Abstract:
A production method for an insertion end, especially for an insertion end of a drilling, chiseling or boring tool, including the following steps: a longitudinal groove is formed in the outer surface of a preferably cylindrical end piece of a blank, whereby the longitudinal groove acquires an open end section on a front face of the end piece. The outer surface of the end piece is surrounded by a die tool that engages into the longitudinal groove outside of its open end section. The open end section is closed in that the surrounded end piece is compressed by means of a stamp acting on the front face. The segmented, multi-component die tool preferably lies flush against the outer surface of the end piece outside of the longitudinal grooves.

Description:
[0001]    This claims the benefit of German patent application DE 10 2010 002 167.9, filed Feb. 22, 2010 and hereby incorporated by reference herein. 
         [0002]    The present invention relates to a production method for an insertion end, especially for an insertion end of a drilling, chiseling or boring tool. 
       BACKGROUND 
       [0003]    German patent DE 3745046 C discloses an insertion end commonly used in modern drills. This essentially cylindrical insertion end has two closed longitudinal grooves situated across from each other. Latching elements of a tool-receiving socket can engage into the closed longitudinal grooves and secure the drill bit so that it cannot fall out of the tool-receiving socket. The insertion end also has one or more longitudinal grooves that are open on one side. One axial, open end of the open longitudinal grove is flush with the front face of the insertion end. The insertion end can be pushed by means of a rotary catch that is located on the tool-receiving socket and that intermeshes into the open longitudinal groove. 
       SUMMARY OF THE INVENTION 
       [0004]    It is an object of the present invention to provide a production method for an insertion end, especially for an insertion end of a cutting, for instance, drilling, chiseling or boring tool, comprising the following steps: a longitudinal groove is formed in the outer surface of a preferably cylindrical end piece of a blank, whereby the longitudinal groove acquires an open end section on a front face of the end piece. The outer surface of the end piece is surrounded by a die tool that engages into the longitudinal groove away from, i.e. outside, of its open end section. The open end section is closed in that the surrounded end piece is compressed by means of a stamp acting on the front face. The segmented, multi-component die tool preferably lies flush against the outer surface of the end piece outside of the longitudinal grooves around the entire circumference, preferably along the entire axial extension of the end piece. 
         [0005]    With the method, the closed longitudinal grooves that serve to lock a drilling, chiseling or boring tool can be produced without the need for cutting process steps. The surrounding die tool acquires the shape of the longitudinal groove, up to its end section. During the compression, which acts onto the free, relatively large front face in the axial direction, sufficient material of the end piece can be pushed in the radial direction to close off the longitudinal groove in spite of the massive form of the blank. 
         [0006]    The die tool can engage into the longitudinal groove with a molded part, whereby this molded part is shorter than the longitudinal groove. Moreover, the molded part can completely fill the longitudinal groove with a positive fit, up to the open end section. 
         [0007]    In one embodiment of the production method, an additional longitudinal groove having an open end section on the front face is formed in the outer surface. The die tool engages into the additional longitudinal groove, whereby the die tool completely fills the additional longitudinal groove with a molded part. The additional longitudinal groove is preferably formed along with the longitudinal groove in one process step, for instance, by means of extrusion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The description that follows explains the invention on the basis of figures and embodiments provided by way of examples. The figures show the following: 
           [0009]      FIG. 1  a drill bit; 
           [0010]      FIG. 2  a blank; 
           [0011]      FIG. 3  the blank with stamped longitudinal grooves; 
           [0012]      FIG. 4  a cross section through the blank of  FIG. 3  along the plane IV-IV; 
           [0013]      FIG. 5  a longitudinal section of a die tool with an inserted blank from  FIG. 3 ; 
           [0014]      FIG. 6  like  FIG. 5 , but rotated by 90° around the axis; 
           [0015]      FIG. 7  cross section in the plane VII-VII of  FIG. 5 ; 
           [0016]      FIG. 8  cross section in the plane VIII-VIII of  FIG. 5 ; 
           [0017]      FIG. 9  stamping die in action; 
           [0018]      FIG. 10  cross section through the stamping die in the plane X-X of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The same or functionally equivalent elements are designated by the same reference numerals in the figures unless otherwise indicated. 
         [0020]      FIG. 1  shows an example of a drill bit  10  that is especially suited for boring work to break stone or construction materials. The drill bit  10  has a shank  11  which, by way of an example, is shaped in the form of a spiral. There is a drilling head  12  at one end of the shank  11 . Whereas the shank  11  is made of metal, the drilling head  12  can be made of a hard metal (carbide) to perform more demanding breaking work. An insertion end  13  is formed at the other end of the shank  11 . As will be explained below, the shank  11  and the insertion end  13  can be made of the same grade of steel and are manufactured out of one blank  14 . 
         [0021]    The insertion end  13  is preferably based on a cylindrical base body. Two closed longitudinal grooves  16  and two longitudinal grooves  17  that are open on one side are formed in the outer surface  15  of the insertion end  13 . The longest extension of each of the longitudinal grooves  16 ,  17  is oriented parallel to an axis  18  of the insertion end  13 . The longitudinal groove  17  that is open on one side extends all the way to a front face  19  of the insertion end  13 , as a result of which one end section  20  of the open longitudinal groove  17  is not surrounded by any material of the insertion end  13  in the axial direction  21 , that is to say, it is open in the axial direction  21 . The other axial end section  22  of the open longitudinal groove  17  is preferably limited, i.e. closed, in the axial direction  21  by material of the insertion end  13 . The axial end sections  23 ,  24  of the closed longitudinal groove  16  are both closed and surrounded by material of the insertion end  13  in the axial direction. The number and angular arrangement of the longitudinal grooves  16 ,  17  are only indicated by way of example; in particular, the number of longitudinal grooves  17  can be either greater or smaller. 
         [0022]    The longitudinal grooves  17  that are open on one side and the closed longitudinal grooves  16  are produced without cutting process steps such as, for instance, milling. 
         [0023]    The starting point for the drill bit  10  can be a cylindrical blank  14 . This blank  14  is cut, for example, from a steel wire having a suitable diameter. The diameter of the steel wire preferably matches the largest diameter of the drill bit  10  that is to be manufactured. In the example shown, the diameter is based on the diameter of the insertion end  13 , which is greater than the diameter of the shank  11 . In a non-cutting forming process, the section  25  of the blank  14  for the shank  11  is reduced to the requisite diameter, for instance, by means of extrusion or rolling. The formed blank now has an end piece  26  that forms the base body for the later insertion end  13  and for the typically much longer section  25  for the later shank  11  ( FIG. 2 ). The diameter of the end piece  26  can be slightly adjusted if this is necessary, for example, for calibration purposes. The diameter of the end piece  26  can be greater than 1 cm, for example, 1.7 cm. If the diameter of the shank  11  in the case of a different drill bit is greater than that of the insertion end  13 , the diameter of the blank  14  is reduced accordingly to the diameter of the insertion end  13 . 
         [0024]    Extrusion is employed to form first longitudinal grooves  27  in the end piece  26  of the blank  14  as well as second longitudinal grooves  28  in the outer surface  33 . During the extrusion process, the end piece  26  is extruded through an annular die starting with a front face  29 . In this process, the contour of the inside of the annular die is replicated on the end piece  26 , and the open longitudinal grooves  27 ,  28  are formed to correspond to the appropriately selected contour. The longitudinal grooves  27 ,  28  can be formed together with a single annular die or else consecutively with two or more annular dies. The formed blank  14  is shown in a side view ( FIG. 3 ) and in a cross section in the plane IV-IV perpendicular to the axis  18  ( FIG. 4 ). All of the longitudinal grooves  27 ,  28  extend all the way to an exposed front face  29  of the end piece  26 , as a result of which they acquire an open end section  30 . The longitudinal grooves  27 ,  28  can have various cross sections and be of a length along the axis  18  that differs from the one shown. 
         [0025]    The blank  14  with the longitudinal grooves  27 ,  28  is placed into a segmented or multi-component die tool  31 .  FIGS. 5 and 6  show longitudinal sections through the die tool  31  that are rotated with the inserted blank  14  by 90° relative to each other around the axis  18 .  FIGS. 7 and 8  show two cross sections through the die tool  31  and through the blank  14  perpendicular to the axis  18  relative to  FIG. 5  in different axial positions in the planes VII-VII and VIII-VIII, respectively. 
         [0026]    The die tool  31  preferably has several segments  32  that are placed onto the outer surface  26 ′ of the end piece  26  and that surround the end piece  26  like a ring so as to be flush with its outer surface  26 ′. Preferably, the end piece  26  is completely surrounded along its axial extension by the segments  32 . 
         [0027]    Preferably, the die tool  31  surrounds the end piece  26  or the blank  14  in the axial direction as well. The inner contour  33  of the segments  32  can be essentially hollow-cylindrical, from which first molded parts  34  and molded parts  35  project inwards. The molded parts  34 ,  35  are adapted to the shape of the longitudinal grooves  27 ,  28  in such a way that they can completely engage into the longitudinal grooves  27 ,  28 , while the inner contour  33  lies flush on the outer surface  26 ′ of the end piece  26 . The molded parts  34 ,  35  are elongated along the axis  18  and their cross section can match the cross section of the longitudinal grooves  27 ,  28 . 
         [0028]    The first molded part  34  leaves free the open, axial end section  30  of the first longitudinal groove  27  (see  FIG. 7 ). The end section  30  remains free, for example, over an axial length in the range from 5 mm to 15 mm and preferably over the entire cross section of the longitudinal groove  27 . The other sections of the longitudinal groove  27  can be completely filled by the first molded part  34 . 
         [0029]    The second molded part  35 , in contrast to the first molded part  34 , fills the open, axial end section  30  of the second longitudinal groove  28 . Preferably, the second molded part  35  completely fills the second longitudinal groove  28 , as a result of which the side surfaces of the second molded part  35  lie on the side surfaces of the longitudinal groove  28  with a positive fit. For this purpose, the length of the second molded part  35  can be of at least the same length as the second longitudinal groove  28 , whereby the length along the axis  18  is ascertained. Preference is given to a second molded part  38  that extends beyond the front face  19  along the axis  18 , for instance, the second molded part  35  is longer than the second longitudinal groove  28 . 
         [0030]    A stamping die  36  is pressed onto the exposed front face  29  of the end piece  26  ( FIG. 9 ).  FIG. 10  shows a cross section of the stamping die relative to the axis  18 . In one embodiment, the stamping die  36 , as depicted in  FIG. 8 , has a plane or concave stamping surface  37 . This stamping surface  37  exerts a uniform pressure over the front face  29  along the axis  18 . The applied pressure lies in the range from 10,000 bar to 100,000 bar. The end piece  26  is compressed. Since the circumference of the end piece  26  is surrounded by the die tool  31 , the material cannot escape the pressure and yield in the radial direction. The hollow space formed by the end section  30  (e.g. shown in  FIG. 5 ) of the first longitudinal groove  27 , which is not filled by the first molded part  34 , allows the displaced material to be accommodated. The filling of the end section  30  closes the first longitudinal groove  27  that had previously been open on one side. The second longitudinal groove  28 , in contrast, remains open, since its end section  30  is filled by the second molded part  35 . 
         [0031]    The stamping die  36  can have longitudinal grooves  37  whose angular position and cross section essentially match the cross section of the second longitudinal grooves  28 . The projecting second molded parts  35  can engage into the longitudinal grooves  37  of the stamping die  36  when this stamping die  36  is pressed against the front face  29 . 
         [0032]    The processed blank  14  has an insertion end  13  that now forms at least one closed longitudinal groove  16  consisting of the first longitudinal groove  27 , filled in at one end, and an open longitudinal groove  17  consisting of the second longitudinal groove  28 . The processed blank  14  can be further processed. The shank  11  can be shaped, for example, by rolling, cutting or forging to form a spiral. A drilling head  12  is placed onto the shank  11  and attached by soldering or welding.