TOOL

Abstract

The invention relates to a tool for the machining of bores. The tool includes a tool body with a centre axis and a tool end face. At least two secondary cutting edges are formed on the tool body; each secondary cutting edge of the at least two secondary cutting edges, starting from a cutting corner corresponding with the secondary cutting edge on the tool end face, extending in the direction of the centre axis towards a shaft end of the tool in a helical manner with a specific twist pitch. A support collar adjoins each of the secondary cutting edges at a distance, measured in the direction of the centre axis, of at least 0.18 times up to at most 0.28 times the specific twist pitch from the corresponding cutting corner, which support collar extends in the circumferential direction at least up to 1700 to the corresponding cutting corner.

Claims

1. Tool for the machining of bores, comprising: a tool body with a centre axis and a tool end face, wherein at least two secondary cutting edges are formed on the tool body, each secondary cutting edge of the at least two secondary cutting edges, starting from a cutting corner corresponding with the secondary cutting edge on the tool end face, extending in the direction of the centre axis towards a shaft end of the tool in a helical manner with a specific twist pitch, wherein a support collar adjoins each of the secondary cutting edges at a distance, measured in the direction of the centre axis, of at least 0.18 times up to at most 0.28 times the specific twist pitch from the corresponding cutting corner, which support collar extends in the circumferential direction at least up to 1700 to the corresponding cutting corner.

2. Tool according to claim 1, wherein the supporting collar adjoins the corresponding secondary cutting edge at a distance, measured in the direction of the centre axis, of at least 0.22 times to at most 0.25 times the specific twist pitch from the corresponding cutting corner.

3. Tool according to claim 1, wherein the supporting collar starts at an angle of at least 650 to at most 1200 measured in the circumferential direction from the corresponding cutting corner, and/or ends at an angle of at least 1700 to at most 240.

4. Tool according to claim 1, wherein each of the secondary cutting edges is corresponding with a guide chamfer, which extends from the corresponding cutting corner to the corresponding support collar.

5. Tool according to claim 1, wherein the support collar comprises a length, measured in the direction of the centre axis, which is at least 0.2 times, preferably up to at most 1 times, the diameter of a flight circle of the tool defined by the cutting corners.

6. Tool according to claim 1, wherein each secondary cutting edge of the at least two secondary cutting edges is corresponding with a chip flute extending helically from the tool end face in the direction of the centre axis towards the shaft end.

7. Tool according to claim 1, wherein the support collar extends in the direction of the centre axis at least substantially up to an end of the chip flutes facing the shaft end.

8. Tool according to claim 1, wherein at least one lubricating groove is formed in the supporting collar, wherein the at least one lubricating groove extends in circumferential direction without lubricating groove twist pitch, or with a lubricating groove twist pitch different from the specific twist pitch, in particular opposite to the specific twist pitch, or with lubricating groove twist pitch identical to the specific twist pitch.

9. Tool according to claim 1, wherein the guide chamfers comprise a width which is at most 5%, preferably at most 3%, of the diameter of the flight circle defined by the cutting corners.

10. Tool according to claim 1, wherein the support collar is divided in the circumferential direction by at least one lubricating groove into a plurality of support collar regions, wherein a sum of the widths of the support collar regions of the support collar is at least twice as large, preferably three times as large, as the width of the guide chamfer corresponding with the support collar.

11. Tool according to claim 1, wherein the tool has exactly two secondary cutting edges or exactly three secondary cutting edges.

12. Tool according to claim 1, wherein the tool is designed as a drilling tool, in particular as a twist drill.

13. Tool according to claim 1, wherein a main cutting edge is corresponding with each secondary cutting edge of the at least two secondary cutting edges on the tool end face, wherein the main cutting edge merges into the associated secondary cutting edge at the respective cutting corner.

Description

[0043] The invention is explained in more detail below with reference to the drawing. Thereby show:

[0044] FIG. 1 a schematic representation of a first embodiment of a tool in use for the machining of a bore;

[0045] FIG. 2 the principle of operation of the tool;

[0046] FIG. 3 another illustration of the tool according to FIG. 1;

[0047] FIG. 4 an illustration of a second embodiment of the tool;

[0048] FIG. 5 an illustration of a third embodiment of the tool;

[0049] FIG. 6 an illustration of a fourth embodiment of the tool, and

[0050] FIG. 7 an illustration of a fifth embodiment of the tool.

[0051] FIG. 1 shows a representation of a first embodiment of a tool 1 for machining a bore 3 in a workpiece 5. The tool 1 comprises a tool body 7 with a centre axis M and a tool end face 9. Exactly two secondary cutting edges 11 are formed on the tool body 7, in particular on a circumference thereof, in the first embodiment example shown here. The secondary cutting edges 11 and all the elements further associated with them are identically formed in the tool 1 shown here, so that in the following, for reasons of conciseness, only one of the secondary cutting edges 11 and the associated elements will be dealt with in more detail.

[0052] The secondary cutting edges 11 extend from a cutting corner 13 corresponding with the respective secondary cutting edge 11 on the tool end face 9 in the direction of the centre axis M towards a shaft end 15 of the tool 1, shown in particular in FIG. 4, in a helical manner with a specific twist pitch. The specific twist pitch is indicated in particular in the unit length in the direction of the centre axis per revolution of the helical secondary cutting edges 11. Adjacent to each of the secondary cutting edges 11in the circumferential directionat a distance Ab, measured in the direction of the centre axis M, from the associated cutting corner 13 is a support collar 17 which extends in the circumferential direction at least up to an angle of 170, preferably 180, measured from the corresponding cutting corner 13.

[0053] The distance Ab is from at least 0.18 times to at most 0.28 times the specific twist pitch. In particular, the support collar 17 starts at this distance Ab from the cutting corner 13.

[0054] Alternatively, the distance of the support collar 17 from the cutting corner 13 is preferably from at least once a flight circle diameter D of the tool 1, which is defined by the cutting corners 13, to at most 1.8 times the flight circle diameter D, preferably from at least once the flight circle diameter D to at most 1.5 times the flight circle diameter D, preferably from at least 1.2 times the flight circle diameter D to at most 1.4 times the flight circle diameter D. This applies in particular to a tool 1 whose secondary cutting edges 11 have a helix angle of 30.

[0055] Preferably, the distance Ab is from at least 0.22 times to at most 0.25 times the specific twist pitch.

[0056] The support collar 17, which is set back axially from the cutting corner 13, advantageously creates a guide that guides the tool 1 in a particularly stable manner in the bore 3. This applies in particular to deep bores, especially with a bore depth of more than 5 times the flight circle diameter D. This applies in particularas shown schematically in FIG. 1to the machining of a bore 3 in which the tool 1 emerges from the workpiece 5 at an inclined surface 19. As can be seen in FIG. 1, the tool 1 loses its guidance in the area of a cutting corner 13 and thus at the same time a secondary cutting edge 11shown here at the lower cutting corner 13 and the corresponding secondary cutting edge 11so that it is loaded on one side and thus deflected from its axis of rotation. This is now effectively counteracted by the support collar 17 which, due to its axial back offset, is supported in an area of the bore 3 where material is still available for support even on the side where there is no more material in the area of the bore exit. Accordingly, a lapse, in particular a jamming of the tool 1 in the bore 3 is avoided; the bore 3 obtains an excellent roundness and straightness, and the danger of tool breakage is drastically reduced for the tool 1.

[0057] Each secondary cutting edge 11 is corresponding with a main cutting edge 21 at the tool end face 9, which merges into the assigned secondary cutting edge 11 at the respective cutting corner 13.

[0058] In particular, forces relevant to the machining of the workpiece 5 are shown here, especially a main cutting force Fc, which is perpendicular to the image plane in the direction of view of the observer and acts on one of the main cutting edges 21, a passive force Fp acting in the radial direction, as well as a supporting force FSt acting on the supporting collar 17. The corresponding functioning of the tool 1 and the significance of these forces are explained in more detail in connection with FIG. 2.

[0059] Each secondary cutting edge 11 is corresponding with a guide chamfer 23 which extends from the corresponding cutting corner 13 to the corresponding support collar 17. In particular, the guide chamfer 23 ends in the direction of the centre axis M where the support collar 17 begins.

[0060] Preferably, the tool 1 has as many guide chamfers 23 as it has secondary cutting edges 11.

[0061] Each secondary cutting edge 11 is corresponding with a chip flute 25 extending helically from the tool end face 9 in the direction of the centre axis M towards the shaft end 15.

[0062] The guide chamfers 23 each preferably comprise a width that is at most 5%, preferably at most 3% of the flight circle diameter D.

[0063] In a preferred embodimentas shown herethe tool 1 is designed as a drilling tool, in particular as a twist drill. However, it is also possible that the tool 1 is designed, for example, as a reamer or in another suitable way.

[0064] FIG. 2 shows a schematic representation of the operation of the tool 1 in connection with the machining of the bore 3 shown in FIG. 1 when the tool 1 exits in the region of the inclined surface 19.

[0065] Identical and functionally identical elements are provided with the same reference signs in all figures, so that reference is made to the previous description in each case.

[0066] At a) a top view of the tool end face 9 is shown, whereby here again the forces acting on the main cutting edge 21, which is still in engagement with the material of the workpiece 5, are shown schematically. The main cutting force Fc acts perpendicularly on the main cutting edge 21, the passive force Fp acts radially to the centre axis M, and a resulting force Fres results from this by vectorial additionwhereby the arrows shown are not drawn to scale. There is no longer any force acting on the other main cutting edge 21, which has already emerged from the inclined surface 19. Therefore, the resulting force Fres tries to push tool 1 away from the axis of rotation.

[0067] At b) a cross-sectional view through the tool 1 at the axial height of the support collar 17 is shown. It is clear that the support collar 17 provides support for the tool 1 in the bore 3 diametrically opposite the resulting force Fres, which is represented here by a resulting support force FSt-res. Also shown is a supporting force FSt acting diametrically opposite the main cutting force Fc. In the axially recessed area of the supporting collar 17, material of the workpiece 5 is still present on all sides in the bore 3, against which the tool 1 can effectively support itself with the supporting collar 17. This prevents the tool from being pushed away from the axis of rotation and thus prevents the bore 3 from lapsing. As a result, the support collar 17 has the advantage that the support of the tool 1 in the bore 3 is shifted axially backwards away from the area of the cutting corners 13 in the direction of the shaft end 15, which has a positive effect overall on the support and guidance of the tool 1, whereby particularly advantageous effects are achieved, however, in the case of deep bores andas specifically shown herein the case of an oblique bore exit.

[0068] FIG. 3 shows a further representation of the first embodiment of the tool 1 according to FIG. 1. Here, at a), a representation from the side is again reproduced, with certain points being highlighted: At A, a point which is offset by 1800 about the central axis from the point A shown in FIG. 3b), the point A being associated with the cutting corner 13, which in turn is corresponding with the support collar 17 visible to the viewer in FIG. 3a); at B, a point at which the support collar 17 begins in the circumferential direction; and at C, a point at which the support collar 17 ends in the circumferential direction. In a), point A, which is analogous to point A, is only shown because point A is hidden from the viewer in the representation according to a).

[0069] Also shown is a length L that the support collar 17 comprises in the direction of the centre axis M.

[0070] The length L is preferably from at least 0.2 times, preferably 0.5 times the flight circle diameter D, preferably in particular up to the single value of the flight circle diameter D.

[0071] At b) again a top view of the tool end face 9 is shown, where again the points A, B and C defined above are drawn.

[0072] The support collar 17 extends in the circumferential directionmeasured from the corresponding cutting corner 13, that is, from point Apreferably over an angular range starting at at least 65, preferably at least 80, and ending at at least 170, preferably at most 240. This means that point B measured from point A is at least at 65, preferably at least at 80, whereby point C measured from point A is at least at 170, preferably at most at 240, whereby all angle indications refer to a full circle with 360.

[0073] In particular, the support collar 17, measured in the circumferential direction from the corresponding cutting corner 13, preferably starts at an angle of at least 65, preferably from at least 800 to at most 120. The point B is thus in particular measured from the point A at an angle which is from at least 650 to at most 120.

[0074] Alternatively or additionally, the support collar 17 ends at an angle of at least 1700 to at most 2400 measured in the circumferential direction from the corresponding cutting corner 13; the point C is therefore at an angle measured from the point A, in particular, of at least 1700 to at most 240.

[0075] FIG. 4 shows a representation of a second embodiment of the tool 1. Here, the supporting collar 17starting from, i.e. beginning at the distance Abmeasured from the corresponding cutting corner 13, extends in the direction of the centre axis M at least substantially up to an end 27 of the chip flutes 25 facing the shaft end 15, preferably up to the end 27.

[0076] FIG. 5 shows a representation of a third embodiment of the tool 1, wherein at least one lubricating groove 29, in particular exactly one lubricating groove 29, is formed in the support collar 17 here. Here, the lubricating groove 29 extends along the corresponding secondary cutting edge 11 with a lubricating groove twist pitch which is identical to the specific twist pitch of the secondary cutting edge 11.

[0077] FIG. 6 shows a representation of a fourth embodiment of the tool 1, wherein here a plurality of lubricating grooves 29 are formed in the support collar 17. These lubricating grooves 29 extend with a lubricating groove twist pitch different from the specific twist pitch of the secondary cutting edge 11, here in particular opposite to this specific twist pitch. In this way, hydraulic pockets can advantageously be provided in the form of the lubricating grooves 29, in which pressurised or flowing coolant/lubricant helps to stabilise the tool 1 in the bore 3.

[0078] It is also clear from the illustrations of FIGS. 5 and 6 that the support collar 17 can be divided in the circumferential direction by at least one lubricating groove 29 into a plurality of support collar regions 31, in the simpler case of FIG. 5 into two support collar regions 31. A sum of the widths of the support collar regions 31 of the support collar 17 is thereby preferably at least twice as large, preferably three times as large, as the width of the guide chamfer 23 associated with the support collar 17.

[0079] In a manner not shown here, it is also possible for the lubricating groove 29 to extend in the circumferential direction without a lubricating groove twist pitch.

[0080] Finally, FIG. 7 shows a representation of a fifth embodiment of the tool 1, which has exactly three secondary cutting edges 11 and correspondingly also exactly three main cutting edges 21 corresponding with each of these secondary cutting edges 11. This tool 1 is also designed as a drilling tool, in particular as a twist drill, here in particular as a three-flute cutter.