Abstract:
The indexable insert of the present invention has a cutting edge at the end of a stick-shaped portion projecting from a tool base. The base is shaped to ensure effective clamping, thereby avoiding chatter and backlash. A cutting edge and a rake face are provided at the end of the stick-shaped portion, which is also provided with a side relief face so that chips cut from the workpiece are smoothly carried away. The cutting edge extends sideways beyond the side relief face so that the insert can effectively cut the walls of small and deep holes.

Description:
This application is based on an application No. 10-245675 filed in Japan, the content of which is incorporated hereinto by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to an indexable insert for cutting processing and a cutting tool having the indexable insert. More specifically, it relates to an indexable insert and a cutting tool having the indexable insert suitable for inner diameter processing of a small hole or a very small hole in a small-sized component such as a component for OA equipment, an electronic component, or a small diameter bearing. 
     2. Description of the Prior Art 
     Conventionally used as an inner diameter processing tool have been a throwaway type in which a chip  22  is fastened to a front end of a holder  21  so as to be attachable or detachable as shown in  FIG. 6 and a  brazing type in which a chip  32  is fastened by brazing to a front end of a holder  31  as shown in FIG.  7 . 
     The brazing type requires a lot of time to replace the chip  32  when the chip&#39;s edge is damaged, which is not economical. Accordingly, the throwaway type is currently used in most cases. 
     The throwaway type is generally used for processing a large-diameter hole in a large-sized component such as an automobile component, however, this type is not used for processing a very small-diameter hole in a small-sized component such as a component for OA equipment or an electronic component. A solid cutting tool as shown in  FIG. 8  is generally used for processing the very small-diameter hole. 
     Referring to  FIG. 8 , the integral cutting tool is constituted by a chip  45  and a sleeve  46  for supporting the chip  45  by fastening. The chip  45  is generally formed by cutting a cylindrical member, so that a cutting edge  44  and a holder  43  are integrally composed of the same material. 
     The chip  45  of such a solid type has a structure in which the holder  43  is inserted into the sleeve  46 , and is fixed to the sleeve  46  by tightening a set bolt (not shown) from the outside of the sleeve  46 . 
     In such a structure, a force for the sleeve  46  to clamp the indexable insert  45  is weak, so that chatter vibration is liable to be generated in the chip  45 . The repetition accuracy of the cutting edge  44  is low. Further, the diameter at a front end of the sleeve  46  is larger than that of the cutting edge  44  of the chip  45 , so that a front end surface of the sleeve  46  expands in a collar shape toward the chip  45 . Therefore, the front end surface of the sleeve  46  is positioned so as to close a hole of a work piece at the time of inner diameter cutting processing, resulting in poor cutting chip discharge properties. Further, when the sleeve  46  is used, undercut processing cannot be performed. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in order to solve the above-mentioned problems of the prior art. 
     A primary object of the present invention is to provide an indexable insert having good clamping properties. Another object of the present invention is to provide a cutting tool for reliably clamping the indexable insert not to generate chatter vibration. Still another object of the present invention is to provide a cutting tool with high index accuracy at the position of a cutting edge. A further object of the present invention is to provide a high-performance indexable insert being superior in cutting chip discharge properties and capable of performing undercut processing and an inner diameter cutting processing. 
     The above-mentioned objects of the present invention are achieved by an indexable insert as set forth in claim  1  and a cutting tool as set forth in claim  5 . 
     As described in claim  1 , an indexable insert according to the present invention has a base and a stick-shaped portion which are integrally formed. The base comprises a bottom surface placed on a seating surface of a holder and a first side surface and a second side surface. The indexable insert is attachable to the holder such that backlash is prevented by clamping the first side surface and the second side surface. 
     A cutting edge and a rake face are provided at a front end of the stick-shaped portion. Moreover, one side surface of the stick-shaped portion is a side relief face, and connects with the base with no step. Accordingly, cutting chips are satisfactorily removed. 
     The indexable insert is formed of the same material. Accordingly, it is preferable that the diameter of the stick-shaped portion and the thickness of the base are the same, as described in claim  2 . 
     As described in claim  3 , when a side curved surface and a recessed notch connecting with the side relief face are formed on the rake face, cutting chips are smoothly guided to the side relief face. 
     When the cutting edge has brought into a concavely curved shape, as described in claim  4 , cutting chips are curled, so that the cutting chips are easily removed. 
     A cutting tool according to the present invention constrains the indexable insert by a first clamp surface and a second clamp surface, as described in claim  5 . More specifically, a side surface of the base of the indexable insert is clamped at four points by a projection at a front end of the first clamp surface, two projections at a front end and a rear end of the second clamp surface, and a set bolt at a rear end of the first clamp surface. Accordingly, neither backlash nor chatter vibration is produced in the indexable insert attached to the holder during cutting. 
     The base of the indexable insert fitted in an insert pocket of the holder is not concealed as in a case where a sleeve is used but is exposed from the holder. That is, a top surface of the indexable insert fixed to the holder is exposed from the holder. Therefore, the indexable insert is easily attached to the holder. Moreover, the indexable insert can be firmly fixed to the holder using a bolt, a clamp, or the like. Accordingly, it is possible to prevent chatter vibration from being generated in the indexable insert. 
     The side relief face of the indexable insert connects with one side surface of the holder so as to be flush therewith, so that the holder does not prevent the cutting chips from being removed. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a top plan view of an indexable insert according to one embodiment of the present invention.  FIG. 1B  is a perspective view taken along a line X shown in  FIG. 1A , and  FIG. 1C  is a perspective view taken along a line Y shown in  FIG. 1B ; 
         FIG. 2A  is a top plan view of a cutting tool according to one embodiment of the present invention in which the indexable insert of  FIG. 1A  is mounted on a holder, and  FIG. 2B  is a perspective view taken along a line Z shown in  FIG. 2A ; 
         FIG. 3A  is a top plan view of a cutting tool according to another embodiment of the present invention in which an indexable insert is fixed by a clamp, and  FIG. 3B  is a front view thereof; 
         FIG. 4  is an illustration showing how cutting processing is performed using a cutting tool according to one embodiment of the present invention; 
         FIG. 5  is an illustration showing how cutting processing is performed using a cutting tool according to another embodiment of the present invention; and 
         FIGS. 6 ,  7  and  8  are respectively schematic views showing a conventional cutting tool. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1A  is a top plan view of an indexable insert  1  according to one embodiment of the present invention,  FIG. 1B  is a perspective view taken along a line X shown in  FIG. 1A  (a front view of the indexable insert  1 ), and  FIG. 1C  is a perspective view taken along a line Y shown in  FIG. 1B  (a left side view of the indexable insert  1 ). 
     Referring to  FIGS. 1A  to  1 C, the indexable insert  1  has a flat plate-shaped base  3  at its rear (on the right side of FIGS.  1 A and  1 B). The base  3  comprises a bottom surface  3 a which is abutted, when it is attached to a holder, described later, against the holder, and a first side surface  3 b and a second side surface  3 c. The first side surface  3 b and the second side surface  3 c extend so as to cross each other in an acute-angled manner at the rear. Near the center of the base  3 , a bolt hole  4  through which a bolt is to be passed is formed along the thickness of the base  3 . 
     A stick-shaped portion  7  extends toward a front end of the indexable insert  1  (on the left side of  FIGS. 1A and 1B ) from the base  3 . The stick-shaped portion  7  extends in a direction parallel to the first side surface  3 b, and its rear end crosses the second side surface  3 c. A front cutting edge  5  is formed at a front edge of the stick-shaped portion  7 , and a rake face  6  is formed so as to connect with the front cutting edge  5 . The front cutting edge  5  has its part projecting sideward so as to form a side relief face  7 a along the length of the stick-shaped portion  7 . 
     The rake face  6  has a chip breaker projected surface  6 a at its rear, and has a side curved surface  6 c at its front. An edge of the side curved surface  6 c connecting with the side relief face  7 a has a recessed notch  6 b. 
     In such construction, cutting chips cut by the front cutting edge  5  pass through the side curved surface  6 c of the rake face  6 , and are guided from the recessed notch  6 b to the side relief face  7 a. 
     As shown in  FIG. 1C , the front cutting edge  5  is concavely curved downward, so that the cutting chips are easily curled in a spiral shape, and the curled cutting chips are easily discharged to the side relief face  7 a from the side curved surface  6 c through the recessed notch  6 b. 
       FIG. 2A  is a top plan view of a cutting tool  8  according to one embodiment of the present invention in which the indexable insert  1  is mounted on a holder  9 .  FIG. 2B  is a perspective view taken along a line Z shown in  FIG. 2A  (a front view of the cutting tool  8 ). For convenience, the root of the holder  9  is omitted, and a fixing bolt is also omitted in  FIGS. 2A and 2B . 
     Referring to  FIGS. 2A and 2B , the holder  9  is a prism-shaped longitudinal member having a root extending rightward (not shown), and the root is fixed to a machine. An insert pocket  11  in which the base  3  of the indexable insert  1  is to be fitted is formed on a top surface  10  at a front end of the holder  9 . The insert pocket  11  comprises a seating surface  12  parallel to the top surface  10 , a first clamp side surface  11 a cut from a front end surface of the holder  9 , and a second clamp side surface  11 b cut from a side surface  9 b of the holder  9 . 
     The bottom surface  3 a of the base  3  of the indexable insert  1  is placed on the seating surface  12  of the insert pocket  11 . A fixing bolt (not shown) is inserted through the bolt hole  4  from above the base  3 . A tapped hole  13  is formed in a position communicating with the bolt hole  4  of the base  3 . Accordingly, a front end of the fixing bolt which is inserted through the bolt hole  4  is screwed into the tapped hole  13 . The indexable insert is thus fixed to the holder  9 . 
     The top surface of the indexable insert  1  fixed to the holder  9  is exposed from the holder  9 . Therefore, the indexable insert  1  is easily attached to the holder  9 . Moreover, the indexable insert  1  can be firmly fixed to the holder  9  using a bolt, a clamp, or the like, as described above. Accordingly, it is possible to prevent chatter vibration from being generated. 
     When the indexable insert  1  is fixed to the holder  9 , the stick-shaped portion  7  of the indexable insert  1  is brought into a state where it projects from the front end of the holder  9 . By inserting the stick-shaped portion  7  into a small hole of a work piece, therefore, the small hole can be processed as if an ear were picked by an ear pick. 
     Although the indexable insert  1  is firmly fixed to the holder  9 , the following constraining structure is also employed such that no backlash is produced in the indexable insert  1  in the present embodiment. 
     As shown in  FIG. 2A , when the indexable insert  1  is fitted in the insert pocket  11 , the first side surface  3 b of the base  3  is opposite to the first clamp side surface  11 a of the insert pocket  11 , and the second side surface  3 c of the base  3  is opposite to the second clamp side surface  11 b of the insert pocket  11 . A slightly expanding projection  11 c is formed at a front end of the first clamp side surface  11 a. Projections  11 c are respectively formed at both a front end and a rear end of the second clamp side surface  11 B. Further, a through tapped hole  9 a is formed at a rear end of the first clamp surface  11 a on one side surface of the holder  9  (the upper surface in FIG.  2 A). A set bolt B is fitted in the through tapped hole  9 a. After the indexable insert  1  is fitted in the insert pocket  11  and is fixed thereto by the fixing bolt, therefore, the set bolt B is tightened. Accordingly, a side surface of the base  3  is locked at four points by the three projections  11 c and the set bolt B in the insert pocket  11 . Even when there is a slight difference between an inner shape of the insert pocket  11  and an outer shape of the base  3  of the indexable insert  1 , therefore, the indexable insert  1  can be reliably fixed to the holder  9 . As a result, neither backlash nor chatter vibration is produced in the indexable insert  1  during processing. 
     The side relief face  7 a of the indexable insert  1  fixed to the holder  9  is flush with the one side surface  9 b of the holder  9 . Therefore, the front end of the holder  9  does not prevent cutting chips from being discharged, as described later. 
       FIGS. 3A and 3B  are respectively a top plan view and a front view of a cutting tool  8  according to another embodiment of the present invention in which the fixing bolt is replaced with a clamp for fixing an indexable insert to a holder. 
     A clamp  21  is provided so as to be rotatable along an upper surface  10  of a holder  9 . Although a rotary supporting shaft  22  of the clamp  21  vertically penetrates the holder  9  in the present embodiment, it may not penetrate the holder  9 . 
     An indexable insert  1  is fitted in an insert pocket  11 , and the clamp  21  is rotated so that its front end presses the indexable insert  1 . A screw  23  at the top of the rotary supporting shaft  22  is tightened. Consequently, the indexable insert  1  is fixed by the clamp  21 . 
     When the indexable insert  1  is fixed by the clamp  21 , a bolt hole  4  may not be provided in a base  3  of the indexable insert  1 . 
     In  FIGS. 3A and 3B , the same reference numerals are assigned to the same portions as those shown in  FIGS. 2A and 2B . 
       FIG. 4  is an illustration showing how cutting processing is performed using the cutting tool  8  according to one embodiment of the present invention. The stick-shaped portion  7  of the indexable insert  1  is inserted into a hole  50  of a work piece W, to perform boring, for example. By using the cutting tool  8 , the side relief face  7 a formed in the stick-shaped portion  7  is flush with the one side surface  9 b of the holder  9 . Accordingly, the front end surface of the holder  9  does not project toward the side relief face  7 a with a step, so that the cutting chips are smoothly discharged. Specifically, a discharge path of the cutting chips is not blocked up in the vicinity of an outlet of the hole  50  of the work piece W. Accordingly, the cutting chips can be smoothly discharged. Particularly in the present embodiment, the rake face  6  of the indexable insert  1  is provided with the side curved surface  6 c, and the side curved surface  6 c connects with the side relief face  7 a by the recessed notch  6 b. Accordingly, the cutting chips are guided to the outlet of the hole  50  of the work piece W from the recessed notch  6 b through the side relief face  7 a, resulting in very good cutting chip discharge properties. 
       FIG. 5  illustrates another embodiment of the present invention. As shown in  FIG. 5 , an indexable insert  1  may be attached to a holder  9  such that the axial direction of the holder  9  and the axial direction of a stick-shaped portion  7  of the indexable insert  1  are not parallel to each other, and an angle is provided therebetween. In such an attaching structure, undercut processing is possible in a hole  50  of a work piece W. 
     The indexable insert  1  of this invention may be made of cermet material or hard metal material. The holder  9  may be made of an alloy steel such as Cr—Mo alloy steel, Ni—Cr alloy steel or Ni—Cr—Mo alloy steel, or an alloy steel which elements such as Cr, W, Mn, Mo and V are added to an Carbide alloy steel including five elements of C, Si, Mn, P and S. 
     An illustrative manufacturing method of the indexable insert  1  will be explained as follows: 
     Grains of starting materials such as TiC, WC, Co, TiC, TaC are crushed and mixed to form mixed powder. The obtained mixed powder is filled up in a forming die which has a similar figure to the indexable insert  1  and pressed to form a press molded body. Then the press molded body is sintered. After sintering of the obtained body of the indexable insert  1 , the two side faces of the above stick-shaped portion  7 , namely the side relief face  7 a and the side face opposite to the said side relief face  7 a, and the rake face  6  are subjected to the polishing process to form a finished product of the indexable insert  1 . According to this method, the manufacturing cost is much lowered because amount of the polishing process is minimized. 
     On the other hand, the holder  9  can be obtained by subjecting a blank bar of the above alloy steel to cutting processing with cutting tools such as end-mill tools. 
     While the embodiment of the present invention has thus been described in detail, it should be understood that the embodiment is merely illustrative of the technical principles of the present invention but not limitative of the same. The spirit and scope of the present invention are to be limited only by the appended claims.