Cutting tool

Abstract

The invention relates to a cutting tool, in particular for the turning out of drillings, comprising a clamping piece (10) for fixing the tool in a clamp holder. Said clamping piece (10) comprises two clamping surfaces (30), which converge on each other in the direction of the one side (32) of the clamping piece (10) and in the direction of the other side (34) of the clamping piece (10) run into a roof-type surface (36) and, on the side of the clamping piece (10) facing away from the clamp holder, connect to a rod-like neck piece (12), which tapers in cross-section relative to the clamping piece (10) the free end of which is connected to a cutting piece (14) as one piece, provided with a cutting edge (16) on the external end thereof to which a face (18) of the cutting piece (14) connects in the direction of the neck piece (12). A high degree of reinforcement for the neck piece and the cutting piece arranged on the free end thereof with the blade or the blade edge thereof is achieved, whereby the neck piece (12) has two reinforcement pieces running along the same, transverse to the plane of the cutting edge (16), which are embodied in the manner of reinforcing ribs (20, 22) which convergently taper in the direction of the cutting piece (14), which are diametrically opposed in relation to the neck piece (12) and have the greatest width thereof at the point of transition into the clamping piece (10).

Description

[0001] The invention relates to a cutting tool, in particular for hollowing drill holes, having a clamp component for securing the tool in a tool holder, a neck component tapered in cross-section relative to the clamp component adjoining on the side of the clamp component facing away from the tool holder, and an integral cutting component provided at its extremity with a cutting edge which adjoins a face of the cutting component in the direction of the neck component. A comparable cutting tool is disclosed in EP-B-0 385 280. The solution disclosed relates to an inner cutter for machining the interior surface of drill holes, for example, for cutting circumferential grooves into the drill hole wall, for precision machining of the drill hole wall by finish turning of the drill hole wall, for thread cutting in a bore hole, and the like.

[0002] The cutting edge of the tool moves in a radial direction of advance during parting in machining the interior wall of a drill hole. In the process the cutting edge must be positioned with the greatest accuracy possible in a diametral advance plane extending parallel to this radial direction of advance. Only with the cutting edge in this position is an optimal clearance angle obtained. Spacing the cutting edge away from the diametral advance plane results in clearance angles which may lead to unfavorable results in metal removal, such as vibration of the tool. For this reason very precise rotary positioning of the tool in the tool holder must be achieved, and the position of the tool must not vary appreciably when a load is applied to the tool. Distances between the cutting edge and this diametral plane are especially critical in the case of drill holes of small diameter which are to be machined, since in this situation even a slight variation of such spacing from zero results in major change in the clearance angle. In order to prevent such occurrence, the cutting tool disclosed in the European prior publication has on its clamp component clamping surfaces at least to some extent converging toward each other, surfaces by means of which the cutting tool may be secured on a processing machine, such as one in the form of a lathe, it being possible to bring such converging surfaces in contact with correspondingly converging contact surfaces of the tool holder. By means of the mould closure referred to a precisely defined rotary position of the disclosed clasp tool may be achieved in that radial enlargement in the seating recess in the tool holder and the radial projection on the shaft component of the clasp tool result, through the action of the clamping means, in rigorously defined application of the clamping surfaces of the radial projection to the contact surfaces of the enlargement, change in the cutting position perpendicular to the diametral advance plane when load is applied to the tool being prevented, since the rotary position of the cutting tool relative to the tool holder is ensured in that application of the clamping surfaces to the application surface acts on a radius enlarged in relation to the radius of the receptacle bore.

[0003] In order to permit machining of drill holes of extremely small diameter, it has been recognized in the disclosed solution as advantageous to configure the clasping tool as one piece. Other advantages to this end are achieved if the clasping tool consists of a cutting alloy, since, because of the large elasticity modulus of cutting alloy tools, the cutting edge remains precisely in the position originally set even under relatively high loads, so that change in the cutting position relative to the diametral advance plane when a load is applied is virtually eliminated.

[0004] It has been found, however, that, despite the measures described, the disclosed cutting tool approaches its limits when drill holes of extremely small diameter, less than one millimeter, such as 0.7 mm, are to be machined. Despite the advantageous tool holding, the integrated configuration of the tool, and its construction by use of cutting alloy materials, these disclosed measures do not make it possible to advance in this range of operation with boring diameters smaller than 1 mm to achieve the machining qualities desired.

[0005] EP-A-0 947 267 discloses a generic tool having a holder in which a plate with three cutting edges may be secured by means of a threaded connection. The free end of the holder on which the cutting tool may be seated has recesses by means of which reinforcing ribs are produced so that, despite the holder components reduced by the cut-out recesses, such good reinforcement is obtained for the cutting plate that vibrations impairing the machining quality during machining are absorbed and the holder is reinforced. Because of the flat application of the plate with three cutting edges on the end of the holder and the disclosed possibility of fastening by means of a screw connection, misadjustment of the machining edge may occur and in addition the configuration of the disclosed solution is so large that application of this for drill holes of extremely small diameter is not possible.

[0006] On the basis of this state of the art the object of the invention accordingly is to improve the conventional cutting tool for the purpose of making it possible, while retaining the advantages of this tool, to machine drill holes of extremely small diameters, such as ones appreciably smaller than 1 mm, while maintaining high quality standards. It is claimed for the invention that this object is attained by the combination of characteristics specified in current claim 1.

[0007] A high degree of reinforcement is achieved for the neck component of the cutting tool and the cutting component with cutting edge mounted on its free end is achieved in that, as specified in the preamble of claim 1, the retaining component has, extending transversely to the plane of the cutting edge, two reinforcing components such as reinforcing ribs which taper as they converge in the direction of the cutting component are positioned diametrically opposite each other in relation to the retaining component, and assume their greatest width at the point of their transition to the shank component. In the case of a conventionally designed retainer the reinforcing ribs of the cutting component permit sure absorption of the machining forces introduced into the cutting component by way of the retaining component into the shank component and then into the holding component to be associated with the machine. In particular, the reinforcing ribs counter vibrations occurring during machining with the cutting component and retain the latter precisely in its required machining plane. Since the reinforcing ribs extend perpendicular to the plane of the cutting component with its cutting edge, they occupy little structural space and, because of their convergent configuration, permit engagement of the cutting components even in drill holes of small diameter.

[0008] In that the reinforcing ribs preferably are obtained from the neck component by a grinding process from the neck component and always have two different grinding patterns with different, preferably concave, radii of curvature in the direction of the cutting component, very high supporting forces can be achieved for the cutting component and the structural space required for the reinforcing ribs is optimized as well, so that a high degree of stiffening is achieved with geometrically small reinforcing ribs, which thus permit engagement of the cutting component also in drill holes for a machining process whose diameter is smaller than 1 mm, and 0.7 mm in particular.

[0009] Other advantageous embodiments of the cutting tool claimed for the invention are specified in the additional dependent claims.

[0010] The invention in its additional advantageous embodiment is described in detail in what follows with reference to an exemplary embodiment, illustrated in a greatly enlarged diagram in the drawing, in which

[0011] FIG. 1 presents a perspective view of the cutting tool;

[0012] FIG. 2 a bottom view of the cutting tool shown in FIG. 1;

[0013] FIG. 3 an additionally enlarged view of a section of the front, head, part of the cutting tool shown in FIG. 1;

[0014] FIGS. 4 and 5 a section along line I-I and II-II respectively in FIG. 3.

[0015] The cutting tool illustrated in the figures is used in particular for hollowing drill holes having a bore diameter <1 mm, preferably in the area of 0.7 mm. The cutting tool has a clamping component 10 for securing the tool in tool holder not shown. Use may be made, for example, of the tool holders as described in European Patent 0 385 280 issued to the applicant. The side of the clamping component 10 facing away from the tool holder is adjoined by a neck component 12 tapered in relation to the clamping component 10, such neck component 12 having integral with it on its free end a cutting component 14 which is provided at its extremity with a cutting edge 16 which adjoins a face 18 of the cutting component 14 in the direction of the neck component 12. The direction of machining with the tool is indicated in FIGS. 1 to 3 by an arrow identified by an “X.”

[0016] As is to be seen in FIG. 2 in particular, the neck component 12 has, extending along it, transversely to the plane with the cutting edge 16, two reinforcing components in the form of two reinforcing ribs 20, 22. The two reinforcing ribs 20, 22 taper convergently in the direction of the cutting component 14. In addition, the two reinforcing ribs 20, 22 are positioned diametrically opposite each other relative to the neck component 12, in particular in relation to the longitudinal axis 24 of the cutting tool. The neck component 12 extends more or less in rotation symmetry around the longitudinal axis 24 in question and the two reinforcing ribs 20, 22 extend like vanes on both sides of the longitudinal axis 24 along the neck component 12. In addition, the reinforcing ribs 20, 22 reach their greatest width at the point of their transition to the clamping component 10, which may also be designated shank or shank component of the cutting tool.

[0017] The two reinforcing ribs 20, 22, as well as the other geometric configurations of the cutting tool, are obtained in particular by a grinding process and the reinforcing ribs 20, 22 thus obtained from the neck component 12 each exhibits in the direction of the cutting component 14 two different grinding patterns with different, preferably concave, radii of curvature. In order to ensure a high degree of engagement depth for the cutting edge 16, the grinding patterns selected for the two reinforcing ribs 20, 22 accordingly have greater curvature in the direction of the cutting edge 16 than in the direction of the clamping component 10.

[0018] The free surface 26 of the cutting component 14, which is situated at the front end in the direction of machining X, is slanted backward at an angle A, preferably 5°, from the vertical (see FIG. 2). The respective front free surface 26 of the cutting component is, in turn, itself slanted backward at an angle B, preferably 8° (see FIG. 3). As is also to be seen from FIG. 2, the face 18 in turn is slanted backward at an angle C, preferably 5°, from the horizontal, specifically, in the direction of the clamping or shank component 10. In addition, the cutting edge 16 undergoes transition at its free end in the direction of machining X to a supporting surface 28 (see FIG. 23) which extends parallel to the direction of machining X, the outer circumferential surface of this supporting surface 28 projecting beyond the neck component 12 by an amount of excess E. Consequently, by its excess E the supporting surface and the cutting edge forms a kind of hook tool relative to the neck component 12.

[0019] The illustrations in FIGS. 1 and 4 show that the clamping component 10 has essentially two clamping surfaces 30 which converge toward each other in the direction of the bottom 32 of the clamping component 10 and which undergo transition to semicircular roofage 36. In this way the clamping component 10 may be secured in a corresponding seat of a clamping component by means of an adjusting screw not shown in detail. A clamping component such as this is described in greater detail in EP-B-0 385 280 and accordingly will not be discussed further at this point. In the area of the clamping component 10, which is bounded by the two clamping surfaces 30, a coolant feed channel 38 extends parallel to the direction of machining X. A cooling lubricant in particular may be fed by way of the coolant feed channel 38 in the direction of engagement of the cutting edge 16 with a tool to be machined (not shown). At the point at which the coolant feed channel 38 empties into the open, the neck component 12 is more greatly retracted relative to the clamping component 10 (see FIG. 3) than on the diametrically opposite point in the area of the top 34 of the cutting tool. A kind of domed support for the cutting component 14 proper with its cutting edge 16 is produced on the basis of the respective configuration, along with accompanying grinding patterns 23, 25 for the external outline of the cutting tool, at least in one diametral plane, as is illustrated in FIG. 2.

[0020] Hard alloys such as MG12, TN 35, TI25, or TF45 have been found to be especially well suited. The cutting tool configuration also illustrated in the figures is that of a “right-hand” embodiment; mirror-image configuration of the figures presented yields a corresponding “left-hand” embodiment, should such prove to be necessary for the machining purpose pursued.

Claims

1. A cutting tool, in particular for hollowing drill holes, having a clamping component (10) for fastening the tool in a tool holder, the clamping component (10) having two clamping surfaces (30) which converge toward each other in the direction of one side (32) of the clamping component (10) and in the direction of the other side (34) of the clamping component (10) change in shape to that of roofage (36), and a rod-shaped neck component (12) tapered in cross-section relative to the clamping component (10) adjoining on the side of the clamping component (10), the cutting component (14) being provided on its outer end with a cutting edge (16) which is adjoined by a face (18) of the cutting component (14) in the direction of the neck component (12), characterized in that the neck component (12) has extending along it transversely to the plane of the cutting edge (16) two reinforcing components which, in the form of reinforcing ribs (20, 22) taper as they converge in the direction of the cutting component (14), such reinforcing ribs (20, 22) being positioned diametrically opposite each other in relation to the neck component (12) and assume their greatest width at the point of their transition to the clamping component (10).

2. The cutting tool as claimed in claim 1, wherein the reinforcing ribs (20, 22) are obtained by a grinding process from the neck component (12) and exhibit two different grinding patterns (23, 25) with different, preferably concave, radii of curvature in the direction of the cutting component (14).

3. The cutting tool as claimed in claim 2, wherein, in the direction of the cutting neck (14), the grinding patterns (23, 25) selected for the reinforcing ribs (20, 22) exhibit greater curvature than in the direction of the clamping component (10).

4. The cutting tool as claimed in one of claims 1 to 3, wherein the free surface (26) of the cutting component (14), which is positioned on the foremost end in the direction of machining (X), is tilted backward from the vertical by an angle (A), preferably 5°.

5. The cutting tool as claimed in claim 4, wherein the foremost free surface (26) of the cutting component (14) is tilted backward from the cutting edge (16) by an additional angle (B), preferably 8°.

6. The cutting tool as claimed in one of claims 1 to 5, wherein the face (18) is tilted backward from the horizontal in the direction of machining (X) by a third angle (C), preferably 5°.

7. The cutting tool as claimed in one of claims 1 to 6, wherein the free end of the cutting edge (16) becomes, in the direction of machining, a supporting surface (28) which extends parallel to the direction of machining (X) and projects beyond the neck component (12) by the amount of an excess (E).

8. The cutting tool as claimed in one of claims 1 to 7, wherein the clamping component (10) has two clamping surfaces (30) which converge toward each other in the direction of the bottom (32) of the clamping component (10) and change in shape to that of semicircular roofage (36) in the direction of the top (34) of the clamping component (10).

9. The cutting tool as claimed in claim 8, wherein a coolant feed channel (38) extends parallel to the direction of machining (X) in the area of the clamping component (10) which is bounded by the two clamping surfaces (30).

10. The cutting tool as claimed in claim 9, wherein the neck component (12) recedes farther into the clamping component (10) as it undergoes transition to the latter, at the point at which the coolant feed channel (38) empties into the open than on the diametrically opposite side.