DRILLING TOOL, IN PARTICULAR SPIRAL DRILL

Abstract

In a drilling tool, in particular a spiral drill, in particular for drilling rock, comprising a tool-side fastening end, a workpiece-side cutting end and an interposed cutting part comprising at least one main helical groove extending along the cutting part, which is defined by a substantially constant helix pitch, and at least one partially cylindrical and/or partially conical helix web outer face extending along the cutting part, defined by at least one main helical groove, it is provided that a plurality of groove sections are formed in the helix web outer face, which extend transversely to the direction of the pitch of the main helical groove.

Description

The invention relates to a drilling tool, in particular a spiral drill, in particular for drilling rock. Such a drilling tool is usually shaft-shaped, wherein in most cases, the outer side of an initial shaft is uniformly cylindrical. A fastening end of the drilling tool can also be conical in order to fix a particularly accurate axial position of the drilling tool relative to the drilling drive.

The drilling tool is usually provided with a cutting end or drilling head which is possibly reinforced by a hard metal plate which is inserted in a slot at the cutting end of the drilling tool and fastened. The drilling head or the cutting end are characterised by a main cutting angle which usually lies between 100° and 150°.

When positioning the drilling tool, the cutting end initially engages in the workpiece and as drilling is continued, a cutting part located between the fastening end and the cutting end comes into engagement with the workpiece, whereby a cylindrical hole is cleared in the workpiece.

The cutting part forming the predominant part of the drilling tool usually has two main helical grooves extending along the cutting part, via which the drilling dust is to be removed from the cutting end. Furthermore, the known cutting part forms a partially cylindrical or partially conical helix web outer face extending along the cutting part, defined by the two main helical grooves, which usually extends with the same pitch parallel and between two main helical grooves. From the partially cylindrical helix web outer face, the cutting part is formed with a step-shaped profile jump at the transition to the respective main helical groove, by which means a helically extending edge or cutting edge is formed. On viewing the cross-section of the drill, the helix web outer face runs along the constant outside diameter of the cylindrical shaft base body of the drilling tool. Various types of drilling tool are known to increase the drilling efficiency of the drilling tool. Known from DE 20 2005 016 682 U1, for example, is a drilling tool whose main helical groove is stepped at its groove flank facing the drilling head. The individual steps run with the same pitch within the main helical groove.

EP 0 685 629 B1 discloses a rock drill in which two parallel removal flutes are incorporated in the drill shaft. In this way, two parallel-running removal flutes having different flute cross-sections should be provided.

Known from DE 297 23 908 U1 is a rock drill a main helical groove divided into a plurality of parallel-running, separate drilling groove sections, wherein the drilling groove sections are either separated by annular elevations or corresponding indentations, each having the same pitch. DE 103 42 817 A1 discloses a drill having a main helical groove in which a plurality of helical, annular projections running parallel to the main helical groove are incorporated, forming a plurality of drilling groove sections of parallel profile.

All the known aforesaid drilling tool designs suffer from the disadvantage that the strength of the drilling tool is significantly impaired by the additional profiling to form larger or separate helical drilling grooves. As a result of the additional helical groove sections, stress peaks are formed at the cutting part of the drilling tool defined by the helical groove sections and the concomitant weakening of the material, which stress peaks can lead to premature failure of the drilling tool.

It is the object of the invention to overcome the disadvantages of the prior art, in particular to further develop a drilling tool of the generic type in such a manner that the drilling efficiency is increased without impairing the fatigue strength of the drilling tool.

This object is achieved by the features of patent claim 1.

According to the invention, a plurality of groove sections are incorporated in the partially cylindrical helix web outer face, in particular on one or several imaginary helical tracks around the cutting part of the drilling tool, which groove sections extend transversely or at an appreciable angle, in particular of 200 to 900, to the direction of the pitch of the main helical groove. The individual groove sections preferably run rectilinearly on the helix web outer surface and in particular have a constant groove radial depth and/or groove width and/or groove length. The plurality of groove sections can lie concentrically to the longitudinal axis of the drilling tool on a closed annular track. An arrangement of the plurality of groove sections along one or more imaginary helical tracks has provide more advantageous, particularly compared to the arrangement of the plurality of groove sections on a closed annular track, in that the fatigue strength is higher in the helical-track-like arrangement. It was shown that in the arrangement of the groove sections on a closed annular track, the stress peaks induced during operation in the material delimiting the plurality of groove sections are higher than in the helical-track-like arrangement of the plurality of grooves. Tests have shown that the drilling efficiency can be increased significantly with the measure according to the invention. The plurality of groove sections located transversely to the main helical groove in the helix web outer face effect a significant reduction in the friction between the workpiece and the drilling tool, wherein on the one hand, less drive energy needs to be introduced into the drilling tool and on the other hand, the drilling tool is far less thermally loaded. It was also shown that no adverse influence on the fatigue strength of the drilling tool is noticeable due to the groove sections according to the invention in the helix web outer face where the drilling tool is configured to be the strongest in some sections.

In a preferred embodiment of the invention, the plurality of groove sections extend with a substantially greater circumferential direction component than axial direction component. It is clear that the annular sections can also extend exclusively in the axial direction. It was shown, however, that a dominant circumferential direction component is more advantageous in regard to the drilling efficiency.

In a preferred embodiment of the invention, the plurality of groove sections are arranged parallel to one another. As a result of the parallel arrangement and the spacing of the plurality of groove sections from one another necessarily incurred, it is possible to increase the drilling dust removal effect of the plurality of grooves without weakening the drilling tool too severely.

The plurality of groove sections preferably each extend from an edge of the main helical groove facing the cutting end to an edge of the main helical groove facing the fastening end, in particular linearly circumferentially. They preferably extend from one edge to the other on the shortest path along the helix web outer face.

In a preferred further development of the invention, the plurality of groove sections lie on at least one common auxiliary helical track whose pitch is smaller than the pitch of the main helical groove. The helix pitch is defined by an axial width (in mm) of a full-circumference 3600 revolution of the helix. The pitch of the at least one auxiliary helical track is preferably smaller than the pitch of the main helical groove in such a manner that the helical course of the auxiliary helical track during one revolution is interrupted at least once, preferably several times, in particular more than five to ten times, by the main helical groove. In this arrangement of the plurality of groove sections on a single helical track extending along the drilling tool, of different pitch to the pitch of the main helical groove, optimal fatigue strength results were achieved, whereby the drilling efficiency can be increased as a result of improved removal of drilling dust and a reduction in the thermal loading of the drilling tool.

In a preferred embodiment of the invention, the pitch of the main helical track is at least twice, in particular five times, preferably ten times, in particular twelve or fifteen times larger than the helix pitch of the imaginary auxiliary helical track on which the plurality of groove sections inserted exclusively in the helix web outer face are positioned.

The helix pitch of the imaginary auxiliary helical track and/or the helix pitch of the main helical groove preferably remain constant along the total axial extension of the cutting part. In this way, substantially continuous and blockage-free removal of drilling dust can be achieved along the main helical groove and the plurality of groove sections.

In a preferred embodiment of the invention if a diameter of the cylindrical shaft base body of the drilling tool, in particular the partially cylindrical helix web outer face is 5 mm, 6 mm, 6.5 mm, 7 mm, 8 mm, 9 mm or 10 mm, a helix pitch of the auxiliary helical track in a range of 0.5 mm to 3 mm, preferably of 1 mm to 2.5 mm, preferably of 1.5 to 2 mm is selected. In this case, in particular the helix pitch of the main helical groove is determined in a range of 15 mm to 40 mm, preferably of 20 mm to 30 mm.

In a further development of the invention, a width of the plurality of groove sections and/or a radial depth of the plurality of groove sections is smaller than a groove width of the main helical groove or a radial depth of the main helical groove. The groove width is defined from the shortest distance between two opposing edges of the main helical groove at the radial level of the cylindrical outer web face between two main helical grooves. The radial depth of the main helical groove is defined by the radial distance of its radial low to the partially cylindrical outer web face between two adjacent main helical grooves.

A radial depth of the plurality of groove sections is preferably less than 1 mm, preferably less than 0.5 mm, in particular equal to 0.1 mm. A width of the plurality of groove sections can be less than 1 mm, in particular equal to about 0.5 mm, 0.6 mm or 0.7 mm.

In a preferred embodiment of the invention, the plurality of groove sections lie interrupted by the at least one main helical groove on an imaginary (uninterrupted) auxiliary helical track. The auxiliary helical track covering the plurality of groove sections winds in particular substantially over then entire axial length of the cutting part.

The auxiliary helical track covering the plurality of grooved sections preferably opens substantially into the drilling end, wherein either one of the groove sections opens at the drilling end or at least in a very close proximity to the drilling end.

In a further development of the invention, each groove section opens from a main helical groove edge into the adjacent, opposing main helical groove edge.

In a further development of the invention, the helix pitch direction of the imaginary auxiliary helical track is either in the opposite direction to or preferably in the same direction as the helix pitch direction of the main helical groove.

Further properties, features and advantages of the invention will become apparent from the following description of a preferred embodiment of the invention with reference to the appended drawings, in which:

FIG. 1 shows a side view of a drilling tool according to the invention; and

FIG. 2 shows a cross-sectional view of the drilling tool according to FIG. 1 along the line of intersection II-II.

In FIGS. 1 and 2, the spiral drill according to the invention is generally provided with the reference numeral 1. The spiral drill 1 has a substantially cylindrical basic shaft form.

The spiral drill 1 forms a fastening end 3 which is designed to be cylindrical and has recesses 5, 7 at the end in order to ensure a defined position with regard to the drilling tool drive (not shown). The cylindrical fastening end 3 extends substantially over a quarter to a third of the total length of the spiral drill 1.

In the axial direction X, the fastening end 3 is followed by the cutting part 11 whose maximum cylindrical outside diameter is slightly smaller than that of the fastening end 3.

In the ideally cylindrical base body of the cutting part 11 at the beginning of the production process of the spiral drill, two parallel-running spiral main helical grooves 13, 15 are incorporated, which extend with constant pitch along the cutting part 11 to a drilling head or cutting end 17 of the spiral drill 1, which defines at least two main cutting edges.

Between the main helical grooves 13, 15 there remain two partially cylindrical helix web outer faces 21, 23 of the cylindrical base body of the cutting part, which are spaced apart from one another by a main helical groove 13, 15 and run parallel to one another, and have the same pitch as the two main helical grooves 13, 15. The width (shortest distance between two opposing boundary edges of a helix web outer face 21, 23) of each helix web outer face 21, 23 substantially corresponds to the width (shortest distance between the opposing edges defining the main helical groove 13, 15) of the main helical groove 13, 15. The helix pitch (axial width in the case of a full-circumference 360° revolution of the helix) of the helix web outer faces 21, 23 and the main helical grooves 13, 15 is about 20 to 30 mm.

In both partially cylindrical helix web outer faces 21, 23, an interrupted auxiliary helical track can be identified, formed by a plurality of equal-length groove sections 27. The groove sections 27 cover the constant-pitch auxiliary helical track and the plurality of groove sections 27 are indicated in alignment with one another relative to the revolution of the auxiliary helical track. The helix pitch of the plurality of groove sections 27 is significantly smaller than that of the main helical grooves 13, 15 or the helix web outer faces 21, 23.

The constant helix pitch of the interrupted auxiliary helical track is about 1.5 to 2 mm for a 360° revolution. Each groove section 27 of the auxiliary helical track has a radial depth of about 0.1 mm and a width of about 0.5 to 0.7 mm.

The individual groove sections 27 lie parallel to one another and have a significantly larger circumferential direction component than axial direction component. The circumferential direction component is slightly smaller than a right angle to the axial direction X.

As can be seen in FIG. 1, each groove section 27 opens at an angle of 30° to 60° at the transition edge between the helix web outer face 21, 23 and the respective main helical groove 13, 15 into the main helical groove 13, 15 which is indicated in FIG. 2 by the asymmetrical nose opening of the groove sections 27. As can be seen in FIG. 2, both main helical grooves 13, 15 have a convex groove base.

As a result of the small helix pitch, the auxiliary helical track is interrupted several times by the main helical groove 13, 15, wherein each groove section 27 of the auxiliary helical track opens from a main helical groove edge into the opposing edge, extending continuously free from kinks.

It was shown that with the auxiliary helical track defined by the groove sections 27 having the same pitch direction in relation to the pitch direction of the main helical groove, the removal of drilling dust can be increased and the friction between the helix web outer face and the workpiece can be significantly reduced. The removal of heat from the drilling tools is also improved by the fan-like arrangement of interrupted groove sections 27 according to the invention because the groove sections effect cooling by producing air turbulence at the outer side of the spiral drill 1.

The features disclosed in the preceding description, the figures and the claims can be important both singly and in any combination for implementing the invention in the different embodiments.

REFERENCE LIST

• 1 Spiral drill
• 3 Fastening end
• 5, 7 Recesses
• 11 Cutting part
• 13, 15 Main helical groove
• 17 Cutting end
• 21, 23 Helix web outer faces
• 27 Groove sections
• x Axial direction

Claims

1. A drilling tool, in particular a spiral drill, in particular for drilling rock, comprising a tool-side fastening end, a workpiece-side cutting end and an interposed cutting part comprising at least one main helical groove extending along the cutting part, which is defined by a substantially constant helix pitch, and at least one partially cylindrical and/or partially conical helix web outer face extending along the cutting part, defined by said at least one main helical groove, characterised in that a plurality of groove sections are formed in the helix web outer face, which extend transversely to the direction of the pitch of the main helical groove.

2. The drilling tool according to claim 1, characterised in that the plurality of groove sections are arranged parallel to one another.

3. The drilling tool according to claim 1 or 2, characterised in that the plurality of groove sections each extend from an edge of the main helical groove facing the cutting end to an edge of the main helical groove facing the fastening end.

4. The drilling tool according to any one of the preceding claims, characterised in that the plurality of groove sections lie on at least one common auxiliary helical track whose pitch is smaller than the pitch of the main helical groove.

5. The drilling tool according to claim 4, characterised in that the pitch of the at least one auxiliary helical track is smaller than the pitch of the main helical groove in such a manner that the helical course of the auxiliary helical track during one revolution is interrupted at least once, preferably several times, in particular more than five to ten times, by the main helical groove.

6. The drilling tool according to claim 4 or 5, characterised in that the pitch of the main helical track is at least twice, in particular five times, preferably ten times, in particular twelve or fifteen times larger than the pitch of the auxiliary helical track.

7. The drilling tool according to any one of claims 4 to 6, characterised in that the pitch of the auxiliary helical track and/or the at least one pitch of the main helical groove remain unchanged along the cutting part (11).

8. The drilling tool according to any one of claims 4 to 7, characterised in that if a diameter of the drilling tool is 5 mm, 6 mm, 6.5 mm, 7 mm, 8 mm, 9 mm or 10 mm, a pitch of the auxiliary helical track in a range of 0.5 mm to 3 mm, preferably of 1 mm to 2.5 mm, preferably of 1.5 to 2 mm is selected, wherein in particular the pitch of the main helical groove is selected in a range of 15 mm to 40 mm, preferably of 20 mm to 30 mm.

9. The drilling tool according to any one of the preceding claims, characterised in that a width of the plurality of groove sections and/or a radial depth of the plurality of groove sections is smaller than a width of the main helical groove or a depth of the main helical groove.

10. The drilling tool according to any one of the preceding claims, characterised in that a radial depth of the plurality of groove sections is less than 1 mm, preferably less than 0.5 mm, in particular equal to about 0.1 mm.

11. The drilling tool according to any one of the preceding claims, characterised in that a width of the plurality of groove sections is less than 1 mm, in particular equal to about 0.5 mm, 0.6 mm or 0.7 mm.

12. The drilling tool according to any one of the preceding claims, characterised in that the plurality of groove sections lie interrupted by the at least one main helical groove on an auxiliary helical track, wherein the auxiliary helical track defined by the plurality of groove sections winds in particular in constant pitch substantially over then entire axial length of the cutting part.

13. The drilling tool according to claim 9, characterised in that the auxiliary helical track forming the plurality of grooved sections substantially opens into the drilling end.

14. The drilling tool according to any one of the preceding claims, characterised in that each groove section opens from a main helical groove edge into the opposing main helical groove edge.

15. The drilling tool according to any one of the preceding claims, characterised in that the pitch direction of the auxiliary helical track is in the opposite direction to or preferably in the same direction as the pitch direction of the main helical groove.