Rotary tool for chip removal comprises a cutting tip having a brittle wear resistant outer and tough less wear resistant inner portions the tip connected to the tool shank by a end threaded pull rod

(54) TITLE Tool for rotary cutting, tool tip and method for manufacturing the tool tip (56) PUBLICATIONS CITED:

(57) SUMMARY:

The present invention relates to a tool and a tool tip for cutting processing, whereby the tool preferably rotates around its longitudinal center axis in the active position. The invention also relates to a method for manufacturing a tool tip. The tool tip (10”) contains two types of carbide, a tough, less wear-resistant variety in the inner part (40”) and a more brittle, more wear-resistant variety in the outer part (41”). The tool tip is manufactured by injection molding, whereby the two types have the same shrinkage factor. The inner part (40) is completely enclosed by the outer part (41) except in the feed direction and the return direction. The tool tip has a thread (25) formed in the tougher carbide to withstand high tensile stresses.

The numbers in parentheses indicate international identification code, INlD code. Letter in brackets indicates international document code.

<td>K PRV Patent uses the following document codes for its patent documents X^code code plain text A publicly available patent application_L generally available^U- TI translation of the requirements in the European patent application C t tskr'ft * '² correction of translation of the claims in the European patent application^p . . .. . T3 translation of European patent documents C2 text¹⁴ translation of European patent law in second language T5 corrected translation of European patent text C3 dial patent knft tv. .... · . , ... '° controlled translation of European patent law C5 dial patent scnft * το i · j - -L · · . . .. ... T9 edited translation of European patent law Ce corrected first page to patent document E patent document as amended E8 corrected first page to patent document as amended &lt;^E9 corrected patent text as amended * published under older legislation y</td>

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<td>AP</td><td>African Regional Industrial Property Organization (ARIPO)</td><td>CN CO CR</td><td>China Colombia Costa Rica</td><td>At KM KN</td><td>Kiribati Comorema St. Kitts</td><td>RU RW SA</td><td>Russian Federation Ruanda Saudi Arabia</td>

<td>EA</td><td>Eurasian Patent Office</td><td>CU</td><td>Cuba</td><td>CP</td><td>Them. People's Republic of Korea</td><td>SB</td><td>Solomon Islands</td>

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<td>European Patent Office</td><td>CY</td><td>Cypem</td><td>KW</td><td>Kuwait</td><td>SD</td><td>Sudan</td>

<td rowspan="2">OA</td><td>(EPO)</td><td>CZ</td><td>The Czech Republic</td><td>OK</td><td>Cayman Islands</td><td>SEE</td><td>Sweden</td>

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<td>¹ World Intellectual</td><td>DM</td><td>Dominica</td><td>LC</td><td>Saint Lucia</td><td>SK</td><td>Slovakia</td>

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<td>CG</td><td>Congo</td><td>YES</td><td>Jordan</td><td>PK</td><td>Pakistan</td><td>ZR</td><td>Zaire</td>

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516 366

Background of the invention

The present invention relates to a tool for rotary, cutting processing, comprising a tool body, a tool tip and fastening means. The invention also relates to a separate tool tip and to a method of manufacturing a tool tip.

Known technology

It is previously known to use replaceable cutting edges on various types of tools for cutting processing. The known technology, however, has its practical limitation for strength engineering reasons when it comes to milling and drilling tools that rotate around their central axis, because the cutting edges are then exposed to varying cutting speeds.

Through SE-A-9501687-9, a drill with an injection-molded detachable tool tip anchored in a tool body by means of a tie rod is previously known. A disadvantage of the known drill, as with most drills, is that it is not optimized for varying cutting speeds. In addition, the thread in the known drill has a tendency to crack at high tensile stresses.

It is previously known by, for example, WO 98/28455 to press a core and an enclosing tube of material powder in two stages. The material powder consists of tungsten carbide (WC) together with cobalt (Co), which is compressed between a punch and a pad and then sintered so that the bond metal melts and binds the carbides to form tool material for chip removal machining. The intention of the known technique is to achieve two different properties depending on the radial position in a solid body. A disadvantage of this technique is problems with cracks in the radially outer part or porosities in the radially inner part.

Purpose of the invention

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The purpose of the present invention is to provide a design for milling and drilling tools with replaceable cutting edges, whereby said design eliminates the problems with known technology.

Another aim of the present invention is to provide a stable tool preferably for drilling or milling where the radially outer parts of the cutting edges, which are exposed to relatively high cutting speed, have better wear resistance than the radially inner parts of the cutting edges.

Another aim of the present invention is to provide a tool preferably for drilling or milling where the radially inner parts of the cutting edges, which are exposed to relatively low cutting speed, have higher toughness than the radially outer parts of the cutting edges.

Another aim of the present invention is to provide a tool preferably for drilling or milling where the risk of the tool tip breaking is minimized.

Yet another purpose of the present invention is to provide a tool tip with a thread which can withstand high tensile stresses.

Yet another object of the present invention is to provide a method for manufacturing a tool tip of injection molded carbide whereby the degree of freedom for geometric appearance is essentially unlimited and whereby grinding work is minimized.

Yet another purpose of the present invention is to provide a method for manufacturing a tool tip of injection molded carbide whereby cracks and porosities are avoided.

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

List of figures

Fig. 1 shows a drilling tool according to the present invention, in perspective view partially in cross section. Fig. 2 shows a tool tip according to the present invention in a side view. Fig. 3 shows the tool tip in another side view. Fig. 4 shows the tool tip in bottom view. Fig. 5 shows a cross-section according to the line VV in Fig. 3. Fig.

516 366 shows a cross-section similar to that of Fig. 5 from an alternative embodiment of a tool tip according to the present invention. Fig. 7 shows a cross-section similar to that in Fig. 5 from a further alternative embodiment of a tool tip according to the present invention. Fig. 8 shows a drill body according to the present invention in a side view. Fig. 9 shows drill body in a top view. Fig. 10 shows the end of the drill body in an enlarged side view. Fig. 11 shows a device, in bottom view, for making a tool tip according to the present invention. Fig. 12 shows a cross-section according to the line XII-XII in Fig. 11. Fig. 13 shows the device in a second manufacturing step in cross-section corresponding to Fig. 11. Fig. 14 shows the device in the second step in a cross-section according to the line XIV-XIV in Fig. 13.

Detailed description of the invention

The embodiment shown in Fig. 1 of a tool according to the invention is a so-called spiral drill, which in this case includes a tool tip 10, a drawbar 11, a tool body 12, a locking screw 50, a spring 51 and a stop screw 52. With this tool is it possible to loosen and change the tool tip even though the tool body is clamped in the machine. The drill tool has also been described in SE-A-9501687-9 and SE-A-9603478-0.

The tool tip 10 is provided at its end facing away from the tool body 12 with at least one cutting edge 19, which is given a different design depending on the area of ​​use. Thus, the cutting edge or cutting edges are essentially straight and parallel to the longitudinal center axis of the tool tip in the case of an end mill, while the cutting edges are circular in the case of a radius cutter. The front end 21 of the tool tip 10 shows in the figures an edge 19 for drilling comprising a cross cut 24.

The tool tip 10 and the tool body 12 comprise support 22 and front surfaces 14, respectively, in accordance with SE-A-9702500-1.

The tool tip 10 is made of injection-moulded carbide. As can be seen from Fig. 2-4, the tool tip comprises two upper release surfaces 15, a support surface 22 and first 17 and second 18 curved surfaces connecting them. All these surfaces and

516 366 associated edges are made of injection-molded carbide. Cutting lines between the other curved surfaces or chip channels 18 and the release surfaces 15 form main cutting edges 19, preferably via, not shown, reinforcement phases.

Lines of intersection between the first curved surfaces 17 and the chip channels 18 form bisect ridges 20. The chip channels can alternatively be adapted for a tool body with straight chip channels. The largest diameter of the tool tip is made up of the diametrical distance between the 20 radially outermost points of the cutting edges. The height of the tool tip is essentially equal to the diameter. The largest diameter of the support surface 22 is preferably smaller than the largest diameter of the tool tip, so that clearance is achieved during processing. Flush holes 23, essentially parallel to the center axis CL, run through the tool tip from the support surface 22 and open into the respective upper release surface 15. The flush holes cut a normal to the center axis CL on either side of the center axis.

The support surface 22 has a basic circular shape and includes two groove parts 22A, 22B. Each groove part essentially covers the entire support surface 22 and comprises a number of separate, identical grooves or grooves. The tracks in the track sections have two main directions, which are perpendicular to each other. Essentially, each groove in both groove portions 22A, 22B intersects the jacket surface of the tool body in two places. Each groove is elongated and is essentially V-shaped in cross-section. Each groove has two flanks which, via a sharp or rounded transition, connect to a bottom. The flanks form an acute angle with each other. The angle is in the range 40° to 80°, preferably 55° to 60°. Each flank is preferably designed flat and connects to the corresponding flank via an obtuse-angled inner, soft or sharp, transition. The number of grooves in each groove section depends on how the front surface of the tool body is designed and the number is chosen in the range of 5 to 20 grooves. The design of the track parts 22A, 22B gives a significantly larger specific surface than if it were flat. The groove parts 22A, 22B cover at least 80%, preferably 90-100%, of the available area on the support surface 22. The tool tip has a bottom hole with an integrated thread 25 intended to cooperate with a threaded free end of the drawbar 11. This gives the possibility of arranging the cutting edges in towards the center axis for drilling. In that in Fig. 4 shown embodiment, the groove parts 22A, 22B have been manufactured by direct injection and sintering or by grinding.

516 366

The tool body is provided with chip channels 18A, which follow the booms of the drill along a helical path at an essentially constant distance from the center axis CL. The chip channels can extend along the entire body or along part of it. The chip channels can alternatively be straight.

The tool body 12 is provided at its end facing the tool tip 10 with a front surface 14 against which the support surface 22 of the tool tip 10 is arranged to abut. The largest diameter of the front surface is smaller than the largest diameter of the tool tip, but preferably equal to the smallest diameter of the tool tip.

The tool body has flushing channels 23A. The tool body 12 can be made of steel, carbide or high speed steel. One free end or shaft part of the tool body 12 is intended to be attached to a rotatable spindle (not shown) in a drilling machine, while the opposite other free end comprises a front surface 14 and a hole 15A.

The free end of the tie rod is arranged to protrude through the hole 15A. The front surface 14 has a basic circular shape and includes two groove parts 16A, 16B. Each groove portion 15 essentially covers half of the front surface 14 and comprises a number of separate, identical grooves or grooves. The tracks in the track sections have two main directions S1, S2, which are perpendicular to each other. A second track portion 16A is delimited by a first track portion 16B. Substantially each groove in the first groove portion 16B intersects the casing surface of the tool body in two places while substantially each groove in the second groove portion 16A intersects the casing surface of the tool body in one location. Each groove is elongated and is essentially V-shaped in cross-section. Each groove has two flanks which, via a sharp or rounded transition, connect to a bottom. Each groove has a width W. The flanks form an acute angle with each other. The angle is in the range 40° to 80°, preferably 55° to 60°. Each flank is preferably designed flat and connects to the corresponding flank via an obtuse-angled inner, soft or sharp, transition. The number of grooves in each groove section depends on how the support surface of the tool tip is designed and the number is chosen in the range of 5 to 20 grooves. The bottom can alternatively be described with a radius of about 0.2 to 0.4 mm. The design of the track parts 16A, 16B gives a significantly larger specific surface than if it were flat.

The track parts 16A, 16B cover at least 80%, preferably 90-100%, of the available area on the front surface 14.

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In the embodiment shown in Fig. 9, the first groove portion 16B has been produced, by roller milling or grinding, with a feeding direction parallel to the direction S2. After that, the second groove part 16A has been machined with the same tool in a direction parallel to the direction S1. In order to obtain full depth in each groove in the second groove part 16A, it is suitable for the tool to be fed one piece into the first groove part 16B. Said tool will then also process material that is part of the first groove part 16B, as can be seen from, for example, Fig. 9, whereby whole or partially pyramidal tips are formed at the end of the second groove part 16A in the first groove part 16B. In the embodiment shown, the area of ​​the second track portion 16A is slightly larger than the area of ​​the first track portion 16B. During assembly, the grooves in the groove parts of the tool body and the tool tip must be adjusted so that the flush and chip channels are aligned with each other in the respective part.

Mounting of the tool tip 10 on the tool body 12 takes place in the following manner. The tie rod is inserted into a bore in the shaft part and through the tool body 12 until the front part of the tie rod protrudes centrally from the front surface 14. Then the spring 51 is inserted and the stop screw 52 is threaded. The steps mentioned are of a one-time nature, as the user normally only needs to change the tool tip. Next, the threaded end is inserted into the recess 25, after which the tool tip is rotated and threaded onto the tie rod. Then the support surface 22 of the tool tip is brought into contact with the front surface 14 by hand so that the grooves in the groove parts in the tool body 12 and the tool tip 10 and the flush and chip channels are aligned with each other. When the locking screw 50 is rotated, the tool tip 10 will be pulled firmly against the front surface, that is, the position according to Fig. 1 has been reached. The tool tip 10 is now properly anchored in the tool body 12. In this position, the tie rod is mainly intended to retain the tool tip when pulling the tool out of the machined hole, while the ridges and grooves take up the forces and moments that arise during cutting. However, the force from the drawbar is so great that the joint between the tool tip and the body is not allowed to slip during return feeding.

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

516 366 the tool tip 10 in a fixed position in the tool body during assembly, partly to always ensure when using the cutting tool that the tool tip 10 is kept in its fixed position.

When the tool tip 10 is to be replaced, proceed in the reverse manner as during assembly, whereby the tool tip 10 can be removed from the tool body 12 and replaced.

The invention is also useful for cutters. The tool tip is preferably coated with layers of e.g. AI₂O₃,TiN and/or TiCN. In some cases, it may be justified to solder on super-hard materials such as CBN or PCD on the cutting edges.

Likewise, it is possible to utilize other means of restraint than a central drawbar; for example, it is possible to hold the tool tip by means of a bayonet coupling as indicated in SE-A-9603325-3.

In addition, it should be pointed out that the embodiments described above relate to tools that rotate relative to their longitudinal or central axis of the workpiece and that the holding member rotates with the tool. The designs can also be used as stationary, but then in combination with a rotating workpiece.

Thus far, the present description has described prior art essentially as described in SE-A-9702500-1. A new feature of the tool and tool tip according to the present invention is to provide a stable tool preferably for drilling or milling where the radially outer parts 41-41" of the tool tip, which are exposed to relatively high cutting speed, have better wear resistance than the radially inner parts 40- 40" of the tool tip at the same time as the bottom hole 25 is arranged in a relatively tough carbide, which can withstand high tensile stresses, see Fig. 5-7. This is accomplished by filling a first mold 60 for injection molding via the inlet 62 with a first mixture under high pressure and a certain temperature, about 180 °C. The mold includes a first cylindrical or elliptical cavity or recess in case the tool tip has the appearance of Fig. 5 and Fig. 6, respectively, and a centrally located, externally threaded core 65. The method is explained in more detail with reference to Fig. 10-13 from which a further alternative embodiment of a tool tip 41", Fig. 7, according to the present invention appears. In this embodiment, the contour of the cavity has the appearance of a peanut, in bottom view according to Fig.

516 366 , to form a core 61 that encloses the flush holes 23 and the bottom hole 25. The mold 60 includes an externally threaded pin 65 to form the threaded bottom hole 25. The flush holes and the bottom hole are formed when the pin and the slightly conical core pins 66 are reflowed by the mixture during the first phase of injection molding . The mixture consists of cemented carbide powder with a relatively high cobalt content and a carrier, for example plastic, which is mixed and formed into pellets or granules. This creates a core 61 comprising flush holes 23 and an internal thread 25. The core 61 is then enclosed, after cooling, by a second mold 63 for injection molding, Figs. 13 and 14, preferably by two new jaws replacing the first jaws used in the first injection . The second mold 63 includes parts for forming chip channels and the other parts of the tool tip. The conical core pins 66 are used to fix the insert during the second injection. Thus, the core 61 is fixed centrally in the second mold after which a second mixture 67 is injected via the inlet 64 into the second mold. The second mixture 67 differs from the first mixture mainly in that the amount of cobalt is smaller in the second mixture. The difference in metallic bonding phase is in the range of 1-10 weight percent units. By "cobalt" is meant here a metallic binding phase which can alternatively be exchanged for or include other metals, for example nickel, Ni. Furthermore, existing tools can be used with the replacement of only the forming jaws at the first injection. In terms of manufacturing technology, this is a good solution because the core pins can accompany the core 61 and position it during its further processing. In the position according to Fig. 14, the threaded pin 65 is no longer needed. After the second step of the injection molding, after cooling, a blank for a tool tip has been obtained, which after sintering forms a tool tip of at least two types of carbide after the cutting edges 19 and cross cutting 24 have been ground. The core 61, after sintering, defines the inner part 40", while the second mixture 67 constitutes the outer part 41". The underside of the tool tip is machined to obtain the previously described waffle pattern 22.

With the help of this method, the geometry of the tool tip can also be chosen independently of the limitations of the conventional compression molding method. For example, chip breakers can be formed on surfaces that until now could only be ground in.

516 366

The tool tip thus contains two types of carbide, a tough, less wear-resistant type in the inner part 40-40" and a more brittle, more wear-resistant type in the outer part 41-41. The tool tip is manufactured by injection molding, whereby the two types have the same shrinkage factor, therefore problems with cracks in the outer part or porosity in the inner part, which can occur with conventional pressing, are eliminated. The tool tip has been shown in three alternative embodiments, two (Fig. 5 and 7) with an inner core, completely enclosed by the outer part except in the feed direction and the return direction, and one (Fig. 6) with a continuous elliptical center part, not completely enclosed by the outer part. Regarding the difference in cobalt content between the inner part and the outer part, this is in the range of 1-10% by weight. The inner part is made of a material with 6-20% by weight of cobalt, while the material in the outer part contains 5-15% by weight of cobalt. In two of the embodiments, the inner part 40, 40' does not reach the flushing channels 23. The center part of the tool tip is designed in a tougher carbide so that its thread 25 can withstand high tensile stresses and so that its cutting front end 21, such as the crosscut 24, can withstand low cutting speeds .

The invention is in no way limited to the embodiments described above, but can be freely varied within the scope of the subsequent patent claims. Thus, the bottom hole 25 can be replaced by a projection protruding from the support surface to attach the tool tip to the drill body.

516 366 io