Drill head for a drill and drill

Abstract

A drill head is provided with three main cutting edges each having a straight direction of extension with a predominant radial direction component. The directions of extension limit two adjacent main bore dust discharge sectors, each spanning a main sector angle. Three drill head cutting legs each forming a main cutting edge where the three main cutting edges have different lengths along their directions of extension. Concentric ring shaped removal areas overlap at least partially such that a triple removal area coverage is provided in an outer ring zone and a double removal area coverage is provided in an inner ring zone.

Claims

1. A drill head for a drill, the drill head comprising: a mounting side configured for mounting the drill head on a drill shaft of the drill; and a free cutting side configured for cutting a workpiece, the free cutting side comprising: a first main cutting edge having a straight first direction of extension with a first predominant radial direction component pointing towards an axial work rotation axis of the drill head; a second main cutting edge having a straight second direction of extension with a second predominant radial direction component pointing towards the axial work rotation axis; and a third main cutting edge having a straight third direction of extension with a third predominant radial direction component pointing towards the axial work rotation axis; wherein the first direction of extension and the third direction of extension define a first main bore dust discharge sector spanning a first main sector angle; wherein the first direction of extension and the second direction of extension define a second main bore dust discharge sector spanning a second main sector angle; wherein each of the first main sector angle and the second main sector angle is greater than 120; and wherein the first direction of extension and the second direction of extension intersect at an intersection point that is radially offset from the axial work rotation axis.

2. The drill head according to claim 1, wherein the first main sector angle is equal to the second main sector angle.

3. The drill head according to claim 1, wherein the second direction of extension and the third direction of extension define an auxiliary bore dust discharge sector spanning an auxiliary sector angle, and wherein the auxiliary sector angle is less than or equal to 110 and greater than 20.

4. The drill head according to claim 3, wherein the first main cutting edge comprises a chisel tip and a short portion connected to the chisel tip, wherein the short portion and at least a portion of the chisel tip are positioned within the auxiliary bore dust discharge sector, and wherein a direction of extension of the short portion divides the auxiliary bore dust discharge sector into two auxiliary bore dust discharge sub-sectors having equal auxiliary sub-sector angles.

5. The drill head according to claim 3, wherein the auxiliary sector angle is less than or equal to 110 and greater than 50.

6. The drill head according to claim 3, wherein the auxiliary sector angle is between 100 and 90.

7. The drill head according to claim 1, wherein the first main cutting edge has a first length, wherein the second main cutting edge has a second length that is less than the first length, wherein the third main cutting edge has a third length that is less than the second length, wherein the first main cutting edge comprises a chisel tip positioned symmetrically relative to the axial work rotation axis, and a long portion and a short portion positioned diametrically opposite to each other relative to the axial work rotation axis and each flowing uninterruptedly into the chisel tip.

8. The drill head according to claim 1, wherein the first main cutting edge, the second main cutting edge, and the third main cutting edge do not intersect one another, wherein the first main cutting edge and the second main cutting edge each extend from a radially outer end to a radially inner end with a constant slope relative to an axial direction of the drill head, and wherein the radially inner ends and the radially outer ends are defined by a change of the slope.

9. The drill head according to claim 1, wherein the drill head is not rotationally symmetric about the axial work rotation axis.

10. The drill head according to claim 1, wherein the drill head comprises a Y-shaped body comprising a base leg, a first side leg, and a second side leg, and wherein wall surfaces of the base leg, the first side leg, and the second side leg have a concave shape in a radial direction of the drill head and limit corresponding bore dust discharge sectors that extend parallel to the axial work rotation axis and fade into a corresponding helical turning of the drill shaft.

11. The drill head according to claim 1, wherein the first main bore dust discharge sector and the second main bore dust discharge sector are free of further cutting edges.

12. The drill head according to claim 1, wherein the first main bore dust discharge sector extends in an axial direction of the drill head from a lateral surface of a drilling cone spanned by the first main cutting edge, the second main cutting edge, and the third main cutting edge, wherein the second main bore dust discharge sector extends in the axial direction of the drill head from the lateral surface of the drilling cone, and wherein a tip of the drilling cone is located on the axial work rotation axis.

13. The drill head according to claim 1, wherein each of the first main sector angle and the second main sector angle is between 125 and 150.

14. The drill head according to claim 13, wherein each of the first main sector angle and the second main sector angle is between 130 and 135.

15. The drill head according to claim 1, wherein the first main cutting edge has a first length, wherein the second main cutting edge has a second length that is less than the first length, wherein the third main cutting edge has a third length that is less than the second length.

16. The drill head according to claim 1, wherein the first main cutting edge, the second main cutting edge, and the third main cutting edge are formed in one piece with the drill head.

17. A drill comprising: a drill shaft comprising a plug-in end for inserting the drill shaft into a drilling apparatus; a triple channelled bore dust discharge helix defined in the drill shaft; and a drill head installed at a receiving end of the drill shaft positioned opposite the plug-in end, the drill head comprising: a mounting side mounted on the drill shaft; and a free cutting side configured for cutting a workpiece, the free cutting side comprising: a first main cutting edge having a straight first direction of extension with a first predominant radial direction component pointing towards an axial work rotation axis of the drill; a second main cutting edge having a straight second direction of extension with a second predominant radial direction component pointing towards the axial work rotation axis; and a third main cutting edge having a straight third direction of extension with a third predominant radial direction component pointing towards the axial work rotation axis; wherein the first direction of extension and the third direction of extension define a first main bore dust discharge sector spanning a first main sector angle; wherein the first direction of extension and the second direction of extension define a second main bore dust discharge sector spanning a second main sector angle; wherein each of the first main sector angle and the second main sector angle is greater than 120; and wherein the first direction of extension and the second direction of extension intersect at an intersection point that is radially offset from the axial work rotation axis.

18. A drill head for a drill, the drill head comprising: a mounting side configured for mounting the drill head on a drill shaft of the drill; and a free cutting side configured for cutting a workpiece, the free cutting side comprising: a first main cutting edge having a straight first direction of extension with a first predominant radial direction component pointing towards an axial work rotation axis of the drill head and having a first length along the first direction of extension; a second main cutting edge having a straight second direction of extension with a second predominant radial direction component pointing towards the axial work rotation axis and having a second length along the second direction of extension; and a third main cutting edge having a straight third direction of extension with a third predominant radial direction component pointing towards the axial work rotation axis and having a third length along the third direction of extension; wherein the first length, the second length, and the third length are different from one another; and wherein the first main cutting edge, the second main cutting edge, and the third main cutting edge each extend with a constant slope relative to an axial direction of the drill head from a radial outer end to a radially inner end, wherein the radially inner ends and the radially outer ends are defined by a change of the slope.

19. The drill head according to claim 18, wherein each of the first main cutting edge, the second main cutting edge, and the third main cutting edge extends in the axial direction of the drill head and spans a lateral surface of a drilling cone, wherein a tip of the drilling cone is located on the axial work rotation axis, and wherein the first length, the second length, and the third length are defined by respective portions of the first main cutting edge, the second main cutting edge, and the third main cutting edge that lie within the lateral surface.

20. The drill head according to claim 18, wherein the first direction of extension and the third direction of extension define a first main bore dust discharge sector, wherein the first direction of extension and the second direction of extension define a second main bore dust discharge sector, wherein the first main bore dust discharge sector and the second main bore dust discharge sector each extend in the axial direction of the drill head from a lateral surface of a drilling cone spanned by the first main cutting edge, the second main cutting edge, and the third main cutting edge, wherein a tip of the drilling cone is located on the axial work rotation axis, and wherein the first main cutting edge forms a crest between the first main bore dust discharge sector and the second main bore dust discharge sector.

21. The drill head according to claim 20, wherein the first main bore dust discharge sector spans a first main sector angle, wherein the second main bore dust discharge sector spans a second main sector angle, and wherein each of the first main sector angle and the second main sector angle is greater than 120.

22. The drill head according to claim 18, wherein the second direction of extension and the third direction of extension define an auxiliary bore dust discharge sector spanning an auxiliary sector angle, and wherein the auxiliary sector angle is equal to or less than 110.

23. The drill head according to claim 18, wherein the first main cutting edge comprises a chisel tip, and a long portion and a short portion formed diametrically opposite one another relative to the axial work rotation axis, and wherein the chisel tip is located on the axial work rotation axis.

24. The drill head according to claim 18, wherein the first main cutting edge runs ahead of the second main cutting edge relative to a work rotation direction of the drill head, wherein the second main cutting edge runs ahead of the third main cutting edge relative to the work rotation direction, and wherein the third main cutting edge runs ahead of the first main cutting edge in work rotation direction.

25. The drill head according to claim 18, wherein a sum of the first length, the second length, and the third length is less than 110% of a nominal diameter of the drill bit, and wherein a sum of the first length, the second length, the third length, and a length of a chisel of the drill head is between 120% and 140% of the nominal diameter of the drill bit.

26. The drill head according to claim 18, wherein the second length is between 60% and 80% of the first length.

27. The drill head according to claim 18, wherein the third length is between 40% and 60% of the first length.

28. The drill head according to claim 27, wherein the third length is between 55% and 80% of the second length.

29. The drill head according to claim 18, wherein a sum of the first length and a length of a chisel of the drill head is between 0.5 and 0.8 times as long as a nominal diameter of the drill head, wherein the third length is between 0.1 and 0.25 times as long as the nominal diameter of the drill head, and wherein the second length is between 0.15 and 0.35 times as long as the nominal diameter of the drill head.

30. A drill comprising: a drill shaft comprising a plug-in end for inserting the drill shaft into a drilling apparatus; a triple channelled bore dust discharge helix defined in the drill shaft; and a drill head installed at a receiving end of the drill shaft positioned opposite the plug-in end, the drill head comprising: a mounting side mounted on the drill shaft; and a free cutting side configured for cutting a workpiece, the free cutting side comprising: a first main cutting edge having a straight first direction of extension with a first predominant radial direction component pointing towards an axial work rotation axis of the drill and having a first length along the first direction of extension; a second main cutting edge having a straight second direction of extension with a second predominant radial direction component pointing towards the axial work rotation axis and having a second length along the second direction of extension; and a third main cutting edge having a straight third direction of extension with a third predominant radial direction component pointing towards the axial work rotation axis and having a third length along the third direction of extension; wherein the first length, the second length, and the third length are different from one another; and wherein the first main cutting edge, the second main cutting edge, and the third main cutting edge each extend with a constant slope relative to an axial direction of the drill head from a radial outer end to a radially inner end, wherein the radially inner ends and the radially outer ends are defined by a change of the slope.

31. A drill head for a drill, the drill head comprising: a mounting side configured for mounting the drill head on a drill shaft of the drill; and a free cutting side configured for cutting a workpiece, the free cutting side comprising: a first main cutting edge having a straight first direction of extension with a first predominant radial direction component pointing towards an axial work rotation axis of the drill head and defining a first removal area positioned concentrically relative to the axial work rotation axis; a second main cutting edge having a straight second direction of extension with a second predominant radial direction component pointing towards the axial work rotation axis and defining a second removal area positioned concentrically relative to the axial work rotation axis; and a third main cutting edge having a straight third direction of extension with a third predominant radial direction component pointing towards the axial work rotation axis and defining a third removal area positioned concentrically relative to the axial work rotation axis; wherein the first removal area, the second removal area, and the third removal area overlap one another along an outer ring zone extending from a common outer end circumference of the first removal area, the second removal area, and the third removal area to an intermediate circumference boundary, such that the first main cutting edge, the second main cutting edge, and the third main cutting edge provide triple removal within the outer ring zone; wherein the first removal area and the second removal area overlap one another along an inner ring zone extending from the intermediate circumference boundary toward the axial work rotation axis, such that the first main cutting edge and the second main cutting edge provide double removal within the inner ring zone; and wherein the first main cutting edge, the second main cutting edge, and the third main cutting edge each extend from a radially outer end, located on the common outer end circumference, to a radially inner end with a constant slope in an axial direction of the drill head.

32. The drill head according to claim 31, wherein the first removal area does not overlap the second removal area or the third removal area along an inner circular zone extending from the inner ring zone to the axial work rotation axis.

33. The drill head according to claim 32, wherein the first main cutting edge comprises a long portion and a short portion positioned diametrically opposite one another relative to the axial work direction axis.

34. The drill head according to claim 33, wherein the long portion and the short portion of the first main cutting edge provide double removal within the inner circular zone.

35. The drill head according to claim 31, wherein an inner portion of the second removal area overlaps a portion of the first removal area along the inner ring zone.

36. The drill head according to claim 31, wherein the inner ring zone extends over at least 45% of a radius of the drill head, and wherein the intermediate circumference boundary extends through a radially inner end of the third main cutting edge.

37. The drill head according to claim 31, wherein the first direction of extension and the third direction of extension define a first main bore dust discharge sector spanning a first main sector angle, wherein the first direction of extension and the second direction of extension define a second main bore dust discharge sector spanning a second main sector angle, wherein the first main bore dust discharge sector and the second main bore dust discharge sector each extend in an axial direction of the drill head from a lateral surface of a drilling cone spanned by the first main cutting edge, the second main cutting edge, and the third main cutting edge, wherein a tip of the drilling cone is located on the axial work rotation axis, wherein the first main cutting edge forms a crest between the first main bore dust discharge sector and the second main bore dust discharge sector, and wherein each of the first main sector angle and the second main sector angle is greater than 120.

38. The drill head according to claim 31, wherein the first main cutting edge has a first length, wherein the second main cutting edge has a second length, wherein the third main cutting edge has a third length, wherein the first length, the second length, and the third length are different from one another, and wherein each of the radially inner end and the radially outer end is defined by a change in the slope.

39. The drill head according to claim 31, wherein each of the first main cutting edge, the second main cutting edge, and the third main cutting edge extends on a corresponding cutting leg of the drill head with a constant direction component in an axial direction of the drill head and spans a lateral surface of a drilling cone, and wherein a tip of the drilling cone is located on the axial work rotation axis.

40. The drill head according to claim 31, wherein the first direction of extension and the second direction of extension intersect one another at a first intersection point that is radially offset from the axial work rotation axis by a first radial distance, wherein the second direction of extension and the third direction of extension intersect one another at a second intersection point that is radially offset from the axial work rotation axis by a second radial distance, wherein the first direction of extension and the third direction of extension intersect one another at a third intersection point that is radially offset from the axial work rotation axis by a third radial distance, and wherein the first radial distance, the second radial distance, and the third radial distance are different from one another.

41. A drill comprising: a drill shaft comprising a plug-in end for inserting the drill shaft into a drilling apparatus; a triple channelled bore dust discharge helix defined in the drill shaft; and a drill head installed at a receiving end of the drill shaft positioned opposite the plug-in end, the drill head comprising: a mounting side mounted on the drill shaft; and a free cutting side configured for cutting a workpiece, the free cutting side comprising: a first main cutting edge having a straight first direction of extension with a first predominant radial direction component pointing towards an axial work rotation axis of the drill and defining a first removal area positioned concentrically relative to the axial work rotation axis; a second main cutting edge having a straight second direction of extension with a second predominant radial direction component pointing towards the axial work rotation axis and defining a second removal area positioned concentrically relative to the axial work rotation axis; and a third main cutting edge having a straight third direction of extension with a third predominant radial direction component pointing towards the axial work rotation axis and defining a third removal area positioned concentrically relative to the axial work rotation axis; wherein the first removal area, the second removal area, and the third removal area overlap one another along an outer ring zone extending from a common outer end circumference of the first removal area, the second removal area, and the third removal area to an intermediate circumference boundary, such that the first main cutting edge, the second main cutting edge, and the third main cutting edge provide triple removal within the outer ring zone; wherein the first removal area and the second removal area overlap one another along an inner ring zone extending from the intermediate circumference boundary toward the axial work rotation axis, such that the first main cutting edge and the second main cutting edge provide double removal within the inner ring zone; and wherein the first main cutting edge, the second main cutting edge, and the third main cutting edge each extend from a radially outer end, located on the common outer end circumference, to a radially inner end with a constant slope in an axial direction of the drill head.

42. A drill head for a drill, the drill head comprising: a mounting side configured for mounting the drill head on a drill shaft of the drill; and a free cutting side configured for cutting a workpiece, the free cutting side comprising: a first main cutting edge having a straight first direction of extension with a first predominant radial direction component pointing towards an axial work rotation axis of the drill head; a second main cutting edge having a straight second direction of extension with a second predominant radial direction component pointing towards the axial work rotation axis; and a third main cutting edge having a straight third direction of extension with a third predominant radial direction component pointing towards the axial work rotation axis; wherein the first direction of extension and the second direction of extension intersect one another at a first intersection point that is radially offset from the axial work rotation axis by a first radial distance; wherein the second direction of extension and the third direction of extension intersect one another at a second intersection point that is radially offset from the axial work rotation axis by a second radial distance; wherein the first direction of extension and the third direction of extension intersect one another at a third intersection point that is radially offset from the axial work rotation axis by a third radial distance; and wherein the first radial distance, the second radial distance, and the third radial distance are different from one another.

43. The drill head according to claim 42, wherein each of the first radial distance, the second radial distance, and the third radial distance is less than 25% of a nominal diameter of the drill head, wherein the shortest of the first radial distance, the second radial distance, and the third radial distance is less than 10% of the nominal diameter of the drill head, and wherein at least one of the first radial distance, the second radial distance, and the third radial distance is greater than 10% and less than 20% of the nominal diameter of the drill head.

44. The drill head according to claim 42, wherein the first main cutting edge, the second main cutting edge, and the third main cutting edge each extend from a radially outer end to a radially inner end with a constant slope in an axial direction of the drill head, wherein each of the radially inner end and the radially outer end is defined by a change in the slope, wherein the radially inner end of at least one of the first main cutting edge, the second main cutting edge, and the third main cutting edge runs ahead of the corresponding radial direction component, and wherein the radially inner end of at least one of the first main cutting edge, the second main cutting edge, and the third main cutting edge lags behind the corresponding radial direction component.

45. The drill head according to claim 42, wherein the first main cutting edge, the second main cutting edge, and the third main cutting edge are formed in one piece with the drill head.

46. A drill comprising: a drill shaft comprising a plug-in end for inserting the drill shaft into a drilling apparatus; a triple channelled bore dust discharge helix defined in the drill shaft; and a drill head installed at a receiving end of the drill shaft positioned opposite the plug-in end, the drill head comprising: a mounting side mounted on the drill shaft; and a free cutting side configured for cutting a workpiece, the free cutting side comprising: a first main cutting edge having a straight first direction of extension with a first predominant radial direction component pointing towards an axial work rotation axis of the drill head; a second main cutting edge having a straight second direction of extension with a second predominant radial direction component pointing towards the axial work rotation axis; and a third main cutting edge having a straight third direction of extension with a third predominant radial direction component pointing towards the axial work rotation axis; wherein the first direction of extension and the second direction of extension intersect one another at a first intersection point that is radially offset from the axial work rotation axis by a first radial distance; wherein the second direction of extension and the third direction of extension intersect one another at a second intersection point that is radially offset from the axial work rotation axis by a second radial distance; wherein the first direction of extension and the third direction of extension intersect one another at a third intersection point that is radially offset from the axial work rotation axis by a third radial distance; and wherein the first radial distance, the second radial distance, and the third radial distance are different from one another.

Description

(1) Further characteristics, advantages and features of the invention follow from the below description of a preferred embodiment by means of the enclosed drawings:

(2) FIG. 1 shows a frontal view from the top of the drill head according to the invention, in particular with regard to the first aspect of the invention;

(3) FIG. 2 shows a further frontal view from the top of the drill head according to the invention, in particular with regard to the second aspect of the invention;

(4) FIG. 3 shows a frontal view from the top of the drill head according to the invention, in particular with regard to the third aspect of the invention;

(5) FIG. 4 shows a frontal view from the top of the drill head according to the invention, in particular with regard to the fourth aspect of the invention;

(6) The drill head 1 according to the invention has substantially a Y shape comprising a base leg 2, from which two side legs 4, 6 extend away substantially symmetrically to the extension of the base leg. The nominal drill diameter is determined by short sides 23, 43, 63, which point radially outwardly, of the Y legs, which, during the course of a work rotation of the drill, move along a cylinder jacket surface, which defines the borehole wall. The work rotation axis R of the drill runs through the center of the drill head and furthermore forms the center of a drill head circumference. The drill head is embodied from a full hard metal body, which extends in downwards direction of the drawing sheet along the rotation axis of the drill. Heading outer long sides 24, 44, 64, which lead into trailing outer long sides 62, 22, 42 of the respective heading Y leg, in each case connect to the short sides 23, 43, 63 of the Y leg, so as to head in drill work rotation direction.

(7) On the respective free cutting edge sides, which face the person looking at the drawing, a main cutting edge 21, 41, 61 is in each case embodied as crest between respective rake and relief faces, which in each case lift away from the drill head in axial feed direction of the drill, as is suggested by contour lines. The cutting edges are of different lengths and extend radially inwardly, straight from a radially outer end 25, 45, 65, which is formed by means of a D-shaped rounding, up to the short sides 23, 43, 63, which face outwardly. The directions of extension 29, 49, 69 of the cutting edges in each case encompass a direction component K, which mainly faces radially towards the work rotation axis R of the drill, as well as a direction component in axial drill feed direction, which is not illustrated in top view.

(8) The main cutting edges comprise portions having a constant slope in axial drill feed direction, which are limited by the roundings at the radially outer ends 25, 45, 65 and by transitions to bore dust guide surfaces, which are suggested by contour lines 48, 68, 68. The portions having a constant slope define an imaginary lateral or jacket surface of a drilling cone.

(9) The cutting edges divide the drill head into two main bore dust discharge sectors A, B as well as an auxiliary bore dust discharge sector C with the directions of extension thereof 29, 49, 69. The bore dust discharge sectors extend from the jacket surface into helical turns of the drill (not illustrated). The main drill bore dust discharge sectors A, B in each case span a main sector angle , of 135. The auxiliary bore dust discharge sector C spans an auxiliary sector angle of 90.

(10) The long main cutting edge 21, which is located on the Y basis leg, comprises a long portion 21a, a short portion 21b, which is located opposite the long portion 21a relative to the work rotation axis R, and a chisel tip 80, which extends across the rotation axis of the drill and which is located point symmetrically in the form of a double curve, the turning point of which is located on the work rotation axis R of the drill. The long portion 21a, the short portion 21b and the chisel tip form an uninterrupted cutting edge course, wherein the long and the short portion are located in the drilling cone jacket surface and the chisel tip sticks out of the drilling cone for being centered in axial direction.

(11) The short portion 21a divides the side legs 4, 6 substantially centrally and offset parallel to the direction of extension 29 of the long portion 21b. The short portion 21a extends into the auxiliary bore dust discharge sector C and divides the latter into two partial sectors of approximately the same size.

(12) The middle main cutting edge 41, which directly trails the long main cutting edge 21 in work rotation direction 99, is embodied so as to be shorter than the long main cutting edge 21, but longer than the short main cutting edge 61, which directly heads the long main cutting edge 21 in work direction. On the radially inner ends 47, 67 of the middle main and short main cutting edges, the slope thereof decreases relative to the axial direction, which is suggested in the drawing by means of cross lines to the edges. While the long main cutting edge 21 comprising the chisel section mainly performs the drill feed work, the second longest main cutting edge 41 and the shortest main cutting edge 61 have the additional function of transporting away bore dust and to stabilize the drill head in the borehole in accordance with a three-point support.

(13) A bore dust guide section, which guides released material from the main bore dust discharge sector B into the adjacent auxiliary bore dust discharge sector C and vice versa, if applicable, connects to the middle main cutting edge 41 below the drilling cone, as is suggested by means of the lines 48. A guide surface, which is connected to the short main cutting edge 61 and which is suggested by means of the lines 68, 68, forms a groove channel with the sides of the longest main cutting edge 21, which connects the main bore dust discharge sector A to the auxiliary bore dust discharge sector C for the transverse transport of bore dust.

(14) The main cutting edges run at an angle of less than 30 to the respective radial direction component K, wherein the longest main cutting edge 21 is embodied so as to lead radially inwardly relative to the work rotation direction on the Y basis leg 2 and the medium-long main cutting edge 41 on the Y side leg 4 and the shortest main cutting edge 61 is embodied so as to trail radially inwardly. While the two longer cutting edges 21, 41 effect a major tendency towards the respective directly heading bore dust discharge sector A, B due to the heading orientation in response to the bore dust removal, the trailing orientation of the shortest cutting edge 61 in particular facilitates a bore dust removal from the auxiliary bore dust discharge sector C into the trailing main bore dust discharge sector A.

(15) In a respective heading outer long side 24, 44, 64 of the Y legs, a groove 26, 46, 66 is embodied on the radially outer leg end. In downwards direction of the sheet, the groove runs parallel to the rotation axis of the drill towards the bore dust discharge helix of the drill shaft. Additional bore dust can be discharged by means of the recess on the leg end.

(16) As can in particular be seen in FIG. 2, the drill head 1 comprises three drill head cutting edge legs 2, 4, 6, which extend away from a common work rotation axis R, which coincides with the axial rotation axis of that drill, to the drill shaft of which (not illustrated), the drill head is welded with the mounting side (not illustrated).

(17) A respective outer long side 24, 44, 64 of the drill head cutting edge legs 2, 4, 6, which heads in work rotation direction 99 of the drill head, steadily leads into a respective trailing outer long side 62, 22, 42 of a respective drill head cutting edge leg 6, 2, 4, which heads in work rotation direction. The outer long sides 22, 42, 62, 24, 44, 64 are curved towards the drill head rotation axis in a mainly constant manner, so that grooves form, which lead from the free cutting edge sides of the drill head to helical turns of the drill shaft.

(18) Even though it is not illustrated in the top view of the drill head, it should be clear that the drill head extends in downwards direction of the drawing sheet.

(19) The three main cutting edges 21, 41, 61 have different lengths along their respective direction of extension 29, 49, 69 from their radial outer end 25, 45, 65 to the respective radial inner end 27, 47, 67.

(20) The crest of the main cutting edges 21, 41, 61 are located exactly in the jacket surface of the drilling cone, the tip of which is located on the work axis of rotation R. Bore dust discharge sectors, which extend up to the helical turns of the drill shaft (not illustrated) in axial direction of the drill, start at the respective transitions of crest to rake and relief faces of the main cutting edges.

(21) The lengths d1, d2, d3, d1 of the main cutting edges illustrated in the figure are projected into the drawing plane in accordance with the top view and thus do not correspond to the length along the main cutting edges, which can be measured in a three-dimensional space on the drill head and which, however, can be calculated from the axial direction component of the main cutting edges by means of trigonometric formulas. Length specifications, however, refer to the purely radial lengths in drawing plane.

(22) The main cutting edges 21, 41, 61 extend straight, in each case from a radially outer end 25, 45, 65, to a radially inner end 27, 47, 67. The constant slope changes in axial feed direction on the radially outer and inner ends along the main cutting edges, which is suggested in the figure by means of contour lines at right angles to the main cutting edges. A steady transition to substantially -shaped roundings 92, 94, 96, which lead into the outer short sides 23, 43, 63 of the drill head cutting legs 2, 4, 6, is formed on the radially outer ends 25, 45, 65. The susceptibility to breakage of the outer areas of the main cutting edges as well as the rotational friction and tilting chance of the drill head during operation decreases by rounding the transitions from the main cutting edges 21, 41, 61 to the outer short sides of the drill head cutting edge legs 2, 4, 6.

(23) The main cutting edges run straight at an angle of incline of between about 15 and about 40, based on a plane vertically to the work axis of rotation R, between the respective radially outer end 25, 45, 65 and the radially inner end 27, 47, 67.

(24) Compared to the incline of the straight portions of the main cutting edges 21a, 21b of the longest main cutting edge and the further main cutting edges 41, 61, the chisel tip 80 has a larger slope based on a vertical plane to the drill rotation axis, so that the chisel protrudes as centering tip in drill feed direction upstream of the cutting edges. The long portion 21a and the short portion 21b extend parallel offset to one another relative to a common cutting axis (not illustrated), which intersects the work rotation axis of the drill. The long portion 21a and the short portion 21b are located within the drilling cone and together with the chisel 80 form an uninterrupted cutting edge, which spans the drill head in a roof-shaped manner.

(25) Based on the work rotation direction 99 of the longest main cutting edge 21, the second longest main cutting edge or middle main cutting edge 41 is arranged so as to trail. On the radially inner end 47, the second longest cutting edge levels off in a drill head surface contour, which serves as a bore dust guide aid for the bore dust transport between the bore dust discharge sectors. The shortest cutting edge or short main cutting edge 61 is arranged so as to trail the second longest cutting edge 41 in work rotation direction.

(26) The main bore dust discharge sector defined between the direction of extension 29 of the longest cutting edge 21 and the direction of extension 69 of the shortest cutting edge 61, following the work rotation direction 99, as well as the main bore dust discharge sector, which is defined by the direction of extension 49 of the second longest cutting edge 41 and the direction of extension 29 of the longest cutting edge 21, again following the work rotation direction, in each case span a sector angle , of about 135. An auxiliary bore dust discharge sector is defined between the direction of extension 69 of the shortest cutting edge 61 and the direction of extension 49 of the second longest cutting edge 41 and spans an angle of about 90.

(27) A cutting edge-free area in the form of a groove, which extends in downwards direction of the sheet, along which the bore dust can flow into the main bore dust discharge sectors as well as into the auxiliary bore dust discharge sector, is embodied between the radially inner end 47 of the second longest main cutting edge 41 and the chisel tip. A cutting edge-free distance in the form of a valley, which faces downwards, is likewise embodied between the radially inner end 67 of the shortest cutting edge 61 and the chisel tip, for discharging bore dust.

(28) The entire drill head 1 is made of one piece of carbide and is welded completely to the shaft of the drill, in which a triple helix is embodied, via a mounting side (not illustrated).

(29) A majority (more than 50 percent) of the radially outer short sides 23, 43, 63 of the drill head cutting edge legs 2, 4, 6 is embodied as a respective straight trailing portion 23, 43, 63 so as to be inclined radially inwardly, in order to minimize the hole friction.

(30) As can be seen in particular in FIG. 3, bore dust discharge areas, which are curved concavely towards the work rotation axis, extend between the Y legs of the drill head parallel to the work rotation axis in downwards of the sheet direction and lead into helical turns of the drill shaft, which are not illustrated in detail.

(31) The main cutting edges 21, 41, 61 have different lengths and extend from a respective radially outer end 25, 45, 65, which is offset radially inwardly relative to the radially outermost short side 23, 43, 63 of the Y legs in the direction of a work rotation axis R of the drill through a rounding of about 4% of the nominal drill diameter towards radially inner ends 27, 47, 67.

(32) The directions of extension 29, 49, 69 of the main cutting edges 21, 41, 61 intersect one another in intersection points S1, S2, S3, which are not arranged on the work rotation axis R and at different distances L2, L4, L6 thereto. The intersection point S2 between the directions of extension of the long portion 21a of the longest main cutting edge or long main cutting edge 21 and the second longest main cutting edge or middle main cutting edge 41 encompasses the largest purely radial distance L6 to the work rotation axis R. The intersection point S1 between the directions of extension of the second longest main cutting edge 41 and the shortest main cutting edge or short main cutting edge 61 encompasses the second largest radial distance L4 from the work rotation axis R. The directions of extension 29, 69 of the long portion 21a of the longest main cutting edge 21 and of the shortest main cutting edge 61 meet one another at the intersection point S3, which is closest to the work rotation axis. The short portion 21b of the long main cutting edge 21 intersects the direction of extension of the short main cutting edge 61 in the intersection point S5 and intersects the direction of extension of the middle main cutting edge 41 in the intersection point S4.

(33) The main cutting edges 21, 41, 61 in each case run at a different angle to a respective pure radial direction component K. The angles are between about 2 and 20. Due to the different orientation based on the rotation axis of the drill, none of the main cutting edges fits into an impact recess, which was created in a preceding impact stroke by means of a different one of the main cutting edges.

(34) The short portion 21b of the longest cutting edge 21 is embodied in the auxiliary bore dust discharge sector.

(35) The direction of extension of the short portion 21b of the longest main cutting edge 21 runs parallel to the direction of extension 21 of the majority of the longest main cutting edge, which is formed by means of the long portion 21a, and also intersects the directions of extension 49, 69 of the shortest 61 and second longest 41 main cutting edges outside of the work axis of rotation R.

(36) A distance of cutting edges is in each case left open between the chisel tip 80 and the ends 47, 67 of the second longest 41 and the shortest 61 main cutting edges. In this area of these distances, depressions are included into the drill head 1 along the longest main cutting edge 21 (suggested by means of contours 68, 68, 48), in which bore dust pours away from the main bore dust discharge sectors into the auxiliary bore dust discharge sector and vice versa.

(37) As can be seen in particular in FIG. 4, the extensions of the main cutting edges 21, 41, 61 pass through respective removal areas 21, 21, 41, 61 in the form of a circle or ring within or above the jacket or lateral surface during a 360 rotation of the drill head. The long cutting edge 21, which comprises the chisel tip 80, defines a first removal area with a long portion 21a and a second removal area with the short portion 21b about the work rotation axis R. The middle cutting edge 41 defines a ring-shaped removal area 41, which extends from a circle about the radially outer end of the short portion 21b, which intersects the slope change at the radially inner end 47 of the second longest cutting edge, to the radially outer end 45 of the middle cutting edge 41. The ring-shaped removal area 61 of the short cutting edge 61 extends from the radially inner end 67 thereof to the radial outer end 65.

(38) In a cutting zone IV, in which only the longest main cutting edge 21 operates, the removal area 21 of the long portion 21a thereof is covered by the removal area 21 of the short portion 21b. Free bore dust is thus either transported away through the long portion 21a and the half of the chisel tip 80, which faces the long portion, or after 180 through the short portion 21b and the half of the chisel tip 80, which faces the short portion.

(39) A double cutting zone III, in which the removal area of the long portion 21a of the long cutting edge and the removal area of the middle cutting edge 41 overlap, connects directly radially outside to the cutting zone IV. The cutting zone IV and double cutting zone III together form an inner ring zone II, in which only a double removal area coverage or overlap exists. Coarse drill cuttings can thus pour away easily and the impact energy is transferred effectively to the drill piece via a slight cutting edge surface.

(40) In the outer ring zone I, the removal areas 21, 41, 61 of the long portion 21a of the long cutting edge 21, the middle cutting edge 41 and the short cutting edge 61 overlap one another, so as to transport away as much bore dust as possible, and so as to evenly distribute the tool forces to increase the stability.

(41) The outer ring zone I extends from an outer circumference U, which is defined by the radial outer ends 25, 45, 65 of the main cutting edges 21, 41, 61, up to an intermediate circumference boundary L, which is determined by the radial inner end 67 of the short cutting edge 61.

(42) Due to the different orientation based on the rotation axis of the drill, none of the main cutting edges fits into an impact recess, which was created by another one of the main cutting edges in a preceding impact stroke. The drill cuttings are furthermore guided away from the drill head center to the bore dust discharge grooves.

(43) The features disclosed in the above description, the figure and the claims can be significant for the realization of the invention in the different embodiments, either alone as well as in combination.

REFERENCE SIGNS

(44) 1 drill head 2 basis leg 4, 6 side leg 21, 41, 61 main cutting edge 21, 21, 41, 61 removal areas 21a long portion 21b short portion 22, 42, 62 trailing outer long sides 23, 43, 63 outer short sides 23, 43, 63 straight trailing portion 24, 44, 64 heading outer long sides 25, 45, 65 radially outer ends 27, 47, 67 radially inner ends 29, 49, 69 directions of extension 48 bore dust guiding portion 68, 68 drill head contours 80 chisel tip 92, 94, 96 roundings 99 work rotation direction , main sector angle auxiliary sector angle A, B main bore dust discharge sector C auxiliary bore dust discharge sector d.sub.1, d.sub.1, d.sub.2, d.sub.3 lengths K direction component L.sub.2, L.sub.4, L.sub.6 radial distance R work rotation axis S.sub.1, S.sub.2, S.sub.3, S.sub.4, S.sub.5 intersection points U outer end circumference L intermediate circumference boundary