Abstract:
The present invention relates to a replaceable cutting tip and, more particularly, to such cutting tips attachable to the cutting tip holders by a threaded connection. The cutting tip for a cutting tool includes a working end portion disposed along an axis of the cutting tip and including one or more cutting edges for machining a workpiece, and a mounting portion disposed along the axis of the cutting tip. The mounting portion includes a frustoconical supporting surface tip portion and a frustoconical threaded portion. The present invention also relates to a cutting tool per se.

Description:
BACKGROUND AND SUMMARY  
       [0001]     The present invention relates to cutting tools including replaceable cutting tips and, more particularly, to such cutting tools with the cutting tips attachable to the cutting tip holders by a threaded connection.  
         [0002]     In making threaded connections between two parts, it is possible to permit faster connection of the parts by forming the internal and external threads in a cone or frustoconical shape. In this way, the externally threaded part does not have to be screwed into the internally threaded part from a leading end of the internally threaded part to its final position. Instead, the leading end of the externally threaded part can be inserted into the internally threaded part past internal threads at the leading end of the internally threaded part that define diameters that are larger than the diameter defined by the leading end of the externally threaded part. The leading end of the externally threaded part can be inserted into the internally threaded part up to the point where internal threads begin to contact the external threads. After this point, the externally threaded part is ordinarily turned only a few rotations relative to the internally threaded part before the two parts are in their final relative positions. It is desirable to minimize friction between the internally and externally threaded portions to permit the parts to be quickly turned to their final relative positions.  
         [0003]     It is often extremely important in operations such as machining of metal or other workpieces that the location of a cutting edge of a cutting tool be precisely controlled and controllable. Complex machinery is provided to mill, drill, bore, or otherwise perform shaping operations on workpieces by precisely controlling the location of a cutting tool relative to the workpiece. Cutting tools often include replaceable inserts or cutting heads that are attached to permanent toolholders such as shanks that are moved relative to the workpiece.  
         [0004]     The accuracy of the mounting of the cutting inserts or heads relative to the toolholder is a factor in the accuracy of the operation to be performed on the workpiece. In the case, for example, of a rotating tool, an insert or tool head that is displaced axially relative to a rotating shank to which it is attached can damage the workpiece and may necessitate the rejection of an expensive part. It is therefore desirable to minimize the possibility of movement of an insert or tool head relative to a toolholder. In many tools, threaded connections or portions of threaded connections form axial and/or radial supports or part of a radial and/or axial supporting arrangement for radially and/or axially supporting and positioning a tool head relative to a toolholder. Often, during cutting operations, substantial radial and axial forces are applied to threaded connections between a tool head and a toolholder, which can damage the threads.  
         [0005]     In accordance with an aspect of the present invention, a cutting tip includes a working end portion disposed along an axis of the cutting tip and including one or more cutting edges for machining a workpiece, and a mounting portion disposed along the axis of the cutting tip and including a frustoconical supporting surface tip portion and a frustoconical threaded portion.  
         [0006]     In accordance with another aspect of the present invention, a cutting tool includes a replaceable cutting tip including a working end portion disposed along an axis of the cutting tip and including one or more cutting edges for machining a workpiece, and a mounting portion disposed along the axis of the cutting tool and including a frustoconical supporting surface tip portion and a frustoconical threaded tip portion. The cutting tool also includes a cutting tip holder, the holder including a holder mounting portion including a frustoconical abutment surface holder portion for abutting the frustoconical supporting surface tip portion to position the cutting tip axially and radially in an operating position relative to the cutting tip holder and a frustoconical threaded holder portion for mating with the frustoconical threaded tip portion. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The features and advantages of the present invention are well understood by reading the following detailed description in conjunction with the drawings in which like numerals indicate similar elements and in which:  
         [0008]      FIG. 1  is an exploded, side, partially cross-sectional view of a cutting tool according to an embodiment of the present invention;  
         [0009]      FIG. 2  is a side, cross-sectional view of a portion of an assembled cutting tool according to an embodiment of the present invention;  
         [0010]      FIG. 3  is an exploded, side, partially cross-sectional view of a portion of a cutting tool according to an embodiment of the present invention;  
         [0011]      FIG. 4  is an exploded, side, partially cross-sectional view of a portion of a cutting tool according to an embodiment of the present invention;  
         [0012]      FIG. 5  is an exploded, side, partially cross-sectional view of a portion of a cutting tool according to an embodiment of the present invention;  
         [0013]      FIG. 6  is an exploded, side, partially cross-sectional view of a portion of a cutting tool according to an embodiment of the present invention;  
         [0014]      FIG. 7  is a perspective view of a cutting tool according to an embodiment of the present invention;  
         [0015]      FIG. 8  is a schematic side view of an externally threaded portion of a cutting tool according to an embodiment of the present invention;  
         [0016]      FIG. 9  is a schematic side view of an externally threaded portion of a cutting tool according to an embodiment of the present invention;  
         [0017]      FIG. 10  is a schematic side view of an internally threaded portion of a cutting tool according to an embodiment of the present invention; and  
         [0018]      FIG. 11  is a schematic side view of an internally threaded portion of a cutting tool according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0019]     A cutting tool  21  according to an embodiment of the present invention is shown in  FIG. 1 . The cutting tool  21  includes a replaceable cutting tip  23  including a working end portion  25  including a first end  27  and a second end  29 . The replaceable cutting tip  23  is made of hard material, such as for example cemented carbide, e.g. tungsten carbide (WC) sintered together with cobalt (Co). The replaceable cutting tip  23  is molded or pressed and/or ground. The working end portion  25  is disposed along an axis A of the cutting tip  21  and includes one or more cutting edges  31  proximate the first end  27  for machining a workpiece (not shown). The cutting tip  23  also includes a mounting portion  33  disposed along the axis A of the cutting tool  21 . The mounting portion  33  includes a frustoconical supporting surface tip portion  35  and a frustoconical threaded tip portion  37 .  
         [0020]     The cutting tool  21  also includes a cutting tip holder  39 . The holder  39  includes a holder mounting portion  41  including a frustoconical abutment surface holder portion  43  for abutting the frustoconical supporting surface tip portion  35  to support and position the cutting tip axially and radially in an operating position ( FIG. 2 ) relative to the cutting tip holder  39  and a frustoconical threaded holder portion  45  for mating with the frustoconical threaded tip portion  37 .  
         [0021]     Ordinarily, when, as seen in  FIG. 2 , the cutting tip  23  is positioned in the operating position relative to the cutting tip holder  39 , a space or volume V 1  is defined between a first imaginary frustoconical surface S 1  defined by radially outermost portions  47  of the frustoconical threaded tip portion  37  and a second imaginary frustoconical surface S 2  defined by radially outermost portions  49  of the frustoconical threaded holder portion  45 . Ordinarily, when the cutting tip  23  is positioned in the operating position relative to the cutting tip holder  39 , a space or volume V 2  is also or alternatively defined between a third imaginary frustoconical surface S 3  defined by radially innermost portions  51  of the frustoconical threaded tip portions  37  and a fourth imaginary frustoconical surface S 4  defined by radially innermost portions  53  of the frustoconical threaded holder portion  45 .  
         [0022]     In all or substantially all kinds of threaded connections, there is some minimal space between innermost and outermost thread surfaces. Compared with the usual spacing between innermost and outermost thread surfaces, the spaces V 1  and/or V 2  are large enough such that, by providing the space V 1  and/or V 2 , there is reduced risk of damage to the extreme inner and outer portions of the threads when a force is exerted on the cutting tip or the cutting tip holder, and friction between the extreme inner and outer portions of the threads is reduced or eliminated. Radial forces on the cutting tip  23  can be borne entirely or substantially entirely by the frustoconical abutment surface holder portion  43  and the frustoconical supporting surface tip portion  35  instead of by the radially outermost and innermost portions of the threads. Axial forces on the cutting tip  23  can also be borne entirely or substantially entirely by the frustoconical abutment surface holder portion  43  and the frustoconical supporting surface tip portion  35  instead of by the threads, although some axial force on the threads may be desirable to hold the cutting tip securely relative to the cutting tip holder  39 .  
         [0023]      FIGS. 1 and 2  show the frustoconical supporting surface tip portion  35  and the frustoconical threaded tip portion  37  each having the same cone angle, just as the frustoconical abutment surface holder portion  43  and the frustoconical threaded holder portion  45  can also have the same cone angle. However, the frustoconical supporting surface tip portion and the frustoconical threaded tip portion, as well as the frustoconical abutment surface holder portion and the frustoconical threaded holder portion, can have the different cone angles ( FIGS. 8-11 ). For example, the threaded portion of the tip or holder can have a greater or a lesser cone angle than the supporting or abutment surface portions of the tip or holder, respectively.  
         [0024]     In  FIGS. 1 and 2 , the first imaginary frustoconical surface S 1  defined by the radially outermost portions  47  of the frustoconical threaded tip portion  37  may be disposed radially inwardly of the imaginary frustoconical surface S 5  extending from the frustoconical supporting surface tip portion  35 . The largest diameter of the frustoconical threaded tip portion  37  is disposed radially inwardly of the closest portion of the frustoconical supporting surface tip portion  35 . In  FIGS. 1 and 2 , a cutting tip  23  with external threads, i.e., the threads face away from the axis A, and a cutting tip holder  39  with internal threads, i.e., the threads face toward the axis A, is shown. However, as seen in  FIG. 3 , a similar result can be achieved where the tool  121  may have a cutting tip  123  that may have internal threads  137  and the cutting tip holder  139  may have external threads  145 . Thus, in  FIG. 3 , a first imaginary frustoconical surface S 6  defined by radially outermost portions  147  of the frustoconical threaded tip portion  137  may be disposed radially outwardly of a second imaginary frustoconical surface S 7  extending from the frustoconical supporting surface tip portion  135 . A largest diameter of the frustoconical threaded tip portion  137  is disposed radially outwardly of the frustoconical supporting surface tip portion  135 .  
         [0025]     A variety of different permutations involving switching between internally or externally threaded portions on the cutting tip or the cutting tip holder are possible. For example, if desired, instead of the arrangement shown in  FIG. 3 , an internally threaded cutting tip may have the outermost portions of its threaded portion define an imaginary surface even with the imaginary surface extending from the frustoconical supporting surface while the externally threaded cutting tip holder may have a largest diameter portions of its threaded portion be disposed radially inward of a closest portion of the frustoconical abutment surface. Also, an internally threaded cutting tip may have a largest diameter portion of its threaded portion be disposed radially outward of a closest portion of the frustoconical supporting surface while the externally threaded cutting tip holder may have a largest diameter portion of its threaded portion  145  define an imaginary surface that is radially inward of a closest portion of the frustoconical abutment surface  143  as shown in phantom in  FIG. 3 .  
         [0026]     Analogous variations can be provided when the cutting tip has external threads and the cutting tip holder has internal threads. For example,  FIG. 4  shows a tool  221  with a cutting tip  223  having an externally threaded tip portion  237  and a supporting surface tip portion  235  and a cutting tip holder  239  having an internally threaded holder portion  245  and an abutment surface holder portion  243 . Here, an imaginary surface S 8  defined by radially outermost portions  249  of the internally threaded holder portion  245  is radially outward of an imaginary surface S 9  extending from the abutment surface holder portion  243 . A largest diameter portion of the internally threaded holder portion  245  is radially outward of a closest portion of the abutment surface holder portion  243 .  
         [0027]      FIG. 5  shows a tool  321  with a cutting tip  323  having an externally threaded tip portion  337  and a supporting surface tip portion  335  and a cutting tip holder  339  having an internally threaded holder portion  345  and an abutment surface holder portion  343 . Here, an imaginary surface S 10  defined by radially outermost portions  349  of the internally threaded holder portion  345  may be radially outward of an imaginary surface S 11  extending from the abutment surface holder portion  343 . A largest diameter portion of the internally threaded holder portion  345  is radially outward of a closest portion of the abutment surface holder portion  343 . Also, an imaginary surface S 12  defined by radially outermost portions  347  of the frustoconical threaded tip portion  337  may be radially inward of an imaginary surface S 13  extending from the supporting surface tip portion  335 . A largest diameter portion of the externally threaded tip portion  337  is radially inward of a closest portion of the supporting surface tip portion  335 .  
         [0028]     In the embodiments seen in  FIGS. 1-2 , the frustoconical supporting surface tip portion  35  is closer to the first end  27  of the working end portion  25  than the frustoconical threaded tip portion  37 . This is also true in the embodiments seen in  FIGS. 3-5 . However, if desired, as seen in  FIG. 6 , a frustoconical supporting surface tip portion  435  may be farther from the first end  427  of the working end portion  425  than the frustoconical threaded tip portion  437 . In the tool  421  having a frustoconical supporting surface tip portion  435  farther from the first end  427  of the working end portion  425  than the frustoconical threaded tip portion  437 , an imaginary surface S 14  defined by radially outermost portions  447  of the frustoconical threaded tip portion  437  may be radially inward of an imaginary surface S 15  extending from the supporting surface tip portion  435 . The smallest diameter portion of the frustoconical threaded tip portion  437  is disposed radially inward of the closest portion of the supporting surface tip portion  435 .  
         [0029]     In other embodiments, a tool with a frustoconical supporting surface tip portion farther from the first end of the working portion of the tool than the frustoconical threaded tip portion can vary in much the same way that the tools with the frustoconical supporting surface tip portion closer to the first end of the working portion of the tool than the frustoconical threaded tip portion as in the embodiments discussed in  FIGS. 1-5 . In other words, the largest diameter of internal threads of the cutting tip holder may be radially outside of the closest portion of the abutment surface of the cutting tip holder; the largest diameter of internal threads of the cutting tip may be radially outside of the closest portion of the supporting surface of the cutting tip; the largest diameter of external threads of the cutting tip holder may be radially inside the closest portion of the abutment surface of the cutting tip holder; the largest diameter of external threads of the cutting tip may be radially inside the closest portion of the supporting surface of the cutting tip, etc.  
         [0030]     Turning, specifically, to the cutting tip, as seen in  FIGS. 1 and 2 , a cutting tip  21  can include a non-circular surface portion  55 . The non-circular surface portion  55  may be useful for securing the cutting tip  23  to the cutting tip holder  39  by means of a tool such as a wrench and the non-circular surface may include, for example, a plurality of flat surfaces  57 , such as a hexagon.  
         [0031]     The cone angle(s) of the supporting surface  35  and the threaded portion  37  may be the same or different. Ordinarily, the cone angle(s) will be greater than or equal to 15° and less than or equal to 30°.  
         [0032]     As seen in  FIGS. 2 and 7 , the cutting tip  23  may include one or more flushing channels  59  extending through the cutting tip from a first axial end of the cutting tip to a second axial end of the cutting tip. The cutting tip holder  39  may include one or more flushing channels  61  communicating with the flushing channel  59  in the cutting tip  23 . Lubricant or coolant may be introduced to the point where the cutting tip  23  contacts a workpiece through the flushing channels  59  and  61 .  
         [0033]     In the embodiments described thus far, real and imaginary frustoconical surfaces have been described as being “radially inward” or “radially outward” of other real or imaginary frustoconical surfaces. In some cases, however, such as where a cone angle of an internally or externally threaded portion is less than or greater than the cone angle of a supporting or abutment surface portion as shown in  FIGS. 8-11  the imaginary surface IST extending from the outermost portions of the threaded portion T will intersect the abutment or supporting surface SS (or the imaginary surface ISS extending from the abutment or supporting surface) so that part of the imaginary extension IST from the threaded portion T is radially outside of the abutment or supporting surface SS or the imaginary surface ISS of the abutment or supporting surface, and part of the imaginary extension IST from the threaded portion T is radially inside of the abutment or supporting surface SS or the imaginary surface ISS of the abutment or supporting surface. In  FIGS. 8 and 9 , showing externally threaded components, the largest diameter DT of the threaded portion T is smaller than the smallest diameter DS of the closest portion of the abutment or supporting surface SS, i.e., more than merely a change of cone angle. In  FIGS. 10 and 11 , showing internally threaded components, the largest diameter DT of the threaded portion T is larger than the smallest diameter DS of the closest portion of the abutment or supporting surface SS, i.e., more than merely a change of cone angle. The internally and externally threaded components intended to mate with the externally and internally threaded components with radially offset threaded and abutment or supporting surfaces of  FIGS. 8-11  may but need not also have radial offsets between threaded and supporting and abutment surfaces.  
         [0034]     In the present application, the use of terms such as “including” is open-ended and is intended to have the same meaning as terms such as “comprising” and not preclude the presence of other structure, material, or acts. Similarly, though the use of terms such as “can” or “may” is intended to be open-ended and to reflect that structure, material, or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or acts are presently considered to be essential, they are identified as such.  
         [0035]     While this invention has been illustrated and described in accordance with a preferred embodiment, it is recognized that variations and changes may be made therein without departing from the invention as set forth in the claims.