Thread milling tool

Abstract

The invention relates to a thread milling tool (1) extending along an axis of rotation (2) and comprising a thread milling section (3) and a drill tip (4) adjoining the thread milling section (3), wherein the thread milling section (3) has three cutting flutes (5) and at least one thread milling tooth (6), while the drill tip (4) has three main cutting edges (4a), each of which reaches a main cutting circle (7) when viewed in parallel to the axis of rotation (2), the main cutting circle (7) defining a drilling diameter that can be produced by the drill tip (4), wherein each main cutting edge (4a) has a main cutting surface (4b) that is connected to one cutting flute (5) of the cutting flutes (5) and reaches the main cutting circle (7) at a respective radial main cutting angle (11) when viewed in parallel to the axis of rotation (2), wherein at least one radial main cutting angle (11) of the radial main cutting angles (11) is positive.

Description

[0001] DRILL THREAD MILLS

[0002] The present invention relates to a drill thread milling cutter which extends along a rotational axis and has a thread milling section and a drill tip adjoining the thread milling section, wherein the thread milling section has three chip flutes and a plurality of thread milling teeth, wherein the drill tip has three main cutting edges which, viewed in the direction parallel to the rotational axis, each reach a main cutting edge cutting circle, wherein the main cutting edge cutting circle defines a drilling diameter which can be produced by the drill tip, wherein each main cutting edge has a main cutting edge cutting surface which is each connected to a chip flute of the chip flutes and, viewed in the direction parallel to the rotational axis, each reach the main cutting edge cutting circle at a radial main cutting edge cutting angle.

[0003] A double-edged drill thread milling cutter is known from US 4,651,374 A. With this known drill thread milling cutter, it is possible to first drill a generally cylindrical hole into a workpiece. For this purpose, the known drill thread milling cutter has two cutting edges with which the hole can be produced. Once the hole has been drilled, the known drill thread milling cutter is advanced radially, i.e. moved from the center of the hole to a position parallel to the hole axis. Milling teeth are arranged on the shank of the known drill thread milling cutter, with which a thread can then be cut into the hole by means of circular thread milling. The milling teeth engage together in the hole wall, and the thread is produced by rotating the known drill thread milling cutter and simultaneously executing a screw movement of the known drill thread milling cutter.

[0004] When machining long-chipping materials, such as wrought aluminum alloys, with the well-known drill and thread milling cutter, problems arise because the chips generated during drilling are so long that they can no longer be adequately removed from the hole. As a result, these chips contact the milling teeth and sometimes become lodged between them, damaging them. Furthermore, with the well-known drill and thread milling cutter, there is a need to increase the feed rate during drilling.

[0005] The object of the present invention is to provide a drill thread milling cutter that has a longer service life and higher feed rate when machining long-chipping materials. This object of the present invention is achieved by the subject matter of claim 1. Advantageous developments of the invention can be found in the dependent claims, which can be freely combined with one another, the description, the exemplary embodiments, and the drawings.

[0006] The drill thread milling cutter extends along a rotational axis and has a thread milling section and a drill tip adjoining the thread milling section, wherein the thread milling section has three chip flutes and a plurality of thread milling teeth, wherein the drill tip has three main cutting edges, which in the direction of view parallel to the rotational axis each reach a main cutting edge cutting circle, wherein the main cutting edge cutting circle defines a drilling diameter that can be produced by the drill tip, wherein each main cutting edge has a main cutting edge cutting surface, which is each connected to a chip flute of the chip flutes and in the direction of view parallel to the rotational axis each reach the main cutting edge cutting circle at a radial main cutting edge cutting angle, wherein at least one radial main cutting edge cutting angle of the radial main cutting edge cutting angles is positive.

[0007] Due to at least one positive radial main cutting edge rake angle, the chips are compressed more strongly in the area of ​​the drill tip during drilling and are broken up even when machining long-chipping materials. The chips can therefore be more effectively removed from the area of ​​the drill tip, which increases tool life and also the feed rate because chip removal is required less or even completely during drill thread milling. The feed rate is further increased by the drill tip having three main cutting edges. The larger chip volume with three main cutting edges compared to two main cutting edges is better managed thanks to the improved chip breaking, as the chips are broken up shorter.

[0008] Preferably, the radial main cutting edge rake angle of each main cutting edge rake face is positive because this realizes the described advantages on all three main cutting edges.

[0009] The radial main cutting edge rake angle is defined according to the usual convention. The radial main cutting edge rake angle has a first angle leg that is a tangent to the main cutting edge rake face where the main cutting edge touches the main cutting edge flight circle in a direction parallel to the rotation axis. The radial main cutting edge rake angle has a second angle leg that is oriented such that its radial extension with respect to the rotation axis would penetrate the rotation axis perpendicular to it.

[0010] The main cutting edge rake angle is measured in the direction of view parallel to the axis of rotation on the side of the axis of rotation and, according to the usual convention, is positive if the second angle leg leads the main cutting edge rake face with respect to a cutting-active direction of rotation from the drill tip, where the main cutting edge rake face is initially extended inwards from the drill tip from its contact with the main cutting edge flight circle, and negative if the second angle leg would lag behind the main cutting edge rake face accordingly.

[0011] During circular milling, which occurs after drilling with the drill bit, the thread milling section creates a thread in a hole wall created by the drill bit.

[0012] According to a further development of the drill thread milling cutter, the at least one positive radial main cutting edge rake angle is in the range of 3° to 12°, preferably 5° to 10°. If the at least one positive radial main cutting edge rake angle is in the range of 3° to 12°, preferably 5° to 10°, the chips are broken particularly short, while at the same time the main cutting edge is sufficiently stable against cutting edge chipping when machining long-chipping materials.

[0013] Preferably, the radial main cutting edge rake angle of each main cutting edge is positive and lies in the range of 3° to 12°, preferably 5° to 10°. The radial main cutting edge rake angles are preferably equal in magnitude.

[0014] According to a further development of the drill thread milling cutter, at least the main cutting edge of the main cutting edges that reaches the main cutting edge cutting circle at the at least one positive radial main cutting edge rake angle when viewed parallel to the rotation axis is concavely curved when viewed parallel to the rotation axis. The concavely curved main cutting edge draws the chip into the chip groove during drilling, so that the chip fragments are very quickly transported away from the engagement of the main cutting edge. Preferably, each main cutting edge is concavely curved when viewed parallel to the rotation axis.

[0015] Preferably, each main cutting edge rake face of the main cutting edges reaches the main cutting edge flight circle with a concave curve when viewed parallel to the axis of rotation. According to a further development of the drill thread milling cutter, at least the main cutting edge of the main cutting edges whose main cutting edge rake face reaches the main cutting edge flight circle at the at least one positive radial main cutting edge rake angle when viewed parallel to the axis of rotation reaches the main cutting edge flight circle chamfered when viewed perpendicular to the axis of rotation, thus forming a chamfered main cutting edge. The chamfered main cutting edge makes the drill tip shorter and more stable in the axial direction with respect to the axis of rotation and additionally ensures that no or at least fewer chippings occur on the main cutting edge in the region of the main cutting edge flight circle. Preferably, each main cutting edge of the main cutting edges is chamfered in a similar manner.

[0016] According to a further development of the drill thread milling cutter, the chamfered main cutting edge is chamfered at a chamfer angle in the range of 55° to 65°, wherein the chamfer angle is defined in a longitudinal section through the chamfered main cutting edge, where it is chamfered, and the rotational axis, wherein the longitudinal section contains the chamfered main cutting edge and the rotational axis, wherein the chamfer angle is dimensioned on the rotational axis side. If the chamfer angle is in the range of 55° to 65°, the milling forces during circular milling are particularly well reduced. Preferably, each main cutting edge is chamfered similarly at a chamfer angle in the range of 55° to 65°.

[0017] According to a further development of the drill thread milling cutter, the drill tip has three thinnings through which a center cutting edge is formed by the drill tip, wherein each center cutting edge of the center cutting edges reaches a main cutting edge of the main cutting edges at an edge angle, wherein the edge angle is spanned there in the direction of view parallel to the axis of rotation by the center cutting edge and the main cutting edge, wherein the center cutting edge reaches the main cutting edge, wherein at least one edge angle of the edge angles is an obtuse edge angle.

[0018] The three point thinnings ensure that the drill bit has a pyramid-shaped cross-cutting area, which improves the drilling behavior of the drill bit. The initial contact between the material to be machined and the drill bit is therefore more precise. As soon as the drill bit penetrates the material, the process forces act on the edges of the cross-cutting edges from the pyramid-shaped cross-cutting area and additionally support the self-centering ability of the drill bit. This prevents displacement even on uneven surfaces. The edge angles each have a first angle leg that is a tangent to the center cutting edge, where the center cutting edge reaches a center cutting edge flight circle defined with respect to the center cutting edges; the center cutting edge flight circle is centrally penetrated by the rotation axis.The edge angles each have a second angle leg, which is a tangent to the main cutting edge where the main cutting edge reaches the center cutting edge's flight circle. The edge angles are measured on the side of a frontal clearance surface of the drill tip associated with the center cutting edges.

[0019] Because it is blunt, the obtuse edge angle is in the range from greater than 90° to less than 180°, preferably from 140° to 160°. The obtuse edge angle improves chip breaking at the transition from the main cutting edge to the center cutting edge.

[0020] According to a further development of the drill thread milling cutter, at least one center cutting edge of the center cutting edges reaches the main cutting edge of the main cutting edges in a straight line when viewed parallel to the rotation axis, the main cutting edge rake face of which reaches the main cutting edge cutting circle at the at least one positive radial main cutting edge rake angle when viewed parallel to the rotation axis. The at least one straight center cutting edge can be produced particularly easily and thus cost-effectively by grinding the drill tip and simultaneously ensures particularly precise centering of the drill tip.

[0021] The center cutting edges of the center cutting edges usually reach a center cutting edge flight circle when viewed parallel to the axis of rotation, which is pierced centrally by the axis of rotation and has a smaller diameter than the main cutting edge flight circle.

[0022] The chip flutes usually reach a core circle when viewed parallel to the axis of rotation in a radial direction from the outside to the radial inside, with the core circle being pierced centrally by the axis of rotation. The drill thread milling cutter therefore usually has a main cutting edge cutting circle and a core circle, with the diameter of the core circle usually being at least 20% to a maximum of 40% of the diameter of the main cutting edge cutting circle, preferably 25% to 35%. Because the chips are broken up more effectively by the at least one positive radial main cutting edge rake angle, the diameter of the core circle can be up to a maximum of 40% of the diameter of the main cutting edge cutting circle, because even then the volume of the chip flutes is still sufficient to remove the chips due to the short chip breakage.Increasing the diameter of the core circle is desirable because it improves the stability of the thread milling section, which also contributes to increasing the feed rate.

[0023] According to a further development of the drill thread milling cutter, at least the main cutting edge of the main cutting edges whose main cutting edge rake face, viewed parallel to the rotation axis, reaches the main cutting edge cutting circle at the at least one positive radial main cutting edge rake angle, bends off from a center cutting edge of the center cutting edges, viewed parallel to the rotation axis, forming an edge. This makes the chips break off even more easily and further prevents the chips from accumulating as a relatively wide, spiral band that can become lodged in the chip flutes and / or the thread milling teeth. Preferably, each main cutting edge of the main cutting edges bends off from a center cutting edge of the center cutting edges in a similar manner.

[0024] According to a further development of the drill thread milling cutter, at least the chip flute of the chip flutes to which the main cutting edge is connected, which reaches the main cutting edge flight circle at the at least one positive radial rake angle when viewed parallel to the axis of rotation, rises in a spiral manner at a pitch angle on the axis of rotation, wherein the pitch angle is in the range from 5° to 25°, preferably from 10° to 20°, which includes a preferred pitch angle of 15° in each case. The spiral chip flute improves the axial removal of chips broken up by the main cutting edge, which reaches the main cutting edge flight circle at the at least one positive radial rake angle when viewed parallel to the axis of rotation. Each chip flute preferably rises in a similar spiral manner.The lead angle is defined in the direction perpendicular to the rotation axis by the rotation axis and a flute tangent. The flute tangent is a tangent to a curve following the flute, and the lead angle is measured on the rotation axis side. The curve thus follows an edge of the flute. The lead angle, which is in the range of 5° to 25°, preferably 10° to 20°, can be constant or variable. If the lead angle is constant, it is preferably in the range of 10° to 20°, which preferably includes 15°.

[0025] According to a further development of the drill thread milling cutter, the thread milling teeth do not reach the main cutting edge when viewed parallel to the rotational axis. This protects the thread milling teeth from contact with the workpiece during drilling by the drill bit. According to a further development of the drill thread milling cutter, the drill bit and the thread milling section are a monolithic unit. This allows for a more stable, once-set arrangement of the drill bit relative to the thread milling section, for example, by grinding the drill bit and the thread milling section from a common raw material bar.

[0026] According to a further development of the drill thread milling cutter, each of the radial main cutting edge rake angles is positive. As a result, the advantages described with regard to the at least one positive radial main cutting edge rake angle are realized analogously for the remaining main cutting edges.

[0027] According to a further development of the drill thread milling cutter, each positive radial main cutting edge rake angle lies in the range of 3° to 12°, preferably 5° to 10°, of the radial main cutting edge rake angles. Thus, the advantages described with regard to the at least one positive radial main cutting edge rake angle are realized analogously with regard to its preferred angular ranges on the remaining main cutting edges.

[0028] According to a further development of the drill thread milling cutter, the number of main cutting edges is limited to three. Especially when each radial main cutting edge rake angle is positive, a sufficient feed rate can be achieved with just three main cutting edges. This reduces the manufacturing costs of the drill thread milling cutter compared to manufacturing with more than three main cutting edges.

[0029] According to a further development of the drill thread milling cutter, the number of chip flutes is limited to three. Especially when each radial main cutting edge rake angle is positive, three chip flutes are sufficient to remove the chips generated when drilling long-chipping materials without exposing the thread milling teeth to an increased risk of collision with these chips. This reduces the manufacturing costs of the drill thread milling cutter compared to a production with more than three chip flutes.

[0030] According to a further development, the drill thread milling cutter has an internal coolant channel structure which has at least one coolant outlet in the drill tip on the side of a plurality of main cutting edge flanks, wherein each main cutting edge flank is assigned to one of the main cutting edges on the end face, and / or a coolant outlet in one of the chip grooves of the chip grooves. If the coolant outlet is formed and arranged in the drill tip on the side of the main cutting edge flanks, chips are better removed from a drill base during drilling. If the coolant outlet is formed and arranged in one of the chip grooves of the chip grooves, chip removal in this chip groove is improved. Accordingly, it is particularly advantageous if the coolant outlet is formed and arranged in the drill tip on the side of the main cutting edge flanks and a further coolant outlet is formed and arranged in one of the chip grooves of the chip grooves.

[0031] According to a further development, the drill thread milling cutter has at least one countersinking cutting edge formed and arranged at a rear end of the thread milling section relative to the drill tip. The countersinking cutting edge creates a circumferential chamfer on a hole edge at the end of the drilling operation.

[0032] Further advantages and benefits of the invention will become apparent from the following description of an embodiment with reference to the accompanying figures.

[0033] From the figures show

[0034] Fig. 1: a schematic representation of a drill thread milling cutter in a

[0035] side view;

[0036] Fig. 2: a schematic representation of the drill thread milling cutter according to Fig. 1 in a

[0037] front view;

[0038] Fig. 3a: a schematic representation of a detail from Fig. 2;

[0039] Fig. 3b: a schematic representation of a further detail from Fig. 2;

[0040] Fig. 4: a schematic longitudinal section of a front area of ​​the

[0041] Drill thread milling cutter according to Fig. 1;

[0042] Fig. 5a: a schematic representation of a cross section according to the section line VV in Fig. 5;

[0043] Fig. 5b: a schematic representation of a detail from Fig. 5.

[0044] Fig. 1 shows a schematic representation of a drill thread milling cutter 1 viewed perpendicular to a rotation axis 2.

[0045] The drill thread milling cutter 1 extends along the rotation axis 2 and has a

[0046] Thread milling section 3 and a drill bit 4 adjoining the thread milling section 3, wherein the thread milling section 3 and the drill bit 4 are a monolithic unit ground from a round bar.

[0047] The thread milling section 3 has three webs 3a, each of which ascends in a spiral manner with respect to the rotational axis 2, as shown by a combination of Fig. 1 and Fig. 2. The webs 3a form the thread milling section 3 and the drill bit 4 adjoining the thread milling section 3. In the circumferential direction with respect to the rotational axis 2, the webs 3a are spaced from one another, so that the thread milling section 3 has three chip flutes 5, each of which ascends in a spiral manner with respect to the rotational axis 2 at a chip flute angle 5a and thus reaches the drill bit 4. The chip flute angle 5a can also be referred to as a spiral angle.

[0048] The flute angle 5a is defined by a tangent applied to an edge curve of each flute 5 and the rotation axis 2. The illustrated flute angle 5a can be enlarged in a true-angle manner so that its angle leg on the rotation axis 2 side coincides with the rotation axis 2, with the other angle leg being the applied tangent. The flute angle 5a is 15° as an example and thus lies within the range of 5° to 25° and also within the narrower range of 10° to 20°.

[0049] The thread milling section 3 also has several thread milling teeth 6 which have no thread pitch.

[0050] The drill thread milling cutter 1 produces a hole in a workpiece through the drill bit 4 by rotating the drill bit 4 relative to the rotational axis 2 and axially immersing it in a workpiece in the axial direction relative to the rotational axis 2 until a desired drilling depth in the workpiece is reached.

[0051] The drill thread milling cutter 1 produces a thread in the drilled workpiece through the thread milling section 3 by radially plunging the drill thread milling cutter 1 into the workpiece in the immersed state in a radial direction with respect to the rotational axis 2 while still being rotationally driven. During radial plunging, the drill tip 4 first plunges radially into the drilled workpiece, followed by the thread milling teeth 6, with simultaneous axial movement of the drill thread milling cutter 1 out of the bore, so that the drill thread milling cutter 1 is removed from the drilled workpiece following a helical curve with the thread milling teeth 6 in contact with the drilled workpiece and in the process performs a 360° rotation with respect to the rotational axis 2. When the 360° rotation is complete, the thread has been completely produced. After the thread has been completely produced, the drill thread milling cutter 1 is returned radially to the center of the bore and axially removed from the bore.

[0052] The drill thread milling cutter 1 further has an end portion 100 into which the chip flutes 5 extend. The end portion 100 further has three countersinking cutting edges 101, which create a circumferential chamfer in the drilled workpiece when the drill thread milling cutter 1 reaches the drilling depth.

[0053] The drill thread milling cutter 1 further has an inlet channel 102 in the end section 100. The inlet channel 102 opens into a main coolant channel 103. The main coolant channel 103 extends in the end section 100 and in the thread milling section 3. In the thread milling section 3, the main coolant channel 103 opens into three outlet channels 104, which extend in the thread milling section 3 and in the drill bit 4. The outlet channels 104 each form an acute angle, measured on the side of the drill bit 4, with the rotational axis 2 and ensure that coolant exits from the drill bit 4. The main coolant channel 103 and the inlet channel 102 each extend parallel to and centrally to the rotational axis 2.

[0054] Fig. 2 shows the drill bit 4 in a viewing direction parallel to the rotation axis 2 in a front view.

[0055] The drill bit 4 has three main cutting edges 4a, each of which reaches a concavely curved main cutting edge flight circle 7 when viewed parallel to the rotation axis 2; in Fig. 2, for reasons of clarity, only the main cutting edge at the approximately 8 o'clock position is designated with the reference symbol 4a. The main cutting edge flight circle 7 is pierced centrally by the rotation axis 2 and defines a drilling diameter that the drill bit 4 creates in the workpiece during the described drilling.

[0056] Each main cutting edge 4a has a main cutting edge rake face 4b, which is connected to one of the chip flutes 5, as shown by a combination of Fig. 1 and Fig. 2; in Fig. 2, for reasons of clarity, only the main cutting edge rake face at approximately the 8 o'clock position is provided with the reference number 4b, the same applies to the chip flute 5. Each main cutting edge rake face 4b follows its main cutting edge 4a in a viewing direction parallel to the axis of rotation 2, so that each main cutting edge rake face 4b also reaches the main cutting edge flight circle 7 with a concave curve. Fig. 2 further shows that the drill bit 4 has three point thinnings 8, each in the form of a ground facet 8, each of which is opposite one of the main cutting edges 4a in a cutting-active direction of rotation 2a of the drill bit 4; In Fig. 2, for reasons of clarity, only the point thinning in the area of ​​a 6 o'clock position is provided with the reference number 8.

[0057] Each thinning 8 forms a center cutting edge 9, which in the direction of view parallel to the axis of rotation 2 reaches one of the main cutting edges 4a in a straight extension, so that the main cutting edge 4a is bent from its respective center cutting edge 9 with an edge formation opposite to the cutting-active direction of rotation 2a, wherein the edge formation takes place on a center cutting edge flight circle 9b.

[0058] Each center cutting edge 9 has a center cutting face 9a, each of which reaches one of the main cutting faces 4b in a straight line viewed parallel to the rotation axis 2. Viewed parallel to the rotation axis 2, the center cutting edges 9 reach the center cutting edge cutting circle 9b, which is centrally pierced by the rotation axis 2 and accounts for approximately 40% of the main cutting edge cutting circle 7, which is in the range of 30% to 50% in terms of the size ratio of the center cutting edge cutting circle 9b to the main cutting edge cutting circle 7 and is thus a relative measure of the size of the main cutting edges 4a with respect to the size of the center cutting edges 9 viewed parallel to the rotation axis 2. The thinnings 8 reduce an originally larger cross-cutting edge area 10 of the drill bit 4. The cross-cutting edge area 10 is pyramid-shaped, is centrally pierced by the rotation axis 2, and connects the center cutting edges 9 to one another.

[0059] Fig. 2 further shows that each main cutting edge 4a has a radially inner frontal flank 4c, which it shares with its associated center cutting edge 9. Each main cutting edge 4a further has a radially outer frontal flank 4d, in that each main cutting edge 4a is chamfered on the side of the main cutting edge flight circle 7, so that the main cutting edge 4a bends axially in the region of the radially outer flank 4d in the direction of the thread milling section 3.

[0060] Fig. 2 further shows that the drill bit 4 has three further ground flanks 8a, each of which adjoins one of the point thinnings 8 with a radial edge formation, wherein the outlet channels 104 are each arranged between one of the further flanks 8a and one of the point thinnings 8 outside the center cutting edge flight circle 9b, so that it is ensured that the coolant outlet takes place in the direction of view parallel to the axis of rotation 2 in the area of ​​the chip flutes 5.

[0061] Fig. 2 further shows that the chip flutes 5 extend from radially outside to radially inside when viewed parallel to the rotation axis 2, such that the chip flutes 5 reach a core circle 5b, which is centrally pierced by the rotation axis 2. The diameter of the center cutting edge cutting circle 9b is larger than the diameter of the core circle 5b, so that the center cutting edges 9 consequently protrude beyond the core circle 5b when viewed parallel to the rotation axis 2 and are thus at least partially cutting in the area of ​​the chip flutes 5.

[0062] Fig. 3a shows an enlarged detail of Fig. 2 where one of the main cutting edges 4a reaches the main cutting edge flight circle 7 in a concave curve, and this is exemplary for all main cutting edges 4a.

[0063] Fig. 3a shows that the main cutting edge rake face 4b reaches the main cutting edge flight circle 7 at a radial main cutting edge rake angle 11, wherein the main cutting edge rake angle 11 is drawn as it is oriented and arranged in the cross section according to Fig. 5b.

[0064] The radial main cutting edge rake angle 11 has a first angle leg 11a, which is a tangent to the main cutting edge rake face 4b, where the main cutting edge rake face 4b touches the main cutting edge flight circle 7 in the direction of view parallel to the rotation axis 2. The radial main cutting edge rake angle 11 has a second angle leg 11b, which is oriented such that its radial extension with respect to the rotation axis 2 would pierce the rotation axis 2 perpendicular to it.

[0065] The radial main cutting edge rake angle 11 is positive according to the usual convention, because the second angle leg 11b leads the main cutting edge rake face 4b with respect to the cutting-active direction of rotation 2a, where the main cutting edge rake face 4b is initially extended inwards from the drill tip 4 from its contact with the main cutting edge flight circle 7. The main cutting edge rake angle 11 is 6.5°, for example, which is in the range from 3° to 12° and in the range from 5° to 10°, respectively. Fig. 3b shows a further enlarged detail of Fig. 2 where one of the

[0066] Main cutting edges 4a bend at an obtuse edge angle 12 from one of the center cutting edges 9, and this is exemplary for all main cutting edges 4a and center cutting edges 9.

[0067] The tip 12a of the obtuse edge angle 12 lies on the center cutting edge flight circle 9b, viewed parallel to the rotation axis 2. The obtuse edge angle 12 has a first angle leg 12b, which is a tangent to the center cutting edge 9, where the center cutting edge 9 reaches the center cutting edge flight circle 9b. The obtuse edge angle 12 has a second angle leg 12c, which is a tangent to the main cutting edge 4a, where the main cutting edge 4a reaches the center cutting edge flight circle 9b. The obtuse edge angle 12 is dimensioned on the flank surface 4c side and, because it is obtuse, is therefore in the range from greater than 90° to less than 180°, preferably from 140° to 160°. The center cutting edge 9 leads the main cutting edge 4a, which it reaches, with respect to the cutting-active direction of rotation 2a.

[0068] Fig. 4 shows a longitudinal section of the drill thread milling cutter 1 in the area of ​​the drill tip 4 and the thread milling section 3 where the drill tip 4 connects to the thread milling section 3. The longitudinal section includes the rotation axis 2. The viewing direction in Fig. 4 is perpendicular to the rotation axis 2.

[0069] In Fig. 4, it is evident for each of the main cutting edges 4a by way of example that the main cutting edges 4a are chamfered at a chamfer angle 13 in the direction of view perpendicular to the axis of rotation 2 and thus, as can be seen in a joint view of Fig. 1 and Fig. 2, reach the main cutting edge flight circle 7. In the longitudinal section according to Fig. 4, the chamfer angle 13 has a first angle leg 13a, which is a tangent to the main cutting edge 4a where it is chamfered. The chamfer angle 13 has a second angle leg 13b, which runs parallel to the axis of rotation 2; the chamfer angle 13 can be enlarged in a true-angle manner such that the second angle leg 13b coincides with the axis of rotation 2, or such that the axis of rotation 2 forms the second angle leg. The chamfer angle 13 is measured on the side of the thread milling section 3 and is, for example, 60°, which is in the range of 55° to 65°.

[0070] In Fig. 4, it is furthermore evident, by way of example, for each of the main cutting edges 4a that a drilling casing cutting edge 14 is assigned to each main cutting edge 4a, wherein each drilling casing cutting edge 14 extends parallel to the rotation axis 2 and is dimensionally shorter in the axial direction with respect to the rotation axis 2 than the main cutting edge 4a to which it is assigned. In Fig. 4, it is furthermore evident, by way of example, for each of the drilling casing cutting edges 14 that the drilling casing cutting edges 14, on the side of the thread-milling section 3, adjoin a rear cutting edge 15 of the drill tip 4.

[0071] In Fig. 4, it is further evident, for each of the main cutting edges 4a, that the main cutting edges 4a project beyond the thread milling teeth 6. In other words, the thread milling teeth 6 do not reach the main cutting edge flight circle 7.

[0072] In Fig. 4 it is further evident for each thread milling tooth 6 by way of example that the thread milling teeth 6 have a trapezoidal profile in the longitudinal section according to Fig. 4.

[0073] Fig. 1, 2, 3a, 3b and 4 show a drill thread milling cutter 1 which is particularly well suited for machining long-chipping materials because the three main cutting edges 4a formed in the area of ​​the drill tip 4 each have a main cutting edge rake face 4b which reaches the main cutting edge flight circle 7 at a positive main cutting edge rake angle 11 and thus breaks the chips shorter. The concave shape of the main cutting edge rake faces 4b, at which they each reach the main cutting edge flight circle 7, draws the broken chips more deeply into the chip grooves 5. By chamfering the main cutting edges 4a at the chamfer angle 13, the forces generated during thread milling are reduced and the stability of the main cutting edge 4a in the area of ​​the main cutting edge flight circle 7 is increased.

[0074] The thinnings 8 shorten the otherwise larger cross-cutting area 10, which improves the centering of the drill bit 4. Because the edge formation between the center cutting edges 9 and the main cutting edges 4a occurs at the obtuse edge angle 12, the chips are broken up more effectively. Compared to two main cutting edges, the drill thread milling cutter 1 has a higher feed rate due to the three main cutting edges 4a, which is enhanced by the improved chip breaking.

[0075] The coolant supply and the countersinking cutting edges 101 described with reference to Fig. 1 and Fig. 2 do, in each case and in combination with one another, improve the performance of the drill thread milling cutter 1, but are, in each case and in combination with one another, optional. This is not to say that other features of the drill thread milling cutter 1 may also be optional, which must be assessed in each individual case, taking into account the use in drilling and / or thread milling and the properties required. Fig. 5a shows a schematic representation of a cross-section of the drill thread milling cutter 1 along the section line VV in Fig. 1 and in the direction of the arrows assigned to this section line in Fig. 1. The circle arranged at 12 o'clock in Fig. 5a encloses the cross-sectional area, which Fig. 5b shows on an enlarged scale.In Figure 5b, the main cutting edge rake angle 11 is shown as it is usually measured, namely in a cross-section oriented and arranged according to the section line VV in Figure 1. Following the usual convention, the main cutting edge rake angle 11 is positive, which can also be referred to as an "acute angle."

[0076] Due to the fact that the main cutting edge rake angle 11 is positive, the chips removed by the main cutting edge 4a are drawn into the main cutting edge rake face 4b from the radial outside, i.e. where the tip of the main cutting edge rake angle 11 touches the main cutting edge cutting circle 7 in the cross section according to Fig. 5a, whereby the chips are removed from the area of ​​the main cutting edge cutting circle 7.

Claims

REQUIREMENTS 1. Thread milling cutter (1) extending along an axis of rotation (2) and having a thread milling section (3) and a drill tip (4) adjoining the thread milling section (3), wherein the thread milling section (3) has three flutes (5) and several thread milling teeth (6), wherein the drill tip (4) has three main cutting edges (4a) which, in the direction of view parallel to the axis of rotation (2), each reach a main cutting circle (7), wherein the main cutting circle (7) defines a drill diameter producible by the drill tip (4), wherein each main cutting edge (4a) has a main cutting rake face (4b) which is connected to a flute (5) from the flutes (5) and, in the direction of view parallel to the axis of rotation (2), each reaches the main cutting circle (7) at a radial main cutting rake angle (11), wherein at least one radial main cutting rake angle (11) of the radial main cutting rake angles (11) is positive.

2. Drill thread milling cutter (1) according to claim 1, wherein the at least one positive radial main cutting rake angle (11) is in the range of 3° to 12°, preferably 5° to 10°.

3. Drill thread milling cutter (1) according to one of the preceding claims, wherein at least the main cutting chip surface (4b) of the main cutting chip surfaces (4b) which in the viewing direction parallel to the axis of rotation (2) reaches the main cutting circle (7) under the at least one positive radial main cutting rake angle (11) is concavely curved in the viewing direction parallel to the axis of rotation (2).

4. Drill thread milling cutter (1) according to one of the preceding claims, wherein at least the main cutting edge (4a) is chamfered from the main cutting edges (4a), the main cutting edge rake surface (4b) of which reaches the main cutting circle (7) in the viewing direction parallel to the axis of rotation (2) at the at least one positive radial main cutting rake angle (4b), in the viewing direction perpendicular to the axis of rotation (2) and thus forms a chamfered main cutting edge (4a).

5. Drill thread milling cutter (1) according to claim 4, wherein the chamfered main cutting edge (4a) is chamfered at a chamfer angle (13) in the range of 55° to 65°, wherein the chamfer angle (13) in a longitudinal section through the chamfered main cutting edge (4a) where it is chamfered, and the axis of rotation (2) is spanned, wherein the longitudinal section includes the chamfered main cutting edge (4a) and the axis of rotation (2), wherein the chamfer angle (13) is dimensioned on the side of the axis of rotation (2).

6. Drill thread milling cutter (1) according to one of the preceding claims, wherein the drill tip (4) has three points (8) by which a central cutting edge (9) is formed by the drill tip (4), wherein each central cutting edge (9) reaches a main cutting edge (4a) at an edge angle (12), wherein the edge angle (12) is spanned in the viewing direction parallel to the axis of rotation (2) by the central cutting edge (9) and the main cutting edge (4a), wherein the central cutting edge (9) reaches the main cutting edge (4a), wherein at least one edge angle (12) is an obtuse edge angle (12).

7. Drill thread milling cutter (1) according to claim 6, wherein at least one center cutting edge (9) of the center cutting edges (9) reaches the main cutting edge (4a) of the main cutting edges (4a) in the direction of view parallel to the axis of rotation (2) under a straight extension, the main cutting edge rake surface (4b) of which reaches the main cutting circle (7) in the direction of view parallel to the axis of rotation (2) under the at least one positive radial main cutting rake angle (11).

8. Thread milling cutter (1) according to claim 6 or 7, wherein at least the main cutting edge (4a) of the main cutting edges (4a), whose main cutting edge rake surface (4b) reaches the main cutting circle (7) in the viewing direction parallel to the axis of rotation (2) under the at least one positive radial main cutting edge rake angle (11), bends in the viewing direction parallel to the axis of rotation (2) from a center cutting edge (9) of the center cutting edges (9) under an edge formation. Thread milling cutter (1) according to one of the preceding claims, wherein at least the chip flute (5) is helically ascends from the chip flutes (5) to which the main cutting edge rake face (4b) is connected, which, in the viewing direction parallel to the axis of rotation (2), reaches the main cutting circle (7) at an angle of at least one positive radial main cutting rake angle (11) at a helix angle (5a) on the axis of rotation (2), wherein the helix angle (5a) is in the range of 5° to 25°, preferably from 10° to 20°. Thread milling cutter (1) according to one of the preceding claims, wherein the thread milling teeth (6) do not reach the main cutting circle (7) in the viewing direction parallel to the axis of rotation (2). Thread milling cutter (1) according to one of the preceding claims, wherein the drill tip (4) and the thread milling section (3) are a monolithic unit (3, 4).Thread milling cutter (1) according to any one of the preceding claims, wherein each radial main cutting edge rake angle (11) is positive. Thread milling cutter (1) according to claim 12, wherein each positive radial main cutting edge rake angle (11) is in the range of 3° to 12°, preferably 5° to 10°. Thread milling cutter (1) according to any one of the preceding claims, wherein the number of main cutting edges (4a) is limited to three. Thread milling cutter (1) according to any one of the preceding claims, wherein the number of flutes (5) is limited to three.

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