Throw-away cutting tool

Abstract: A throw-away cutting tool is disclosed. The tool body (11) of the cutting tool consists of a rod-like shank (12) and a bit mounting component (13) arranged at the front end of the shank (12). The shank (12) is made of cemented carbide, and is formed with a mounting wall extending toward the front end of the tool body (11). The bit mounting component (13) is made of steel or sintered metal, and is formed with a bit mounting seat (14) defined by a bottom wall (14A) and side walls (14B; 14C). In the above cutting tool, high resistance against the cutting force produced by cutting operation can be obtained and separation of the shank (12) and the bit mounting component (13) can be prevented. Additionally, high rigidity of the tool body (11) is ensured, the damping capacity of the tool body (11) is increased, and therefore vibration and chatter of the cutting tool can be effectively prevented.

Description: Background of the invention The present invention relates to a throw-away cutting tool such as a tool, a boring bar, or a milling cutter having an indexable cutter insert (hereinafter referred to simply as "bit") mounted to a bit mounting seat formed at the front portion of a tool body, and in particular, relates to a cutting tool having a shank made of cemented carbide and the bit mounting seat made of steel or sintered metal capable of machining. A cutting tool such as a tool, a boring bar, or a milling cutter having a shank made of cemented carbide in order to increase the damping capacity and to restrain chatter of the tool body is known. However, in a throw-away cutting tool mounted with a bit employed as a cutting edge, a bit mounting seat cannot be easily formed when the tool body is made of cemented carbide. For this reason, in a prior art cutting tool, the tool body is constructed with a front end portion made of steel or sintered metal and a rear portion made of cemented carbide; the front end portion is formed with a bit mounting seat; the front portion is fixed to the rear portion. Figures 1 and 2 illustrate an example of such a cutting tool. In the figures, a tool body 1 consists of a cylinder-shaped shank 2 made of cemented carbide and a bit mounting component 3 made of steel or sintered metal. The bit mounting component 3 is formed with a bit mounting seat 4 at the front portion thereof. A bit 5 is secured to the bit mounting seat 4 by a clamping mechanism 6. The rear end 3A of the shank 2 is formed into a cylinder shape having the same diameter as the shank 2. The front end 3B of the bit mounting component 3 is formed into a semicircular cross section by removing the upper half portion of the front end 3B from a plane including an axis O of the cylinder. The rear end face of the bit mounting component 3 is soldered to the front end face of the shank 2 so that the bit mounting component 3 is fixed to the shank. The upper plane face 3C of the bit mounting component 3 is provided with a bit mounting seat 4 and a clamping mechanism 6. The bit is formed as a positive type bit having an upper face 3C used for a cutting face 3C in the shape of an equilateral triangle. A plurality of cutting edges 5C are formed at the intersections between the upper face 3C and three side faces 5B used for flank faces. The bit mounting seat 4 for mounting the bit 5 is defined by a bottom wall 4A recessed from the upper plane face and side walls 4B and 4C rising up from the bottom wall 4A. The angle between the side walls 4B and 4C is set at 60°. The bit mounting seat 4 is arranged such that the cutting edge 5C of the bit 5 is perpendicular to the axis O of the circular cylinder and slightly projects from the bit mounting component 3 in the direction of the axis O. The clamping mechanism 6 consists of a clamping bolt 6A secured to the bit mounting component 3 and a clamping piece 6B having a clamping claw 6C at the front end thereof, so that the upper face 5A is pressed by the claw 6C, and lower face 5D opposite to the upper face 5A is adhered to the bottom wall 4A so as to secure the bit 5 to the bit mounting seat 4. The position of the bit 5 is fixed by contacting two of three side faces 5B with the side walls 4B and 4C and by securing the bit 5 with the clamping mechanism 6. A relief 4D is formed at the intersection of the side walls 4B and 4C. In the above constructed throw-away cutting tool, the tool body 1 is constructed by means of soldering the front face of the cylinder shaped shank 2 to the rear end face, which has the same diameter as the shank 2 of the bit mounting component 3. Therefore, the soldered layer between the front end face of the shank 2 and the rear end face of the bit mounting component 3 exists along the direction perpendicular to the axis O of the tool body 1. US-A-38 85 282 discloses a machining tool comprising a holder and an insert for carrying a cutting tool or bit, the bit being attachable to the holder by means of a conical recess in the insert, a clamping member which fits into the recess and a screw with opposite handed threads which screws into bores in the clamping member and the holder, respectively. The bit is supported on its lower side by the upper side of the holder. It is an object of the present invention to provide a throw-away cutting tool which can solve the above problems in the prior art cutting tools. According to the invention, there is provided a throw-away cutting tool comprising a tool body consisting of a rod-like shank made of cemented carbide and a bit mounting component made of steel or sintered metal arranged at the front end of the tool bode. The shank is formed with a mounting wall extending toward the front end of the tool body. The bit mounting component is in the shape of a plate. A bit mounting seat is formed at the front end of the bit mounting component. A bit is mounted to the bit mounting seat. The bit mounting component is fixed to the shank adhering the lower face of the bit mounting component to the mounting wall so as to bear cutting force exerted on the bit by the mounting wall. The bit mounting component is formed with side walls for supporting the side faces of the bit. The side walls rise from the mounting wall of the shank in the direction of the thickness of the bit mounting component. A portion of the mounting wall connected to the side wall is employed as a mounting wall contacting the lower face of the bit. In the cutting tool having the above construction, since the mounting wall extends along the lengthwise direction of the tool body, the cutting force directed toward the perpendicular direction of the axis of the tool body is received by the mounting wall perpendicular to the cutting force. Therefore, in the cutting tool, the cutting force does not act to separate the shank and the bit mounting component. Furthermore, in the cutting tool, since the shank made of cemented carbide extends as far as the vicinity of the cutting edge, high rigidity of the tool body is ensured, and the damping capacity of the tool body is increased, so that vibration and chatter of the cutting tool can be effectively prevented. The present invention is described in more detail in the following by way of example with reference to the enclosed drawings, in which: Figure 1 is plan view of the front end of a conventional cutting tool; Figure 2 is a side view of the cutting tool in Figure 1; Figure 3 is a plane view of the front end of a cutting tool according to the first embodiment of the invention; Figure 4 is a side view of the front end of the cutting tool in Figure 3; Figure 5 is an end view of the front end of the cutting tool in Figure 3 along the direction of the axis O; Figure 6 illustrates a bit mounting component 13 according to the first embodiment, wherein (A) is a side view, and (B) is a plan view; Figure 7 is a plan view of the front end of a variation of a cutting tool of the first embodiment; Figure 8 is a side view of the front end of the cutting tool in Figure 8; and Figure 9 is an end view of the front end of the cutting tool in Figure 8 along the direction of the axis O. Figures 3 through 5 illustrate a throw-away cutting tool in accordance with the first embodiment of the present invention. As shown in the figures, in the embodiment as in the above prior art cutting tool, a tool body 11 consists of a shank 12 and a bit mounting component 13; the bit mounting component 13 is formed with a bit mounting seat 14 to which a bit 15 is secured by a clamping mechanism 16. The shank 12 is made of cemented carbide and is formed substantially in the shape of a cylinder. The front end of the shank 12 is formed with a square-shaped mounting wall 12A by removing the upper portion of the front end thereof from a plane face under and parallel with respect to the axis O of the tool body 11. The shank 12 is formed with a vertical wall rising from the mounting wall 12A and an inclined wall downslope toward the front end of the shank 12 and connected to the radially outer face of the shank 12 (see Figure 4). Figure 6 shows a bit mounting component 13 which is secured to the mounting face 12A. As shown in Figure 6, the bit mounting component 13 is in the form of a plate-like square configuration corresponding to the mounting wall 12A and is made of tougher material than cemented carbide constructing the shank 12, such as steel or sintered metal, capable of machining. The bit mounting component 13 is formed with a portion of a bit mounting seat 14 according to the configuration of a bit 15 mounted thereto by removing a wall portion including a corner toward the thickness of the bit mounting component 13 so as to form an opening 13A. As in the prior art cutting tool, the bit 15 is formed in a plate-like positive type bit having substantially an equilateral triangle shape in plane viewed. A plurality of cutting edges 15C are formed at the intersections between the upper face 15A used for a cutting face and side faces 15B used for flank faces. The opening 13A is in the shape of an equilateral triangle in plane view according to the configuration of the bit 15. The opening 13A is defined by two faces 13A and 13B having an angle set at 60° therebetween. The bit mounting component 13 is soldered to the front end of the shank 12 such that the lower face 13D is adhered to the mounting wall 12A and the opening 13A is directed toward the front end of the tool body 11. The thickness of the bit mounting component 13 is set in the range such that the upper face 13E includes the axis O of the tool body 11 when the bit mounting component 13 is fixed to the mounting wall 12A. The side faces 13B and 13C are employed as mounting walls of the bit mounting seat 14 and are formed in inclined faces downslope toward the center of the opening 13A according to the clearance angle of the side faces 15B of the bit 15. The bit mounting seat 14 is defined by the side faces 13B and 13C extending along the thickness of the bit mounting component 13 and a portion of the mounting wall 12A surrounded by the side faces 13B and 13C. That is, the portion of the mounting wall 12A surrounded by the side faces 13B and 13C is employed as a bottom wall 14A of the bit mounting seat 14 and is recessed from the upper face 13E of the bit mounting component 13; and the side faces 13B and 13C are employed as side walls 14B and 14C and rise from the bottom wall 14A and connected to the upper face 13E of the bit mounting component 13. The bit 15 is located on the bit mounting seat 14 such that the lower face 15D thereof contacts the bottom wall 14A, and two of the side faces 15B contact the side walls 14B and 14C, and are secured to the bit mounting seat 14 by the clamping mechanism 16. The bit 15 is positioned on the bit mounting seat 14 such that the cutting edge 15C is perpendicular to the axis O and projects slightly toward the front from the front end face of the shank 12 and the bit mounting component 13. The clamping mechanism 16 consists of a clamping bolt 16A secured to the bit mounting component 13 and a clamping piece 16B having a clamping claw 16C at the front end thereof, so that the upper face 15A is pressed by the clamping claw 16C and the lower face 15D opposite to the upper face 5A is adhered to the bottom wall 14A so as to secure the bit 15 to the bit mounting seat 14. In the cutting tool constructed as above, the cutting force exerted on the bit 15 is received by the bottom wall 14A, i.e., the mounting wall 12A formed along the lengthwise direction of the shank 12 made of cemented carbide. Therefore, in the above cutting tool, the cutting force does not act to shear the soldered layer between the shank 12 and the bit mounting component 13, so that high resistance against the cutting force can be obtained and separation of the bit mounting component 13 and the shank 12 can be prevented. Furthermore, in the cutting tool, since the shank 12 made of cemented carbide extends as the bottom wall 12A as far as vicinity of the cutting edge 15C and supports the bit 15, high rigidity of the tool body 12 is ensured, and the damping capacity of the tool body 11 is increased; therefore vibration and chatter of the cutting tool can be effectively prevented. Moreover, in the cutting tool of the above embodiment, since the bit mounting seat 14 is constructed with a plane face of the bottom wall 14A of the shank 12 and side walls 14B and 14C which are formed by hollowing out a portion of the bit mounting component 13 toward the direction of the thickness thereof, the bit mounting seat 14 can be easily formed. That is, since the bit mounting seat 14 can be formed by simple machining, and the depth of the bit mounting seat 14 can be easily chosen by the choosing of the thickness of the bit mounting component 13, and the machining procession can be simplified. In the description of the first embodiment, although the bit mounting component 13 or 17 is soldered to the shank 12, the present invention is not so limited. That is, as shown in Figs 7 to 9, the bit mounting component 13 can be secured to the shank 12 by means of a screw hole 18 formed in the bit mounting component 13, a through hole 19, a spot facing 20 formed in the shank 12, and a screw 21 secured in the tapped hole 18 for pulling the bit mounting component 13 toward the mounting wall 12A. In this construction, since the soldering layer does not exist, precise positioning of the bit mounting seat 14 can be carried out. As mentioned above, in the cutting tool having the above structure, since the mounting wall secures the bit mounting component along the direction perpendicular to the direction of the cutting force, the cutting force does not act acts to shear the soldered layer between the shank and the bit mounting component, so that high resistance against the cutting force can be obtained and separation of the shank and the bit mounting component can be prevented. Furthermore, in the cutting tool, since the shank made of cemented carbide extends as far as thee vicinity of the cutting edge, high rigidity of the tool body is ensured, and the damping capacity of the tool body is increased, so that vibration and chatter of the cutting tool can be effectively prevented.

Claims: A throw-away cutting tool comprising: a tool body (11) having a front end and a rear end, said tool body having a rod-like shank (12) made of cemented carbide and a bit mounting component (13) made of at least one of steel and sintered metal arranged at the front end of the tool body (11), said bit mounting component (13) being in the shape of a plate having an upper face (13E) and a lower face (13D), a bit mounting seat (14) formed at the front end of the bit mounting component (13), and an indexable cutter insert (15) being mounted to the bit mounting seat (14) and having an upper face (15A), a lower face (15D) and side faces (15B) peripherally lying between the upper face (15A) and the lower face (15D); wherein said shank (12) has a mounting wall (12A) extending toward the front end of the tool body (11) and said bit mounting component (13) is fixed to the shank (12), adhering the lower face (13D) of the bit mounting component (13) to the mounting wall (12A) so as to bear cutting force exerted on the indexable cutter insert by the mounting wall (12A), and wherein said bit mounting component (13) comprises at least one side wall (13B; 13C) for supporting the side faces (15B) of the indexable cutter insert (15), said wall (13B; 13C) rising from the mounting wall (12A) of the shank (12) in the direction of the thickness of the bit mounting component (13), and a portion of the mounting wall (12A) connected to the side wall (13B; 13C) is employed as a mounting wall contacting the lower face (15D) of the indexable cutter insert (15).

Inventors: ARAI TATSUO, NAKAYAMA MASAAKI, OKAWA MASAYUKI, SAITO JUNICHI, ARAI, TATSUO, NAKAYAMA, MASAAKI, OKAWA, MASAYUKI, SAITO, JUNICHI, ARAI, TATSUO, C/O TSUKUBA-SEISAKUSHO, NAKAYAMA, MASAAKI, C/O TSUKUBA-SEISAKUSHO, OKAWA, MASAYUKI, C/O TSUKUBA-SEISAKUSHO, SAITO, JUNICHI, C/O TSUKUBA-SEISAKUSHO
Applicants: MITSUBISHI MATERIALS CORP, MITSUBISHI MATERIALS CORPORATION
Application year: 1992
Main classification: B23B27
IPC codes: B23B27