Abstract:
A tool for chip removing machining has an axial channel, the tool being a one-piece unit, the tool having a first end and a second end, the first end comprising cutting edges, the second end forming an end of a shank of the tool. The second end of the shank is cylindrical and the axial channel has a diminishing cross-sectional area in a direction from the second end towards the first end.

Description:
BACKGROUND AND SUMMARY 
   The present application is a continuation of International Application No. PCT/SE2004/001274, filed Sep. 6, 2004, which claims priority to SE 0302452-8, filed Sep. 12, 2003, both of which are incorporated by reference. 

   The present invention relates to a tool for rotary chip removal machining. 
   It is previously known through U.S. Pat. No. 4,850,759 to provide a solution to the problem of providing milling and drilling tools in small dimensions with interchangeable cutting inserts. However in some cases at high rotational speeds, the known tool tends to vibrate and create unwanted patterns or vibrational marks in the work piece. Furthermore, the known tools are relatively expensive. 
   It is desirable to provide a tool that is economically favorable. 
   It is desirable to provide a tool, which allows good cooling. 
   It is desirable to provide a tool in which the flushing channel allows for good flow of flushing medium. 
   It is desirable to provide a tool that allows regrinding. 
   It is desirable to provide a tool in which the flushing channel allows for great freedom in cutting head geometry. 
   According to an aspect of the present invention, a tool for chip removing machining, the tool has an axial channel, the tool being a one-piece unit, the tool having a first end and a second end, the first end comprising cutting edges, the second end forming an end of a shank of the tool, wherein the second end of the shank is cylindrical and the axial channel has a diminishing cross-sectional area in a direction from the second end towards the first end. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Below embodiments of the present invention will be described with reference to the enclosed drawings, wherein  FIG. 1A  shows tool according to the present invention in a side view,  FIG. 1B  shows a top view of the tool in  FIG. 1A  and  FIG. 1C  shows a cross-section according to the line C-C in  FIG. 1A . 
   

   DETAILED DESCRIPTION 
   The embodiment of a tool  10  according to the present invention shown in  FIGS. 1A-1C  comprises a one-piece unit having a cutting head  11 , a waist  12  and a fastening means or shank  13 . The tool comprises a through-going axial or central channel  14 . The channel is adapted for transferring flush medium to cutting edges  15 ,  16  of the cutting head  11 . The channel  14  is configured also to diminish the mass of cemented carbide in the tool  10 . 
   The cutting edges are provided at the end  21  of the tool  10  facing away from the shank  13 , which are given different design depending on the area of application. A preferred shape of the forward end of the tool  10  is shown in detail in  FIG. 1B . The tool  10  is performed in hard material, preferably cemented carbide, and comprises three helical first cutting edges  15  and three second cutting edges  16 , all integral with the tool. The number of major cutting edges may alternatively be one, two or four to six. The first cutting edges  15  preferably lie in a common, imaginary cylinder, which is concentric with the axis CL of rotation of the tool. Each chip flute  17  is concavely formed and extends from a connected second cutting edge  16  at the free end  21  of the tool. The second cutting edge  16  has a radial extension inwards from the imaginary cylinder, whereof one cutting edge, substantially connects to the axis of rotation CL of the tool such that the tool can be able to drill downwards into the work piece. Each pair of cutting edges  15 ,  16  is fed with flush medium via a hole  18 . The three holes  18  are arranged in a ring suitably symmetrically about the axis CL of rotation of the tool. The holes  18  connect to the central channel  14 , which terminates in the area of the other free end  19  of the tool. The channel  14  is of circular cross-section forming several circular spaces of different diameters. At least the second cutting edge  16  intersects an imaginary extension of the circular axial channel  14 , which means that there is provided perforated cemented carbide material axially in front of the channel  14 . The holes  18  intersect the central channel  14 . The circular central channel  14  terminates axially distant from the first free end  21  of the tool  10 . The forward end  14 A of the axial channel  14  comprises material at least partly blocking the axial channel. 
   The outer diameter of the cylindrical shank  13  is designated by (D. The shank encloses a first internal space  14 B, preferably cylindrical, having a largest diameter (A. The diameter (A is 25 to 80% of the outer diameter (D. The first internal space  14 B connects to a first conical transition space  14 C joining a second internal space  14 D. The outer diameter of the cylindrical waist  12  is designated by (d. The waist encloses the second internal space  14 D, preferably cylindrical, having a largest diameter (B. The diameter (B is 25 to 80% of the outer diameter (d. The second internal space  14 D connects to a second conical transition space  14 E joining a third internal space  14 F. The diameter of the third internal space  14 F is smaller than the diameters (A and (B. The axial length of the second conical transition space  14 E is larger than the axial length of the first conical transition space  14 E. The third internal space  14 F ends at the wall  14 A that is perforated by the holes  18  at three positions. The holes  18  are preferably parallel with the axis CL. Thus, the channel  14  comprises three cylindrical spaces  14 B,  14 D,  14 F interconnected by conical steps  14 C,  14 E. Thereby, a through the tool going channel  14  for flush medium has been formed via the portions  14 B- 14 F and  18 . The largest wall thickness of the tool between the envelope surface of the tool and the axial channel  14  is situated closer to the first end  21  than to the second end  19  to minimize deflection. The ratio of the greatest axial length of the tool to the outer diameter (D is for example about 4 to 6. 
   In addition shall be pointed out that the described embodiment relates to milling or drilling tool arrangements, i.e. tool arrangements which rotate about their longitudinal center axes. Milling cutters with small diameters are expected to be the first area of application for the present invention but also drilling tools fall within the scope of the invention. 
   Thus, the present invention provides numerous advantages relative to prior art. The tool is economically favorable since it saves cemented carbide. The tool allows good cooling and flow of flushing medium due to the geometry of the axial channel. The tool allows regrinding. The wall thickness is largest at the waist  12  adjacent the cutting head where the bending moment is greatest. This also allows for great freedom when choosing cutting head geometry. 
   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. 
   The invention is in no way limited to the above-described embodiments but may be freely varied within the limits of the subsequent claims.