Abstract:
The cutout bit includes a first bit segment configured to be free of flutes. The cutout bit also includes a second bit segment extending from the first bit segment at a first location. Moreover, the cutout bit includes a third bit segment extending from the second bit segment and terminating in a tip. In addition, the cutout bit includes a first flute extending along only the second bit segment. The cutout bit also includes a second flute extending along both the second bit segment and the third bit segment. The second flute extends from the first location to the tip.

Description:
BACKGROUND  
       [0001]     This invention relates to the field of cutout bits for use with rotary tools. During a construction project it may be desirable to create large wall areas with drywall. To efficiently perform this task, large drywall panels are initially secured to wood studs and/or other supporting structure thereby covering planned openings in the large wall areas such as those for electrical outlet boxes and window and door frames. Thereafter, openings are cut in the large drywall panels to expose the electrical outlet boxes, window and door frames, and/or other underlying structures. The underlying structures typically provide templates or guides for cutting the corresponding openings in the drywall. Indeed, a drywall cutting tool is lightly urged against the peripheries of the underlying structures while maneuvering the cutting tool therearound to create the openings. This results in time savings when compared to creating such openings in the large drywall panels prior to securing the drywall to the support structure.  
         [0002]     A conventional twist drill bit typically will not move smoothly around the periphery of an underlying structure; if guided against the structure it will typically abrade or cut into the structure, thereby undesirably dulling itself and marring the underlying structure. Additionally, a conventional twist drill bit may perform well in the axial direction, but typically performs inadequately when moved in the lateral direction since its flute configuration is configured primarily for drilling in the axial direction.  
         [0003]     Consequently, special tools have been developed for cutting openings in drywall and performing similar operations on wood and/or other materials. Such tools are generally used as bits in routers. These bits typically must cut axially through a workpiece and then laterally (i.e., in directions perpendicular to their lengths) through the workpiece to make the desired openings. To this end, such a bit has historically included a shank for insertion into a router, a tip portion with one or more axial cutting features, a smooth non-fluted guide portion at the proximal end of the tip portion for guiding the bit against an underlying structure, and possibly more lateral cutting features extending between the guide portion and the shank. While omissions of axial drilling features from the guide portions of some such bits may have facilitated tracing the bits around underlying structures, the lack of axial drilling features has also undesirably limited drilling efficiencies of the bits.  
         [0004]     Thus, there is a need for a cutout bit that provides improved axial drilling features in a guide portion of the bit that can nevertheless trace smoothly around underlying structures.  
       SUMMARY  
       [0005]     In accordance with one embodiment of the present invention, there is provided a cutout bit that includes a first bit segment configured to be received in a chuck of a rotary power tool, the first bit segment being free of flutes. The cutout bit also includes a second bit segment having defined therein a plurality of flutes that extend helically along the second bit segment. In addition, the cutout bit includes a third bit segment having only a single flute defined therein, the single flute (i) extending helically along the third bit segment, and (ii) being aligned with one of the plurality of flutes defined in the second bit segment.  
         [0006]     In accordance with another embodiment of the present invention, there is provided a cutout bit that includes a first bit segment configured to be free of flutes. The cutout bit also includes a second bit segment extending from the first bit segment at a first location. In addition, the cutout bit includes a third bit segment extending from the second bit segment and terminating in a tip. The cutout bit additionally includes a first flute extending along only the second bit segment, as well as a second flute extending along both the second bit segment and the third bit segment. The second flute extends from the first location to the tip.  
         [0007]     In accordance with yet another embodiment of the present invention, there is provided a cutout bit having a first bit segment configured to be received in a chuck of a rotary power tool. The cutout bit further includes a second bit segment having a first flute portion that extends helically along the second bit segment. Moreover, the cutout bit includes a third bit segment having a second flute portion that extends helically along the third bit segment. When the cutout bit is viewed in a cross sectional view at the third bit segment, (i) the cutout bit defines a circular shaped bit periphery, and (ii) the second flute portion defines a curve extending from a first flute end to a second flute end. Also, the first flute end and the second flute end both lie on the bit periphery. Moreover, when the curve is plotted on an X-Y graph in which a straight line extending between the first flute end and the second flute end defines an X-axis of the X-Y graph, the curve possesses both (i) a local maximum that is interposed between the first flute end and the second flute end, and (ii) a local minimum that is interposed between the first flute end and the second flute end.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a side plan view of an exemplary cutout bit according to the present invention;  
         [0009]      FIG. 2  is a cross-sectional view of the single-fluted radially dull portion of the exemplary bit of  FIG. 1  (taken along line  2 - 2  of  FIG. 1 );  
         [0010]      FIG. 3  is a cross-sectional view of the multi-fluted radially sharp portion of the exemplary bit of  FIG. 1  (taken along line  3 - 3  of  FIG. 1 );  
         [0011]      FIG. 4  is an untwisted cross-sectional depiction of the shank and the multi-fluted radially sharp portion of the exemplary bit of  FIG. 1  (relative to line  4 - 4  of  FIG. 1 );  
         [0012]      FIG. 5  is a cross-sectional view of a multi-fluted radially sharp portion of an exemplary alternative cutout bit (relative to line  5 - 5  of  FIG. 1 );  
         [0013]      FIG. 6  is a perspective view of an exemplary operational alignment of the exemplary bit of  FIG. 1 ;  
         [0014]      FIG. 7  is a side plan view of exemplary operations of the exemplary bit of  FIG. 1 ;  
         [0015]      FIG. 8  is an X-Y graph depicting the shape of the curve C that is defined by the flute of the single-fluted radially dull portion of the exemplary bit of  FIG. 1  when the bit is viewed cross-sectionally as shown in  FIG. 2 ;  
         [0016]      FIG. 9  is a front plan view of the exemplary bit of  FIG. 1  (facing the tip);  
         [0017]      FIG. 10  is a cross-sectional view of the single-fluted radially dull portion of the exemplary bit of  FIG. 1  (taken along line  10 - 10  of  FIG. 9 ); and  
         [0018]      FIG. 11  is a cutaway side plan view of the single-fluted radially dull portion of the exemplary bit of  FIG. 1  (proximal to the tip).  
     
    
     DESCRIPTION  
       [0019]     Like reference numerals indicate like parts and/or features throughout the description and the drawings.  
         [0020]      FIG. 1  is a side plan view of an exemplary cutout bit  100  according to the present invention. In the exemplary embodiment, bit  100  is machined from grade M50 molybdenum high speed steel and then heat treated (triple tempered as well known in the art) to 60-65 Rockwell C hardness. In alternative embodiments, bit  100  may be made from any other suitable material(s) and/or process(es).  
         [0021]     Bit  100  includes a shank  120 . Shank  120  is configured to, among other things, be grasped by a chuck  140  (see  FIG. 6  and  FIG. 7 ). In the exemplary embodiment, shank  120  is generally cylindrical. In alternative embodiments, shank  120  may be implemented in whole or in part as a hexagonal prism, a rectangular prism, any other suitable prismoid, and/or any other suitable shape, and shank  120  may include any other suitable fitting or coupling features.  
         [0022]     Bit  100  further includes a multi-fluted radially sharp portion  160  extending axially from shank  120 , and further includes a single-fluted radially dull portion  180  extending axially from portion  160 . Portion  180  includes a single-fluted radially dull tip  200 . Tip  200  is conical with an effective included angle  220  of about 160 degrees. Bit  100  further includes a right hand spiraling helical flute  240  extending from shank  120  through portion  160  and through portion  180  at a helix angle  260  of about 30 degrees. It is noted that flute  240  spirals all the way through tip  200 . Flute  240  has an axial span  280 .  
         [0023]     Bit  100  further includes a right hand spiraling helical flute  300  extending from shank  120  through portion  160  coaxially to flute  240  at helix angle  260  such that flute  300  is double-helically disposed from flute  240 . However, it is noted that flute  300  does not extend into or through portion  180  (and, thus, flute  300  also does not extend into or through tip  200 ). Flute  300  has an axial span  320  that is less than span  280 .  
         [0024]      FIG. 2  is a cross-sectional view of portion  180  of exemplary bit  100  (taken along line  2 - 2  of  FIG. 1 ). As at least partially discernable in  FIG. 2 , with reference to a rotational direction  340  flute  240  includes a leading edge  360  and a trailing edge  380 . Edge  360  is ground down, somewhat flattened, or otherwise dulled or blunted throughout portion  180  such that it essentially acts as a “non-cutting” edge throughout portion  180  (i.e., it does not cut or abrade a workpiece significantly when portion  180  rotates in direction  340  and the portion  180  is urged against the workpiece). Additionally, edge  380  is configured to act as a non-cutting edge when portion  180  rotates in direction  340 . Thus, portion  180  is “radially dull” (i.e., a non-cutting portion) when rotating in direction  340 . Throughout portion  180  flute  240  has a width in the direction  400  and a depth in the direction  420 .  
         [0025]      FIG. 3  is a cross-sectional view of portion  160  of exemplary bit  100  (taken along line  3 - 3  of  FIG. 1 ). As at least partially discernable in  FIG. 3 , edge  360  is relatively sharp throughout portion  160  such that it essentially acts as a “cutting” edge throughout portion  160  (i.e., it cuts or abrades a workpiece significantly when portion  160  rotates in direction  340  and the portion  160  is urged against the workpiece). Thus, portion  160  is “radially sharp” (i.e., a cutting portion) when rotating in direction  340 . Throughout portion  160 , edge  360  extends from portion  160  at a positive rake angle  440  of about 15 degrees and a clearance angle  460  of about 35 degrees. Meanwhile, throughout portion  160  edge  380  is configured act as a non-cutting edge when portion  160  rotates in direction  340 . Throughout portion  160  flute  240  has a width in the direction  480  and a depth in the direction  500 . Width of flute  160  (in the direction  480 ) is less than the width of flute  180  (in the direction  400 ), and the depth of flute  160  (in the direction  500 ) is less than the depth of flute  180  (in the direction  420 ).  
         [0026]     As also at least partially discernable in  FIG. 3 , with reference to direction  340  flute  300  includes an edge  520  and an edge  540 . Edge  520  is relatively sharp throughout portion  160  (i.e., it essentially acts as a cutting edge throughout portion  160 ). Thus, portion  160  is additionally radially sharp relative to direction  340 . Throughout portion  160 , edge  520  extends at a positive rake angle  560  and a clearance angle  580 . Throughout portion  160 , edge  540  is configured act as a non-cutting edge when portion  160  rotates in direction  340 . Throughout portion  160  flute  300  has a width in the direction  600  and a depth in the direction  620 . Width of flute portion  160  (in the direction  600 ) is about equal to the width of the flute portion  160  (in the direction  480 ), and the depth of the flute portion  160  (in the direction  620 ) is about equal to the depth of the flute portion  160  (in the direction  500 ). Moreover, angle  560  is about equal to angle  440 , and angle  580  is about equal to angle  460  such that flute  300  is generally symmetrical to flute  240  throughout portion  160 .  
         [0027]      FIG. 4  is an untwisted cross-sectional depiction of shank  120  and portion  160  of exemplary bit  100  (relative to line  4 - 4  of  FIG. 1 ). It is noted that in  FIG. 4  flute  240  and flute  300  are depicted as “untwisted” or straight merely for clarity of exposition. However, it should be appreciated that flute portions  240 ,  300  possess a helical configuration as shown in  FIGS. 1, 6 , and  7 . As at least partially discernable in  FIG. 4 , at shank  120  flute  240  terminates or “runs out” with a tapered portion  640  and flute  300  runs out with a tapered portion  660 . Portion  660  is generally symmetrical to portion  640 .  
         [0028]      FIG. 5  is a cross-sectional view of a multi-fluted radially sharp portion  680  of an exemplary alternative cutout bit  700  (relative to line  5 - 5  of  FIG. 1 ). Bit  700  is configured the same as bit  100  with the exception that throughout portion  680  a generally convex or “hollow grind” facet  720  is added as well as a hollow grind facet  740  as shown in  FIG. 5 . Facet  720  is generally symmetrical to facet  740 .  
         [0029]      FIG. 6  is a perspective view of an exemplary operational alignment of exemplary bit  100 . As at least partially discernable from  FIG. 6 , in the exemplary operations a conventional metal electrical outlet or junction box  800  defining a generally rectangular interior opening  820  has been mounted to studding or another wall support (not shown). Further, a drywall panel  840  has been nailed to studding or another wall support (not shown), covering box  800 . It is noted that box  800  is merely exemplary and bit  100  may alternatively be used to cut around the inside of a window or door frame or inside and/or around any other suitable structure(s).  
         [0030]     In the exemplary operations, a user mounts shank  120  in chuck  140  of a drill, rotary power tool, or other suitable rotational power source (not illustrated in detail). With the power source rotating bit  100  in direction  340 , the user cuts an opening  860  through panel  840  corresponding to the shape of box  800 . In cutting opening  860 , the user first moves tip  200  generally axially along line  880  to drill though panel  840 , and then cuts around the periphery of box  800  by moving bit  100  laterally around box  800  with portion  180  (see  FIG. 7 ) substantially abutting and sliding against box  800 . A depth gauge may be used with the power source and bit  100  to ensure that portion  180  is inserted to an appropriate depth and that portion  160  (see  FIG. 1 ) remains substantially clear of box  800 .  
         [0031]      FIG. 7  is a side plan view of exemplary operations of exemplary bit  100 . As at least partially discernable from  FIG. 7 , upon the introduction of tip  200  to panel  840 , portion  180  essentially acts like a twist drill bit to axially drill through panel  840  with more efficiency than many designs not having twist-drill bit-like features. Meanwhile, the radial dullness of portion  180  (see also  FIG. 2 , particularly edge  360 ) avoids significant damage to box  800  and/or to bit  100  as compared to conventional twist drill bits. Additionally, the tapered run outs (see  FIG. 4 , particularly portion  640  and portion  660 ) of flute  240  and flute  300  provide increased shear strength as compared to many designs not having such features, thereby enhancing the integrity of bit  100 , especially in smaller diameters.  
         [0032]     Bit  700  is used in a like manner to bit  100 . The addition of facet  720  and facet  740  (see  FIG. 5 ) to bit  700  may increase its axial drilling efficiency and provide for increased cutting life.  
         [0033]      FIG. 8  is an X-Y graph depicting the shape of curve C that is defined by the single flute of the portion  180  of the drill bit  100  when the bit is viewed in a cross sectional view at the portion  180  as shown in  FIG. 2 . When the drill bit  100  is viewed as such, the drill bit  100  defines a circular shaped bit periphery BP. Also when the drill bit  100  is viewed in the above manner, the single flute of the portion  180  defines a curve C that extends from a first flute end FE 1  to a second flute end FE 2  as shown in  FIGS. 2 and 8 . Note that the first flute end FE 1  and the second flute end FE 2  both lie on the bit periphery BP as shown in  FIG. 2 . Also note that as shown in  FIG. 8 , when the curve C is plotted on an X-Y graph in which a straight line SL (see  FIG. 2 ) extending between the first flute end FE 1  and the second flute end FE 2  defines an X-axis of said X-Y graph, the curve C possesses both (i) a local maximum that is interposed between the first flute end FE 1  and the second flute end FE 2 , and (ii) a local minimum that is interposed between the first flute end FE 1  and the second flute end FE 2 .  
         [0034]      FIG. 9  is a front plan view of bit  100  (facing tip  200 ). As at least partially discernable in  FIG. 9 , bit  100  is configured to be rotated about an axis  900  and edge  360  includes a generally radially outward dulled portion  920  and a sharp portion  940  extending generally radially inwardly from portion  920 . Portion  940  is radially offset from axis  900  by a distance  960 .  
         [0035]      FIG. 10  is a cross-sectional view of portion  180  of bit  100  (taken along line  10 - 10  of  FIG. 9 ). As at least partially discernable in  FIG. 10 , portion  940  of edge  360  (see also  FIG. 9 ) axially opens (or opens into) flute  240  at a positive rake angle  980  of about 30 degrees.  
         [0036]      FIG. 11  is a cutaway side plan view of portion  180  of bit  100  (proximal to tip  200 ). As at least partially discernable in  FIG. 11 , portion  920  (of edge  360 ; see also  FIG. 9 ) meets tip  200  at a positive axial relief or clearance angle  1000 , and portion  180  further includes a tip base edge  1020  that extends from portion  920  and generally radially bounds tip  200 . To facilitate production of bit  100 , edge  1020  may bound tip  200  with an axial relief or clearance angle  1040  that varies as edge  1020  extends around tip  200 .  
         [0037]     Although the present invention has been described with respect to certain exemplary embodiments, it will be appreciated by those of skill in the art that other implementations and adaptations are possible. Moreover, there are advantages to individual advancements described herein that may be obtained without incorporating other aspects described above. Therefore, the spirit and scope of the appended claims should not be limited to the description of the exemplary embodiments contained herein.