Patent Publication Number: US-2023132425-A1

Title: Cutting insert, cutting tool, and method for manufacturing machined product

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage entry according to 35 U.S.C. 371 of PCT Application No. PCT/JP2021/012220 filed on Mar. 24, 2021, which claims priority to Japanese Application No. 2020-054422 filed on Mar. 25, 2020. The contents of the Japanese application are incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to a cutting insert, a cutting tool and a method for manufacturing machined product, which are used in a cutting process of a workpiece. More specifically, the present disclosure relates to a cutting tool for use in a milling process. 
     BACKGROUND 
     For example, a cutting insert discussed in Japanese Unexamined Patent Publication No. 2004-314301 (Patent Document 1) has been known as a cutting insert for use in a cutting process of a workpiece, such as metal. The cutting insert discussed in Patent Document 1 has a quadrangular plate shape. The cutting insert discussed in Patent Document 1 has a cutting edge located on an intersection of an upper surface and a lateral surface, and a fixing hole that opens into the upper surface and a lower surface. 
     In recent years, there is a demand for downsizing of cutting inserts. However, the downsizing of the cutting inserts may lead to a tendency of a small thickness between a through hole (fixing hole) and the lateral surface, and may cause deterioration in durability. Hence, there is a demand for improved durability of the cutting inserts. 
     SUMMARY 
     A cutting insert in a non-limiting aspect of the present disclosure has an upper surface, a lower surface, a lateral surface, a through hole and a cutting edge. The upper surface having a polygonal shape has a long side and a short side. The lower surface is located on a side opposite to the upper surface. The lateral surface is located between the upper surface and the lower surface. The through hole opens into a center of the upper surface and a center of the lower surface. The cutting edge is located on the short side. The lateral surface has a first lateral surface that is located along the long side and has an outwardly protruded shape in a top view. The first lateral surface has a first plane, a second plane, a third plane and a first inclined surface. The first plane is overlapped with a central axis of the through hole in a front view, and is parallel to the central axis. The second plane is located closer to the short side than the first plane, and is parallel to the central axis. The third plane is located more away from the short side than the first plane, and is parallel to the central axis. The first inclined surface is located between the second plane and the upper surface, and comes closer to the central axis as coming closer to the long side. The first inclined surface is located away from the first plane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view illustrating a cutting insert in a non-limiting embodiment of the present disclosure; 
         FIG.  2    is a plan view of the cutting insert illustrated in  FIG.  1    as viewed from above; 
         FIG.  3    is a plan view of the cutting insert illustrated in  FIG.  1    as viewed from above; 
         FIG.  4    is a side view of the cutting insert illustrated in  FIG.  2    as viewed from an A1 direction; 
         FIG.  5    is a side view of the cutting insert illustrated in  FIG.  2    as viewed from an A2 direction; 
         FIG.  6    is a sectional view taken along line VI-VI illustrated in  FIG.  2   ; 
         FIG.  7    is a sectional view taken along line VII-VII illustrated in  FIG.  2   ; 
         FIG.  8    is a sectional view taken along line VIII-VIII illustrated in  FIG.  2   ; 
         FIG.  9    is a sectional view taken along line IX-IX illustrated in  FIG.  2   ; 
         FIG.  10    is a perspective view illustrating a cutting tool in a non-limiting embodiment of the present disclosure; 
         FIG.  11    is a plan view of the cutting tool illustrated in  FIG.  10    as viewed from a side of a first end; 
         FIG.  12    is a side view of the cutting tool illustrated in  FIG.  11    as viewed from an A3 direction; 
         FIG.  13    is an enlarged view of a region B1 illustrated in  FIG.  10   ; 
         FIG.  14    is a schematic diagram illustrating one of steps in a method for manufacturing a machined product in a non-limiting embodiment of the present disclosure; 
         FIG.  15    is a schematic diagram illustrating one of the steps in the method for manufacturing a machined product in the non-limiting embodiment of the present disclosure; and 
         FIG.  16    is a schematic diagram illustrating one of the steps in the method for manufacturing a machined product in the non-limiting embodiment of the present disclosure. 
     
    
    
     EMBODIMENTS 
     &lt;Cutting Inserts&gt; 
     The cutting insert  1  (hereinafter also referred to as “insert  1 ”) in a non-limiting embodiment of the present disclosure is described in detail below with reference to the drawings. For the convenience of description, the drawings referred to in the following illustrate, in simplified form, only main members necessary for describing the non-limiting embodiment. The insert  1  may therefore include any arbitrary structural member not illustrated in the drawings referred to. Dimensions of the members in each of the drawings faithfully represent neither dimensions of actual structural members nor dimensional ratios of these members. 
     The insert  1  may have an upper surface  3 , a lower surface  5 , a lateral surface  7 , a through hole  9 , and a cutting edge  11  as in a non-limiting embodiment illustrated in  FIGS.  1  to  9   . As used herein, the terms “the upper surface  3 ” and “the lower surface  5 ” are used for the sake of convenience, but do not indicate upper and lower directions. For example, the upper surface  3  need not be directed upward when using the insert  1 . 
     The upper surface  3  may have a polygonal shape as in the non-limiting embodiment illustrated in  FIG.  1   . For example, the upper surface  3  may have a hexagonal shape. The lower surface  5  may be located on a side opposite to the upper surface  3 . Similarly to the upper surface  3 , the lower surface  5  may have a polygonal shape, for example, a hexagonal shape. The insert  1  may have a polygonal plate shape. 
     The polygonal shape may be an approximately polygonal shape, but need not be a strict polygonal shape. For example, a plurality of sides in the upper surface  3  need not be individually a strict straight line, but may be curved in a front view (top view) of the upper surface  3 . A plurality of corners in the upper surface  3  need not be individually a strict corner. 
     The plurality of sides in the upper surface  3  may have a long side  13  and a short side  15 . That is, the upper surface  3  may have the long side  13  and the short side  15 . Similarly to the upper surface  3 , the lower surface  5  may also have a long side and a short side. In cases where the plurality of sides in the upper surface  3  have two sides different in length, a relatively long side of these two sides may be the long side  13 , and a relatively short side may be the short side  15 . 
     A corner  17  located between the long side  13  and the short side  15  may have an obtuse angle as in the non-limiting embodiment illustrated in  FIG.  2   . The corner  17  is less likely to be fractured in this embodiment. The corner  17  is not limited to a strict corner formed by an intersection of the long side  13  and the short side  15 . For example, the corner  17  may have a convex curvilinear shape or a combined shape made up of a straight line and a curved line in a top view. 
     The lateral surface  7  may be located between the upper surface  3  and the lower surface  5 . The lateral surface  7  may connect to the upper surface  3  and the lower surface  5  as in a non-limiting embodiment illustrated in  FIG.  4   . 
     The through hole  9  is usable for inserting, for example, a screw when fixing the insert  1  to a holder. Instead of the screw, for example, a clamping member may be used to fix the insert  1  to the holder. 
     The through hole  9  may open into a center of the upper surface  3  and a center of the lower surface  5 . If the upper surface  3  has a polygonal shape, corners located at opposite angles on the upper surface  3  may be individually connected by a straight line, and a point of intersection of these straight lines may be regarded as the center of the upper surface  3 . Similarly, if the lower surface  5  has a polygonal shape, corners located at opposite angles on the lower surface  5  may be individually connected by a straight line, and a point of intersection of these straight lines may be regarded as the center of the lower surface  5 . A starting point of a diagonal may be a portion where extension lines of individual sides constituting the polygonal shape intersect with each other. If the lower surface  5  does not have the polygonal shape, the center of the lower surface  5  may be determined by, for example, a position of a center of gravity of the lower surface  5  in a front view (bottom view) of the lower surface  5 . 
     A central axis O1 of the through hole  9  may be an imaginary straight line passing through a center of the upper surface  3  and a center of the lower surface  5 . A central axis of the insert  1  may also be the imaginary straight line passing through the center of the upper surface  3  and the center of the lower surface  5 . In other words, the central axis O1 of the through hole  9  may coincide with the central axis of the insert  1 . 
     The upper surface  3  may have 180° rotational symmetry around the central axis O1 in a top view. The lower surface  5  may have 180° rotational symmetry around the central axis O1 in a bottom view. 
     The insert  1  is not limited to a specific size. For example, a maximum width in a top view of the upper surface  3  may be set to approximately 6-25 mm. A height from the upper surface  3  to the lower surface  5  may be set to approximately 1-10 mm. The height from the upper surface  3  to the lower surface  5  may denote a maximum value of a distance between the upper surface  3  and the lower surface  5  in a direction parallel to the central axis O1. The height from the upper surface  3  to the lower surface  5  may be rephrased as a width of the lateral surface  7  in a direction along the central axis O1. 
     The cutting edge  11  may be located on the short side  15 . The cutting edge  11  is usable for cutting out a workpiece if a machined product is manufactured using the insert  1 . 
     If the cutting edge  11  is located on the short side  15 , one of the upper surface  3  and the lateral surface  7  may have a rake surface region, and one of the upper surface  3  and the lateral surface  7  may have a flank surface region. The upper surface  3  may have the rake surface region, and the lateral surface  7  may have the flank surface region as in the non-limiting embodiment illustrated in  FIG.  1   . 
     The insert  1  may further have another cutting edge located on a side of the lower surface  5  in addition to the cutting edge  11 . For example, the lower surface  5  may have a short side located below the short side  15 , and the insert  1  may have another cutting edge located on the short side of the lower surface  5 . This makes it possible to obtain the insert  1  of double-sided type. 
     The lateral surface  7  may have a first lateral surface  19 . The first lateral surface  19  may be located along the long side  13 . The first lateral surface  19  may have an outwardly protruded shape in a top view as in the non-limiting embodiment illustrated in  FIG.  2   . 
     The first lateral surface  19  may have a first plane  21 , a second plane  23 , a third plane  25  and a first inclined surface  27 . 
     The first plane  21 , the second plane  23  and the third plane  25  may be used as a surface that comes into touch (contact) with a holder when fixing the insert  1  to the holder. The first plane  21  may be overlapped with the central axis O1 in a front view (side view) as in a non-limiting embodiment illustrated in  FIG.  4   . The first plane  21  may be parallel to the central axis O1. The second plane  23  may be located closer to the short side  15  than the first plane  21 . The second plane  23  may be parallel to the central axis O1. The third plane  25  may be located more away from the short side  15  than the first plane  21 . The third plane  25  may be parallel to the central axis O1. The term “parallel” is not limited to a strict parallel, but may denote that an inclination of approximately ±5° is allowed. 
     The first plane  21 , the second plane  23  and the third plane  25  may be individually a flat surface. However, the first plane  21 , the second plane  23  and the third plane  25  need not be a strict flat surface. The first plane  21 , the second plane  23  and the third plane  25  may be an approximately flat surface, and specifically may be slightly curved or may have small irregularities to such a degree that cannot be seen if the insert  1  is viewed as a whole. For example, the first plane  21 , the second plane  23  and the third plane  25  may have small irregularities of approximately several tens of μm. 
     The first inclined surface  27  may be located between the second plane  23  and the upper surface  3 . The first inclined surface  27  may come closer to the central axis O1 as coming closer to the long side  13  as in a non-limiting embodiment illustrated in  FIG.  6   . A positional relationship with the central axis O1 may be evaluated on the basis of an imaginary straight line O1a parallel to the central axis O1. The first inclined surface  27  may be located away from the first plane  21  as in the non-limiting embodiment illustrated in  FIG.  4   . 
     In cases where the first lateral surface  19  has the outwardly protruded shape as a whole, and the first plane  21 , the second plane  23  and the third plane  25  are individually parallel to the central axis O1 as described above, it is easy to ensure a thickness between the through hole  9  and the first lateral surface  19  even though the insert  1  is downsized. If the first inclined surface  27  is located between the second plane  23  and the upper surface  3 , the first inclined surface  27  tends to be located close to the cutting edge  11 . In cases where the first inclined surface  27  comes closer to the central axis O1 as coming closer to the long side  13 , a ridgeline  29  where the first inclined surface  27  intersects with the upper surface  3  has a large thickness, and the ridgeline  29  has high strength. Hence, even if the ridgeline  29  conflicts a workpiece during manufacture of a machined product, the ridgeline  29  is less prone to fracture. In cases where the first inclined surface  27  is located away from the first plane  21  located next to the through hole  9 , it is easy to ensure the thickness between the through hole  9  and the first lateral surface  19  even though the first inclined surface  27  is disposed on the first lateral surface  19 . The insert  1  therefore has enhanced durability. 
     The second plane  23  may connect to the first plane  21  or, alternatively, may be located away from the first plane  21 . The third plane  25  may connect to the first plane  21  or, alternatively, may be located away from the first plane  21 . The first inclined surface  27  may connect to the second plane  23  or, alternatively, may be located away from the second plane  23 . The first inclined surface  27  may connect to the upper surface  3  or, alternatively, may be located away from the upper surface  3 . For example, the second plane  23  and the third plane  25  may individually connect to the first plane  21  as in the non-limiting embodiment illustrated in  FIG.  4   . The first inclined surface  27  may connect to each of the second plane  23  and the upper surface  3 . 
     An inclination angle θ1 of the first inclined surface  27  relative to the central axis O1 may be constant or changed. In cases where the first inclined surface  27  has a portion where the inclination angle θ1 becomes smaller as coming closer to the first plane  21  as in a non-limiting embodiment illustrated in  FIGS.  6  and  7   , a part of the first inclined surface  27  which is located close to the through hole  9  tends to have a relatively small inclination angle θ1. This makes it easier to ensure the thickness between the through hole  9  and the first lateral surface  19 . In the above embodiment, a part of the first inclined surface  27  which is located close to the cutting edge  11  tends to have a relatively large inclination angle θ1. Consequently, a part of the ridgeline  29  which is located close to the cutting edge  11  has enhanced strength. This leads to high durability of the insert  1 . 
     The inclination angle θ1 may become smaller as an entirety of the first inclined surface  27  comes closer to the first plane  21 . The inclination angle θ1 is not limited to a specific value. For example, the inclination angle θ1 may be set to 1-20°. The inclination angle θ1 may be evaluated on the basis of an imaginary straight line O1a. This is also true for an inclination angle θ2 described later. 
     A width W1 of the first inclined surface  27  along the central axis O1 may be constant or changed. In cases where the first inclined surface  27  has a part which of the width W1 becomes smaller as coming closer to the first plane  21  as in the non-limiting embodiment illustrated in  FIG.  4   , a part of the width W1 in the first inclined surface  27 , which is located close to the through hole  9 , tends to be relatively small. It is therefore easy to ensure the thickness between the through hole  9  and the first lateral surface  19 . In the above embodiment, a part of the width W1 in the first inclined surface  27 , which is located close to the cutting edge  11 , tends to be relatively large. Consequently, a part of the ridgeline  29  which is located close to the cutting edge  11  has enhanced strength. This leads to high durability of the insert  1 . 
     The width W1 may become smaller throughout the first inclined surface  27  as coming closer to the first plane  21 . The width W1 is not limited to a specific value. For example, the width W1 may be set to 0.3-1 mm. An area of the first inclined surface  27  may be smaller than an area of the second plane  23 . 
     The first inclined surface  27  may be located closer to the short side  15  than the through hole  9  in a transparent plan view of the first lateral surface  19 . In this embodiment, the first inclined surface  27  tends to be located close to the cutting edge  11 . Consequently, the insert  1  has high durability. The configuration described above may be evaluated in a top view. 
     The ridgeline  29  may have a part that comes closer to the lower surface  5  as coming closer to the first plane  21  in a front view of the first lateral surface  19 . An entirety of the ridgeline  29  may be extended so as to come closer to the lower surface  5  as coming closer to the first plane  21  in a front view of the first lateral surface  19 . 
     The first lateral surface  19  may further have a second inclined surface  31 . The second inclined surface  31  may be located between the third plane  25  and the lower surface  5 . The second inclined surface  31  may be located more away from the central axis O1 as coming closer to the long side  13  as in a non-limiting embodiment illustrated in  FIG.  9   . The second inclined surface  31  may be located away from the first plane  21  as in the non-limiting embodiment illustrated in  FIG.  4   . 
     The insert  1  has enhanced durability, for example, in cases where the lower surface  5  has a short side as in the upper surface  3 , and the insert  1  has a cutting edge (hereinafter referred to as “a lower cutting edge” for the sake of convenience) located on the short side of the lower surface  5 . In cases where instead of the cutting edge  11 , the lower cutting edge is used in a cutting process, a ridgeline where the second inclined surface  31  intersects with the lower surface  5  has high strength, and it is easy to ensure the thickness between the through hole  9  and the first lateral surface  19 . This leads to the enhanced durability of the insert  1  even in the case of using the lower cutting edge in a cutting process. 
     The second inclined surface  31  may have a part whose inclination angle θ2 relative to the central axis O1 becomes smaller as coming closer to the first plane  21 . The second inclined surface  31  may also have a part whose width W2 in a direction along the central axis O1 becomes smaller as coming closer to the first plane  21 . An area of the second inclined surface  31  may be smaller than an area of the third plane  25 . 
     The second plane  23  may connect to the lower surface  5  or, alternatively, may be located away from the lower surface  5 . In cases where the second plane  23  connects to the lower surface  5  as in the non-limiting embodiment illustrated in  FIG.  4   , it is easy to ensure a large area of the second plane  23 . It is therefore easy to ensure the thickness between the through hole  9  and the first lateral surface  19 , thus leading to high durability of the insert  1 . Additionally, the insert  1  tends to be stably fixed to the holder, thus leading to high constraint stability of the insert  1 . 
     The third plane  25  may connect to the upper surface  3  or, alternatively, may be located away from the upper surface  3 . In cases where the third plane  25  connects to the upper surface  3  as in the non-limiting embodiment illustrated in  FIG.  4   , it is easy to ensure a large area of the third plane  25 . It is therefore easy to ensure the thickness between the through hole  9  and the first lateral surface  19 , thus leading to high durability of the insert  1 . Additionally, the insert  1  tends to be stably fixed to the holder, thus leading to high constraint stability of the insert  1 . 
     A first boundary  33  between the first plane  21  and the second plane  23  may be inclined or parallel to the central axis O1 in a front view of the first lateral surface  19 . In cases where the first boundary  33  is parallel to the central axis O1 as in the non-limiting embodiment illustrated in  FIG.  4   , a thickness of the insert  1  between the first plane  21  and the second plane  23  and the through hole  9  is less subject to variation. The insert  1  therefore has high durability. 
     In a front view of the first lateral surface  19 , a second boundary  35  between the first plane  21  and the third plane  25  may be inclined or parallel to the central axis O1. In cases where the second boundary  35  is parallel to the central axis O1 as in the non-limiting embodiment illustrated in  FIG.  4   , a thickness of the insert  1  between the first plane  21  and the third plane  25  and the through hole  9  is less subject to variation. The insert  1  therefore has high durability. 
     An area of the first plane  21  may be smaller than each of the area of the second plane  23  and the area of the third plane  25 . The area of the second plane  23  may be equal to or different from the area of the third plane  25 . 
     The first plane  21  may be located more outward than the second plane  23  and the third plane  25  in a top view. The first plane  21  may be located most outward on the first lateral surface  19  in a top view. 
     A length L11 in a direction along the long side  13  on the first plane  21  may be smaller than each of a length L12 in a direction along the long side  13  on the second plane  23 , and a length L13 in a direction along the long side  13  on the third plane  25 . The length L11 may be evaluated by a maximum value of the length L11. This is also true for the length L12 and the length L13. 
     For example, cemented carbide and cermet are usable as a material of the insert  1 . Examples of composition of the cemented carbide may include WC-Co, WC-TiC-Co and WC-TiC-TaC-Co, in which WC, TiC and TaC may be hard particles and Co may be a binding phase. 
     The cermet may be a sintered composite material obtainable by compositing metal into a ceramic component. Examples of the cermet may include titanium compounds composed mainly of titanium carbide (TiC) or titanium nitride (TiN). Of course, it should be clear that the material of the insert  1  is not limited to the above compositions. 
     A surface of the insert  1  may be coated with a coating film by using chemical vapor deposition (CVD) method or physical vapor deposition (PVD) method. 
     Examples of composition of the coating film may include titanium carbide (TiC), titanium nitride (TiN), titanium carbon nitride (TiCN) and alumina (Al 2 O 3 ). 
     &lt;Cutting Tools&gt; 
     A cutting tool  101  in a non-limiting embodiment of the present disclosure is described below with reference to  FIGS.  10  to  13   . In  FIG.  10    and the like, a rotation axis O2 of the cutting tool  101  is indicated by a two-dot chain line, and a rotation direction of the rotation axis O2 is indicated by an arrow Y1. 
     The cutting tool  101  may have a holder  103  and an insert  1  as in the non-limiting embodiment illustrated in  FIGS.  10  to  13   . If the cutting tool  101  has the insert  1 , excellent cutting performance is attainable because of the high durability of the insert  1 . 
     The cutting tool  101  may be rotatable around the rotation axis O2. The cutting tool  101  may be used for a milling process. 
     The holder  103  may have a columnar shape extended along the rotation axis O2 from a first end  103   a  to a second end  103   b . The columnar shape may be an approximately columnar shape, but need not be a strict columnar shape. 
     The holder  103  may have a pocket  105  located on a side of the first end  103   a . The pocket  105  is a part that permits attachment of the insert  1 . The pocket  105  may open into an outer peripheral surface of the holder  103  and an end surface on a side of the first end  103   a.    
     The insert  1  may be located in the pocket  105 . There may be one or a plurality of pockets  105 . If the holder  103  has the plurality of pockets  105  as in the non-limiting embodiment illustrated in  FIG.  11   , the cutting tool  101  may have a plurality of inserts  1 , and the inserts  1  may be located one by one in the pockets  105 . 
     In cases where the holder  103  has the plurality of pockets  105 , these pockets  105  may be located around the rotation axis O2 at equal intervals or unequal intervals. 
     The insert  1  may be fitted to the pocket  105  so that at least a part of the cutting edge  11  is protruded from the holder  103 . For example, the insert  1  may be attached to the holder  103  so that the cutting edge  11  is protruded from the holder  103  toward a workpiece. In this embodiment, the lower surface  5  and the lateral surface  7  may be in contact with the holder  103 . 
     The insert  1  may be attached to the pocket  105  with a screw  107 . Specifically, the insert  1  may be attached to the holder  103  by inserting the screw  107  into the through hole  9  of the insert  1 , and by inserting a front end of the screw  107  into a screw hole formed in the pocket  105  so as to fix the screw  107  to the screw hole. 
     For example, steel and cast iron are usable as a material of the holder  103 . If the material of the holder  103  is steel, the holder  103  has high toughness. 
     &lt;Methods for Manufacturing Machined Product&gt; 
     Methods for manufacturing a machined product  203  in non-limiting embodiments of the present disclosure are described below with reference to  FIGS.  14  to  16   . 
     The machined product  203  may be manufactured by carrying out a cutting process of a workpiece  201 . The methods for manufacturing the machined product  203  in the non-limiting embodiments may have the following steps: 
     (1) rotating the cutting tool  101  represented by the above non-limiting embodiment; 
     (2) bringing the cutting tool  101  being rotated into contact with the workpiece  201 ; and 
     (3) moving the cutting tool  101  away from the workpiece  201 . 
     Specifically, firstly, the cutting tool  101  may be relatively brought near the workpiece  201  while rotating the cutting tool  101  around the rotation axis O2 in a Y1 direction as in the non-limiting embodiment illustrated in  FIG.  14   . Subsequently, the workpiece  201  may be cut out by bringing the cutting edge  11  of the cutting tool  101  into contact with the workpiece  201  as in the non-limiting embodiment illustrated in  FIG.  15   . Thereafter, the cutting tool  101  may be relatively moved away from the workpiece  201  as in a non-limiting embodiment illustrated in  FIG.  16   . 
     It becomes possible to offer excellent machinability by carrying out the above processes. Specifically, if the cutting tool  101  having the insert  1  is used in the method for manufacturing the machined product  203  in the non-limiting embodiment of the present disclosure, the insert  1  has high durability. It is therefore possible to obtain the machined product  203  having a highly precise finished surface. 
     Although the workpiece  201  is fixed and the cutting tool  101  is moved in the individual processes in the non-limiting embodiment illustrated in  FIGS.  14  to  16   , it is not intended to limit to this embodiment. 
     For example, the workpiece  201  may be brought near the cutting tool  101  in the step (1). Similarly, the workpiece  201  may be moved away from the cutting tool  101  in the step (3). If it is desired to continue the cutting process, the step of bringing the cutting edge  11  of the insert  1  into contact with different portions of the workpiece  201  may be repeated while keeping the cutting tool  101  rotated. 
     Examples of material of the workpiece  201  may include carbon steel, alloy steel, stainless steel, cast iron and nonferrous metals.