Technical Field

The invention relates to a machining tool and to a method for forming a hole.

Background of the Invention

Some conventional machining tools, such as e.g. reamers, may have a disadvantage in that their lifetime may be limited because of wear of a guiding portion thereof.

Summary of the Invention

The invention provides a machining tool with improved durability. Further, the invention provides a method for forming a hole, in which said machining tool is used for treating an initial hole.

To this end, the invention provides a machining tool (e.g. a drill, a reamer) , which (machining tool) comprises a tool base body (e.g. an elongated tool base body) defining a

central longitudinal axis and having a leading end (with respect to the central longitudinal axis) and a trailing end (with respect to the central longitudinal axis) , the trailing end being configured to be attached to a tool supporter (e.g. the trailing end may be configured so as to be fixedly

attached to a tool supporter in a releasable manner, or e.g. the trailing end may be configured so as to be integrally formed with a tool supporter as one piece) , a first set of cutting inserts which are arranged on the tool base body at a first axial area (e.g. a first axial area along the central longitudinal axis) thereof in a manner so as to be circumferentially spaced from each other (e.g.

circumferentially equally spaced from each other, or e.g.

circumferentially spaced from each other with an irregular angular spacing between each other, e.g. circumferentially spaced from each other with an irregular angular spacing between each other, wherein at least two cutting inserts have a predetermined angular spacing (e.g. of 180°) between each other) around the central longitudinal axis and which together (i.e. the cutting inserts of the first set of cutting inserts as a whole) define a first outer cutting diameter (e.g. define a first outer cutting contour having a first outer cutting diameter) , and a set of guiding portions which (guiding portions) are arranged on the tool base body at a second axial area (e.g. a second axial area along the central longitudinal axis) thereof, which (second axial area) is adjacent (e.g. directly adjacent) to the first axial area in a direction to be more proximal to the trailing end than the first axial area (i.e. in a direction such that the second axial area is more proximal to the trailing end of the tool base body than the first axial area) , and (the guiding portions) are arranged around the central longitudinal axis in a manner so as to be circumferentially spaced from each other (e.g.

circumferentially equally spaced from each other, or e.g.

circumferentially spaced from each other with an irregular angular spacing between each other, e.g. circumferentially spaced from each other with an irregular angular spacing between each other, wherein at least two guiding portions have a predetermined angular spacing (e.g. of 180°) between each other, and/or e.g. circumferentially spaced from each other such that each guiding portion is aligned to a respective one of the cutting inserts of the first set of cutting inserts) and to define together an outer guiding diameter (i.e. the guiding portions as a whole define an outer guiding diameter) (e.g. define an outer guiding contour having an outer guiding diameter) , wherein the said guiding portions are formed by corresponding first outer surface portions of the tool base body, which first outer surface portions have a first surface roughness which is lower than a second surface roughness of surrounding second outer surface portions of the tool base body, which (surrounding second outer surface portions) surround the said first outer surface portions.

The first surface roughness of the first outer surface portions may be a result of/have been provided by outside diameter grinding.

The first surface roughness of the first outer surface portions may have an Rz-value (DIN EN ISO 4287:2010-07) equal to or smaller than 1, optionally an Rz-value (DIN EN ISO

4287:2010-07) in a range of 0.5 to 0.8.

The outer guiding diameter may be smaller than the first outer cutting diameter, wherein, the outer guiding diameter, e.g., may be smaller than the first outer cutting diameter by an amount (e.g. by a radial length) in the range from lym to lOym.

The first axial area may define (e.g. have) a first axial length (along the central longitudinal axis) , the second axial area may define (e.g. have) a second axial length (along the central longitudinal axis) , and the second axial length may differ from the first axial length by a maximum of 10%.

The tool base body may further comprise a set of ribs (integrally formed with the tool base body as one piece) , wherein each rib extends longitudinally in a direction from the leading end of the tool base body towards the trailing end of the tool base body, and wherein each rib has a rib-width (transverse to its length) , wherein the cutting inserts of the first set of cutting inserts are arranged on the ribs, and wherein the first outer surface portions of the tool base body, which form the guiding portions, are formed by

corresponding radially outer (e.g. radially outer with respect to the central longitudinal axis) surfaces of the ribs.

Each guiding portion may have an elongated shape defining a length and may extend, along its length, along the

longitudinal extension of the respective rib (e.g.

longitudinally along the radially outer surface of the

respective rib) , and wherein each guiding portion has a width (transverse to its length) which may be less than the rib- width, wherein, e.g., the width of the respective guiding portion may be equal to or less than 50% of the rib-width.

The second axial area may be directly adjacent (in axial direction) to the first axial area (e.g., the second axial area may axially abut against the first axial area) .

The machining tool may further comprise a second set of cutting inserts (, which second set of cutting inserts, e.g., does not have in common any cutting inserts with the first set of cutting inserts, ) which are arranged on the tool base body at a third axial area (e.g. a third axial area along the central longitudinal axis) thereof in a manner so as to be circumferentially spaced from each other around the central longitudinal axis and which (cutting inserts) together define a second outer cutting diameter (i.e. the cutting inserts of the second set of cutting inserts as a whole define a second outer cutting diameter) (e.g. define a second outer cutting contour having a second outer cutting diameter) , wherein the second outer cutting diameter is larger than the first outer cutting diameter, and wherein the third axial area is more proximal to the trailing end of the tool base body than the second axial area. Along the central longitudinal axis, a distance (e.g. an axial distance, e.g. a distance along the central longitudinal axis) between the second axial area and the third axial area may be larger than a distance (e.g. an axial distance, e.g. a distance along the central longitudinal axis) between the first axial area and the second axial area, wherein,

optionally, the distance (e.g. the axial distance, e.g. a distance along the central longitudinal axis) between the second axial area and the third axial area may be at least 100 times larger than the distance (e.g. the axial distance, e.g. a distance along the central longitudinal axis) between the first axial area and the second axial area.

The machining tool may further comprise a third set of cutting inserts (, which third set of cutting inserts, e.g., does not have in common any cutting inserts with the first set of cutting inserts and/or the second set of cutting inserts, ) which are arranged on the tool base body at a fourth axial area thereof in a manner so as to be circumferentially spaced from each other around the central longitudinal axis and which (cutting inserts of the third set of cutting inserts) together define a third outer cutting diameter (i.e. the cutting inserts of the third set of cutting inserts as a whole define a third outer cutting diameter) (e.g. define a third outer cutting contour having a third outer cutting diameter) , wherein the third outer cutting diameter is less than the first outer cutting diameter, and wherein the fourth axial area is more proximal to the leading end of the tool base body than the first axial area.

The cutting inserts of at least one set of cutting inserts (i.e. the cutting inserts of the first set of cutting inserts and/or the cutting inserts of the second set of cutting inserts and/or the cutting inserts of the third set of cutting inserts), on a radial outer (e.g. radial outer with respect to the central longitudinal axis) front corner thereof facing the leading end of the tool base body, may be formed with a respective radial outer recess, and the recesses (i.e. all the said recesses of the respective cutting inserts of one single set of cutting inserts) together may define an outer

circumferential groove (i.e. may form a (circumferentially) interrupted outer circumferential groove) .

When seen in a cross-section of the said outer

circumferential groove (i.e. in a cross-section of the said outer circumferential groove taken in a direction transverse to a circumferential direction with respect to the central longitudinal axis), the ends (e.g. the end portion facing the leading end of the tool base body and the end portion facing the trailing end of the tool base body) of the respective recess may be provided with a respective chamfer.

The ribs may be formed in a helical shape with respect to the central longitudinal axis (e.g. may extend along the central longitudinal axis in a helical manner) , with a

corresponding helix angle. The corresponding helix angle may be negative or positive (e.g. with respect to a rotational direction of the machining tool) and (an absolute value of) the corresponding helix angle may be equal to or less than 30°, optionally equal to or less than 15°.

The cutting inserts of a respective set of cutting inserts (e.g. the cutting inserts of the first set of cutting inserts and/or the cutting inserts of the second set of cutting inserts and/or the cutting inserts of the third set of cutting inserts) may be arranged on lateral side walls of the ribs, wherein the said lateral side walls are all oriented towards a same circumferential direction with respect to the central longitudinal axis. The said lateral side walls may all be oriented towards a same circumferential direction with respect to the central longitudinal axis such that they face a cutting direction defined by the respective set of cutting inserts.

The cutting inserts of a respective set of cutting inserts (e.g. the cutting inserts of the first set of cutting inserts and/or the cutting inserts of the second set of cutting inserts and/or the cutting inserts of the third set of cutting inserts) may be arranged around the central longitudinal axis in an irregular manner (e.g. in a manner such that an angular spacing between a respective cutting insert and a directly adjacent cutting insert in one circumferential direction is different from an angular spacing between the respective cutting insert and a directly adjacent cutting insert in another circumferential direction, e.g. in a manner such that an angular spacing between two directly adjacent cutting inserts is different from angular spacings between all other directly adjacent cutting inserts).

A number of the cutting inserts of the respective set of cutting inserts may be even and the cutting inserts of the respective set of cutting inserts may be arranged in

respective pairs (e.g. each two cutting inserts of the

respective set of cutting inserts may form a respective pair, wherein one respective cutting insert of the respective set of cutting inserts is only part of one single pair) around the central longitudinal axis such that an angular spacing between the cutting inserts of a respective pair is 180°.

At least one of the respective sets of cutting inserts (e.g. the first set of cutting inserts and/or the second set of cutting inserts and/or the third set of cutting inserts) may form cutting edges acting in a radial direction of the tool base body. At least one of the respective sets of cutting inserts (e.g. the first set of cutting inserts and/or the second set of cutting inserts and/or the third set of cutting inserts) may form cutting edges acting in an axial direction of the tool base body.

The cutting inserts of the respective set of cutting inserts may have a hardness larger than the hardness of the tool base body.

The cutting inserts of at least one set of cutting inserts (e.g. the cutting inserts of the first set of cutting inserts and/or the cutting inserts of the second set of cutting inserts and/or the cutting inserts of the third set of cutting inserts) may be formed from polycrystalline diamond,

optionally from polycrystalline diamond with a sub-micron grain size, further optionally from polycrystalline diamond with an average grain size up to 2 ym, further optionally from polycrystalline diamond with an average grain size from 2 ym up to 10 ym, further optionally from polycrystalline diamond with an average grain size from 10 ym up to 25 ym, further optionally from polycrystalline diamond with a combination of average grain sizes between 2 ym and 30 ym.

The tool base body may be formed from (solid) carbide.

The invention further provides a method for forming a hole in which a machining tool as described above is used for treating an initial hole (i.e. a hole formed prior to the treating) . The method for forming a hole comprises the steps of: pre-forming an initial hole in a workpiece, which initial hole defines a longitudinal hole axis, treating the initial hole (i.e. treating an inner circumferential wall of the initial hole) by a machining tool as described above, wherein said treating comprises: rotating the machining tool and advancing the rotating machining tool into the initial hole with the central longitudinal axis of the machining tool being coaxial to the longitudinal hole axis of the initial hole, wherein the initial hole and the machining tool are adapted such that a first machining contact between the workpiece and the machining tool in the initial hole is established by the first set of cutting inserts before any other set of cutting inserts (e.g. the second set of cutting inserts, and/or e.g. the third set of cutting inserts) comes into machining contact with the workpiece, whereby the workpiece (i.e. the inner circumferential wall of the initial hole (pre-) formed in the workpiece) is firstly machined in the initial hole by the first set of cutting inserts so as to create a first treated hole portion (i.e. a first treated portion of the inner circumferential wall of the initial hole) .

The treating may further comprise further advancing the machining tool into the initial hole such that the guiding portions of the machining tool come into guiding contact with the first treated hole portion, whereby the machining tool is further axially guided by means of the guiding portions before any set of cutting inserts other than the first set of cutting inserts (e.g. the second set of cutting inserts, and/or e.g. the third set of cutting inserts) comes into machining contact with the workpiece.

The treating may further comprise further advancing the machining tool into the initial hole such that all sets of cutting inserts (e.g. the first set of cutting inserts, e.g. the second set of cutting inserts, e.g. the third set of cutting inserts) come into machining contact with the

workpiece (e.g. are in machining contact with the workpiece simultaneously, e.g. are in machining contact with the

workpiece in an alternating manner, e.g. are in machining contact with the workpiece in a subsequent manner, e.g. are in machining contact with the workpiece such that, at a given time, one or more of the sets of cutting inserts act on the workpiece) , while the machining tool is axially guided by the said guiding contact (provided by the guiding portions) , to thereby finally form the hole.

Brief Description of the Drawings

In the following, the invention will be described by means of embodiments with reference to the figures. In the figures:

Fig. 1 is a side view of a machining tool

according to one embodiment of the present invention,

Fig. 2 is an enlarged view of a front section of the machining tool of Fig. 1,

Fig. 3 is a cross-sectional view of the machining tool of Fig. 1 along line A-A,

Fig. 4 is a cross-sectional view of the machining tool of Fig. 1 along line B-B,

Fig. 5 is a side view of a machining tool

according to another embodiment of the present invention,

Fig. 6 is an enlarged view of a front section of the machining tool of Fig. 5,

Fig. 7 is a side view of a machining tool

according to another embodiment of the present invention,

Fig. 8 is a side view of one cutting insert according to another embodiment, Fig. 9 is an enlarged view of Fig. 8,

Fig. 10 is a front view of a machining tool

according to another embodiment,

Fig. 11 is a front view of a machining tool

according to another embodiment,

Figs. 12a-12d are side views of a machining tool and a workpiece illustrating a method for forming a hole according to one embodiment,

Fig. 13 is a flow-diagram illustrating the method for forming a hole.

Throughout the figures, same reference signs are used for same structural parts.

Detailed Description of the Invention

According to figures 1 to 12d, a machining tool 10 (e.g. a reamer, a drill) comprises a tool base body 20 defining a central longitudinal axis 30 and having a leading end 40 and a trailing end 50, the trailing end 50 being configured to be attached to a tool supporter (not shown) , a first set of cutting inserts 60 which are arranged on the tool base body 20 at a first axial area 70 thereof in a manner so as to be circumferentially spaced from each other around the central longitudinal axis 30 and which together define a first outer cutting diameter 80 (shown, e.g., in Fig. 6), and a set of guiding portions 90 which are arranged on the tool base body 20 at a second axial area 100 thereof, which is adjacent to the first axial area 70 in a direction to be more proximal to the trailing end 50 than the first axial area 70, and are arranged around the central longitudinal axis 30 in a manner so as to be circumferentially spaced from each other and to define together an outer guiding diameter 110 (shown, e.g., in Fig. 6), wherein the said guiding portions 90 are formed by corresponding first outer surface portions 120 of the tool base body 20, which first outer surface portions 120 have a first surface roughness which is lower than a second surface roughness of surrounding second outer surface portions 130 of the tool base body 20, which surround the said first outer surface portions 120.

The first surface roughness of the first outer surface portions 120 has an Rz-value (DIN EN ISO 4287:2010-07) equal to or smaller than 1.

The outer guiding diameter 110 is smaller than the first outer cutting diameter 80.

The first axial area 70 defines a first axial length 140 and the second axial area 100 defines a second axial length 150 (shown, e.g., in Fig. 2) . In the embodiments of Figs. 5,

6, 7 and 12a-12d, the second axial length 150 and the first axial length 140 are at least substantially equal.

The tool base body 20 further comprises a set of ribs 160, wherein each rib 160 extends longitudinally in a direction from the leading end 40 of the tool base body 20 towards the trailing end 50 of the tool base body 20. Each rib 160 has a rib-width 170 (shown, e.g., in Fig. 4) . The cutting inserts 60 of the first set of cutting inserts 60 are arranged on the ribs 160, and the first outer surface portions 120 of the tool base body 20, which form the guiding portions 90, are formed by corresponding radially outer surfaces 180 of the ribs 160. Each guiding portion 90 has an elongated shape defining a length 190 (shown, e.g., in Fig. 2) and extends, along its length 190, along the longitudinal extension of the respective rib 160, wherein each guiding portion 90 has a width 200

(shown, e.g., in Fig. 2) which is less than the rib-width 170. In the embodiments shown in the figures, the width 200 of the respective guiding portion 90 is about 15%-25% of the rib- width 170.

The machining tool 10 shown in Figs. 5, 6, 7, and 12a-12d further comprises a second set of cutting inserts 210 which are arranged on the tool base body 20 at a third axial area 220 thereof in a manner so as to be circumferentially spaced from each other around the central longitudinal axis 30 and which together define a second outer cutting diameter 230 (shown, e.g., in Fig. 5), wherein the second outer cutting diameter 230 is larger than the first outer cutting diameter 80, and wherein the third axial area 220 is more proximal to the trailing end 50 of the tool base body 20 than the second axial area 100.

The second axial area 100 is directly adjacent to the first axial area 70, and, thereby, along the central

longitudinal axis 30, a distance between the second axial area 100 and the third axial area 220 is larger than a distance between the first axial area 70 and the second axial area 100.

The machining tool 10 shown in Figs. 1, 2, 5, 6, 7 and 12a-12d further comprises a third set of cutting inserts 240 which are arranged on the tool base body 20 at a fourth axial area 250 thereof in a manner so as to be circumferentially spaced from each other around the central longitudinal axis 30 and which together define a third outer cutting diameter 260 (shown, e.g., in Fig. 5), wherein the third outer cutting diameter 260 is less than the first outer cutting diameter 80, and wherein the fourth axial area 250 is more proximal to the leading end 40 of the tool base body 20 than the first axial area 70.

As shown in the figures, the cutting inserts 60, 210, 240 of a respective set of cutting inserts 60, 210, 240 are arranged on lateral side walls 270 of the ribs 160, wherein the said lateral side walls 270 are all oriented towards a same circumferential direction with respect to the central longitudinal axis 30 such that they face a cutting direction defined by the respective set of cutting inserts 60, 210, 240.

As shown, e.g., in Fig. 2, the respective sets of cutting inserts 60, 210, 240 form cutting edges 280 acting in a radial direction of the tool base body 20 and cutting edges 290 acting in an axial direction of the tool base body 20.

As shown in the figures, the ribs 160 are formed in a helical shape with respect to the central longitudinal axis 30 with a corresponding helix angle. In the embodiments of

Figs. 1, 2, 5, 6, and 12a-12d, the helix angle is positive with respect to the central longitudinal axis 30 (and, e.g., with respect to a rotational direction of the machining tool as indicated, e.g., in Fig. 5) . In the embodiment of Fig. 7, the helix angle is negative with respect to the central longitudinal axis 30 (and, e.g., with respect to a rotational direction of the machining tool as indicated, e.g, in this figure) .

In the embodiment shown in Figs. 8 and 9, the cutting inserts 60, 210, 240 of at least one set of cutting inserts 60, 210, 240, on a radial outer front corner 300 thereof facing the leading end 40 of the tool base body 20, are formed with a respective radial outer recess 310. The recesses 310 together define an outer circumferential groove. When seen in a cross-section of the said outer circumferential groove the ends 320 of the respective recess are provided with a respective chamfer 330.

In the following, certain configurations and angular spacings of cutting inserts 401, 402, 403, 404, 405, 406, 407, 411, 412, 413, 414, 415 and 416 of a respective set of cutting inserts 450 are described based on Figs. 10 and 11. In the embodiments of Figs. 10 and 11, the cutting inserts 401, 402, 403, 404, 405, 406, 407, 411, 412, 413, 414, 415 and 416 of the respective set of cutting inserts 450 are arranged around the central longitudinal axis 30 in an irregular manner with regard to an angle between (directly) adjacent cutting

inserts .

In the embodiment of Fig. 10, a number of the cutting inserts 401, 402, 403, 404, 405, 406 and 407 of the set of cutting inserts 450 is seven and, thereby, uneven. An angle between the cutting inserts 401 and 402 is about 51°, an angle between the cutting inserts 402 and 403 is about 48°, an angle between the cutting inserts 403 and 404 is about 54°, an angle between the cutting inserts 404 and 405 is about 50°, an angle between the cutting inserts 405 and 406 is about 53°, an angle between the cutting inserts 406 and 407 is about 49°, and an angle between the cutting inserts 407 and 401 is about 52°. Thus, there is a different angle between each two directly adjacent cutting inserts (401, 402, 403, 404, 405, 406, 407) of the set of cutting inserts 450.

In the embodiment of Fig. 11, a number of the cutting inserts 411, 412, 413, 414, 415 and 416 of the set of cutting inserts 450 is six and, thereby, even. The cutting inserts 411, 412, 413, 414, 415 and 416 of the set of cutting inserts 450 are arranged in respective pairs (cutting inserts 411 and 414 form one pair, cutting inserts 412 and 415 form one pair, and cutting insert 413 and 416 form one pair) around the central longitudinal axis 30 such that an angular spacing between the cutting inserts of a respective pair is 180°. An angle between the cutting insert 416 and 411 is about 60°, an angle between the cutting inserts 411 and 412 is about 55°, and an angle between the cutting inserts 412 and 413 is about 65°. Thus, angles between each two directly adjacent cutting inserts on a half circumferential section of the tool base body are different.

As shown in Figs. 12a-12d and 13, a machining tool 10 as described in this application can be used in a method for forming a hole 600.

The method for forming a hole 600 comprises the steps of: pre-forming (S10) an initial hole 610 in a workpiece 620, which initial hole 610 defines a longitudinal hole axis 630, treating (S20) the initial hole 610 by a machining tool 10 as described in this application, wherein said treating (S20) comprises, as shown in Figs. 12a and 12b: rotating (S30) the machining tool 10 and advancing the rotating machining tool 10 into the initial hole 610 with the central longitudinal axis 30 of the machining tool 10 being coaxial to the longitudinal hole axis 630 of the initial hole 610, wherein the initial hole 610 and the machining tool 10 are adapted such that a first machining contact 640 between the workpiece 620 and the machining tool 10 in the initial hole 610 is established by the first set of cutting inserts 60 before any other set of cutting inserts 210, 240 comes into machining contact with the workpiece 620, whereby the workpiece 620 is firstly machined in the initial hole 610 by the first set of cutting inserts 60 so as to create a first treated hole portion 650.

As shown in Fig. 12c, the treating (S20) further comprises (S40) further advancing the machining tool 10 into the initial hole 610 such that the guiding portions 90 of the machining tool 10 come into guiding contact 660 with the first treated hole portion 650, whereby the machining tool 10 is further axially guided by means of the guiding portions 90 before any set of cutting inserts 210, 240 other than the first set of cutting inserts 60 comes into machining contact with the workpiece 620.

As shown in Fig. 12d, the treating (S20) further comprises (S50) further advancing the machining tool 10 into the initial hole 610 such that all sets of cutting inserts 60, 210, 240 come into machining contact with the workpiece 620, while the machining tool 10 is axially guided by the said guiding contact 660, to thereby finally form the hole 600.

List of Reference Signs

10 : machining tool

20 : tool base body

30 : central longitudinal axis

4 0 : leading end

50 : trailing end

60 : first set of cutting inserts

7 0 : first axial area

8 0 : first outer cutting diameter

90 : set of guiding portions

100 second axial area

110 outer guiding diameter

120 first outer surface portions

130 second outer surface portions

14 0 first axial length

150 second axial length

1 60 set of ribs

17 0 rib-width

1 8 0 radially outer surface portions

1 90 length (of a guiding portion)

200 width (of a guiding portion)

210 second set of cutting inserts

220 third axial area

230 second outer cutting diameter

24 0 third set of cutting inserts

250 fourth axial area

2 60 third outer cutting diameter

27 0 lateral side walls

2 8 0 cutting edges

2 90 cutting edges

30 0 radial outer front corner

31 0 radial outer recess

32 0 ends of a respective radial outer recess 330 chamfer -407 cutting inserts

-416 cutting inserts

: set of cutting inserts : hole

: initial hole

: workpiece

: longitudinal hole axis : first machining contact : first treated hole portion guiding contact