Abstract:
A drill bit for cutting successively larger holes in a substrate includes a conically-shaped body having first and second cutting flutes extending along the length of the body. The first cutting flute includes a first cutting edge and the second cutting flute includes a second cutting edge. The first and second cutting edges are offset relative to each other to create a cutting angle adapted to reduce chatter.

Description:
[0001]    This application claims the benefit of Provisional Application No. 61/438,006 filed on Jan. 31, 2011. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates generally to a drill bit, and more particularly to a drill bit designed to create successively larger holes in a substrate. 
         [0003]    Having the ability to create various sized holes with a single drill bit is advantageous in that it eliminates the need to use multiple drills or to constantly change out drill bits. As a result, cone-shaped drill bits were designed. The cone-shaped drill bits include at least one cutting edge and allow the user to start with a small hole and gradually increase the diameter of the hole by increasing the depth of the drill bit within the substrate being drilled. 
         [0004]    When a specific diameter of hole is desired, a user must be careful to control the depth of the cone-shaped drill bits so that the diameter of the hole is not made too big. This is particularly true of cone-shaped bits that have a smooth outer surface, such as that shown in  FIG. 1 . 
         [0005]    As a result, drill bits, like that shown in  FIG. 2 , were designed to address the problems of depth and diameter. As illustrated, the drill bit includes a plurality of steps that help a user control the depth of the drill bit in a substrate. In use, a user starts the drill bit into a substrate and progresses through the steps until the desired hole diameter is achieved. 
         [0006]    Currently, these cone-shaped drill bits are available with a single cutting flute, as shown in  FIG. 3 , or a pair of diametrically opposed cutting flutes, shown in  FIG. 4 . Both types of drill bits have their advantages and disadvantages. For example, the drill bit of  FIG. 3  is known to provide a very smooth cutting operation, but unfortunately, is also very slow due to the single cutting flute. The drill bit of  FIG. 4  is known to provide faster cutting performance than the drill bit of  FIG. 3 , but unfortunately, is known to have excessive amounts of chatter, thereby making the drill bit difficult to control. As a result, users are often forced to choose between the speed of a dual flute drill bit or the control of the single flute drill bit. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    Accordingly, there is a need for a multi-flute, cone-shaped drill bit that provides the fast cutting performance of the dual flute drill bit and the smooth operation of the single flute drill bit. 
         [0008]    According to one aspect of the present invention, a drill bit for cutting successively larger holes in a substrate includes a conically-shaped body having first and second cutting flutes extending along the length of the body. The first cutting flute includes a first cutting edge and the second cutting flute includes a second cutting edge. The first and second cutting edges are offset relative to each other to create a cutting angle adapted to reduce chatter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The subject matter that is regarded as the invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which: 
           [0010]      FIG. 1  shows a prior art cone-shaped drill bit having a smooth outer surface; 
           [0011]      FIG. 2  shows a prior art cone-shaped drill bit having steps on its outer surface; 
           [0012]      FIG. 3  is a prior art single flute, cone-shaped drill bit; 
           [0013]      FIG. 4  is a prior art dual flute, cone-shaped drill bit; 
           [0014]      FIG. 5  shows a prior art dual flute, cone-shaped drill bit; 
           [0015]      FIG. 6  is a top view of a multi-flute, cone-shaped drill bit according to an embodiment of the invention; 
           [0016]      FIG. 7  is a bottom view of the multi-flute, cone-shaped drill bit of  FIG. 6 ; 
           [0017]      FIG. 8  is a side elevation of the multi-flute, cone-shaped drill bit of  FIG. 6 ; 
           [0018]      FIG. 9  is a side elevation of a multi-spiral flute, cone-shaped drill bit according to an embodiment of the invention; and 
           [0019]      FIG. 10  is a top view of the drill bit of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Referring to  FIGS. 6-8 , a multi-flute, cone-shaped drill bit according to an embodiment of the invention is shown generally at  10 . As shown, the drill bit  10  includes a plurality of steps  11 , increasing in diameter along the length of the drill bit  10  from the tip  15  of the drill bit  10  to the shank  18  of the drill bit  10 , for controlling the depth and diameter of a hole being drilled in a substrate and a pair of cutting flutes  12  and  13 , running along the length of the drill bit  10  for cutting a hole into a substrate. As shown, the flutes  12  and  13  are disposed at angles between  2  and  7  degrees off parallel to the drill bit&#39;s axis,  FIG. 8 . It should be appreciated that while only two cutting flutes are shown, the drill bit  10  may have additional cutting flutes. It should also be appreciated that the flutes  12  and  13  may be disposed at various angles relative to the axis of the drill bit  10 . It should be appreciated that the invention works with smooth outer surface bits as well, such as those in  FIG. 1 . 
         [0021]    Unlike prior art cone-shaped drill bits having two cutting flutes, shown in  FIG. 5 , the drill bit  10  does not dispose the cutting flutes  12  and  13  in a 180 degree spaced-apart, diametrically opposed configuration, resulting in the cutting flutes being positioned on opposite sides of the drill bit. Instead, the cutting flutes  12  and  13  are disposed on the same side of the drill bit  10 , as illustrated in  FIGS. 6 and 7 . The spacing of the cutting flutes  12  and  13  may be spaced-apart between 30 and 179 degrees, depending on the geometry of the flute—cutting edge combination. As shown in  FIG. 7 , the flutes  12  and  13  are spaced 160-170 degrees apart and cutting edges  14  and  16  have a cutting angle relative to center of about 5 to 20 degrees. It should be appreciated that other spacing/cutting angle combinations may be used. 
         [0022]    It was found through testing that the diametrically opposed, 180 degree spacing caused the chatter associated with dual cutting flute drill bits. By arranging the cutting edges  14  and  16  of the flutes  12  and  13  on the same side of the drill bit in an offsetting geometry, the chattering associated with dual cutting flute drill bits could be significantly reduced or eliminated. As a result, the drill bit  10  allows a user to have the cutting performance of a dual flute drill bit and the control of a single flute drill bit. 
         [0023]    As shown in  FIG. 7 , cutting edge  14  is preferably rotated 10-20 degrees relative to cutting edge  16 . It should be appreciated that only one of the cutting edges may be rotated or that both cutting edges may be rotated so that an angle of 10-20 degrees is achieved between cutting edges  14  and  16 . It should also be appreciated that additional rotation angles may be used to reduce chatter. 
         [0024]    Referring to  FIGS. 9 and 10 , a drill bit according to an embodiment of the invention is shown generally at reference numeral  100 . Like drill bit  10 , drill bit  100  includes steps  111  and a pair of cutting flutes  112  and  113 . The cutting flutes  112  and  113  are spiral-type flutes that wrap around the drill bit  100  as they run the length of the drill bit  100 . Like drill bit  10 , the flutes  112  and  113  are disposed in a spaced-apart relation on the same side of the drill bit  100  to significantly eliminate the chatter associated with dual cutting spiral flute drill bits that have a 180 degree spaced-apart, diametrically opposed configuration. The spacing of the spiral cutting flutes  112  and  113  may be spaced-apart between 30 and 179 degrees, depending on the geometry of the flute—cutting edge combination. 
         [0025]    The foregoing has described a drill bit for creating successively larger holes in a substrate. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention. Accordingly, the foregoing description of the preferred embodiment of the invention and the best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation.