Patent Publication Number: US-2005123364-A1

Title: Burnishing burr drill

Description:
RELATED APPLICATIONS  
      This application is a continuation-in-part application of the U.S. patent application Ser. No. 10/384,891, filed on Mar. 10, 2003, now abandoned, the contents of which are herein incorporated by reference. 
    
    
     BACKGROUND OF THE PRESENT INVENTION  
      1. Field of the Present Invention  
      The invention relates to a burnishing Burr drill, and more particularly, to a Burr drill having a plurality of large teeth each having more than one fine teeth on a back thereof. The burnishing Burr drill of the invention therefore is able to drill a hole with a polished wall while keeping a relatively high feed speed.  
      2. Description of Related Arts  
     SUMMARY OF THE PRESENT INVENTION  
      Conventional drills usually have a shank and a head integrally formed thereon. The heads have more than one teeth used for cutting. Sizes of the teeth differ from one to another according to various uses thereof. For example, generally large teeth are used to obtain a high feed speed while small teeth are used for refine. Whenever a fine wall of a hole drilled by large teeth is needed, a fine teeth drill must be used to further work on the hole, which takes time and power.  
      So there are endeavors to find a kind of drill head which is able to both drill a hole at a high feed speed and refine the hole at the same time. The burnishing drill disclosed in U.S. Pat. No. 5,312,208 is such a drill. The drill has a first pair of cutting edges used for getting a high feed speed, and a second and a third pair of cutting edges which is used for refine. However, this drill has three drawbacks. First, the drill only has a pair of cutting edges. This heavily negatively affected a feed speed thereof. In fact, when quantity of cutting edges is reduced as many as two, a high feed speed always cannot be obtained. Secondly, a ratio between a height and width of all cutting edges is too large, which means the cutting edges are too “thin” to have a satisfactory strength. Thirdly, as the second and the third cutting edges are separate and discrete from the first pair of cutting edges, they are especially thin and not able to provide a high product quality.  
      Therefore, the main object of the invention is to provide a burnishing Burr drill with more than two cutting edges which is able to obtain a high feed speed at the same time. Another object of the invention is to provide a burnishing Burr drill a ratio between a height and width of cutting edges of which is much reduced than conventional art and thus has a higher strength.  
      Yet another object is to provide a drill a cutting edges thereof do not separate and discrete from main cutting edges thereof therefore are not so thin that do not have enough strength. And burnishing Burr drill is definitely different with normal drills which are normally used for drilling. The burnishing Burr drill of the invention is normally for grinding and polishing.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a preferred embodiment of the invention.  
       FIG. 2  is a cross-sectional view of a head of the invention as shown in  FIG. 1 .  
       FIG. 3  is a perspective view of another preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      With reference to  FIGS. 1 and 2 , a burnishing Burr drill of the invention is shown. The burnishing Burr drill has a drill head  1  and a shank  2  connected thereto and longitudinally extends downward. The drill head  1  shown in the Figs. is bullet-head shaped. The drill head  1  has more than two, preferably more than 5, large teeth  11  mainly used for cutting and obtaining most feed speed. Each large teeth  111  has a front surface  12  and a back surface  13 . More than one small tooth  131  is formed on the back surface  13  of each large tooth  11 . In use, when the drill head  1  works on a workpeice, the large teeth  11  cut the workpeice material first will define a hole in the workpeice. As the burnishing drill feed forward, the small teeth  131  meet a surface of the hole and further finish a wall of the hole.  
      As shown in  FIG. 3 , the drill head  1  can be made ball-shaped.  
      Although the present invention has been described in detail, it should be understood that various changes, combinations, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as described by the appended claims.