Patent Publication Number: US-2023147380-A1

Title: Rotary cutting tool

Description:
TECHNICAL FIELD 
     The present invention relates to a rotary cutting tool. The present application claims a priority based on Japanese Patent Application No. 2020-050718 filed on Mar. 23, 2020, the entire content of which is incorporated herein by reference. 
     BACKGROUND ART 
     Conventionally, rotary cutting tools are disclosed, for example, in Japanese Patent Laying-Open No. 2012-106334 (PTL 1), Japanese Utility Model Laying-Open No. 58-44135 (PTL 2) and Japanese Utility Model Laying-Open No. 60-165108 (PTL 3). 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Patent Laying-Open No. 2012-106334 
     PTL 2: Japanese Utility Model Laying-Open No. 58-44135 
     PTL 3: Japanese Utility Model Laying-Open No. 60-165108 
     SUMMARY OF INVENTION 
     In a rotary cutting tool including a tool body and a cutting edge tip provided at the tool body, at least one first groove is provided in a rake face of the cutting edge tip, the first groove has a portion inclined with respect to a rotation axis, a front end of the first groove is provided at a front cutting edge or a corner chamfering cutting edge, a rear end of the first groove is provided on an inner side with respect to an outer peripheral cutting edge, and an irregularity of the outer peripheral cutting edge is 30 μm or less. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a front view of a rotary cutting tool according to a first embodiment. 
         FIG.  2    is a rear view of the rotary cutting tool according to the first embodiment. 
         FIG.  3    is a right side view of the rotary cutting tool according to the first embodiment. 
         FIG.  4    is a left side view of the rotary cutting tool according to the first embodiment. 
         FIG.  5    is a plan view of the rotary cutting tool according to the first embodiment. 
         FIG.  6    is a bottom view of the rotary cutting tool according to the first embodiment. 
         FIG.  7    is a perspective view of the rotary cutting tool according to the first embodiment. 
         FIG.  8    is an enlarged view showing a portion surrounded by VIII in  FIG.  5   . 
         FIG.  9    is an enlarged view showing a portion surrounded by IX in  FIG.  7   . 
         FIG.  10    is a cross sectional view taken along a line X-X in  FIG.  5   . 
         FIG.  11    is an enlarged cross sectional view showing a portion surrounded by XI in  FIG.  10   . 
         FIG.  12    is a front view of a rotary cutting tool according to a second embodiment. 
         FIG.  13    is a front view of a rotary cutting tool according to a third embodiment. 
         FIG.  14    is a front view of a rotary cutting tool according to a fourth embodiment. 
         FIG.  15    is a front view of a rotary cutting tool according to a fifth embodiment. 
         FIG.  16    is a diagram showing an exemplary cross sectional shape of a groove. 
         FIG.  17    is a diagram showing an exemplary cross sectional shape of the groove. 
         FIG.  18    is a diagram showing an exemplary cross sectional shape of the groove. 
         FIG.  19    is a diagram showing an exemplary cross sectional shape of the groove. 
         FIG.  20    is a front view of a rotary cutting tool according to a sixth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Problem to be Solved by the Present Disclosure 
     With the conventional rotary cutting tools, it is difficult to cut off chip, disadvantageously. 
     Advantageous Effect of the Present Disclosure 
     A rotary cutting tool capable of cutting off chip can be provided. 
     DESCRIPTION OF EMBODIMENTS 
     First, embodiments of the present disclosure are listed and described. 
     First Embodiment 
       FIG.  1    is a front view of a rotary cutting tool according to a first embodiment.  FIG.  2    is a rear view of the rotary cutting tool according to the first embodiment.  FIG.  3    is a right side view of the rotary cutting tool according to the first embodiment.  FIG.  4    is a left side view of the rotary cutting tool according to the first embodiment.  FIG.  5    is a plan view of the rotary cutting tool according to the first embodiment.  FIG.  6    is a bottom view of the rotary cutting tool according to the first embodiment.  FIG.  7    is a perspective view of the rotary cutting tool according to the first embodiment.  FIG.  8    is an enlarged view showing a portion surrounded by VIII in  FIG.  5   . 
     As shown in  FIGS.  1  to  8   , a rotary cutting tool  1  according to the first embodiment includes a tool body  2  and a cutting edge tip  10  provided at tool body  2 . At least one first groove  11 ,  12 ,  13 ,  14  is provided in a rake face  100  of cutting edge tip  10 , first groove  11 ,  12 ,  13 ,  14  has a portion inclined with respect to a rotation axis  9 , and a front end  11   a ,  12   a ,  13   a ,  14   a  of first groove  11 ,  12 ,  13 ,  14  is provided at a front cutting edge  110 . A rear end  11   b ,  12   b ,  13   b ,  14   b  of first groove  11 ,  12 ,  13 ,  14  is provided on an inner side with respect to an outer peripheral cutting edge  120 , and an irregularity of outer peripheral cutting edge  120  is 30 μm or less. 
     The irregularity is measured as follows. 
     (1) The tool is set on a stage such that a portion of outer peripheral cutting edge  120  can be seen in a direction perpendicular to rake face  100  with the use of a tool microscope at a magnification of 30×. The stage is rotated while maintaining a state in which the optical axis of the tool microscope is perpendicular to rake face  100 , and a cutting edge ridgeline is aligned with a reference line of a calibration marking provided on the lens of the tool microscope so as to fix the rotation axis of the stage. 
     (2) The stage is moved to a position at which the reference line of the calibration marking is tangential to a portion of the irregularity on the innermost peripheral side. 
     (3) A distance in which the stage has been moved in (2) is read by a digital measuring device, and this distance is defined as the magnitude of the irregularity. It should be noted that the irregularity herein refers to, for example, an irregularity resulting from chipping (breakage at the ridgeline) caused at a ridgeline portion of the outer peripheral cutting edge, an irregularity resulting from detachment in the vicinity of the ridgeline on the rake face side, an irregularity resulting from a groove being formed to extend to the outer peripheral cutting edge portion, or the like. 
     By providing front ends  11   a ,  12   a ,  13   a ,  14   a  of grooves  11 ,  12 ,  13 ,  14  at a working portion of front cutting edge  110 , chip can be cut off in the width direction, thereby attaining a small chip width. 
     Even when chip caused by front cutting edge  110  is elongated rearward, the chip is cut off in the length direction at portions at which first grooves  11 ,  12 ,  13 ,  14  obliquely extending rearward with respect to front cutting edge  110  are present. With such a function of cutting off, the chip can be short. When a distance from front cutting edge  110  to each of first grooves  11 ,  12 ,  13 ,  14  becomes long, this function is less likely to be exhibited. 
     In the configuration in which first grooves  11 ,  12 ,  13 ,  14  are oriented outward as shown in  FIG.  8   , front ends  11   a ,  12   a ,  13   a ,  14   a  of first grooves  11 ,  12 ,  13 ,  14  should be provided at the working portion of front cutting edge  110  on the inner peripheral side (the side close to rotation axis  9 ) as much as possible. It should be noted that preferable positions of front ends  11   a ,  12   a ,  13   a ,  14   a  of first grooves  11 ,  12 ,  13 ,  14  are changed depending on a processing condition or a type of workpiece. Thus, the chip caused on the inner peripheral side with respect to front ends  11   a ,  12   a ,  13   a ,  14   a  of first grooves  11 ,  12 ,  13 ,  14  becomes small in width, and even when there is no oblique groove at the rear of front cutting edge  110 , the chip small in width is likely to be curled and fractured, with the result that the chip is also likely to be small in the length direction. Further, since the tool according to the present disclosure is a rotary cutting tool, the chip length on the side close to the outer periphery of front cutting edge  110  is longer than the chip length on the side close to the inner periphery of front cutting edge  110 , with the result that the resulting chip has a shape of fan. Further, the shape of fan of the chip has a small radius, so that the chip is likely to be curled and fractured. On the other hand, chip caused on the outer peripheral side with respect to front ends  11   a ,  12   a ,  13   a ,  14   a  is finely cut off by the function of cutting off by first grooves  11 ,  12 ,  13 ,  14 . 
       FIG.  9    is an enlarged view showing a portion surrounded by IX in  FIG.  7   . As shown in  FIGS.  8  and  9   , rear ends  11   b ,  12   b ,  13   b ,  14   b  of first grooves  11 ,  12 ,  13 ,  14  do not reach outer peripheral cutting edge  120 . Further, rear ends  15   b ,  16   b  of other grooves  15 ,  16  do not reach outer peripheral cutting edge  120 . Therefore, the irregularity of outer peripheral cutting edge  120  can be 30 μm or less. When the irregularity of outer peripheral cutting edge  120  is large, the shape of the irregularity is transferred to the inner surface of the hole of the workpiece, thus resulting in decreased processing precision. Front ends  15   a ,  16   a  of grooves  15 ,  16  do not reach front cutting edge  110 . Each of the shapes of end surfaces of rear ends  11   b ,  12   b ,  13   b ,  14   b  of first grooves  11 ,  12 ,  13 ,  14  is a quadrangular shape, and a direction of the end surface (direction orthogonal to the normal line of the end surface) may be parallel to front cutting edge  110 . 
     Tool body  2  and cutting edge tip  10  constitute rake face  100 . A flute  3  is provided in tool body  2 . Flute  3  is defined by wall surfaces  301 ,  302 . Each of wall surfaces  301 ,  302  is configured to extend along the length direction of tool body  2 . 
       FIG.  10    is a cross sectional view taken along a line X-X in  FIG.  5   .  FIG.  11    is an enlarged cross sectional view showing a portion surrounded by XI in  FIG.  10   . As shown in  FIGS.  10  and  11   , cutting edge tip  10  is embedded in tool body  2 . First grooves  13 ,  14  and grooves  15 ,  16  are formed in rake face  100 , which is a surface of cutting edge tip  10 . Each of first grooves  13 ,  14  and grooves  15 ,  16  has a quadrangular shape. 
     In rotary cutting tool  1  configured as described above, each of first grooves  11 ,  12 ,  13 ,  14  has a portion inclined with respect to rotation axis  9 , and each of front ends  11   a ,  12   a ,  13   a ,  14   a  of first grooves  11 ,  12 ,  13 ,  14  is provided at front cutting edge  110 , with the result that chip is likely to be cut off. Further, since each of rear ends  11   b ,  12   b ,  13   b ,  14   b  of first grooves  11 ,  12 ,  13 ,  14  is provided on the inner side with respect to outer peripheral cutting edge  120  and the irregularity of outer peripheral cutting edge  120  is 30 μm or less, a hole of the workpiece can be made smooth. 
     Second Embodiment 
       FIG.  12    is a front view of a rotary cutting tool according to a second embodiment. As shown in  FIG.  12   , in a rotary cutting tool  1  according to the second embodiment, a first groove  11  is provided to be oriented inward. The expression “oriented inward” means that first groove  11  is inclined to be closer to rotation axis  9  in a direction away from front cutting edge  110 . On the contrary, the expression “oriented outward” means that first groove  11  is inclined to be further away from rotation axis  9  in the direction away from front cutting edge  110 . 
     Front end  11   a  of first groove  11  is provided at front cutting edge  110 . Rear end  11   b  of first groove  11  does not reach outer peripheral cutting edge  120 . The irregularity of outer peripheral cutting edge  120  is 30 μm or less. 
     Thus, in the configuration in which first groove  11  extends inward, front end  11   a  of first groove  11  is preferably provided at front cutting edge  110  on the outer peripheral side as much as possible. Accordingly, chip caused on the outer peripheral side with respect to front end  11   a  of first groove  11  becomes small in width. Even when there is no oblique groove at the rear of front cutting edge  110 , the chip small in width is likely to be curled and fractured, with the result that the chip is also likely to be small in the length direction. Further, this chip may be curled to the inner peripheral side, may be tangled with chip caused on the inner peripheral side with respect to front end  11   a , and may be accordingly cut off, with the result that the chip is likely to be small in the length direction. In the case where the chip is curled to the outer peripheral side, the length of the chip is likely to become short due to contact with the processing surface; however, since the chip is small in width, contact force to the processing surface is small and the processing surface is not damaged. On the other hand, the chip caused on the inner peripheral side with respect to front end  11   a  is finely cut off based on the reason described in the first embodiment why the width of the chip caused on the inner peripheral side becomes small. 
     Further, the chip caused at a portion of front cutting edge  110  on the inner peripheral side with respect to front end  11   a  of first groove  11  is gradually curled and flow on rake face  100 , and are cut off when the chip comes into contact with groove  11 . Otherwise, chip that is insufficiently curled and that is not cut off flows along groove  11  when the chip comes into contact with groove  11 , and heads toward rear end  11   b  of grooves  11 . On this occasion, when rake face  100  and wall surface  301  intersecting with the extending direction of groove  11  indicated by a line  311  are provided in the vicinity of rear end  11   b  of groove  11 , the chip comes into contact with wall surface  301  to attain a small radius of curling, thereby obtaining such an effect that the chip is likely to be cut off. 
     It should be noted that since the radius of curling is normally at least about 5 mm, and often about 10 mm or 20 mm, the above effect can be sufficiently obtained when a space between rear end  11   b  of groove  11  and wall surface  301  is 5 mm or less. 
     Third Embodiment 
       FIG.  13    is a front view of a rotary cutting tool according to a third embodiment. A rotary cutting tool  1  according to the first embodiment is different from rotary cutting tool  1  according to the first embodiment in that one first groove  11  is only provided. Front end  11   a  of first groove  11  is provided at front cutting edge  110 . Rear end  11   b  of first groove  11  does not reach outer peripheral cutting edge  120 . The irregularity of outer peripheral cutting edge  120  is 30 μm or less. Since one first groove  11  is only provided, rotary cutting tool  1  according to the third embodiment can be readily manufactured although the effect by the groove is smaller than that in rotary cutting tool  1  according to the first embodiment. 
     Fourth Embodiment 
       FIG.  14    is a front view of a rotary cutting tool according to a fourth embodiment. As shown in  FIG.  14   , in a rotary cutting tool  1  according to the fourth embodiment, first groove  11  extends outward and a second groove  212  extends inward. That is, it is different from rotary cutting tools  1  of the first and second embodiments in that the extending directions of first groove  11  and second groove  212  are different from each other. Each of front ends  11   a ,  212   a  reaches front cutting edge  110 . On the other hand, each of rear ends  11   b ,  212   b  does not reach outer peripheral cutting edge  120 . 
     Each of front ends  11   a ,  212   a  of first groove  11  and second groove  212  is provided at front cutting edge  110  and has such a shape that it is opened in the longitudinal direction. Each of rear ends  11   b ,  12   b  of first groove  11  and second groove  212  do not reach outer peripheral cutting edge  120  and has such a shape that it is closed in the longitudinal direction. The irregularity of outer peripheral cutting edge  120  is 30 μm or less. By providing second groove  212  oriented inward and first groove  11  oriented outward, both the effects by the groove oriented inward and the groove oriented outward can be exhibited. 
     Further, there is such an effect that chip is likely to be finely cut off at a portion at which first groove  11  and second groove  212  intersect with each other. 
     Fifth Embodiment 
       FIG.  15    is a front view of a rotary cutting tool according to a fifth embodiment. As shown in  FIG.  15   , in a rotary cutting tool  1  according to the fifth embodiment, two first grooves  11 ,  13  are oriented inward, and one second groove  212  is oriented outward. Front end  15   a  of groove  15  does not reach front cutting edge  110 . All the rear ends  11   b ,  212   b ,  13   b ,  15   b  do not reach outer peripheral cutting edge  120 . 
     Front end  11   a ,  13   a  of first grooves  11 ,  13  and front end  212   a  of second groove  212  are provided at front cutting edge  110 . Rear ends  11   b ,  13   b  of first grooves  11 ,  13  and rear end  212   b  of second groove  212  do not reach outer peripheral cutting edge  120 . The irregularity of outer peripheral cutting edge  120  is 30 μm or less. 
     Each of  FIGS.  16  to  19    is a diagram showing an exemplary cross sectional shape of each groove. As shown in  FIG.  16   , the cross sectional shape of first groove  11  is a V shape. A side surface  11   d  of groove  11  forms an angle with respect to rake face  100 . As shown in  FIG.  17   , groove  11  may be constituted of: side surface  11   d  perpendicular to rake face  100 ; and a bottom surface  11   e  parallel to rake face  100 . As shown in  FIG.  18   , a tapered surface  11   f  may be provided in the vicinity of the entrance of groove  11 , and side surface  11   d  and bottom surface  11   e  similar to those in  FIG.  17    may be provided as shown in  FIG.  18   . This shape is hereinafter referred to as “V shape with bottom surface”. As shown in  FIG.  19   , groove  11  may be formed to have an arc shape. The cross sectional shape of each of these grooves  11  is employed in each of the embodiments. 
     That is, the cross sectional shape of first groove  11  may be any one of the V shape, the quadrangular shape, the shape obtained by combining the V shape and the quadrangular shape, and the circular shape. 
     Sixth Embodiment 
       FIG.  20    is a front view of a rotary cutting tool according to a sixth embodiment. As shown in  FIG.  20   , in a rotary cutting tool  1  according to the sixth embodiment, a corner chamfering cutting edge  130  is provided between front cutting edge  110  and outer peripheral cutting edge  120 , and front end  11   a  of first groove  11  is provided at corner chamfering cutting edge  130 . Rear end  11   b  of groove  11  does not reach outer peripheral cutting edge  120 . 
     Example 1 
     As a matter common among examples, tools of examples of the present disclosure and comparative examples were produced in the following manner: a diamond sintered material (hereinafter, referred to as PCD) obtained by sintering diamond having an average particle diameter of 5 μm was brazed to a shaft-shaped tool body, and polishing was performed using a diamond grindstone of #1500 to form cutting edges at the front end and outer periphery of the PCD. Then, for each of PCDs in which groove(s) were to be formed in its rake face, the groove(s) were formed in the rake face of the PCD by using a high-output pulse YAG laser increased in light collection property by a galvanometer mirror. 
     &lt;Differences in Shapes and Orientations of First and Second Grooves&gt; 
     An inspection was performed with regard to an influence of presence or absence of the first and second grooves and differences in shapes of the first and second grooves over chip.  FIGS.  12  to  14    show the basic shape of each tool and examples of the first and second grooves, and  FIGS.  16  to  19    show exemplary cross sectional shapes of the first and second grooves. 
     As comparative examples, the following tools were produced: a tool (tool number 1-b) in which grooves extend to the outer peripheral cutting edge; a tool (tool number 101) in which no first groove is formed; and a tool (tool number 102) in which grooves are parallel to the outer peripheral cutting edge. The shapes, orientations, sizes, and the like of the first and second grooves are shown in Table 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Specification of Tool 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                   
                   
                 Irregularity 
                 Condition 
               
               
                   
                   
                   
                   
                   
                   
                   
                 Groove 
                 of Outer 
                 Machining 
               
               
                   
                   
                 Groove/ 
                 Groove 
                 Groove 
                 Groove 
                   
                 Intermittent 
                 Peripheral 
                 Allowance 
               
               
                 Tool 
                 Groove 
                 Bottom 
                 Depth D 
                 Width W 
                 Interval S 
                 Number of 
                 Length W0 
                 Cutting Edge 
                 in Radius 
               
               
                 Number 
                 Orientation 
                 Shape 
                 [mm] 
                 [mm] 
                 [mm] 
                 Grooves 
                 [mm] 
                 [μm] 
                 [mm] 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 Outward, 
                 V Shape 
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 3 
                 2.5 
               
               
                 1-(2) 
                 45° (FIG. 13) 
                 with Bottom 
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 5 
                 2.5 
               
               
                 1-(3) 
                   
                 Surface 
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 10 
                 2.5 
               
               
                 1-(4) 
                   
                 (FIG. 18) 
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                 1-(5) 
                   
                   
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 20 
                 2.5 
               
               
                 1-(6) 
                   
                   
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 25 
                 2.5 
               
               
                 1-(7) 
                   
                   
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 30 
                 2.5 
               
               
                 1-(8) 
                   
                   
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 35 
                 2.5 
               
               
                 1-(9) 
                   
                   
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 40 
                 2.5 
               
               
                 1-b      
                 Outward, 45°; 
                   
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 130 
                 2.5 
               
               
                   
                 Grooves Extend 
               
               
                   
                 to Outer Peripheral 
               
               
                   
                 Cutting Edge 
               
               
                 1-c     
                 Inward, 
                   
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                   
                 45° (FIG. 12) 
               
               
                 2 
                 Crossed, 
                   
                 0.13 
                 0.17 
                 0.3 
                 3 × 2 
                 0.240 
                 15 
                 2.5 
               
               
                   
                 45° (FIG. 14) 
                   
                   
                   
                   
                 Types 
               
               
                 3 
                 Outward, 45° 
                 Semi-Circular 
                 0.085 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                   
                   
                 Shape (FIG. 19) 
               
               
                 101  
                 Non- 
                 Non- 
                 Non- 
                 Non- 
                 Non- 
                 Non- 
                 Non- 
                 15 
                 2.5 
               
               
                   
                 Applicable 
                 Applicable 
                 Applicable 
                 Applicable 
                 Applicable 
                 Applicable 
                 Applicable 
               
               
                 102  
                 Parallel to 
                 V Shape 
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                   
                 Outer Peripheral 
                 with Bottom 
               
               
                   
                 Cutting Edge 
                 Surface 
               
               
                   
                 (Provided at 
                 (FIG. 18) 
               
               
                   
                 Positions of 0.3, 
               
               
                   
                 0.6 and 0.9 mm 
               
               
                   
                 from Outer Periphery) 
               
               
                   
               
            
           
         
       
     
     In the column “Groove Orientation”, “Outward, 45°” means that each of the first grooves extends and forms an angle of 45° with respect to rotation axis  9  as shown in  FIG.  13   . Each of the angles described in the column “Groove Orientation” means an angle formed with respect to rotation axis  9 . “Groove Intermittent Length WO” means a length, along a radial direction, of a portion of front end  11   a  at which the ridgeline of front cutting edge  110  ceases to exist due to formation of grooves  11  as shown in  FIG.  12   . 
     A position at which the first groove on the outermost periphery intersects with the front cutting edge as measured from outer peripheral cutting edge  120  is 0.3 mm in tool numbers 1 to 1-b, is 0.3 mm in tool number 1-c, is 0.3 mm in tool number 2, is 0.3 mm in tool number 3, and is 0.3 mm in tool number 102 in Table 1. A position at which the second groove on the outermost periphery intersects with the front cutting edge as measured from outer peripheral cutting edge  120  is 0.3 mm in tool number 2 in Table 1. 
     Each of the above-described tools was used to perform a cutting process under the following conditions so as to evaluate chip processability. 
     [Cutting Conditions] 
     Workpiece: aluminum alloy (A6061) 
     Processed hole: pilot hole diameter of 5 mm; depth of 25 mm 
     This hole is finished to be 10 mm in diameter. Therefore, machining allowance is 2.5 mm in radius. 
     Cutting speed: 200 m/min 
     Feed rate: 0.2 mm/rev 
     In this evaluation, chip having a curled shape with a length of 5 mm or less and a width of less than or equal to the machining allowance in radius was determined to be excellent. Evaluation results are shown in Table 2. 
     
       
         
           
               
               
             
               
                   
                 TABLE 2 
               
             
            
               
                   
                   
               
               
                   
                 Result of Processing 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Chip 
                 Chip 
                   
                 State of 
                   
                   
               
               
                 Tool 
                 Width 
                 Length 
                 Chip 
                 Hole Wall 
                 Final 
                 Description of 
               
               
                 Number 
                 [mm] 
                 [mm] 
                 Evaluation 
                 Surface 
                 Evaluation 
                 Final Evaluation 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 1 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
                   
               
               
                 1-(2) 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 1-(3) 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 1-(4) 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 1-(5) 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 1-(6) 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 1-(7) 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 1-(8) 
                 0.3 to 0.9 
                 3 
                 A 
                 Small Damage 
                 C 
                 Damage on Processed 
               
               
                   
                   
                   
                   
                 Occurs 
                   
                 Surface and Deteriorated 
               
               
                   
                   
                   
                   
                   
                   
                 Surface Roughness 
               
               
                 1-(9) 
                 0.3 to 0.9 
                 3 
                 A 
                 Damage 
                 C 
                 Damage on Processed 
               
               
                   
                   
                   
                   
                 Occurs 
                   
                 Surface and Deteriorated 
               
               
                   
                   
                   
                   
                   
                   
                 Surface Roughness 
               
               
                 1-b      
                 0.3 to 0.9 
                 3 
                 A 
                 Large Processing 
                 C 
                 Damage on Processed 
               
               
                   
                   
                   
                   
                 Mark Remains 
                   
                 Surface and Deteriorated 
               
               
                   
                   
                   
                   
                   
                   
                 Surface Roughness 
               
               
                 1-c     
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 2 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 3 
                 0.3 to 0.9 
                 7 
                 B 
                 No Damage 
                 B 
                 B Because Chip is 
               
               
                   
                   
                   
                   
                   
                   
                 Slightly Long to be 
               
               
                   
                   
                   
                   
                   
                   
                 More Than 5 mm 
               
               
                 101  
                 2.5 
                 16 
                 C 
                 No Damage 
                 C 
                 Chip is Long and Chip 
               
               
                   
                   
                   
                   
                   
                   
                 Width is as Large as 
               
               
                   
                   
                   
                   
                   
                   
                 Machining Allowance 
               
               
                 102  
                 0.2 to 1.5 
                 14 
                 C 
                 No Damage 
                 C 
                 Chip is Long 
               
               
                   
               
            
           
         
       
     
     “A” to “C” in the final evaluation in Table 2 mean as follows. 
     Evaluation A: Both the width and length (5 mm or less) of the chip were small, and there was no damage on the processed surface. 
     Evaluation B: The length of the chip was slightly large (5 to 10 mm) but there was no damage on the processed surface. 
     Evaluation C: Damage occurred on the processed surface; no damage occurred but the chip was long to be 10 mm or more and therefore possibility of occurrence of damage is very high; or no damage occurred but the chip was not cut off in the width direction and remained to be wide even though the length of the chip became short. 
     It should be noted that these evaluations are also applied to Tables 4, 6, 8, and 10 below. 
     In each of the tools of tool numbers 1 and 2, the width of the chip was smaller than the machining allowance, and the chip was cut off to have a short length of 3 mm. It is considered that in the tool of tool number 3 in which the cross sectional shape of the first groove was a semicircular shape, the depth of the first groove was shallow with respect to the width of the first groove as compared with the other first groove shapes, with the result that the width of the chip could not be small. Further, due to the same reason, the effect of shortening the length of the chip was small as compared with the other first groove shapes; however, the effect of curling the chip was obtained, and the length of the chip was short to be 3 mm. 
     On the other hand, in tool number 101 in which no first groove is provided, the chip width was as large as the machining allowance, the chip length was 16 mm, the chip was not curled, and thus there was no effect of cutting off the chip. In view of the above results, it is considered that whether to attain the effect of cutting off the chip results from the difference in shape of the first groove, rather than the processing conditions. 
     In the tool of tool number 1-c, a mark resulting from scratching with the chip was observed on wall surface  301  that intersects with the extending direction of each of rake face  100  and groove  11 , thus confirming that wall surface  301  functions to cut off the chip. In view of this, the chip caused by front cutting edge  110  flows along groove  11  and collides with wall surface  301  in the vicinity of rear end  11   b  of groove  11 , thereby attaining the effect of cutting off the chip. 
     Further, when the irregularity of the outer peripheral cutting edge is more than 30 μm, damage occurred on the processed surface to result in deteriorated surface roughness. 
     Example 2 
     &lt;Difference in Angle of First Groove&gt; 
     In the present example, a test was conducted with regard to an influence of an angle of the first groove over the cutting-off of chip. 
     In order to check a difference in cutting-off of chip due to a difference in angle of the first groove, one first groove was provided while the tool shape of Example 1 is basically used. 
     The following tools were produced: a tool in which the angle of the first groove was parallel to the rotation axis (0°); and tools in each of which the angle of the first groove was changed within a range of 3° to 87° with respect to the rotation axis. The shapes, orientations, sizes, and the like of the first grooves are shown in Table 3. Each of the front ends of the first grooves intersects with the front cutting edge. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
             
            
               
                   
                   
               
               
                   
                 Specification of Tool 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                   
                   
                 Irregularity 
                 Condition 
               
               
                   
                   
                   
                   
                   
                   
                   
                 Groove 
                 of Outer 
                 Machining 
               
               
                   
                   
                 Groove/ 
                 Groove 
                 Groove 
                 Groove 
                   
                 Intermittent 
                 Peripheral 
                 Allowance 
               
               
                 Tool 
                 Groove 
                 Bottom 
                 Depth D 
                 Width W 
                 Interval S 
                 Number of 
                 Length W0 
                 Cutting Edge 
                 in Radius 
               
               
                 Number 
                 Orientation 
                 Shape 
                 [mm] 
                 [mm] 
                 [mm] 
                 Grooves 
                 [mm] 
                 [μm] 
                 [mm] 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 103 
                  0° 
                 V Shape 
                 0.13 
                 0.17 
                 Non-Applicable 
                 1 
                 0.170 
                 15 
                 2.5 
               
               
                 11 
                 Outward, 3° 
                 with Bottom 
                 0.13 
                 0.17 
                 Non-Applicable 
                 1 
                 0.171 
                 15 
                 2.5 
               
               
                 12 
                 Outward, 5° 
                 Surface 
                 0.13 
                 0.17 
                 Non-Applicable 
                 1 
                 0.171 
                 15 
                 2.5 
               
               
                 13 
                 Outward, 30° 
                   
                 0.13 
                 0.17 
                 Non-Applicable 
                 1 
                 0.196 
                 15 
                 2.5 
               
               
                 14 
                 Outward, 60° 
                   
                 0.13 
                 0.17 
                 Non-Applicable 
                 1 
                 0.340 
                 15 
                 2.5 
               
               
                 15 
                 Outward, 85° 
                   
                 0.13 
                 0.17 
                 Non-Applicable 
                 1 
                 1.951 
                 15 
                 2.5 
               
               
                 16 
                 Outward, 87° 
                   
                 0.13 
                 0.17 
                 Non-Applicable 
                 1 
                 1.951 
                 15 
                 2.5 
               
               
                 104 
                 90° 
                   
                 0.13 
                 0.17 
                 Non-Applicable 
                 1 
                 Non-Applicable 
                 15 
                 2.5 
               
               
                   
               
            
           
         
       
     
     In view of restrictions in shape or production, the tools are divided into the following three types: a tool in which the position at which the first groove intersects with the front cutting edge is located at 1.0 mm from the outer peripheral cutting edge; a tool in which the position at which the first groove intersects with the front cutting edge is located at 1.5 mm from the outer peripheral cutting edge; and a tool in which the position at which the first groove intersects with the front cutting edge is located at 2.0 mm from the outer peripheral cutting edge. Specifically, the position is located at 1 mm therefrom in each of tool numbers 103, 11, 12, 13, 14, the position is located at 1.5 mm therefrom in tool number 15, and the position is located at 2 mm therefrom in tool number 16 in Table 3. 
     As with tool number 1 of Example 1, the cross sectional shape of the first groove is the shape of  FIG.  18   , and width W of the first groove is 0.17 mm. 
     Width WO of the intermittent portion of the front cutting edge formed by the first groove intersecting with the front cutting edge differs depending on the angle of the first groove, but can be found by calculation. 
     Each of the above-described tools was used to perform a cutting process under the following conditions so as to evaluate chip processability. 
     [Cutting Conditions] 
     The cutting conditions are as follows. 
     Workpiece: aluminum alloy (A6061) 
     Processed hole: pilot hole diameter of 5 mm; depth of 25 mm 
     This hole is finished to be 10 mm. Therefore, machining allowance is 2.5 mm in radius. 
     Cutting speed: 200 m/min 
     Feed rate: 0.2 mm/rev 
     Also in this evaluation, as with Example 1, chip having a curled shape with a length of 5 mm or less and a width of less than or equal to the machining allowance in radius was determined to be excellent. It should be noted that the determination was made also in consideration of occurrence of chattering or the like during processing. 
     Evaluation results are shown in Table 4. 
     
       
         
           
               
               
             
               
                   
                 TABLE 4 
               
             
            
               
                   
                   
               
               
                   
                 Result of Processing 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Chip 
                 Chip 
                   
                 State of 
                   
                   
               
               
                 Tool 
                 Width 
                 Length 
                 Chip 
                 Hole Wall 
                 Final 
                 Description of 
               
               
                 Number 
                 [mm] 
                 [mm] 
                 Evaluation 
                 Surface 
                 Evaluation 
                 Final Evaluation 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 103 
                 0.9 to 1.4 
                 15  
                 C 
                 No Damage 
                 C 
                 Chip is Long 
               
               
                 11 
                 0.9 to 1.4 
                 5 to 7 
                 B 
                 No Damage 
                 B 
                 B Because Chip is 
               
               
                   
                   
                   
                   
                   
                   
                 Slightly Long to be 
               
               
                   
                   
                   
                   
                   
                   
                 More Than 5 mm 
               
               
                 12 
                 0.9 to 1.4 
                 5 
                 A 
                 No Damage 
                 A 
               
               
                 13 
                 0.9 to 1.4 
                 4 to 5 
                 A 
                 No Damage 
                 A 
               
               
                 14 
                 0.9 to 1.4 
                 3 to 5 
                 A 
                 No Damage 
                 A 
               
               
                 15 
                 0.5 to 1.4 
                 3 to 5 
                 A 
                 No Damage 
                 A 
               
               
                 16 
                 0.5 to 1.4 
                 3 to 5 
                 A 
                 No Damage 
                 B 
                 Cutting Sound is 
               
               
                   
                   
                   
                   
                   
                   
                 Slightly Large, 
               
               
                   
                   
                   
                   
                   
                   
                 Which is Considered 
               
               
                   
                   
                   
                   
                   
                   
                 as Sign of Increase 
               
               
                   
                   
                   
                   
                   
                   
                 in Cutting Resistance etc. 
               
               
                 104 
                 2.5 
                 3 
                 C 
                 No Damage 
                 C 
                 Chip Width is as Large as 
               
               
                   
                   
                   
                   
                   
                   
                 Machining Allowance in Radius 
               
               
                   
               
            
           
         
       
     
     In the tool of tool number 11 with the angle of 3°, the chip was curled but the length of the chip was not so short, and therefore the final evaluation was B. In each of the tools of tool numbers 12 to 15 with the angles of 5° to 85°, the effect of cutting off the chip both in width and length by the first groove was observed. 
     The tool of tool number 16 with the angle of 87° attained the effect of cutting off the chip; however, it was observed that chattering occurred slightly when processing the vicinity of the bottom of the hole. Such chattering occurred presumably due to the following reason: the size of W was very large to be 3.25 mm or more, thus resulting in large cutting resistance at this portion. 
     In view of these results, it was understood that the first groove preferably has an angle of 5° or more and 85° or less with respect to the rotation axis. 
     Example 3 
     &lt;Difference in Depth of First Groove&gt; 
     In the present example, an inspection was performed with regard to an influence of the depth of each first groove over the chip. 
     Each of tools was produced in the following manner: the tool shape of tool number 1 of Example 1 was basically used for each tool shape, and the depth of the first groove was changed. The shapes, orientations, sizes, and the like of the first grooves are shown in Table 5. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 5 
               
             
            
               
                   
                   
               
               
                   
                 Specification of Tool 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                   
                   
                 Irregularity 
                 Condition 
               
               
                   
                   
                   
                   
                   
                   
                   
                 Groove 
                 of Outer 
                 Machining 
               
               
                   
                   
                 Groove/ 
                 Groove 
                 Groove 
                 Groove 
                   
                 Intermittent 
                 Peripheral 
                 Allowance 
               
               
                 Tool 
                 Groove 
                 Bottom 
                 Depth D 
                 Width W 
                 Interval S 
                 Number of 
                 Length W0 
                 Cutting Edge 
                 in Radius 
               
               
                 Number 
                 Orientation 
                 Shape 
                 [mm] 
                 [mm] 
                 [mm] 
                 Grooves 
                 [mm] 
                 [μm] 
                 [mm] 
               
               
                   
               
               
                 22 
                 Outward, 45° 
                 V Shape 
                 0.01 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                 23 
                 Outward, 45° 
                 with Bottom 
                 0.07 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                 24 
                 Outward, 45° 
                 Surface 
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                 (Same as 1) 
               
               
                 25 
                 Outward, 45° 
                   
                 0.40 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                 26 
                 Outward, 45° 
                   
                 0.80 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                   
               
            
           
         
       
     
     Width W of each first groove and interval S between the first grooves are the same as those in tool number 1, and the position at which the first groove on the outermost periphery intersects with the front cutting edge was a position of 0.3 mm from the outer peripheral portion. 
     The position of the first groove on the inner peripheral side was a position of 2.5 mm from the outer peripheral portion, and three first grooves were provided in each of the tools. 
     Each of the above-described tools was used to perform a cutting process under the following conditions so as to evaluate chip processability. 
     [Cutting Conditions] 
     Workpiece: aluminum alloy (A6061) 
     Processed hole: pilot hole diameter of 5 mm; depth of 25 mm 
     This hole is finished to be 10 mm. Therefore, machining allowance is 2.5 mm in radius. 
     Cutting speed: 200 m/min 
     Feed rate: 0.2 mm/rev 
     This evaluation is also the same as in Example 1. Evaluation results are shown in Table 6. 
     
       
         
           
               
               
             
               
                   
                 TABLE 6 
               
             
            
               
                   
                   
               
               
                   
                 Result of Processing 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Chip 
                 Chip 
                   
                 State of 
                   
               
               
                 Tool 
                 Width 
                 Length 
                 Chip 
                 Hole Wall 
                 Final 
               
               
                 Number 
                 [mm] 
                 [mm] 
                 Evaluation 
                 Surface 
                 Evaluation 
               
               
                   
               
               
                 22 
                 0.3 to 0.9 
                 5 
                 A 
                 No Damage 
                 A 
               
               
                 23 
                 0.3 to 0.9 
                 4 
                 A 
                 No Damage 
                 A 
               
               
                 24 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 (Same as 1) 
               
               
                 25 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 26 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                   
               
            
           
         
       
     
     In each of the tools of tool numbers 22 to 26 in which the respective depths of the first grooves were 0.01 mm to 0.8 mm, the chip was curled and finely cut off. 
     In view of these results, it was understood that the depth of the first groove is preferably 0.01 mm or more and 0.8 mm or less. 
     Example 4 
     &lt;Difference in Width of First Groove&gt; 
     In the present example, a test was conducted with regard to an influence of a difference in width W of each first groove over the chip. 
     Each of tools was produced in the following manner: the shape of tool number 1 of Example 1 was basically used for each tool shape and the width of the first groove was changed between 0.01 mm and 0.50 mm. The shapes, orientations, sizes, and the like of the first grooves are shown in Table 7. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 7 
               
             
            
               
                   
                   
               
               
                   
                 Specification of Tool 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                   
                   
                 Irregularity 
                 Condition 
               
               
                   
                   
                   
                   
                   
                   
                   
                 Groove 
                 of Outer 
                 Machining 
               
               
                   
                   
                 Groove/ 
                 Groove 
                 Groove 
                 Groove 
                   
                 Intermittent 
                 Peripheral 
                 Allowance 
               
               
                 Tool 
                 Groove 
                 Bottom 
                 Depth D 
                 Width W 
                 Interval S 
                 Number of 
                 Length W0 
                 Cutting Edge 
                 in Radius 
               
               
                 Number 
                 Orientation 
                 Shape 
                 [mm] 
                 [mm] 
                 [mm] 
                 Grooves 
                 [mm] 
                 [μm] 
                 [mm] 
               
               
                   
               
               
                 32 
                 Outward, †45° 
                 V Shape 
                 0.13 
                 0.01 
                 0.3 
                 3 
                 0.014 
                 15 
                 2.5 
               
               
                 33 
                 Outward, 45° 
                 with Bottom 
                 0.13 
                 0.10 
                 0.3 
                 3 
                 0.141 
                 15 
                 2.5 
               
               
                 34 
                 Outward, 45° 
                 Surface 
                 0.13 
                 0.17 
                 0.3 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                 (Same as 1) 
               
               
                 35 
                 Outward, 45° 
                   
                 0.13 
                 0.25 
                 0.3 
                 3 
                 0.354 
                 15 
                 2.5 
               
               
                 36 
                 Outward, 45° 
                   
                 0.13 
                 0.50 
                 0.3 
                 3 
                 0.707 
                 15 
                 2.5 
               
               
                   
               
            
           
         
       
     
     Depth D of each first groove and interval S between the first grooves are the same as those of the tool of tool number 1. The position at which the first groove on the outermost periphery intersects with the front cutting edge was a position of 0.3 mm from the outer peripheral portion. 
     Tool number 34 represents the same tool as that of tool number 1 produced in Example 1. 
     Since the outermost peripheral portion of the first groove is located at a position of 2.5 mm from the outer peripheral portion, the number of the first grooves differs depending on the width of each first groove. 
     Each of the above-described tools was used to perform a cutting process under the following conditions so as to evaluate chip processability. 
     [Cutting Conditions] 
     Workpiece: aluminum alloy (A6061) 
     Processed hole: pilot hole diameter of 5 mm; depth of 25 mm 
     This hole is finished to be 10 mm. Therefore, machining allowance is 2.5 mm in radius. 
     Cutting speed: 200 m/min 
     Feed rate: 0.2 mm/rev 
     This evaluation is also the same as in Example 1. Evaluation results are shown in Table 8. 
     
       
         
           
               
               
             
               
                   
                 TABLE 8 
               
             
            
               
                   
                   
               
               
                   
                 Result of Processing 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Chip 
                 Chip 
                   
                 State of 
                   
               
               
                 Tool 
                 Width 
                 Length 
                 Chip 
                 Hole Wall 
                 Final 
               
               
                 Number 
                 [mm] 
                 [mm] 
                 Evaluation 
                 Surface 
                 Evaluation 
               
               
                   
               
               
                 32 
                 0.3 to 1.6 
                 5 
                 A 
                 No Damage 
                 A 
               
               
                 33 
                 0.3 to 1.2 
                 4 
                 A 
                 No Damage 
                 A 
               
               
                 34 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 (Same as 1) 
               
               
                 35 
                 0.3 to 0.5 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 36 
                 0.3 to 0.7 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                   
               
            
           
         
       
     
     In each of the tools of tool numbers 32 to 36, the chip was curled and cut off, thereby obtaining small chip. 
     Example 5 
     &lt;Difference in Interval Between First Grooves&gt; 
     In the present example, a test was conducted with regard to an influence of a difference in interval S between the first grooves over the chip. 
     Each of tools was produced in the following manner: the shape of tool number 1 of Example 1 was basically used for each tool shape and the interval between the first grooves was changed. The shapes, orientations, sizes, and the like of the first grooves are shown in Table 9. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 9 
               
             
            
               
                   
                   
               
               
                   
                 Specification of Tool 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                   
                   
                 Irregularity 
                 Condition 
               
               
                   
                   
                   
                   
                   
                   
                   
                 Groove 
                 of Outer 
                 Machining 
               
               
                   
                   
                 Groove/ 
                 Groove 
                 Groove 
                 Groove 
                   
                 Intermittent 
                 Peripheral 
                 Allowance 
               
               
                 Tool 
                 Groove 
                 Bottom 
                 Depth D 
                 Width W 
                 Interval S 
                 Number of 
                 Length W0 
                 Cutting Edge 
                 in Radius 
               
               
                 Number 
                 Orientation 
                 Shape 
                 [mm] 
                 [mm] 
                 [mm] 
                 Grooves 
                 [mm] 
                 [μm] 
                 [mm] 
               
               
                   
               
               
                 42 
                 Outward, 45° 
                 V Shape 
                 0.13 
                 0.17 
                 0.10 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                 43 
                 Outward, 45° 
                 with Bottom 
                 0.13 
                 0.17 
                 0.15 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                 44 
                 Outward, 45° 
                 Surface 
                 0.13 
                 0.17 
                 0.30 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                 (Same as 1) 
               
               
                 45 
                 Outward, 45° 
                   
                 0.13 
                 0.17 
                 0.50 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                 46 
                 Outward, 45° 
                   
                 0.13 
                 0.17 
                 1.00 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                 47 
                 Outward, 45° 
                   
                 0.13 
                 0.17 
                 2.00 
                 3 
                 0.240 
                 15 
                 2.5 
               
               
                   
               
            
           
         
       
     
     Depth D of each first groove and width W of the first groove are the same as those in tool number 1. The position at which the first groove on the outermost periphery intersects with the front cutting edge was a position of 0.3 mm from the outer peripheral portion. 
     The tools were produced in each of which interval S between the first grooves differs between 0.10 mm and 2.00 mm. Tool number 44 represents the same tool as that of tool number 1 of Example 1. 
     Since the outermost peripheral portion of the first groove is located at the position of 2.5 mm from the outer peripheral portion, the number of the first grooves differs depending on the interval between the first grooves. 
     Each of the above-described tools was used to perform a cutting process under the following conditions so as to evaluate chip processability. 
     [Cutting Conditions] 
     Workpiece: aluminum alloy (A6061) 
     Processed hole: pilot hole diameter of 5 mm; depth of 25 mm 
     This hole is finished to be 10 mm. Therefore, machining allowance is 2.5 mm in radius. 
     Cutting speed: 200 m/min 
     Feed rate: 0.2 mm/rev 
     This evaluation is also the same as in Example 1. Evaluation results are shown in Table 10. 
     
       
         
           
               
               
             
               
                   
                 TABLE 10 
               
             
            
               
                   
                   
               
               
                   
                 Result of Processing 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Chip 
                 Chip 
                   
                 State of 
                   
               
               
                 Tool 
                 Width 
                 Length 
                 Chip 
                 Hole Wall 
                 Final 
               
               
                 Number 
                 [mm] 
                 [mm] 
                 Evaluation 
                 Surface 
                 Evaluation 
               
               
                   
               
               
                 42 
                 0.3 to 1.3 
                 5 
                 A 
                 No Damage 
                 A 
               
               
                 43 
                 0.3 to 1.2 
                 4 
                 A 
                 No Damage 
                 A 
               
               
                 44 
                 0.3 to 0.9 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 (Same as 1) 
               
               
                 45 
                 0.3 to 0.5 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 46 
                 0.3 to 1.0 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                 47 
                 0.3 to 2.0 
                 3 
                 A 
                 No Damage 
                 A 
               
               
                   
               
            
           
         
       
     
     In each of the tools of tool numbers 43 to 45, the chip was curled and cut off, thereby obtaining small chip. 
     It was observed that in the tool of tool number 42 in which the interval between the first grooves was 0.10 mm, the chip was slightly welded because the front cutting edge had a shape close to a comb shape; however, since the welding was small, the effect of curling and cutting off the chip was not decreased. 
     The embodiments and examples disclosed herein are illustrative and non-restrictive in any respect. The scope of the present invention is defined by the terms of the claims, rather than the embodiments described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. 
     INDUSTRIAL APPLICABILITY 
     The rotary cutting tool can be suitably applied to a drill or reamer used to process a fitting hole of an aluminum alloy or non-ferrous metal. 
     REFERENCE SIGNS LIST 
       1 : rotary cutting tool;  2 : tool body;  9 : rotation axis;  10 : cutting edge tip;  11 ,  12 ,  13 ,  14 : first groove;  15 ,  16 : groove;  11   a ,  12   a ,  13   a ,  14   a ,  15   a ,  16   a ,  212   a : front end;  11   b ,  12   b ,  13   b ,  14   b ,  15   b ,  16   b ,  212   b : rear end;  11   d : side surface;  11   e : bottom surface;  11   f : tapered surface;  100 : rake face;  110 : front cutting edge;  120 : outer peripheral cutting edge;  130 : corner chamfering cutting edge;  212 : second groove;  301 ,  302 : wall surface;  311 : line.