Patent Publication Number: US-2019193226-A1

Title: Method to produce a radial run-out tool as well as a radial run-out tool

Description:
RELATED APPLICATION DATA 
     The present application claims priority under 35 U.S.C § 119(a) to German Patent Application Number 102013218321.6 filed Sep. 12, 2013 which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The invention relates to a method for producing a radial run-out tool, particularly drill or a cutter, comprising a basic body extending in the axial direction, with the basic body having at least two chip grooves as well as a guide chamfer connected to each of the chip grooves, in which a ridge is formed between each of the chip grooves and a radial clearance in the ridge is connected to the guide chamfer, said clearance extending up to the following chip groove. The invention further relates to such type of radial run-out tool, particularly a drill or cutter. 
     EP 1 334 787 B1 discloses such type of radial run-out tool as a drilling tool. The known drill is a solid metal drill with a cutting area connecting to a clamp shaft, with the cutting area housing spiraled chip grooves, which extend up to a drill face. Secondary cutting areas extend along the spiral chip groove, and a guide chamfer is connected to each of the secondary cutting areas in the rotational direction; during operation, the guide chamfer is supported on the inner wall of the borehole and thus ensures guidance for the drill. 
     Such types of solid metal drills are typically produced from a unmachined rod by grinding, in which, in a first process step, the unmachined rod is ground down to a desired nominal ground diameter; in a second process step, the optionally spiraled chip grooves are ground; and finally, and in a third process step, the ridge is ground in order to create radial clearance so that the ridge is some distance away from the borehole wall during the actual drilling process. In addition to this, typically additional grinding steps are provided to generate the desired tip geometry of the drill tip. The three process steps characterized serve to form the cutting area of the radial run-out tool in the axial direction downstream of the drill tip. 
     SUMMARY 
     Starting from this point, the object of the invention was to provide a simplified manufacturing method for such type of radial run-out tool as well as such type of radial run-out tool that is easy to produce. 
     The object is achieved according to the invention by a method with the features of claim  1  as well as by a radial run-out tool with the features of claim  6 . Preferred further embodiments are contained in the respective dependent claims. 
     The radial run-out tool generally extends in the axial direction and is particularly made of solid metal, particularly a solid carbide drill. It has a basic body, in which at least two chip grooves are housed, and a guide chamfer is connected to each of the chip grooves on the circumferential side of the basic body, when it is viewed in the circumferential or rotational direction. A ridge is formed between each of two consecutively positioned chip grooves, and a radial clearance is located in said ridge downstream of the respective guide chamfer. 
     For simplified production of such type of radial run-out tool, particularly a drill or a cutter, it is now provided, in a first process step, for an unmachined rod to be non-concentrically ground such that a radius of the unmachined rod and thus of the basic body varies, depending on the angle, between a maximum radius and a minimum radius. In a second process step, the chip grooves are ground down. All in all, the unmachined rod is ground such that the guide chambers are inevitably formed at the positions with the maximum radius and the radial clearance is likewise inevitably formed based on the non-concentric design. The clearance extends in this case starting from the guided chamfer to the next chip groove. Therefore, during operation, there is a radial clearance between the ridge and an inner wall of a machined workpiece. 
     The particular advantage of this manufacturing method can be seen in that the third grinding step is not required and, in particular, also not intended. Rather, the radial clearance is automatically formed based on the non-concentric cross-sectional geometry. Thus, one manufacturing step as a whole is saved, which leads to cost savings and time savings. 
     The machining of a cutting area following a tool tip thus requires merely the two mentioned process steps; additional grinding steps are not provided for. The two process steps may be carried out essentially in any sequence. It is preferable, however, if the unmachined rod is initially ground non-concentrically before the chip grooves are ground down. 
     In a preferred embodiment, the unmachined rod is ground down, in a first process step, to an elliptical cross-sectional surface. It is generally understood in this case that the basic body tapers continually from the maximum radius to the minimum radius and then continually increases up to a second opposing maximum radius. With this design variant, there are thus exactly two chip grooves, each of which having a guide chamfer. Essentially, the method described here can be transferred to a plurality of geometries, for example those with three or four chip grooves. What is essential in this case is that the radius tapers continually and constantly starting from the maximum radius to the minimum radius. The ridge extends in this case generally along a thoroughly curved, bend- and recess-free circumferential line. Connecting directly to the guide chamfer, the radial clearance increases continuously. The guide chamfer itself thus does not have a uniform radius, as is the case with conventional circular grinding chamfers. Instead, the guide chamfer itself has a relief grind and linear-shaped contact, only when in use and when viewed in the axial direction, with a workpiece wall. 
     According to the elliptical configuration, the minimum radius defines therefore also preferably a small half-axis and a maximum radius defines a large half-axis of the elliptical cross-sectional surface. Thus, it is appropriately provided that the minimum radius is in a range of from 0.75 to 0.98 times, and particularly in a range of from 0.92 to 0.95 times, the maximum radius. This enables sufficient clearance to be achieved on one side and a sufficient support to be achieved in the area of the guide chamfer on the other side. Due to the comparatively minor differences in the two radii, the radius at the guide chamfer is reduced only moderately, which means that a sufficient guide function is ensured. 
     In an appropriate further embodiment, the chip grooves in this case are ground down to extend in a spiral. Correspondingly, the guide chamfers are thus also formed to extend in a spiral. In order to ensure that the guide chamfers are formed at the positions with the maximum radius over the entire cutting area defined by the chip grooves and beyond, when viewed in the rotational direction, the elliptical cross-sectional surface is also formed to extend in a spiral. In this case, it is understood that the maximum radius extends along a spiral line, when viewed in the axial direction. This spiral line is identical to the pattern of the respective guide chamfer in this case. Alternatively, the chip grooves extend in a straight line. 
     In order to produce this non-concentric pattern, a grinding disc is placed in the radial direction toward the next round unmachined rod. The unmachined rod in this case rotates around its center axis. Depending on the angle position, the radial feed position of the grinding disc will then vary such that different radii will form on the unmachined rod depending on the angle. In addition, the radial feed position of the grinding disc will vary, also depending on the axial position of the grinding disc, thus resulting in the desired spiral pattern of the elliptical cross-sectional surface, so that the maximum radius of the ellipse extends in a respective cutting plane along a spiral line. 
     The radial-run out tool is, in particular, a solid carbide drill with a pointy grind. Depending on the requirements and the application purpose, the basic body will have one or more coolant holes, depending on the application area, and is additionally preferably slightly conically tapered starting from the tool tip to a shaft area. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is explained in more detail in the following by means of the figures. The figures show the following in simplified representations: 
         FIG. 1A  a side view of a solid carbide drill with spiral chip grooves according to the prior art; 
         FIG. 1B  a front view of a tool tip of the spiral drill shown in  FIG. 1A ; 
         FIG. 2A  a diagrammed cross-sectional representation of the proportions of such type of drill according to the prior art in the area of a guide chamfer; 
         FIG. 2B  an enlarged representation of the area shown with a circle in  FIG. 2A ; 
         FIG. 3A  a diagrammed cross-sectional representation of the proportions of a drill according to the invention in the area of the guide chamfer; 
         FIG. 3B  an enlarged representation of the area shown with a circle in  FIG. 3A ; 
         FIG. 4  a perspective representation of a non-concentrically ground unmachined rod, which has an elliptical cross-sectional surface that extends in a spiral in the axial direction; 
         FIG. 5A  a view of front cutting plane A-A in  FIG. 4 ; as well as 
         FIG. 5B  a view of cutting plane B-B in  FIG. 4 . 
     
    
    
     Parts having the same effect, having the same reference numbers, are also in the figures. 
     DETAILED DESCRIPTION 
     The solid metal drill  2  shown in  FIG. 1A  is formed as a spiral drill and extends in the axial direction  4  along a center longitudinal axis  5 , which simultaneously also defines a rotational axis. In the rear area, the drill  2  has a clamp shaft  6 , to which a grooved cutting area  8  is connected, which extends to a front-facing tool tip  10 . The drill  2  in this case, as a whole, has a solid carbide basic body  12 , in which chip grooves  14  are ground in the cutting area  8 , with a ridge  15  being formed between each of the cutting grooves. In addition, the basic body  12  has coolant channels  16 . 
     In the exemplary embodiment, the tool tip  10  is ground in the shape of a cone and has two main cutting areas  18 , which are connected to one another via a cross-cutting area. The main cutting areas  18  extend to a radial cutting corner on the outside, to which a secondary cutting area is connected with a guide chamfer  22  formed on the ridge  15  along the respective chip groove  14  extending in the axial direction  4 . During operation, the drill  2  rotates in the rotational direction  24  around its center longitudinal axis  5 . With conventional drills, the guide chamfer  22  is typically formed as a so-called circular grinding chamber; that is, it does not have any radial relief grind and thus no clearance. Therefore, the radius is constant over the entire angle of rotation of the guide chamfer and typically corresponds to a nominal radius to which the unmachined rod is concentrically ground down, in a first process step, with a conventional manufacturing method. 
     A radial clearance  28  is housed in the ridge  15  downstream of the respective guide chamfer  22 , when viewed in the rotational direction  24 . With the conventional manufacturing method, this occurs in a third separate grinding step, after the chip grooves  14  have been placed previously in a second grinding step. 
     These conventional conditions have been diagrammed again for further clarification in  FIGS. 2A and 2B  for the prior art. The dash/dotted circle in  FIG. 2A  shows a circular circumferential line  31 , with a constant radius R. As can be clearly seen again from the representation according to  FIG. 2B , the guide chamfer  22  extends initially precisely on this circular arc line, which results after the first cylindrical grinding step with the conventional method. 
     An exemplary embodiment of the invention will now be explained in greater detail using  FIGS. 3A, 3B, 4, 5A, and 5B . 
     Basically, an unmachined rod  30  is non-concentrically ground, in a first process step, so that an elliptical circumferential line  32  is formed in a respective cross-section of the rod  30 . Accordingly, the radius R varies, that is the distance from the center longitudinal axis  5  to the circumferential side, from a minimum radius R 1  to a maximum radius R 2 . 
     The variation in this case is continual and constant—as is customary with an elliptical cross-section. 
     The deviation of the elliptical circumferential line  32  from the circular circumferential line  31  as results after cylindrical grinding with the prior art can be seen in  FIG. 3A . As can be particularly seen from the enlarged representation of  FIG. 3B , the radius R along the ridge  15  reduces itself continually from the maximum radius R 2 , which defines a nominal radius and simultaneously specifies the position of the guide chamfer  22 , down to the minimum radius R 1 . Depending on how the respective chip groove  14  is formed, that is depending on the angle range over which the chip groove extends, the radius R will continually decrease with respect to the chip groove  14  or it will increase with respect to the chip groove  14 . However, this will not be to the point of the maximum radius R 2 , so that there is assurance that the radial clearance  28  is retained and the ridge  15  will be a certain distance from an interior wall of the workpiece when in use. 
     As is particularly clear from  FIG. 4  in conjunction with  FIGS. 5A and 5B , the unmachined rod  30  serves to form a spiral grooved spiral drill  2 . Accordingly, an elliptical cross-sectional surface  34  of the ground unmachined rod  30  rotates continuously in the axial direction  4  around the center longitudinal axis  5 , so that the maximum radius R 2  or the minimum radius R 1 , when viewed in the axial direction  4 , extends along spiral lines, as this is shown for minimum radius R 1  by a solid line and for maximum radius R 2  by a dotted line in  FIG. 4 .