SE511223C2 - Tool for rotary cutting machining relative to workpiece - Google Patents

Abstract

The tool comprises a tool body (12), a cutting portion (10) and fasteners for fastening (11). The tool body has a front surface and the cutting portion has a support surface, which are provided to dismountably abut against each other substantially in a radial plane. The body has a shank portion (40) and the cutting portion has at least one cutting edge integral with it. The front surface and the support surface comprise cooperating projections and recesses which are provided to transfer cutting forces directed towards the shank portion during machining. The cutting portion consists of injection moulded cemented carbide and comprises a central blind hole provided to co-operate with the fasteners. The blind-hole is integral with the cutting portion in a direction towards the front surface via the central blind hole provided in the cutting portion.

Description

Another object of the present invention is to provide a stable tool, preferably for drilling or milling, where the tool tip can be easily replaced.

Another object of the present invention is to provide a tool and a tool tip in injection molded cemented carbide.

Yet another object of the present invention is to provide a method of making a tool tip whereby the degree of freedom of geometric appearance is substantially unlimited.

These and other objects have been achieved by a tool, a tool tip and a method of making a tool tip as defined in the appended claims with reference to the drawings.

Figure 1 Fig. 1 shows a drilling tool according to the present invention, in perspective view partly sectioned. Fig. 2 shows a tool tip according to the present invention in perspective view. Fig. 3 shows the tool tip in a side view. Fig. 4 shows the tool tip in top view. Fig. 5 shows the tool tip in bottom view. Figs. 6 and 7 show cross-sections along the lines A-A and B-B in Fig. 4. Fig. 8 shows the drill bit according to Fig. 1 in magnification. Figs. 9, 10 and 11 show enlarged cross-sections of cooperating support surfaces in Fig. 8. Figs. 12 and 13 show an alternative embodiment of a tool according to the invention.

The embodiment of a tool according to the invention shown in Fig. 1 is a so-called spiral drill, which comprises a tool tip 10, a drawbar 1 1, a drill body 12 and a nut 13. 511 At its end facing away from the drill body 12, the tool tip 10 is provided with at least one cutting edge 19, which is given a different design according to the area of use. Thus, the cutting edge or cutting edges are substantially straight and parallel to the longitudinal center axis of the tool tip in the case of a pin cutter, while the cutting edges are circular in the case of a radius cutter. The front end of the tool tip 10 shows in the figures an edge 19 for drilling. The appearance and area of use of the tool can vary in many ways.

The tool tip 10 is made of hard material, preferably cemented carbide and preferably in injection molded cemented carbide, and comprises two upper clearance surfaces 15, a support surface 16 and the connecting first 17 and second 18 curved surfaces. All these surfaces and associated edges are made of the same material, i.e. preferably of injection molded cemented carbide. Cutting lines between the other curved surfaces or chip channels 18 and the clearance surfaces 15 form main cutting edges 19, preferably via reinforcement phases, not shown.

Cutting lines between the first curved surfaces 17 and the chip channels 18 form baffle edges 20. The chip channel can alternatively be adapted for a drill body with straight chip channels. The tool tip preferably also comprises a tipping surface 21, which reaches the center of the tool tip and which forms an angle d, Fig. 6, with the axis of rotation 22 of the tool. The angle d is in the range 40 to 50 °, preferably 45 °. The largest diameter of the tool tip is the diametrical distance D between the radially outermost points of the bends 20.

The height Y of the tool tip is substantially equal to the distance D, in order to minimize the wear from chips on the joint between the tool tip and the drill body.

The largest diameter d of the support surface 16 is preferably smaller than the diameter D, so that release is achieved during machining. Coil holes 23, substantially parallel to the axis of rotation 22, pass through the tool tip from the support surface 16 to the mouth in the respective upper clearance surface 15. The coil holes are arranged on a line 1, on either side of the shaft 22.

The support surface 16 is formed with a number of spaced apart, substantially identical and parallel grooves or axes 30. The ridges form a substantially sinusoidal curve in the cross section according to Fig. 8, which pivots about a line which lies substantially in the flat surfaces 29A, 298, described below with reference to Fig. 9. The ridges are elongated and extend along the support surface 16. The ridge 30 further has two flanks 32A, 32B, which tangentially connect to the bottom 31. The bottom can be described with a radius of about 0.2 to 0.4 mm.

The flanks form an acute angle e with each other. The angle e is in the range 40 ° to 80 °, preferably between 55 ° and 60 °. A crown or a curved surface 33A, 33B is arranged on either side of the axis 30. Each surface connects tangentially to the associated flank via a soft transition. Each axis may be substantially parallel to line 1 or form an acute angle with line 1.

Each axis forms an angle f with a line K, which intersects the radially outermost points of the chip channels on the cutting edge side of the support surface 16. The angle is approximately 0 ° to 90 °, preferably 30 ° to 60 °. The ridge has a height h and a maximum width w. The number of axes 30 depends indirectly on the diameter D of the tool tip, the number varying between 2 to 20 axes and as an example it can be mentioned that about 9 axes are arranged on a drill diameter of 18 mm.

At its end facing the drill body 12, the tool tip is provided with the support surface 16, which is provided with a first engaging member 14, which in the embodiment shown comprises a threaded recess 34 and a truncated conical guide surface 35.

At its end facing the tool tip, the drawbar 11 has a second threaded portion 36, which is followed axially rearwards by a conical extension 37, which are intended to co-operate with the first engaging member 14. In the operative position it co-operates. threaded recess 34 with the second threaded portion 36.

At the other end of the drawbar 11 a further externally threaded portion is arranged, which cooperates with a cylindrical nut 13 provided with a key grip 38. The nut is inserted into a bore 39 in the shaft part 40 of the drill body, the nut and the shaft part having cooperating radial contact surfaces at 41. The contact surface 41 provides axial abutment for the nut when tightening. Drilling connects concentrically to a central, smaller channel in the drill body, said channel extending up to and opening centrally in the front surface 24 of the drill body. The drill body is provided with flush channels 23A, which follow the drill booms along a helical path at a substantially constant distance from the axis of rotation 22. The drill body has helical chip channels 18A or straight chip channels and these may extend through the whole body or through a part thereof.

The drill body 12 is provided at its end facing the tool tip 10 with a front surface 24, which is arranged to abut against the support surface of the tool tip 10. The largest diameter of the front surface is smaller than the largest diameter D of the tool tip but preferably equal to the smallest diameter d of the tool tip.

The front surface is formed with a number of spaced apart, identical grooves or grooves 26, which in cross section describe a substantially trapezoidal path.

The grooves are elongated and extend along substantially the entire front surface.

Each groove can be substantially parallel to the line 1 or form an acute angle with the line 1. Each groove forms an angle f with a line K, which intersects the radially outermost points of the chip channels on the cutting edge side of the front surface 24.

The angle is about 0 ° to 90 °, preferably 30 ° to 60 °. Each groove 26 has two flanks 28A, 28B, which, via a sharp or rounded transition, connect to the bottom 27. The flanks form an acute angle α with each other. The angle α is in the range 40 ° to 80 °, preferably 55 ° to 60 °. A flat surface 29A, 29B is arranged on either side of the groove 26. Each surface is preferably flat in shape and connects to the associated flank via a blunt-angled inner, soft or sharp, transition. The number of grooves 26, which depends on how the support surface of the tool tip is designed, is thus equal to the number of ridges that the support surface has, so the number is selected in the range 2 to 20 grooves. The groove has a depth d, and a maximum width z. The bottom can alternatively be described with a radius of about 0.2 to 0.4 mm. The height of the shaft is 50% to 95% of the depth 26 of the groove and the largest width w of the shaft is greater than the largest width z of the groove z. The game ensures that the flanks come into contact with each other and that the bottom does not support the insert, so that rocking is avoided. A corresponding play thus also occurs above the flat surfaces 29A, 29B. The ridges and grooves form, in assembled condition, a joint with a number of wedge-acting connections which lead to an increase in the frictional force with increasing feed force. Another advantage of said wedge action is that it allows a certain inclination of ridges and grooves relative to each other in connection with the beginning of the assembly, these being controlled correctly by their geometry during continued compression. The joint is positioned so that it will usually be in the borehole during drilling. The ridges and rafters should be placed on each surface so that they are as long as possible. The ends of a ridge or track should be as far apart as possible for best torque transmission.

Mounting of the tool tip 10 on the drill body 12 takes place in the following manner.

The drawbar is inserted into the bore 39 and through the central hole of the drill body 12 until the nut 13, which is connected to the axial rear end of the drawbar, abuts against the contact surface 41. The front portion 36 of the drawbar and the conical extension 37 protrude therewith. then centrally from the front surface 24. Thereafter, the threaded portion 36 is inserted into the recess 14 with the tool tip being rotated and threaded on the drawbar until the surfaces 35 and 37 abut each other.

Then the support surface 16 of the tool tip is brought into contact with the front surface by hand. When rotating the nut 13 via a key which is engaged with the key grip 38, the tool tip 10 will be tightened against the front surface, ie the position according to Fig. 1 has been reached. The tool tip 10 is now fully anchored in the drill body 12. In this position, the drawbar is mainly intended to retain the tool tip when pulling the tool out of the machined hole while the axes and grooves absorb the forces and moments that occur during cutting machining. However, the force from the drawbar is so great that the joint between the tool tip and the body is not allowed to loosen when pulled out. The ridges and grooves intersect the chip channels 18, 18A in a substantially common radial segment or radial plane and the chip channels extend axially on both sides of said radial segment.

In this context it should be pointed out that the threaded connection between the tool tip and the drawbar serves two purposes, namely to place the tool tip 10 in a fixed position in the drill body during assembly, and to always ensure that the tool tip 10 is kept in its fixed position when using the cutting tool.

Through the cooperating axes and grooves a force play can be derived at each contact surface or contact line, where flank cooperation takes place, according to T '= P / n [sin (a / 2) / m - cos (a / 2)] 10 15 20 511 223 8 where T 'is the shear force acting on one flank 28A or 28B of n tracks, m is the coefficient of friction and P is a force arising from the measurement. From the connection it can be interpreted that a smaller flank angle gives a higher shear force T 'which counteracts "over-chewing" caused by the drilling torque.

A drill according to the present invention is statically determined and contains a lot of cemented carbide and relieves the drawbar both radially and axially.

As the cutting forces are spread over a larger area, the risk of splitting the support surface 16 of the tool tip is reduced. After mounting, the axes 30 and grooves 26 form contact surfaces, which intersect the radial plane R, Fig. 11, several times, preferably at least four times. radially outside the end of the drawbar 36. The contact surfaces of the axes and grooves are mainly in the radial plane R, ie they pivot about the radial plane R with an amplitude of at most half the profile height h. The profile height is a maximum of 20% of the tool tip height Y.

The total contact area becomes 5 to 10 ° / 0 larger than conventional flat contact surfaces. The tool tip 10 can thus be releasably connected or removed from the front surface 24 when the end 36 of the drawbar 11 is unscrewed, i.e. activated from a first axially front position to a second axially rear position.

When the tool tip 10 is to be replaced, the procedure is reversed as in the assembly, whereby the tool tip 10 can be removed from the drill body 12 and replaced. Figs. 12 and 13 show an alternative embodiment of a tool according to the invention comprising a tool tip 10 ', a drawbar 11', a drill body 12 ', an adjusting screw 50', a spring 51 'and a stop screw 52'. With this tool, it is possible to loosen and change the tool tip even though the drill body is clamped in the machine. The tool tip 10 'and the drill body 12' are substantially the same as described above. However, in the transition between the fastening end and the chip channels, the drill body has an obliquely inwardly and rearwardly directed threaded bore 53 'and an axially rear thread 54' in the bore 39 '.

The axially front end of the drawbar 11 'comprises a concentric widened guide surface 55' and the parts 36 'and 37' previously described in connection with Fig. 8. The axial rear end of the drawbar has a conical extension 56 ', which laterally merges into a cylindrical guide surface 57', the diameter of the guide surface being slightly smaller than the diameter of the bore 39 '.

The drilling tool is mounted by inserting the drawbar into the bore 39 'and through the central hole of the drill body 12'. Then the spring 51 'is inserted into the bore 39', after which the externally threaded stop screw 52 'is screwed into the thread 54' and thus the spring is compressed and pushes the drawbar forward to a stop.

This gives the drawbar an axially forward position, whereby the threads in the tool tip and on the drawbar can co-operate and the tool tip can be screwed onto the drawbar so that the adjusting screw 50 'via the thread 53' can press against the extension 56 'and push the drawbar backwards. Tool tip replacement is as follows. First, loosen the adjusting screw 52 'on the side of the drill shaft, pushing the drawbar 1' 'forward, approximately 2 mm, due to the elastic energy stored in the spring 51'. The spent tool tip is threaded off, preferably by hand, and a new tool tip is threaded onto the drawbar until the conical part of the recess abuts against the front conical portion of the drawbar. Then you can proceed in two different ways. Either the tool tip is moved towards the front surface of the drill body by hand so that ridges and grooves engage with each other, after which the adjusting screw 52 'is tightened and the tool tip is fixed in the operative position. The second way is to let the screw 52 'alone push up the drawbar including the tool tip so that ridges and grooves 2.23 10 engage with each other, the tool tip being axed in the operative position. The conical surface 56 'may abut a corresponding surface in the front end of the bore 39' when the screw 50 'is unscrewed. Thus, the friction between the conical surfaces counteracts rotation of the drawbar when unscrewing the Tool Tip. If the friction is too low, the screw 50 'can be screwed against the cylindrical surface 56' and thereby further lock the drawbar against rotation.

For the two above-mentioned embodiments, the tool tip has a wedge interaction with the tool body so that the clamping force or frictional force, i.e. the resistance to radial movement of the part relative to the body, increases with increasing feed force. In addition, the fastening means are arranged to actuate the tool tip in the same direction as the feed force during drilling, i.e. the drawbar pulls the tool tip axially backwards substantially in the same direction as the feed force acts.

It is to be understood that the geometries of the cooperating ridges and grooves may be varied within the scope of the present invention without departing from the spirit of invention. Thus, the geometries can assume the cross-section of most of the threads (however with a coverage rate of max 95%), e.g. trapezoidal shape on both cooperating surfaces. The invention is also useful for cutters. The tool tip is preferably coated with layers of e.g.

Al 2 O 3, TiN and / or TiCN. In some cases, soldered super-hard materials such as CBN or PCD may be justified on the cutting edges.

It is also possible to use holding means other than a central drawbar; for example, it is possible to hold the tool tip by means of a wedge movable perpendicular to the axis of rotation. In addition, it should be pointed out that the embodiments described above relate to tools which rotate relative to their longitudinal or the central axis of the workpiece and that the holding means rotates with the tool.

The embodiments can also be used as stationary, but then in combination with a rotating workpiece.

An independent patent claim relates to a tool tip, which in its entirety consists of injection-molded cemented carbide, it being possible to use the invention in milling, drilling or reamer inserts for metal processing. When utilizing the invention for metalworking, the tool tip comprises a central, non-through-going recess 14 for a fastening device, the recess having a thread 34 integrated with the insert in general. This refers to inserts which can be clamped from the underside of the tool tip by means of e.g. a screw, so that a large upper surface becomes accessible to cutting edges or chip formers, which previously could not be used. The thread is then selected so that it does not come loose during machining.

The tool tip is manufactured as follows. Carbide and a carrier, for example plastic, are mixed and formed into pellets or granules, after which the mixture is introduced into a spraying machine, after which preheating takes place to a temperature suitable for the mixture, after which the mixture is injected into a mold under high pressure and high temperature, about 180 ° C. arranged with a certain configuration to correspond to the design of the tool tip. Therefore, the mold contains portions for directly or indirectly creating conditions for at least one cutting edge and at least one release surface as well as one or more cores for thread and flushing channels in order to impart to the Tool Tip its design after which the injection molded cemented carbide tip is allowed to solidify. Then the tip is sintered and any subsequent processing such as grinding can be performed on the release surfaces. By means of this method, the geometry of the tip can be selected independently of the limitations of the conventional compression molding method. For example, chip breakers can be formed on surfaces that have hitherto only been able to be ground in.

The invention is in no way limited to the embodiments described above but can be freely varied within the scope of the appended claims.

Claims (7)

15 20 25 30 511 223 13 Patent claims A tool tip for rotary, chip-separating machining comprising at least one cutting edge (19), which is integrated with the tool tip (10; 10 '), the tool tip being intended to be releasably attached to a tool body, characterized in that the tool tip consists entirely of injection molded cemented carbide and that it comprises a central recess (14) formed as a bottom hole, which comprises an internal thread (34), otherwise integrated with the tool tip. Tool tip according to claim 1, characterized in that the tip (10; 10 ') comprises spool holes (23; 23'), substantially parallel to the axis of rotation (22; 22 '), which run through the tool tip from the support surface (16; 16') to the respective upper release surface (15). Tool tip according to one of Claims 1 or 2, characterized in that the tool tip comprises a non-planar support surface (16; 16 ') into which the recess (14) opens. A tool for relatively one workpiece, rotary cutting machining, comprising a tool body (12; 12 '), a tool tip (10; 10') and fasteners (11,36; 11 ', 36'), the tool body having a front surface ( 24; 24 ') and the tool tip comprises at least one cutting edge (19), which is integrated with the tool tip (10; 10') and has a support surface (16; 16 ') arranged to releasably abut against the front surface, the body having a shaft part (40 40 '), characterized in that the tool tip consists entirely of injection-molded cemented carbide and that it comprises a central recess (14) formed as a bottom hole, which comprises an internal thread (34), otherwise integrated with the tool tip, and that the fastening means ( 11,36; 11 ', 36') is arranged to actuate the tool tip in the direction of the front surface by means of a complementary external thread (36; 36 ') Tool according to claim 4, characterized in that the tip (10; 10 ') comprises spool holes (23; 23'), substantially parallel to the axis of rotation (22; 22 '), which pass through the tool tip from the support surface (16; 16'). to the respective upper release surface (15). Tool according to one of Claims 4 or 5, characterized in that the tool tip comprises a non-planar support surface (16; 16 ') into which the recess (14) opens. A method of making an edge-tip tool tip (10; 10 ') intended to be releasably attached to a tool body to form a tool for rotary cutting machining, characterized in that cemented carbide and a carrier are mixed and the mixture is introduced into a spraying machine and heated to a suitable temperature for the mixture, after which the mixture is injected under high pressure and at about 180 ° C into a mold arranged with details, such as portions forming directly or indirectly at least one cutting edge and at least one clearing surface, and one or more cores in order to impart its tool tip design. , of which at least one core has an external thread, after which the mixture solidifies in the mold, after which the tool tip is picked out of the mold and sintered and any subsequent processing such as grinding is performed.