Abstract:
A cutting tool for grooving, parting and turning machining operations is capable of grooving to unlimited depths of cut. The cutting tool includes an indexable double-ended cutting insert having a downwardly extending insert clamping portion resiliently clamped in a self-retaining manner in an insert pocket so that chip formation is not hindered during such machining operations.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to cutting tools for grooving, parting and turning machining operations capable of grooving to unlimited depths of cut. 
       BACKGROUND OF THE INVENTION 
       [0002]    Such a cutting tool is disclosed, for example, in U.S. Pat. No. 7,163,361. A cutting insert is retained in an insert pocket of an insert holder via a forward upright V-shaped surface, an opposing flat rear surface and a V-shaped locating surface associated with the cutting portion. No securing member adjacent the rake surface of the cutting insert is required to secure the cutting insert to the insert pocket, therefore chip formation during a cutting process goes undisturbed, on the other hand, the cutting insert has only one cutting portion. 
         [0003]    U.S. Pat. No. 5,156,502 discloses a double-ended cutting insert having a cutting portion at each end. The cutting insert is designed so that the cutting tool has an unlimited depth of cut. The cutting insert is securely retained in the insert holder between a pair of jaws. The jaw which abuts the upper surface of the central body portion of the cutting insert may well disturb chip formation of chips cut from a workpiece by the front cutting edge of the cutting insert. 
       SUMMARY OF THE INVENTION 
       [0004]    In accordance with the present invention there is provided an indexable double-ended cutting insert. The cutting insert has a vertical insert symmetry axis V about which the cutting insert has 180° rotational symmetry. The insert symmetry axis V defines an upward to downward direction. 
         [0005]    The cutting insert comprises: 
         [0006]    an insert upper surface, an opposing insert lower surface, two opposing insert side surfaces extending therebetween, and opposing end surfaces extending between the insert upper and lower surfaces and between the insert side surfaces; 
         [0007]    a longitudinally extending body portion having a central portion and two insert cutting portions located at opposite ends of the body portion and formed integrally with the central portion; and 
         [0008]    an insert clamping portion extending downwardly from the central portion in a direction away from the insert upper surface. 
         [0009]    Each insert cutting portion has a rake surface formed in the insert upper surface and a relief surface adjacent the rake surface. The rake and relief surfaces meet at an edge, at least a portion of the edge forms a front cutting edge. 
         [0010]    The insert lower surface comprises a bottom surface which is located on the insert clamping portion and faces in a direction away from the insert upper surface, two insert abutment surfaces, two first locating surfaces and two second locating surfaces. The two first locating surfaces and two insert abutment surfaces are located on the insert clamping portion; each first locating surface and each insert abutment surface extends from the bottom surface towards a respective adjacent second locating surface; and each second locating surface is located on a respective insert cutting portion. Each first locating surface defines an insert locating axis A. In an end view of the cutting insert, the insert locating axes A of the two first locating surfaces form an angle α therebetween. 
         [0011]    According to embodiments of the present invention, in an end view of the cutting insert, each insert locating axis A, associated with a front cutting edge on one half of the cutting insert, is perpendicular to a front cutting edge located on a second half of the cutting insert. 
         [0012]    According to embodiments of the present invention, the insert locating axes A are parallel to each other in a side view of the cutting insert. 
         [0013]    According to embodiments of the present invention, in a side view of the cutting insert the insert symmetry axis V is located midway between, and is parallel to, the insert locating axes A. 
         [0014]    According to embodiments of the present invention, the insert abutment surfaces converge downwardly and are inclined to the insert locating axes A. 
         [0015]    According to embodiments of the present invention, the insert abutment surfaces are flat. 
         [0016]    According to embodiments of the present invention, each insert abutment surface is transverse to an adjacent second locating surface and the bottom surface. 
         [0017]    According to embodiments of the present invention, the relief surfaces are located in respective end surfaces and the front cutting edges are straight and form the angle α therebetween. 
         [0018]    In accordance with the present invention, there is provided an insert holder which comprises: 
         [0019]    two parallel holder side surfaces and a front surface extending between the holder side surfaces; and 
         [0020]    an insert pocket, the insert pocket having a pocket upper portion and a pocket clamping portion defining an upward to downward direction. 
         [0021]    The pocket clamping portion comprises a resilient clamping jaw at a front end of the insert pocket. The clamping jaw has a wedge surface which has a wedge abutment surface; a wedge extension surface located on the wedge surface separates the wedge abutment surface from the holder side surfaces and from an upwardly facing upper locating surface. 
         [0022]    The clamping jaw connects to a rigid base jaw which forms a single integrated piece therewith. The base jaw has a base locating surface which faces opposite the wedge surface. The pocket upper portion comprises a cutting portion housing and the upper locating surface. The cutting portion housing is located rearward of the pocket clamping portion in a side view of the insert holder, and the upper locating surface is located on the clamping jaw. When a cutting insert is securely clamped in the insert pocket, the cutting portion housing accommodates a non-operative cutting portion of the cutting insert and only the upper locating surface, the wedge abutment surface and the base locating surface abut given surfaces on the cutting insert. 
         [0023]    According to embodiments of the present invention, the wedge abutment surface is flat. 
         [0024]    According to embodiments of the present invention, the base locating surface and the wedge abutment surface converge downwardly in a direction away from the pocket upper portion. 
         [0025]    According to embodiments of the present invention, the cutting portion housing has a housing locating surface extending from and transverse to the base locating surface. 
         [0026]    According to embodiments of the present invention, in an end view of the insert holder the base locating axis B and the wedge bisector N are located midway between and are parallel to the holder side surfaces. 
         [0027]    According to embodiments of the present invention, the upper locating surface extends transversely to the wedge surface and to the front surface. 
         [0028]    In accordance with the present invention, there is also provided a cutting tool which comprises the insert holder with the cutting insert clamped therein. The second locating surface associated with an operative cutting portion abuts the upper locating surface of the insert holder; the insert abutment surface associated with the operative cutting portion abuts the wedge abutment surface of the insert holder; and the first locating surface associated with the non-operative cutting portion abuts the base locating surface of the insert holder. 
         [0029]    According to embodiments of the present invention, when the cutting tool performs a machining operation, the second locating surface associated with the non-operative cutting portion abuts the housing locating surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    For a better understanding of the present invention and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which: 
           [0031]      FIG. 1  is an isometric view of an assembled tool cutting portion with a cutting insert secured in an insert pocket according to embodiments of the present invention; 
           [0032]      FIG. 2  is an isometric bottom view of the cutting insert shown in  FIG. 1 ; 
           [0033]      FIG. 3  is an end view of the cutting insert of  FIG. 1 , showing hidden lines; 
           [0034]      FIG. 4  is a side view of the cutting insert of  FIG. 1 ; 
           [0035]      FIG. 5  is a partial isometric top view of the insert pocket of  FIG. 1 ; 
           [0036]      FIG. 6  is a side view of the insert pocket of  FIG. 5 ; 
           [0037]      FIG. 7  is an isometric view of the insert pocket of  FIG. 5 ; 
           [0038]      FIG. 8  is a top view of the tool cutting portion of  FIG. 1 ; 
           [0039]      FIG. 9  is a cross section taken along the line X-X of  FIG. 8 ; 
           [0040]      FIG. 10  is an end view of the tool cutting portion of  FIG. 1 ; 
           [0041]      FIG. 11  is a cross-section taken along the line XI-XI of  FIG. 10 ; 
           [0042]      FIG. 12  is an end view of the tool cutting portion of  FIG. 1  showing hidden lines; and 
           [0043]      FIG. 13  is a side view of the assembled tool cutting portion of  FIG. 1 ; 
       
    
    
       [0044]    It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity, or several physical components may be included in one functional block or element. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0045]    In the following description, various aspects of the present invention will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details presented herein. Furthermore, well-known features may be omitted or simplified in order not to obscure the present invention. 
         [0046]    Reference is made to  FIG. 1 , showing an isometric view of an assembled tool cutting portion  10  of a cutting tool  12  in accordance with embodiments of the invention. The cutting tool  12  my have any required shape. The tool cutting portion  10  includes an insert holder  14  and an indexable double-ended cutting insert  16  releasably retainable in an insert pocket  18  on the insert holder  14 . The insert holder  14  is typically made of metal, such as steel. The cutting insert  16  is typically made of extremely hard and wear-resistant material such as cemented carbide, either by form-pressing or by injection molding and sintering carbide powders in a binder. The cemented carbide may be, for example, tungsten carbide. The cutting insert  16  may be coated or uncoated. 
         [0047]    Reference is made to  FIGS. 2 to 4 . The cutting insert  16  has a longitudinally extending body portion  20 , an insert clamping portion  22  and opposing insert upper and lower surfaces  24 ,  26 . The cutting insert  16  has a 180° rotational symmetry about a vertical insert symmetry axis V which passes through the insert upper and lower surfaces  24 ,  26  and defines an upward to downward direction. The cutting insert  16  has two opposing insert side surfaces  28  extending between the insert upper and lower surfaces  24 ,  26 . The cutting insert  16  has opposing end surfaces  30  extending between the insert upper and lower surfaces  24 ,  26  and between the insert side surfaces  28 . The body portion  20  includes a central portion  32  and two insert cutting portions  34  located at opposite ends of the body portion  20  and formed integrally with the central portion  32 . According to some embodiments, each insert cutting portion  34  includes a rake surface  36  formed in the insert upper surface  24 , a relief surface  38  formed on an associated end surface  30  and a front cutting edge  40  formed by the intersection of the rake surface  36  and the relief surface  38 . In accordance with some embodiments, the cutting insert  16  may also be provided with side cutting edges  42 , formed at the intersection of the insert side surfaces  28  with the rake surface  36 . In accordance with some embodiments, each front cutting edge  40  is straight in an end view of the cutting insert  16 . 
         [0048]    The insert clamping portion  22  extends downwards from the central portion  32 . The insert lower surface  26  includes a bottom surface  44  located on the insert clamping portion  22  and facing in a direction away from the insert upper surface  24 . The insert lower surface  26  further includes two first locating surfaces  46  located on opposite ends of the insert clamping portion  22  and facing opposite directions. Each first locating surface  46  (clamping portion locating surface  46 ) extends from the bottom surface  44  to an adjacent second locating surface  48  (cutting portion locating surface  48 ). According to some embodiments, each first locating surface  46  is transverse to a respective adjacent second locating surface  48 . Each second locating surface  48  is located on a respective insert cutting portion  34  and extends between the first locating surface  46  and an associated end surface  30 . 
         [0049]    The insert lower surface  26  further includes two insert abutment surfaces  50  located on opposite ends of the insert clamping portion  22  and facing opposite directions. Each insert abutment surface  50  extends from the bottom surface  44  towards an adjacent second locating surface  48 . According to some embodiments, each insert abutment surface  50  is transverse to a respective adjacent second locating surface  48  and the bottom surface  44 . The insert abutment surface  50  may be flat. 
         [0050]    According to some embodiments, the first locating surfaces  46  may have a concave form defining an insert locating axis A. The concave form may be V-shaped. According to some embodiments, the second locating surfaces  48  may also have a concave form. The concave form of the second locating surfaces  48  may be V-shaped. The insert locating axes A of the two first locating surfaces  46  are skew to one another and in an end view of the cutting insert  16  (see FIG.  3 ), the insert locating axes A of the two first locating surfaces  46  are transverse to one another and form an angle α therebetween. In a side view of the cutting insert  16  (see  FIG. 4 ) the two insert locating axes A may be parallel to each other. The insert symmetry axis V is located midway between and is parallel to the insert locating axes A (see  FIG. 4 ). The insert abutment surfaces  50  are transverse to each other and to the insert locating axes A. 
         [0051]    As seen in  FIG. 4 , in a side view of the cutting insert  16 , the insert symmetry axis V divides the cutting insert  16  into two halves  90   a ,  90   b . Each half of the cutting insert  16  has an associated insert cutting portion  34  including a front cutting edge  40  having an edge length W 1  (see  FIG. 8 ), and an insert locating axis A. The front cutting edge  40  of one half of the cutting insert  16  and the insert locating axis A of the other half of the cutting insert  16  are perpendicular to each other. As will be described hereinbelow, this geometrical characteristic is essential for the correct orientation of the front cutting edges  40  when the cutting insert  16  is seated in the insert holder  14 . In the end view of the cutting insert  16  (see  FIG. 3 ) the front cutting edges  40  are straight and form the acute angle α therebetween. A longitudinal axis L of the cutting insert  16  passes through midpoints of the front cutting edges  40 . The longitudinal axis L is perpendicular to the insert symmetry axis V and to each front cutting edge  40 . 
         [0052]    Reference is made to  FIGS. 5 to 7 . The insert holder  14  has two parallel holder side surfaces  52  and a front surface  54  which extends between the holder side surfaces  52 . The insert pocket  18  has a pocket upper portion  56  and a pocket clamping portion  58 . The pocket upper portion  56  has an upper portion front end  60  adjacent the front surface  54 . The pocket clamping portion  58  includes a resilient clamping jaw  62  located at a front end of the insert pocket  18 . The pocket clamping portion  58  further includes a rigid base jaw  64  located opposite of the clamping jaw  62 . The clamping jaw  62  connects with the rigid base jaw  64  and forms a single integrated piece therewith. The base jaw  64  has a base locating surface  66  and the clamping jaw  62  has a wedge surface  68  facing the base locating surface  66 . The base locating surface  66  may have a convex form which defines a longitudinal base locating axis B. The convex form may be V-shaped. The base locating surface  66  is formed to mate with the first locating surface  46  of the cutting insert  16 . The convex-concave mating helps to prevent lateral movement of the cutting insert  16  with respect to the insert holder  14 . 
         [0053]    According to some embodiments, the wedge surface  68  has a wedge abutment surface  70 . The wedge abutment surface  70  has a wedge bisector N which equally divides the wedge abutment surface  70  in two. According to embodiments of the invention, the base locating axis B and the wedge bisector N are located midway between, and are parallel to, the holder side surfaces  52  (see  FIG. 12 ). A holder symmetry plane P is defined by the wedge bisector N and the base locating axis B. The wedge abutment surface  70  projects from the wedge surface  68  towards the pocket clamping portion  58 . A wedge extension surface  72  located on the wedge surface  68  separates the wedge abutment surface  70  from the holder side surfaces  52  and an upper locating surface  74 . The wedge abutment surface  70  and the base locating surface  66  converge downwardly, forming a wedge-like clamping aperture  76  between the clamping jaw  62  and the base jaw  64 . 
         [0054]    In a side view of the insert holder  14  (see  FIG. 6 ), the pocket upper portion  56  includes a cutting portion housing  78  located further away from the front surface  54  than the pocket clamping portion  58 . According to some embodiments, the cutting portion housing  78  includes a housing locating surface  80  and a housing rear surface  82  (see  FIG. 7 ). The housing locating surface  80  may have a convex form which may be V-shaped. The housing locating surface  80  extends from adjacent the base locating surface  66  towards the housing rear surface  82 . According to some embodiments, the housing locating surface  80  is transverse to the housing rear surface  82  and the base locating surface  66 . The pocket upper portion  56  further includes the upwardly facing upper locating surface  74  located on the clamping jaw  62 . 
         [0055]    According to some embodiments, the upper locating surface  74  may have a convex form. The convex form may be V-shaped. The upper locating surface  74  is formed to mate with the second locating surface  48  of the cutting insert  16 . The upper locating surface  74  extends from adjacent the wedge surface  68  to the front surface  54  and is transverse to the wedge surface  68  and the front surface  54  in a side view of the insert holder  14  (see  FIG. 6 ). In order to avoid the arrangement of the two sets of convex-concave mating surfaces, from being over constrained, the wedge abutment surface  70  is chosen to be flat and the upper locating surface  74  is chosen to be convex (see  FIGS. 9 and 11 ). 
         [0056]    Reference is made to  FIGS. 1 and 8  to  13 . When the cutting insert  16  is securely clamped in the insert pocket  18  of the insert holder  14 , the body portion  20  is located in the pocket upper portion  56  and the insert clamping portion  22  is located in the pocket clamping portion  58 . The insert clamping portion  22  is wedged in the clamping aperture  76 , between the clamping jaw  62  and the base jaw  64 . One insert cutting portion  34  is located in the cutting portion housing  78  and will be referred to herein as a non-operative cutting portion  34 ′. A second insert cutting portion  34  is located in the upper portion front end  60  and will be referred to herein as an operative cutting portion  34 ″. The front cutting edges  40  of the operative and non-operative cutting portions  34 ″,  34 ′ will be referred to herein as operative and non-operative cutting edges  40 ″,  40 ′ respectively. The operative cutting edges  34 ″ are those cutting edges that participate in cutting operations. 
         [0057]    According to some embodiments, there are three abutment regions at which the cutting insert  16  and the insert pocket  18  engage each other. The first abutment region is formed between a second locating surface  48  associated with the operative insert cutting portion  34  and the upper locating surface  74  (see  FIG. 9 ). The second abutment region is formed between the insert abutment surface  50  and the wedge abutment surface  70  (see  FIG. 11 ). The third abutment region is formed between a first locating surface  46  associated with the non-operative cutting edge  40 ′ and the base locating surface  66  (see  FIG. 11 ). The locating axis A associated with the non-operative insert cutting portion  34  coincides with the base locating axis B. 
         [0058]    In this orientation of the cutting insert  16 , the operative cutting edge  40 ″ is perpendicular to the symmetry plane P (see  FIG. 12 ). The edge length W 1  of the operative cutting edge  40 ″ is the widest feature of the tool cutting portion  10 . Therefore, a groove made in a workpiece by the operative cutting edge  40 ″ will have the same width as the edge length W 1 . In order to obtain an unlimited depth of cut, the non-operative cutting edge  40 ′ must have a different orientation than that of the operative cutting edge  40 ″. This is therefore achieved, since as explained hereinabove, the front cutting edges  40  form the angle α therebetween. The insert symmetry axis V of the cutting insert  16  forms an angle α/2 with the holder symmetry plane P, consequently the non-operative cutting edge  40 ′ is positioned in the required orientation. In a top view of the tool cutting portion  10  (see  FIG. 8 ), the non-operative cutting edge  40 ′ has a non-operative edge length W 2 , where W 2 &lt;W 1 . In other words, this inclination in combination with the geometric relationship between the front cutting edges  40  will ensure that the non-operative cutting edge  40 ′ is sufficiently rotated about the longitudinal axis L so that it does not engage any portion of the groove, or cause jamming of chips cut by the operative cutting edge  40 ″. 
         [0059]    When the assembled tool cutting portion  10  is not machining, the housing locating surface  80  does not abut the cutting insert  16 . However, when the cutting tool  12  is used for turning operations (i.e., machining which involves lateral forces), the cutting insert  16  may shift in the insert pocket  18 , or rotate with respect to the insert symmetry axis V. Upon such shifting, the second locating surface  48 , associated with the non-operative cutting portion  34 ′, may engage the housing locating surface  80 , preventing the cutting insert  16  from further shifting in the insert pocket  18 . 
         [0060]    While the present invention has been described with reference to one or more specific embodiments, the description is intended to be illustrative as a whole and is not to be construed as limiting the invention to the embodiments shown. It is appreciated that various modifications may occur to those skilled in the art that, while not specifically shown herein, are nevertheless within the scope of the invention.