrical drill body. Drill bit according to one of claims 8 to 12, characterized in that the course of the curve which determines the outer contour and / or inner contour of the drill bit base is realized by linear sections in each case. Drill bit according to one of claims 8, 9, 10, 12 or 13, characterized in that the contour of the inside of the drill bit base (8, 15, 20) follows a curve (2, 3, 4) which has at least one turning point. Drill bit in particular for rotary drilling of preferably rock, concrete or the like, which essentially consists of a thin-walled, cylindrical drill body (9, 16, 106) open to the drill side and an essentially radially extending drill bit base (8, 15, 20) with axial arranged drill bit shank (6, 13, 101) for fastening the drill bit, characterized in that at least one elevation (10, 18, 19) protruding from the contour of the inside is provided on the inside of the drill bit base in order to destroy the material to be drilled. Drill bit according to claim 15, characterized in that the elevation protruding from the contour of the inside of the drill bit base is an annular bead (10, 18, 19). Drill bit according to claim 15 or 16, characterized in that the elevation protruding from the contour of the inside of the drill bit base is a bead with an oval shape. Drill bit according to claim 16 or 17, characterized in that the bead is interrupted several times over the circumference. Drill bit according to one of claims 15 to 18, characterized in that elevations protruding from the contour of the inside of the drill bit base are of variable height. Drill bit according to one of claims 15 or 19, characterized in that the contour of the inside of the drill bit base in the radially inner region (11) to form a conical cavity (12, 17) up to the location of a center drill (7, 14) at an angle upwards Direction of the drill bit shaft runs. Drill bit, especially for rotary drilling of preferably rock, concrete or the like, consisting of a pot-like drill body or crown part provided with a coaxial insertion shaft, the outer cylindrical wall part of the pot-like crown part being provided with an external conveyor helix for transporting drilling dust, characterized in that that the external feed helix of the drill bit has a drilling dust removal groove (109) which has its smallest slope in the region of the front end (114), the slope of the removal groove (109) towards the shaft end increasing with the width of the groove and the back web width r over the essential height (h2) of the drill bit remains approximately constant. Drill bit according to claim 21, characterized in that the groove depth t in a thin-walled crown part (102) with a wall thickness (s) is constant or variable and the wall thickness has a size s ≈3.5 to 5 mm. Drill bit according to claim 22 or 21, characterized in that the pitch α of the drilling dust groove in the area of the drill head has a size of α1 ≈ 2 to 4 °, which continuously or discontinuously to a size of α4 ≈ 10 to 15 ° in the rear area of the Funding spiral enlarged. Drill bit according to one of claims 21 to 23, characterized in that the groove width n of the conveying helix (109) increases continuously towards the shaft-side region of the conveying helix and that the back width (r) of the conveying spiral web is constant or almost constant in the essential region of the drill bit or only increases slightly.

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