Tool for machining

Abstract

The invention relates to a tool (10) for machining a workpiece. The tool (10) comprises a tool holder (12) with an internal coolant channel (66) and a cutting insert (14) removably fixed to the tool holder (12). Between an upper side (56) of the tool holder (12) arranged above the cutting insert (14) and a superstructure (64) a gap (58) is provided, above which a coolant outlet opening (70) of the coolant channel (66) is arranged. To improve the flow of chips out of the gap (58), the height of the gap (58) increases towards the front.

Description

Technical Field

[0001] The present invention relates to a tool for machining a workpiece. This tool is preferably a turning tool.

[0002] The tool according to the present invention comprises a tool holder and a cutting insert detachably arranged thereon by clamping means. The cutting insert is preferably configured as an indexable cutting insert.

[0003] An internal coolant channel is provided inside the tool holder, whereby coolant and lubricant (hereinafter simply referred to as "coolant") can be conveyed to the area of the machining point, that is, the area of the cutting edge of the cutting insert used for machining.

Background Art

[0004] An exemplary general-purpose tool already known from the prior art is a tool commercially available by the applicant under the model names "Clamping Holder 356" and "Indexable Cutting Insert 315" (trademark). The front part of this type of tool is shown in detail in FIG. 8.

[0005] The tool shown in Fig. 8 is a turning tool particularly suitable for grooving. In this case, the cutting insert is inserted laterally into a cutting insert receptacle provided in the tool holder and fixed to the cutting insert receptacle by a clamping screw. This clamping screw, on the one hand, presses the cutting insert against the base of the cutting insert receptacle having a flat surface on the back side. On the other hand, the clamping screw presses the cutting insert from the periphery with two bearing surfaces that extend obliquely to each other against the corresponding counter bearing surfaces of the cutting insert receptacle. Above the cutting insert facing these bearing surfaces, the cutting insert is likewise at least partially covered by the tool holder, but is not supported against the tool holder on this upper side. The coolant outlet opening is arranged in this upper region of the tool holder, and this outlet opening is directed such that the coolant coming out therefrom hits the upper side of the cutting insert in the region of the active cutting edge. Thus, the cooling of the cutting insert is carried out very close to the active cutting edge.

[0006] In the present case, the term "active" cutting edge is used to refer to the cutting edge of the cutting insert used to machine the workpiece within each clamp. In the example shown in Fig. 8, the cutting insert has two further cutting edges that can also be used for machining the workpiece, but is arranged within the cutting insert receptacle in the position shown in Fig. 8 and is "inactive" in this position.

[0007] It has been proven that the cooling with this tool is definitely advantageous due to the coolant outlet being close to the active cutting edge.

[0008] Due to the fact that the cutting insert is not supported against the tool holder on its upper side, a slight gap is created between the upper side of the cutting insert and the opposite wall portion of the tool holder below the coolant outlet.

[0009] The chips accumulate to a certain extent in this small gap, and it has been observed that this damages the cutting insert. This even means that the chips are literally pushed into this gap, making it almost impossible to replace the cutting insert without destroying it.

[0010] To address this problem, it might initially seem obvious to clamp the cutting insert from above as well, thereby filling this gap. However, with the type of clamp shown in Figure 8, since the cutting insert is supported by the tool holder at a total of four sides (three peripheral bearing points and one rear bearing point), this would result in a static over-determination. Therefore, one of the two lower bearing points has to be omitted. However, since most of the machining forces usually push the cutting insert downwards, this is accompanied by the risk that the cutting insert will lever out of the cutting insert receptacle during use due to the load, which must be avoided at all costs.

[0011] Another idea, in this case, is to simply enlarge the gap between the upper side of the cutting insert and the structure of the tool holder on the opposite side of this upper side, so that chips are less likely to adhere to the gap or are more easily removed from the gap. However, in this case, the coolant channels or the outlet openings of the coolant would get in the way, or the entire structure of the tool holder would need to be enlarged, which cannot be implemented due to spatial constraints.

[0012] As a result, some manufacturers have chosen to completely eliminate the structure of the tool holder above the cutting insert and displace the outlet openings of the coolant of the internal coolant channels laterally. Such a configuration is schematically shown in Figure 9.

[0013] This means that there is no longer a gap between the upper structure of the tool holder and the upper side of the cutting insert, and the space above the upper side of the cutting insert is practically empty. Therefore, the chip accumulation problem described above no longer occurs. The nature of the clamping of the cutting insert within the cutting insert receptacle can also remain the same as that shown in Figure 8.

[0014] However, the disadvantage of the configuration shown in FIG. 9 is that the coolant is hidden by the workpiece to be machined, so that, especially when working in a deep groove or on a shoulder, the coolant has to be sprayed obliquely towards the active cutting edge, which can be problematic. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0015] In view of this, an object of the present invention is to provide a tool of the above-mentioned type that can address the aforementioned problems. In particular, chips should be prevented from accumulating between the upper side of the cutting insert and the tool holder and being pressed in an undesirable manner. Nevertheless, the supply of coolant needs to be as close as possible to the cutting edge, and it is necessary to reliably ensure a stable clamping method for the cutting insert within the tool holder. MEANS FOR SOLVING THE PROBLEM

[0016] According to the present invention, this object is achieved by a tool according to claim 1. This tool exhibits the following features. A cutting insert having a first side, a second side opposite the first side, and a circumferential surface extending between the first side and the second side, on which a first cutting insert bearing portion and a second cutting insert bearing portion extending laterally from the first cutting insert bearing portion are arranged, a third cutting insert bearing portion is arranged on the second side, forms part of the circumferential surface, and an active cutting edge is arranged above the first and second cutting insert bearing portions and away from them; A tool holder having a cutting insert receiving portion configured as at least a relative recess, the cutting insert receiving portion being configured to receive a cutting insert in such a way that a first portion of the cutting insert is disposed in the recess and a second portion of the cutting insert, on which an active cutting edge is disposed, is located outside the cutting insert receiving portion and at least partially protrudes from the tool holder, the cutting insert receiving portion being defined by a recess base and a plurality of walls extending transversely to the recess base, a first holder bearing portion being disposed on a first wall of these walls, in an assembled state of the cutting insert, the first holder bearing portion supporting a first cutting insert bearing portion, a second holder bearing portion being disposed on a second wall of these walls, in an assembled state of the cutting insert, the second holder bearing portion supporting a second cutting insert bearing portion, a third holder bearing portion being disposed in the recess base, in an assembled state of the cutting insert, the third holder bearing portion supporting a third cutting insert bearing portion, in an assembled state of the cutting insert, a third wall extending transversely to the first and second walls of the aforementioned walls faces the upper side of the cutting insert, the tool holder further comprising an internal coolant channel which, in an assembled state of the cutting insert, opens into a coolant outlet opening facing the upper side of the cutting insert of the tool holder, and In a tool provided with clamping means configured to be inserted into an opening provided in a cutting insert starting from a first side of the cutting insert, penetrate through the first and second sides, and removably fasten the cutting insert to the tool holder, and press the cutting insert against corresponding three holder bearing portions of the tool holder using three cutting insert bearing portions, In an assembled state of the cutting insert, a third wall of the cutting insert receiving portion faces the upper side of the cutting insert, a gap is provided between the third wall of the cutting insert receiving portion and the upper side of the cutting insert, the height of the gap increasing along a gap depth direction parallel to the longitudinal axis of the opening starting from a second side of the cutting insert and towards a first side, the height of the gap being defined as the distance from the third wall of the cutting insert receiving portion to the upper side of the cutting insert.

[0017] It should be noted that the term "laterally" does not necessarily mean orthogonal or perpendicular; rather, it should be understood to refer to any direction that is not parallel.

[0018] The three cutting insert bearing parts and the three corresponding holder bearing parts are thus oriented perpendicular to one another. However, this does not necessarily have to be the case and they can also be oriented obliquely to one another at any angle. The first and second cutting insert bearing parts are preferably in each case oriented at an angle of less than 90° to one another and perpendicular to the third cutting insert bearing part. The same therefore preferably applies to the holder bearing parts.

[0019] The cutting insert and holder bearing portion may be point-like or linear, or may be configured as a flat portion.

[0020] Furthermore, it should be pointed out that the circumferential side of the cutting insert extending between the first side and the second side is referred to in this context as the "circumferential surface". However, this does not mean a plane, but rather a surface made up of many partial surfaces that make up the entire circumference of the cutting insert, which may be curved, angled or edged in any way. Instead of the term "circumferential surface", the term "circumferential side" can also be used generally. Similarly, instead of the terms "first side" and "second side" of the cutting insert, more general terms such as "front side" and "rear side" can also be used.

[0021] According to the present invention, the gap between the third wall of the cutting insert receiving portion on the side opposite to the upper side of the cutting insert is configured to widen toward the front of the cutting insert, that is, in the direction from the rear side to the front side. More precisely, the height of the gap in the gap depth direction extending parallel to the longitudinal axis of the opening increases from the rear side of the cutting insert toward the front side of the cutting insert. The height of the gap is defined as the distance from the upper side of the cutting insert to the third wall of the cutting insert receiving portion.

[0022] By widening the gap between the upper side of the cutting insert and the third wall of the cutting insert receiving portion in this way, the chip is pushed forward (toward the first side portion of the cutting insert) from the gap without being pushed into the gap, so that the chip does not easily accumulate in the gap. Also, it is possible to keep the coolant outlet at the same position as shown in FIG. 8. This enables cooling very close to the cutting edge. The method of clamping the cutting insert in the cutting insert receiving portion also remains the same as described above in relation to FIG. 8.

[0023] Therefore, the tool is produced with optimal cooling and a very stable insert seat, and the problem of undesirable pressing of the cutting insert in the cutting insert receiving portion due to chip accumulation between the cutting insert and the cutting insert receiving portion is solved.

[0024] According to a preferred embodiment, the height of the gap continuously increases along the gap depth direction from the rear side of the cutting insert toward the front side of the cutting insert. Therefore, there is no sudden change in the height of the gap along the gap depth direction, and further, along the gap depth direction, when viewed from the rear side of the cutting insert, the height of the gap increases toward the front side of the cutting insert. However, the increase in the height of the gap along the gap depth direction does not necessarily have to be continuous.

[0025] Continuously increasing the height of the gap along the depth direction of the gap is advantageous in that it prevents the lifted chips entering the gap from being trapped in the gap and thus enables them to be quickly released again without being jammed in the gap.

[0026] According to another improvement example, the third wall includes a first plane extending at an acute angle with respect to a second plane arranged above the cutting insert.

[0027] In this configuration, the gap is bounded by two planes. As a result, this gap expands forward in the shape of a funnel, which is advantageous in relation to chip removal from the gap.

[0028] According to the improvement example, the acute angle is between 3° and 60°, preferably between 10° and 45°, and particularly preferably between 15° and 30°. An angle exceeding 15° is particularly preferred in order to prevent self-locking even when the chip is accidentally engaged in the gap.

[0029] The particularly preferred upper limit of 30° for the acute angle is based on the fact that with this kind of orientation of the third wall of the cutting insert receptacle and the two upper planes of the cutting insert, sufficient space still exists for the internal coolant channel and its coolant outlet opening, enabling cooling from above the cutting insert close to the cutting edge. According to a further improvement example, the second plane provided above the cutting insert is parallel to the longitudinal axis of the opening through which the clamping means is introduced. The longitudinal axis of this opening is the axis of symmetry of the opening and preferably coincides with the longitudinal axis of the clamping means.

[0030] It is even more preferable that the third wall of the cutting insert receptacle completely covers the upper part of the cutting insert belonging to the first part of the cutting insert arranged in the recess.

[0031] On the one hand, this simplifies the production of the tool holder, and on the other hand, it protects the inactive part of the cutting insert and leaves sufficient space for the internal coolant channel and its coolant outlet opening. As a result, even though the height of the gap towards the front side increases, the coolant outlet opening can be directed centrally with respect to the active cutting edge.

[0032] According to a further improvement example, the gap is not bounded by two planes (the first and second planes). Instead, in this improvement example, the third wall is configured as a curved surface. When viewed in cross-section, the third wall in this improvement example has a concave curved configuration. When viewed in cross-section, the third wall may be configured as a radius, an ellipse, or a free form. The improved effect of chip removal from the gap also occurs with this type of shape.

[0033] A third possibility is that the third wall comprises two mutually laterally extending surfaces that merge with each other along the edge. For this reason, the two surfaces are angled with respect to each other. In this way, the height of the gap increases more abruptly from this edge towards the front side, resulting in better chip removal from the gap, especially in the front region of the gap.

[0034] It should be pointed out that in both the improvement example of the third wall as a curved surface and the last-mentioned improvement example of the third wall having surfaces angled with respect to each other, on the upper side opposite the cutting insert, there is also a surface (the second surface) that bounds the gap towards the bottom.

[0035] According to another improvement example, the first cutting insert bearing part and the second cutting insert bearing part are oriented at an angle of 60° or more. Correspondingly, the first holder bearing part and the second holder bearing part are also oriented at an angle of 60° or more with respect to each other.

[0036] For example, in the front side plan view, the shape of the cutting insert substantially corresponds to a regular polygon. In the case of a shape similar to an equilateral triangle, the first and second cutting insert bearing portions are oriented at an angle of 60° to each other. In the case of a shape similar to a quadrilateral, pentagon, or hexagon, the aforementioned angles are 90°, 108°, or 120°, respectively.

[0037] According to a further improvement example, a coolant outlet opening is arranged on a component of the tool holder integrally formed with the third wall. This component is preferably a so-called upper structure that at least partially overlaps the cutting insert.

[0038] By integrally forming this upper structure, a stable tool holder made from as few parts as possible can be obtained.

[0039] According to another improvement example, in the state where the cutting insert is assembled, it is preferable that a virtual plane that bisects the coolant channel intersects the upper side, the first cutting insert bearing portion, and the second cutting insert bearing portion. This virtual plane is particularly preferably a plane orthogonal to the longitudinal axis of the clamping means. Further, it is preferable that this virtual plane is oriented at a right angle to the first and second cutting insert bearing portions and parallel to the third cutting insert bearing portion.

[0040] According to a further improvement example, it is preferable that the third cutting insert bearing portion faces a direction orthogonal to the first cutting insert bearing portion and the second cutting insert bearing portion. The third cutting insert bearing portion preferably faces a direction orthogonal to the longitudinal axis of the opening provided in the cutting insert. The first and second cutting insert bearing portions are preferably oriented parallel to the longitudinal axis of the opening.

[0041] In addition, the cutting insert is preferably rotationally symmetric with respect to the longitudinal axis of the opening. "Rotationally symmetric" is used to describe any object that maps onto itself when rotated about a fixed angle less than 360°.

[0042] It is clear that the features described above and those not described below can be used not only in each of the displayed combinations, but also in other combinations or individually, without departing from the scope of the present invention.

Brief Description of the Drawings

[0043] Exemplary embodiments of the present invention are illustrated in the following drawings and will be described in more detail in the following description.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6a

Figure 6b

Figure 7a

Figure 7b

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0044] Figures 1 through 7 show three exemplary embodiments of a tool according to the present invention in different figures. The tool according to the present invention is generally indicated by reference numeral 10.

[0045] The tool 10 includes a tool holder 12 and a cutting insert 14 detachably fastened therein. The tool holder 12 has a substantially beam-shaped clamp portion 16 and a cutting insert receiving portion 18 disposed in front of the front side thereof. The clamp portion 16 is used to clamp the tool holder 12 with a machine tool. The cutting insert receiving portion 18 is used to receive the cutting insert 14.

[0046] A cutting insert receiving portion 20 is provided laterally in the cutting insert receiving portion 18 of the tool holder 12, and the cutting insert receiving portion 20 is used to receive the cutting insert 14. The cutting insert receiving portion 20 is configured as a recess, and at least most of the cutting insert 14 is disposed within the recess forming the cutting insert receiving portion 20, and the cutting insert 14 is configured to be received such that the remaining portion of the cutting insert that contacts the workpiece when the workpiece is being machined is located outside the cutting insert receiving portion 20 (see Figure 2).

[0047] In the plan view from the side shown in FIG. 2, the cutting insert 14 is formed substantially as an equilateral triangle. At each of the three corners of this triangle, the cutting insert 14 has cutting heads 22, 22', 22" with cutting edges 24, 24', 24" for machining the workpiece. The three cutting heads 22, 22', 22" are preferably configured to be identical to each other and can be used in the same way to machine the workpiece. In the orientation of the cutting insert 14 shown in FIGS. 1 and 2, the cutting head 22 is used to machine the workpiece, while the other two cutting heads 22', 22" are not used and are accommodated in the cutting insert receptacle 20. Therefore, the cutting edge 24 of the cutting head 22 is called the "active" cutting edge. When this active cutting edge 24 wears, the cutting insert 14 is removed from the tool holder 12, rotated up to 60°, and fastened to the tool holder 12 again, so that the cutting edge 24' or 24" acts as the active cutting edge.

[0048] The cutting insert 14 is fastened to the tool holder 12 by clamping means 26. In the exemplary embodiment shown in this example, the clamping means 26 is configured as a clamping screw that engages a corresponding screw 27 provided inside the tool holder 12 (see FIG. 5). However, in principle, a clamping bolt instead of a clamping screw can also be used, and this clamping bolt engages an opening without a screw inside the tool holder 12.

[0049] As can be seen in FIG. 2, the clamping means 26 is introduced into the central opening 30 of the cutting insert, starting from the first side 28 of the cutting insert 14. This opening 30 is configured as a through-hole that penetrates both the first side 28 of the cutting insert 14 and the second side 32 of the cutting insert 14 opposite to the first side 28.

[0050] Between a first side portion 28 and a second side portion 32 of the cutting insert 14, there is a circumferential surface 34 extending perpendicular thereto. This circumferential surface 34 extends over the entire circumference of the cutting insert 14 between the first side portion 28 and the second side portion 32. Equivalent to the terms "first side portion" and "second side portion", this circumferential surface 34 may also be referred to as the circumferential side portion of the cutting insert 14.

[0051] The clamping means 26, in its clamped state, presses the cutting insert 14 into the cutting insert receiving portion 20 together with both its second side portion 32 and its circumferential side portion 34. For this purpose, the cutting insert 14 has three cutting insert bearing portions 36, 38, 40 and is in contact with corresponding holder bearing portions 42, 44, 46 of the cutting insert receiving portion 20. The three cutting insert bearing portions 36, 38, 40 extend transversely to each other, and the first two cutting insert bearing portions 36, 38 are oriented at an angle (≧60°) with respect to each other, and the third cutting insert bearing portion 40 extends orthogonally to the first two cutting insert bearing portions 36, 38. The first two cutting insert bearing portions 36, 38 are arranged on the circumferential side portion 34 of the cutting insert 14. The third cutting insert bearing portion 40 is arranged on the second side portion 32 of the cutting insert 14.

[0052] In the assembled state, the cutting insert 14 abuts against a third holder bearing portion 46 disposed at the base 48 of the recess forming the cutting insert receiving portion 20 with the third cutting insert bearing portion 40 disposed on the second side portion 32. Perpendicular to the base 48 of this recess, the cutting insert receiving portion 20 has a plurality of walls 50, 52, 54 surrounding the cutting insert 14 in the circumferential direction. The first holder bearing portion 42 is disposed on the first wall 50 of these walls, and in the assembled state, the first holder bearing portion abuts against the first cutting insert bearing portion 36. The second holder bearing portion 44 is disposed on the second wall 52, and in the assembled state, the second holder bearing portion abuts against the second cutting insert bearing portion 38. The third wall 54 does not abut against the cutting insert 14. In the assembled state of the cutting insert 14, it lies horizontally facing the upper side 86 of the cutting insert 14. Thus, a gap 58 is formed between the third wall 54 of the cutting insert receiving portion 20 and the upper side 56 of the cutting insert 14 (see FIG. 5). The shape of this gap 58 will be described in detail below.

[0053] Clamping means 26 realized as a clamping screw presses the cutting insert 14 together with its three cutting insert bearing portions 36, 38, 40 against the holder bearing portions 42, 44, 46 provided on the walls 50, 52, 54 of the cutting insert receiving portion 20. In the assembled state, it is easy to understand that the clamping screw 26 presses the third cutting insert bearing portion 40 against the third holder bearing portion 46. The pressure of the clamping screw 26 on the first and second cutting insert bearing portions 36, 38 and the first and second holder contact portions 42, 44 is due to the downward movement of the clamping screw 26. This downward movement is due to the fact that in the assembled state of the cutting insert 14, the longitudinal axis 60 of the clamping means is slightly offset with respect to the longitudinal axis 62 of the opening 30 provided in the cutting insert 14 (see FIGS. 4 and 5). Thereby, a mechanically defined and stable insert seat is ensured.

[0054] The upper side 56 of the cutting insert 14 is at least partially covered by the upper structure 64 of the tool holder 12. This upper structure 64 is part of the cutting insert receiving portion 18 of the tool holder 12. The upper structure 64 is integrally connected to the clamping portion 16 of the tool holder 12. Inside this upper structure 64, there is an internal coolant channel 66 (see FIG. 4). The internal coolant channel 66 extends inside the tool holder 12, initially through the clamping portion 16, branches into a transverse hole 68 at the end of the clamping portion 16, and the said transverse hole leads to the upper structure 64. The internal coolant channel 66 finally opens into a coolant outlet opening 70 disposed above the cutting insert 14 within the upper structure 64. In the assembled state of the cutting insert 14, therefore, the coolant outlet opening 70 is aligned with its upper side 56. The coolant outlet opening 70 is preferably oriented in such a manner that the coolant emerging from the coolant outlet opening 70 strikes the active cutting edge 24 disposed on the upper side 56.

[0055] The third wall 54 of the cutting insert receiving portion 20 forms the lower part of the upper structure 64 facing the upper side 56 of the cutting insert 14. The aforementioned gap 58 exists between this third wall 54 and the upper side 56 of the cutting insert 14 (see FIG. 5). This gap 58 starts from the second side 32 of the cutting insert 14 and spreads towards the first side 28 of the cutting insert 14. More precisely, the height h of the gap 58 increases along the depth direction t of the gap starting from the second side 32 towards the first side 28. The height h of the gap 58 refers to the distance between the upper side 56 of the cutting insert 14 and the third wall 54 of the cutting insert receiving portion 20. In contrast, the depth direction t of the gap means the dimension of the gap 58 measured parallel to the longitudinal axis 60 of the clamping means or the longitudinal axis 62 of the opening (see FIG. 5). In the first exemplary embodiment of the tool 10 shown in FIGS. 1 to 5, the third wall 54 has a first plane 72 that defines the gap 58 upwards. On the opposite lower side, the gap 58 is bounded by a second plane 74 disposed on the upper side 56 of the cutting insert 14. The two planes 72, 74 extend at an acute angle α to each other.

[0056] This type of wedge-shaped gap 58 has the advantage that continuous chips entering the gap 58 can flow out of the gap 58 again very easily without clogging the gap 58. At the same time, the arrangement of the coolant outlet opening 70 is not affected thereby, which means that it can still be directly aligned with the active cutting edge 24 in order to provide cooling as close to the cutting edge as possible.

[0057] The size of the angle α is preferably in the range of 3° to 60°. Particularly preferred is the range of 10° to 45°. Even more particularly preferred is the range of 15° to 30°. This type of opening angle has the advantage that self-locking is avoided even if chips are trapped in the gap 58. However, the opening angle α should not be too large. Otherwise, the coolant outlet opening 70 would have to be displaced further upwards, which would have an adverse effect on the cooling of the active cutting edge 24.

[0058] Figures 6a and 6b show a second exemplary embodiment of the tool 10 according to the invention. This exemplary embodiment essentially differs from the first exemplary embodiment shown in Figures 1 to 5 in the way the gap 58 is configured.

[0059] In this case, the third wall 54 forming the underside of the upper structure 64 has two surfaces 76, 78 that are fused to each other along the edge 80 and face each other. In other words, in this exemplary embodiment, the third wall 54 has an angled configuration.

[0060] However, this type of configuration has the special advantage that the gap 58 opens wider outwards without adversely affecting the coolant outlet opening 70. The coolant outlet opening can still remain in place.

[0061] The further outwardly opening gap 58 ensures even better chip removal.

[0062] Figures 7a and 7b show a third exemplary embodiment of the tool 10 according to the present invention. In this case, a third wall 54 forming the lower side of the upper structure 64 is configured as a curved surface 82. This curved surface 82 can be configured as a part of a circle or an ellipse when viewed in cross-section. This curved surface 82 is preferably configured as a concave curved surface so as not to interfere with the coolant outlet opening 70, but can also be configured as a free curved surface.

[0063] All three exemplary embodiments shown in this case are common in that the gap 58 continuously increases from the inside to the outside along the depth direction t of the gap, and as a result, it starts from the rear side 32 of the cutting insert toward the front side 28 of the cutting insert.

[0064] According to all the exemplary embodiments shown here, the coolant outlet opening 70 is arranged such that the coolant jet coming out therefrom hits the active cutting edge 24 at the center as much as possible. A virtual plane 84 that divides the coolant outlet opening 70 into two equal halves intersects the upper side 56, the first cutting insert bearing portion 36, and the second cutting insert bearing portion 38 in the assembled state of the cutting insert 14. This virtual plane 84 preferably intersects a plane 77 arranged perpendicular to the upper side 56, the first cutting insert bearing portion 36, and the second cutting insert bearing portion 38. This virtual plane 84 corresponds to the cross-section IV-IV shown in FIG. 3. Note that the virtual plane 84 is preferably oriented parallel to the first side portion and the second side portions 28, 32 of the cutting insert 14 and is arranged between both side portions.

[0065] Finally, it should be mentioned that, in principle, either of the other two cutting edges 24', 24" can also be used as the active cutting head of the cutting insert 14. For example, when the active cutting head 24 is worn, the cutting insert 14 is separated from the tool holder 12 by loosening the clamping screw 26, rotated by 60°, and then reattached to the tool holder 12. When rotated clockwise by 60°, the cutting head 24" will be used as the active cutting edge. In this case, the first cutting insert bearing portion 36 forms the upper side 56 or the plane 74 disposed thereon, and it is understood that the second cutting insert bearing portion 38 shown in the exemplary embodiment acts as the first cutting insert bearing portion 36.

[0066] Furthermore, the tool holder 12 and the cutting insert 14 can be subject to various design changes without departing from the scope of the present invention, and it should be noted that this is particularly related to the formation of the gap 58 and its outer opening. As shown here, instead of the cutting insert 14 that is essentially triangular, a cutting insert 14 that is square, pentagonal, hexagonal, or polygonal when viewed in a transverse plan view can also be used. In these cases as well, the cutting inserts are abutted along three surfaces oriented laterally with respect to each other, one of which is oriented perpendicular to the longitudinal axis 62 of the opening 30, and the other two are oriented parallel to the longitudinal axis 62 of this opening. Next, the opening angle between the two cutting insert bearing portions 36, 38 will correspond to the interior angle of the regular polygon in each case (for example, 90° for a square cutting insert, 108° for a pentagonal cutting insert, and 120° for a hexagonal cutting insert).

Claims

Claim 1 A tool (10) for machining a workpiece, comprising: a cutting insert (14) having a first side portion (28), a second side portion (32) opposite to the first side portion (28), and a circumferential surface (34) extending between the first side portion (28) and the second side portion (32), wherein a first cutting insert bearing portion (36) and a second cutting insert bearing portion (38) extending transversely to the first cutting insert bearing portion (36) are disposed on the circumferential surface (34), a third cutting insert bearing portion (40) is disposed on the second side portion (32), and an active cutting edge (24) is disposed above a part of the circumferential surface (34) and away from the first and second cutting insert bearing portions (36, 38); A tool holder (12) having a cutting insert receiving portion (20) configured as at least a relative recess, wherein the cutting insert receiving portion (20) has a first portion of a cutting insert (14) disposed in the recess, and a second portion of the cutting insert (14) on which an active cutting edge (24) is disposed is located outside the cutting insert receiving portion (20) and at least partially protrudes from the tool holder (12), and is configured to receive the cutting insert (14) in such a manner that the cutting insert receiving portion (20) is defined by a recess base (48) and a plurality of walls (50, 52, 54) extending laterally with respect to the recess base (48), a first holder bearing portion (42) is disposed on a first wall (50) of these walls, in the assembled state of the cutting insert (14), the first holder bearing portion (42) supports a first cutting insert bearing portion (36), a second holder bearing portion (44) is disposed on a second wall (52) of these walls, in the assembled state of the cutting insert (14), the second holder bearing portion (44) supports a second cutting insert bearing portion (38), a third holder bearing portion (46) is disposed within the recess base (48), in the assembled state of the cutting insert (14), the third holder bearing portion (46) supports a third cutting insert bearing portion (40), in the assembled state of the cutting insert (14), a third wall (54) extending laterally with respect to the first and second walls (50, 52) of the aforementioned walls faces the upper side (56) of the cutting insert (14), the tool holder (12) further comprises an internal coolant channel (66), and the internal coolant channel (66) opens at a coolant outlet opening (70) facing the upper side (56) of the cutting insert (14) in the assembled state of the cutting insert (14), and the tool holder (12) In a tool (10) comprising clamping means (26) configured to be inserted into an opening (30) provided in the cutting insert (14) starting from a first side portion (28) of the cutting insert (14), penetrate the first and second side portions (28, 32), and removably fasten the cutting insert (14) to the tool holder (12), and press the cutting insert (14) against corresponding three holder bearing portions of the tool holder using three cutting insert bearing portions (36, 38, 40). In the assembled state of the cutting insert (14), the third wall (54) of the cutting insert receiving portion (20) faces the upper side (56) of the cutting insert (14), and a gap (58) is provided between the third wall (54) of the cutting insert receiving portion (20) and the upper side (56) of the cutting insert (14). The height (h) of the gap increases along the depth direction (t) of the gap parallel to the longitudinal axis (62) of the opening (30) starting from the second side portion (32) of the cutting insert (14) and going towards the first side portion (28). The height (h) of the gap (58) is defined as the distance from the third wall (54) of the cutting insert receiving portion (20) to the upper side (56) of the cutting insert (14). The third wall (54) is (i) provided with a curved surface (82), or (ii) provided with a first plane (72), and the first plane (72) is arranged on the upper side (56) of the cutting insert (14) and extends at an acute angle (α) with respect to a second plane (74) extending parallel to the longitudinal axis (62) of the opening (30). A tool (10) characterized by this.

2. The tool according to claim 1, wherein the height of the gap (58) continuously increases along the depth direction (t) of the gap from the second side portion (32) of the cutting insert (14) to the first side portion (28) of the cutting insert (14).

3. The tool according to claim 1, wherein the acute angle (α) is between 3° and 60°.

4. The tool according to claim 1, wherein the acute angle (α) is between 10° and 45°.

5. The tool according to claim 1, wherein the acute angle (α) is between 15° and 30°.

6. The tool according to claim 1, wherein the third wall (54) extends laterally with respect to the first plane (72) and has a third surface (78) that merges with the first plane (72) along an edge (80).

7. The tool according to claim 1, wherein the first cutting insert bearing portion (36) and the second cutting insert bearing portion (38) are oriented at an angle of 60° or more with respect to each other.

8. The tool according to claim 1, wherein the coolant outlet opening (70) is arranged on a component (64) of the tool holder (12) formed integrally with the third wall (54).

9. In the assembled state of the cutting insert (14), the virtual plane (84) that bisects the coolant outlet opening (70) intersects the upper side (56), the first cutting insert bearing portion (36), and the second cutting insert bearing portion (38). The tool according to claim 1.

10. The third cutting insert bearing portion (40) extends perpendicular to the longitudinal axis (62) of the opening (30). The tool according to claim 1.

11. The cutting insert (14) is rotationally symmetric with respect to the longitudinal axis (62) of the opening (30). The tool according to claim 1.

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