Patent Publication Number: US-2019168314-A1

Title: Holesaw and pilot bit with threaded tip

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 15/181,986, filed Jun. 14, 2016, which claims priority, under 35 U.S.C. § 119(e), to U.S. Provisional Application No. 62/247,816, filed Oct. 29, 2015, each of which is incorporated by reference. 
    
    
     TECHNICAL FIELD 
     This application relates to a holesaw and pilot bit assembly for use with rotary power tools. 
     BACKGROUND 
     Two types of power tool accessories for cutting larger diameter holes in a workpiece are holesaws and self-feed drill bits. A holesaw generally includes a cup shaped cutting member formed from a flat blade with teeth that is rolled and welded into a cylindrical shape, and then welded to a round base. The holesaw may be mounted to an arbor to couple the holesaw to a rotary power tool such as a drill. A center pilot drill bit may also be received in the holesaw and/or the arbor to help drill a pilot hole to center the holesaw in a workpiece. In use, arbor, holesaw, and pilot bit are assembled and coupled to a rotary power tool such as a drill. The drill is then actuated so that the pilot drill bit enters the workpiece, followed by the holesaw. The holesaw forms a large diameter hole in the workpiece by removing a solid cylindrical plug from the workpiece. An example of a holesaw is the Milwaukee® 49-56-9130 2 9/16″ Big Hawg® Hole Cutter with Spade Pilot Bit, sold by Milwaukee Electric Tool Corp. of Brookfield, Wis. 
     A self-feed drill bit generally includes a shank for coupling to a rotary power tool and an integral cutting head coupled to the shank. The cutting head has a semicircular base, a semi-cylindrical wall coupled to the base having a plurality of teeth, and one or more radial cutters or blades extending from a center of the cutting head to the semi-cylindrical wall. The cutting head may be provided with a pilot bit, which may include a self-feeding threaded tip. In use, the shank is coupled to a rotary power tool such as a drill. The drill is then actuated so that the pilot bit enters the workpiece, followed by the cutting head. The cutting head forms a large diameter in the hole in the workpiece by removing tiny chips from the workpiece. An example of a self-feed drill bit is a DeWALT DW1639 2 9/16″ Self-Feed Bit sold by DeWALT Industrial Tool Co. of Towson, Md. 
     Holesaws are often preferred over self-feed bits for several reasons. First, holesaws are much less messy because they form a solid-plug of waste material, while self-feed bits throw small chips over a wide area around a hole. This can be important when working in an area where debris is not desired. Second, holesaws are much less expensive than self-feed bits. This is because a self-feed bit is made by solid investment casting, while a holesaw is made by bending and welding sheet metal. For example, the Milwaukee® 49-56-9130 2 9/16″ Big Hawg® Hole Cutter with Spade Pilot Bit currently retails for almost double the price of the DeWALT DW1639 2 9/16″ Self-Feed Bit. Third, self-feed bits are generally have a maximum diameter of about 4 inches, while holesaws may have a maximum diameter of 6 inches or more. Finally, self-feed bits generally require a large, high powered corded drill, while holesaws can be used with smaller, lower powered cordless drills. 
     Some drawbacks of holesaws include that a holesaw may be more difficult to use because it requires the user to put a large amount of axial bias on the tool to drive the holesaw through the workpiece. In addition, when used with a cordless power tool such as a cordless drill existing holesaws also have poor runtime performance (i.e., the number of holes that can be drilled on a single battery charge). Further, it can be difficult to remove a plug of waste material from the holesaw. There is a need for a holesaw that overcomes these deficiencies. 
     SUMMARY 
     In an aspect, a holesaw assembly includes a holesaw and a pilot bit. The holesaw includes a hollow cup defining a center axis. The cup has a round base perpendicular to the center axis and a peripheral wall coupled to and extending axially forward of the base to a peripheral edge at a free end of the wall. The pilot bit is received in the holesaw along the center axis. The pilot bit has a shaft received in the base, a cutting head coupled to a front end of the shaft, and an at least partially threaded tip coupled to a front end of the cutting head. The holesaw is free of any radial cutting elements disposed inside the cup between the drill bit and the peripheral wall of the cup. 
     In another aspect, a holesaw assembly includes a holesaw and a pilot bit. The holesaw includes a hollow cup defining a center axis. The cup has a round base perpendicular to the center axis and a peripheral wall coupled to and extending axially forward of the base to a peripheral edge at a free end of the wall. The pilot bit is received in the holesaw along the center axis. The pilot bit has a shaft received in the base, a cutting head coupled to a front end of the shaft, and an at least partially threaded tip coupled to a front end of the cutting head. The holesaw is configured to form and remove a generally cylindrical plug of material from a workpiece. 
     In another aspect, a method of using a holesaw assembly includes providing a holesaw assembly that includes holesaw and a pilot bit. The holesaw has a hollow cup defining a center axis. The cup has a round base perpendicular to the center axis and a peripheral wall coupled to and extending axially forward of the base to a peripheral edge at a free end of the wall. The pilot bit is received in the holesaw along the center axis. The pilot bit has a shaft received in the base, a cutting head coupled to a front end of the shaft, and an at least partially threaded tip coupled to a front end of the cutting head. The holesaw assembly is coupled to a rotary power tool so that the power tool is configured to drive the holesaw and the pilot bit together in a rotational cutting direction. The rotary power tool is actuated to drive the pilot bit and the holesaw into a workpiece to remove a solid, generally cylindrical plug of material from the workpiece. 
     Implementations of these aspects may include one or more of the following features. The base may define a central opening configured to receive the shaft of the drill bit. The peripheral edge of the holesaw may include one or more cutting inserts. The cutting inserts may be composed of a hard metal such as tungsten carbide. The cutting inserts may be brazed or welded to the peripheral edge. Each cutting insert may include a cutting edge and a rake face, the rake face disposed at a hook angle relative to a line parallel to the center axis. The hook angle may be between approximately negative 10° and approximately positive 10°. The peripheral wall may define one or more slots configured to facilitate removal of a plug of material from the holesaw. 
     The pilot bit may comprise a spade bit. The cutting head of the spade bit may comprise a plate-like body with first and second cutting edges extending radially outward from center axis. The plate like body may have a width of approximately 7 mm to approximately 13 mm. The pilot bit may include an auger bit. The cutting head of the auger bit may include a pair of diametrically opposed radially extending cutting edges terminating in a peripheral tooth, and the shaft comprises a shank portion received in the holesaw and a fluted intermediate shaft having at least one spiral flute extending from the cutting head to the shank, the fluted intermediate shaft and the cutting head having substantially the same outer diameter. The tip may have a conical shape with a thread. A portion of the tip may be ground to form a flat. The thread may have a pitch between approximately 1.0 mm and approximately 2.5 mm. 
     An arbor may removably coupled to the base of the cup and configured to receive the shaft of the drill bit. The arbor may have a shank configured to be received in a power tool, an intermediate body, and a central projection configured to be received in a central opening in the holesaw. The central projection may define a bore configured to retain the shaft of the pilot bit. The intermediate body may include one or more lateral projections configured to be received in one or more lateral openings in the holesaw. Coupling the holesaw assembly to a rotary power tool may include mounting the holesaw and the pilot bit on an arbor, and coupling the arbor to the rotary power tool. The holesaw assembly may enable use in a cordless drill to have a runtime improvement of at least 90% as compared to a holesaw with a pilot bit without a threaded tip. 
     In another aspect, a holesaw assembly includes a holesaw having a hollow cup defining a center axis. The cup has a round base perpendicular to the center axis and a peripheral wall coupled to and extending axially forward of the base to a peripheral edge at a free end of the wall. A pilot bit is received in the holesaw along the center axis. The pilot bit has a shaft received in the base, a cutting head coupled to a front end of the shaft, and an at least partially threaded tip coupled to a front end of the cutting head. The holesaw is free of any radial cutting elements disposed inside the cup between the drill bit and the peripheral wall of the cup. 
     Implementations of this aspect may include one or more of the following features. The peripheral edge of the holesaw may include one or more hard metal cutting inserts. Each cutting insert may include a cutting edge and a rake face, the rake face disposed at a hook angle relative to a line parallel to the center axis, the hook angle being between approximately negative 10° and approximately positive 10°. Each cutting insert may include an outer side face offset radially outwardly from the peripheral edge of the holesaw by a first distance, and an inner side face offset radially inwardly from the peripheral edge of the holesaw by a second distance that is greater than the first distance. 
     The drill bit may comprise an auger bit with the threaded tip or a spade bit with the threaded tip. The cutting head may have a plate-like body with first and second side faces extending radially outward from center axis and first and second cutting edges extending radially outward from center axis. The plate like body may have a width of approximately 7 mm to approximately 13 mm. The body may include radial faces connecting radially outward edges of the first and second side faces, each of the radial faces tapering radially inwardly in a circumferential direction from the cutting edge to a trailing edge. The radial faces may taper radially inwardly to cut out regions in an axially rearward direction from the threaded tip. 
     The cutting head may include a pair of diametrically opposed radially extending cutting edges terminating in a peripheral tooth. The shaft may include a shank portion received in the holesaw and a fluted intermediate shaft having at least one spiral flute extending from the cutting head to the shank. The fluted intermediate shaft and the cutting head may have substantially the same outer diameter. The threaded tip may have a conical shape with a thread. A portion of the threaded tip may include at least one flat surface. The holesaw assembly enables use in a cordless drill to have a runtime improvement of at least 90% as compared to a holesaw assembly with a pilot bit having an unthreaded tip. 
     In another aspect, a holesaw assembly includes a holesaw with a hollow cup defining a center axis. The cup has a round base perpendicular to the center axis and a peripheral wall coupled to and extending axially forward of the base to a peripheral edge at a free end of the wall. A pilot bit is received in the holesaw along the center axis. The pilot bit has a shaft received in the base, a cutting head coupled to a front end of the shaft, and an at least partially threaded tip coupled to a front end of the cutting head. The holesaw is configured to form and remove a generally cylindrical plug of material from a workpiece. 
     Implementations of this aspect may include one or more of the following features. The peripheral edge of the holesaw may include one or more hard metal cutting inserts. Each cutting insert may include a cutting edge and a rake face. The rake face may be disposed at a hook angle relative to a line parallel to the center axis. The hook angle may be between approximately negative 10° and approximately positive 10°. The pilot bit may comprise an auger bit with the threaded tip or a spade bit with the threaded tip. The cutting head of the spade bit may include a plate-like body coupled to a front end of the shaft, first and second side faces extending radially outward from center axis, first and second cutting edges extending radially outward from center axis, and radial faces connecting radially outward edges of the first and second side faces. Each of the radial faces may taper radially inwardly in a circumferential direction from the cutting edge to a trailing edge of the body. 
     In another aspect, a holesaw assembly includes a holesaw having a hollow cup defining a center axis. The cup has a round base perpendicular to the center axis, a peripheral wall coupled to and extending axially forward of the base to a peripheral edge at a free end of the wall, and one or more hard metal cutting inserts coupled to the peripheral edge. Each cutting insert includes a cutting edge and a rake face. The rake face is disposed at a hook angle relative to a line parallel to the center axis. The hook angle is between approximately negative 10° and approximately positive 10°. A spade bit is received in the holesaw along the center axis. The spade bit has a shaft received in the base, a cutting head with a plate-like body coupled to a front end of the shaft, and an at least partially threaded tip coupled to a front end of the body. The body includes first and second side faces extending radially outward from center axis, first and second cutting edges extending radially outward from center axis, and radial faces connecting radially outward edges of the first and second side faces. Each of the radial faces taper radially inwardly in a circumferential direction from the cutting edge to a trailing edge. The holesaw assembly may enable use in a cordless drill to have a runtime improvement of at least 90% as compared to a holesaw assembly with a spade bit that has an unthreaded tip. 
     Advantages may include one or more of the following. The holesaw assembly may enable substantially greater runtime than existing holesaws when used with a cordless (battery operated) power tool. In addition, the holesaw assembly may be usable with the user having to place little or no axial bias on the power tool, thus reducing user fatigue. These and other advantages and features will be apparent from the description and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a first embodiment of a holesaw assembly. 
         FIG. 2A  is an exploded perspective view of the holesaw assembly of  FIG. 1 . 
         FIG. 2B  is a side view of the holesaw assembly of  FIG. 1  with the collar on the arbor retracted. 
         FIG. 3A  is a perspective view of a holesaw of the holesaw assembly of  FIG. 1 . 
         FIGS. 3B and 3C  are close up perspective views of two alternative embodiments of a cutting tooth for the holesaw of  FIG. 3A . 
         FIG. 3D  is a front view along line  3 D- 3 D of the two embodiments of a cutting tooth in  FIGS. 3B and 3C . 
         FIG. 3E  is a top view along line  3 E- 3 E of the two embodiments of a cutting tooth in  FIGS. 3B and 3C . 
         FIG. 4A  is a front view of a first embodiment of a pilot bit for use with the holesaw assembly of  FIG. 1 . 
         FIG. 4B  is a perspective view of the pilot bit of  FIG. 4A . 
         FIG. 4C  is a close up side view of the pilot bit of  FIG. 4A  assembled with the holesaw of  FIG. 1 . 
         FIG. 4D  is a close up side view of a cutting head of a second embodiment of a pilot bit for use with the holesaw assembly of  FIG. 1 . 
         FIG. 4E  is a close up side view of a cutting head of a third embodiment of a pilot bit for use with the holesaw assembly of  FIG. 1 . 
         FIG. 4F  is a front end view of the pilot bit of  FIG. 4E . 
         FIG. 4G  is a side view of the pilot bit of  FIG. 4E  assembled with the holesaw and arbor of the holesaw assembly of  FIG. 1 . 
         FIG. 5A  is a side view of a second embodiment of a holesaw assembly. 
         FIG. 5B  is a side view of a pilot bit of the holesaw assembly of  FIG. 5A . 
         FIG. 6  is a perspective view of a third embodiment of a holesaw assembly. 
         FIG. 7  is a perspective view of a fourth embodiment of a holesaw assembly. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1, 2A and 2B , in one embodiment, a holesaw assembly  10  includes a holesaw  12 , an arbor  14  to which the holesaw  12  is removably mounted, and a pilot bit  16  with a threaded tip  82  received in the holesaw  12  and removably coupled to the arbor  14 . 
     Referring also to  FIG. 3A , an embodiment of the holesaw includes a hollow cup  18  defining a center axis X. The cup  18  has a round (generally circular) base  20  substantially perpendicular to the center axis X and a generally cylindrical peripheral wall  22  coupled to and extending axially forward of the base  20  to a peripheral edge  24  at a free end of the wall. The base  20  defines a central opening  26  and a plurality of peripheral apertures  28  spaced radially outward from the central opening  26 . The holesaw  12  may be provided in a variety of different diameters corresponding to various sizes of holes to be cut, e.g., ranging from approximately inch to approximately 6 inches. 
     The peripheral wall  22  defines one or more slots  32  configured to facilitate removal of a plug of material from the holesaw  12 . In the illustrated embodiment, the slots  32  are open to the edge  24  and are generally parallel to the center axis X. However, the slots  32  may be fully enclosed, may be at an angle to the center axis X, and/or may have a different curved or geometric shape. The peripheral edge  24  includes one or more cutting inserts  30 . The cutting inserts  30  may be composed of a hard metal, such as tungsten carbide, and may be received in and brazed or welded to pockets  34  in the peripheral edge  24 . In the illustrated embodiment, each of the slots  32  is positioned in front of one of the cutting inserts  30  in a cutting direction of rotation R of the holesaw  18 . 
     Referring also to  FIGS. 3B and 3C , each cutting insert  30  has a prismatic or three-dimensional polygonal body  31  including a cutting edge  33 , a rake face  37  extending generally axially downward from the cutting edge  31 , a top relief face  35  extending rotationally rearward of the cutting edge  33 . The body  31  also has an outer side face  31 A and an inner side face  31 B extending generally axially downward from the relief face  35 . The outer side face  31 A intersects relief face  37  at an outer top edge  39 A and the inner side face  31 B intersects the relief face  37  at an inner top edge  39 B. The rake face  37  lies in a plane that is at a hook angle α to a line L that is generally parallel to the center axis X. The hook angle α is said to be negative when the rake face  37  and cutting edge  33  are inclined away from the rotational direction R (as shown in  FIG. 3C ), is said to be positive when the rake face  37  and cutting edge  33  are inclined toward the rotational direction R (as shown in  FIG. 3B ), and is said to be zero when the rake face  37  is substantially parallel to the line L. In exemplary embodiments, the hook angle α may be between approximately −10° (e.g., as shown in  FIG. 3C ) and approximately +10° (e.g., as shown in  FIG. 3B ). The hook angles improve cordless runtime, as discussed in more detail below. In alternate embodiments, the cutting inserts  30  may be replaced or supplemented with cutting teeth formed directly in the peripheral edge  24  of the peripheral wall  18 . 
     Referring also to  FIG. 3D , when viewed in a circumferential direction opposite to the direction of rotation R (as indicated by arrow  3 D- 3 D in  FIGS. 3B and 3C ), the top relief face  35  is beveled axially downward in a radially inward direction RI from the outer top edge  39 A to the inner top edge  39 B at a top bevel angle β relative to horizontal H. The top bevel angle improves cordless runtime as discussed in more detail below. 
     The outer side surface  32 A is angled radially outward in an axially forward direction F by an outer offset angle θA so that the outer top edge  39 A is offset in a radially outward direction RO from the rim  24  of the holesaw by an outer offset distance Da. The inner side surface  32 B is angled radially outward in an axially forward direction F by an inner offset angle θB so that the inner top edge  39 B is offset in a radially outward direction RO from the rim  24  of the holesaw by an inner offset distance Db. The inner offset distance Db and the inner offset angle θB are greater than the outer offset distance Da and the outer offset angle θA. In one implantation, the top bevel angle β is approximately 5° to 15° (e.g., approximately 10°), the outer offset angle θA is approximately 2° to 8° (e.g., approximately 5°), the inner offset angle θB is approximately 5° to 11° (e.g., approximately 8°), the outer offset distance Da is approximately 0.4 mm to 0.8 mm (e.g., approximately 0.6 mm), and the inner offset distance Db is approximately 1.0 mm to 1.4 mm (e.g., approximately 1.2 mm). The larger offset angle θB and offset distance Da of the inner side surface  32 B creates a space between the plug formed by the cutting inserts and the rim of the holesaw, which facilitates easier removal of the plug from the holesaw after a cutting operation is complete. 
     Referring also to  FIG. 3E , when viewed from an axially forward end of the holesaw (as indicated by arrow  3 E- 3 E in  FIGS. 3B and 3C ), the outer side surface  31 A and the inner side surface  31 B taper inwardly toward each other from the rake face  37  toward a trailing face  41  by angles ωA and ωB, respectively, relative to a lines Ya and Yb perpendicular to the cutting edge  33 . The outer taper angle ωA may be greater than the inner taper angle ωB. In one implementation, the outer taper angle ωA may be approximately 9° to 13° (e.g., approximately) 11° and the inner taper angle ωB may be approximately 8° to 12° (e.g., approximately 10°). The taper angles improve cordless runtime and plug removal discussed in more detail below. 
     The holesaw  18  may be manufactured using the following process. First, a sheet metal blank  90  may be stamped or cut to form a rectangular blade portion  92  having the peripheral edge  24 , a bottom edge  94 , and lateral edges  95 ,  96 . Next, the rectangular blade portion  92  may be rolled into a cylindrical shape and its lateral edges  95 ,  96  welded together along a seam  98  to form the peripheral wall  22 . A similar sheet metal blank  90  may be stamped or cut to form the circular base  20  with the openings  26 ,  28 . The bottom edge  94  of the peripheral wall  22  may then welded to the base  20 . The cutting inserts  30  then may be brazed or welded to the pockets in the peripheral edge  24 . Finally, the cutting inserts  30  may be ground to their desired geometry. These steps may be performed in a different order. For example, the cutting inserts may be ground to their desired geometry before they are brazed or welded to the pockets in the peripheral edge  24 . 
     Referring again to  FIGS. 1, 2A and 2B , the arbor  14  includes a round or polygonal shaped shank  34  extending along the center axis X and configured to be received in a tool holder or chuck of a rotary power tool such as a drill (not shown). Coupled to a front end of the shank  34  is an intermediate shaft  36 , and coupled to the opposite end of the intermediate shaft  36  is a front end  38  with a central projection  40 . The central projection  40  is configured to be received in the central opening  26  of the holesaw  12 . The central projection  40  may be externally threaded and the center opening  26  may be internally threaded to facilitate their secure attachment to one another. The central projection  40  also defines a central bore  42  configured to receive the pilot bit  16 . Rigidly coupled to the central projection  40  is a cylindrical flange  44 . The cylindrical flange  44  defines a radial bore  46  in communication with the central bore  44 . The radial bore  46  receives a set screw  48  that can be adjusted to retain or release the pilot bit  16  in or from the central bore  44 . 
     The cylindrical flange  44  also defines a pair of axial bores  50  disposed radially outward from the central projection  40 . Axially behind the cylindrical flange  44  and surrounding the intermediate shaft  36  is an annular collar  54  with a pair of projections  52  generally parallel to the center axis X and received in and project from the axial bores  50  in the flange  44 . The projections  52  are configured to be received in the peripheral openings  28  in the holesaw  12 . The annular collar  54  is moveable along the intermediate shaft  36  between a front position (as shown in  FIGS. 1 and 2A ) in which the collar  54  abuts the cylindrical flange  44  and the projections  52  protrude from the axial bores  50 , and a retracted position (as shown in  FIG. 2B ) in which the collar  54  is retracted rearward of the cylindrical flange  44  so that the projections  52  are retracted into the axial bores  50 . Retracting the collar  54  allows the holesaw  12  to be easily removed from or mounted to the arbor  14 . In other embodiments, an arbor may be integral with the holesaw, or may include a quick release mechanism to facilitate removal of the holesaw from the arbor. 
     Referring to  FIGS. 2A and 4A-4C , in one embodiment, the pilot bit  16 , in the form of a spade bit, includes a shank  60 , an intermediate shaft  62 , and a cutting head  64  extending along the center axis X. The shank  60  is generally cylindrical with one or more flats  66 . The shank  60  is receivable in the central opening  26  of the holesaw  12  and is removably mountable in the central bore  44  in the arbor  14  using the set screw  48 . The intermediate shaft  62  is generally cylindrical. The cutting head  64  includes a plate-like body  68  having opposed side faces  72 ,  74  bounded by opposed side edges  76 ,  78  and by a top edge  80 . The plate like body  68  may have a width W of approximately 7 mm to approximately 13 mm. 
     Extending axially forward of the top edge  80  along the center axis X is an at least partially threaded tip  82 . The tip  82  may have a generally conical, frustroconical, or parabolic shape extending from a wide base  81  to a narrower or pointed tip  83 . The tip  82  may have a diameter D at its base  81  of approximately 3 mm to approximately 7 mm, and a height H of approximately 6 mm to approximately 20 mm. One or more threads  85  wrap around the tip in the rotational direction. The threads  85  on the tip  82  may have a thread pitch P (i.e., the axial distance it takes on thread to make one complete revolution about the tip  82 ) of approximately 1.0 mm to approximately 2.5 mm, e.g., approximately 1.5 mm to approximately 2.0 mm. The tip  82  may be threaded along its entirety or be only partially threaded along a portion of its height H and/or circumference. 
     Extending along the top edge  80  and radially outward from the base  81  of the tip  82  are diametrically opposed first and second cutting edges  84 ,  86 . The cutting edges  84 ,  86  intersect side edges  76 ,  78  at cutting points  87 ,  89 . The cutting edges  84 ,  86  may be inclined at an angle β to a line A that is generally perpendicular to the center axis X. In one embodiment, angle β may be positive angle (as shown in  FIG. 4C ) so that the cutting points  87 ,  89  project axially forward of the base  81  of the tip  82 . In other embodiments the angle β may be negative so that the cutting points  87 ,  89  are recessed axially behind the base  81  of the tip  82 , or may be zero so that the cutting points  87 ,  89  are even with the base  81  of the tip  82 . 
     Referring to  FIG. 4C , the pilot bit  16  is axially positioned relative to the holesaw  12  so that the pointed tip  83  and a majority of the threaded portion  85  of the tip  82  extends axially forward of the cutting inserts  30 , while the base  81  of the tip  82  and the cutting edges  84 ,  86  are positioned axially behind the cutting inserts  30 . In this way, the threaded tip  82  enters the workpiece first, followed by the cutting inserts  30  of the holesaw  12 , followed by the cutting edges  84 ,  86  of the pilot bit  16 . The threads  85  on the tip  82  relative to the holesaw enables the holesaw assembly  10  to be used with the user having to place no or minimal axial bias along the center axis X on the power tool to which the holesaw assembly  10 ,  110  is coupled, and also dramatically increases cordless runtime, as discussed further below. 
     Referring to  FIG. 4D , in an alternate embodiment, a pilot bit  16 ′, in the form of a spade bit, includes a shank, an intermediate shaft, and a cutting head  64 ′ similar to those in the pilot bit  16  described above. Extending axially forward of a top edge  80 ′ of the cutting head  64 ′ is an at least partially threaded tip  82 ′ that has been modified as compared to the tip  82  in the pilot bit  16 . The modified partially threaded tip  82 ′ has portions of its conical surface ground to form flats  91 ′ that interrupt threads  85 ′. In other embodiments, the flats may be ground at an angle relative to the center axis X. It is believed that creating these flats  91 ′ reduces the resistance of entry of the tip  82 ′ into a workpiece, which may further increase cordless runtime, as discussed below. 
     Referring to  FIGS. 4E-4G , in another alternate embodiment, a holesaw assembly  110  includes an alternate embodiment of a pilot bit  116  for use with the holesaw  12  and the arbor  14  described above. The pilot bit  116  includes a shank (not shown), an intermediate shaft  162 , and a cutting head  164  extending along the center axis X. The shank is receivable in the central opening of the holesaw  12  and is removably mountable in the central bore in the arbor, as described and shown above. The intermediate shaft  162  is generally cylindrical. The cutting head  164  includes a plate-like body  168  having opposed side faces  172 ,  174  bounded by opposed radial faces  176 ,  178  and by a top edge  180 . The plate like body  168  may have a first width W 1  of approximately 7 mm to approximately 13 mm (e.g., approximately 9.5 mm). 
     Extending axially forward of the top edge  180  along the center axis X is an at least partially threaded tip  182 . The tip  182  may have a generally conical, frustroconical, or parabolic shape extending from a wide base  181  to a narrower or pointed tip  183 . The tip  182  may have a diameter D′ at its base  181  of approximately 3 mm to approximately 8 mm, and a height H′ of approximately 6 mm to approximately 20 mm. One or more threads  185  wrap around the tip in the rotational direction. The threads  185  on the tip  182  may have a thread pitch (i.e., the axial distance it takes on thread to make one complete revolution about the tip  82 ) of approximately 1.0 mm to approximately 2.5 mm, e.g., approximately 1.5 mm to approximately 2.0 mm. The tip  182  may be threaded along its entirety or be only partially threaded along a portion of its height H′ and/or circumference. 
     Extending along the top edge  180  and radially outward from the base  181  of the tip  182  are diametrically opposed first and second cutting edges  184 ,  186 . The cutting edges  184 ,  186  intersect side edges  176 ,  178  at cutting points  187 ,  189 . The cutting edges  184 ,  186  may be inclined at an angle β′ to a line A′ that is generally perpendicular to the center axis X. In the embodiment depicted, angle β′ is a positive angle so that the cutting points  187 ,  189  project axially forward of the base  181  of the tip  182 . In other embodiments the angle β may be negative so that the cutting points  187 ,  189  are recessed axially behind the base  181  of the tip  182 , or may be zero so that the cutting points  187 ,  189  are even with the base  181  of the tip  182 . 
     As shown in  FIG. 4F , the radial faces  176 ,  178  are tapered radially inwardly in a circumferential direction from the cutting edges  184 ,  186  to trailing edges  191 ,  192  of the body  168  at an angle γ relative to a line D perpendicular to the side faces  172 ,  174  of the body  168 . In this manner, the cutting edges have a first radius r 1  that is larger than a second radius r 2  of the trailing edges  191 ,  192 . In addition, as shown in  FIG. 4E , the radial faces  176 ,  178  are recessed radially inwardly at cut-out regions  193 ,  194  formed axially rearward of the cutting tip  182 . For example, the cut-out regions  193 ,  194  may have a second width W 2  (e.g., approximately 5 mm to 8 mm) that is less than the first width W 1 . Finally, the radial faces  176 ,  178  are tapered radially inwardly in an axial direction rearward of the cutting tip  182  at an angle φ, e.g., approximately 1° to 20°. The combination of the tapering of the radial faces  176   m    178  in a circumferential direction and an axial direction, and the cut-out regions  193 ,  194 , inhibit the cutting head  164  from binding too tightly in a plug of material formed by the holesaw, which facilitates easier plug removal from the pilot bit  116 . 
     Referring to  FIG. 4G , the pilot bit  116  is axially positioned relative to the holesaw  12  so that the entirety of the pointed tip  183 , the threaded portion  185  of the tip  182 , and the cutting edges  184 ,  186  extend axially forward of the cutting inserts  130 . In this way, the threaded tip  182  enters the workpiece first, followed by the cutting edges  184 ,  186 , followed by the cutting inserts  30  of the holesaw  12 . The threads  185  on the tip  182  relative to the holesaw enables the holesaw assembly  110  to be used with the user having to place no or minimal axial bias along the center axis X on the power tool to which the holesaw assembly  110  is coupled, and also dramatically increases cordless runtime, as discussed further below. 
     In use, the holesaw assembly  10 ,  110  is assembled by retracting collar  54  of the arbor to its rear position, mounting the holesaw  12  on the arbor  14  by inserting and/or threading the central projection  40  into the central opening  26 , and releasing the collar  54  to its forward position to allow the projections  52  to engage the openings  28  in the holesaw  12 . Next the set screw  48  is loosened, the pilot bit  16 ,  16 ′,  116  is inserted through the central opening  26  in the holesaw  12  into the bore  44  in the arbor  14 , and the set screw  48  is tightened to firmly hold the pilot bit  16 ,  16 ′,  116  in the arbor  14 . The shank  34  of the arbor is coupled to a tool holder of a rotary power tool, such as a drill. The tip  82 ,  82 ′,  182  is placed against the workpiece and the drill is actuated. The threaded tip  82 ,  82 ′,  182  enters the workpiece first, drawing the holesaw assembly  10  into the workpiece, followed by the cutting edges  84 ,  86 ,  184 ,  186  of the pilot bit  16 ,  16 ′,  116  and the cutting inserts  30  of the holesaw  18 . The cutting inserts  30  makes a circular cut to form a substantially circular hole and remove a solid, substantially cylindrical plug of material from the workpiece. 
     The holesaw assembly  10 , including the configuration of the holesaw  12  and the pilot bits  16 ,  16 ′,  116  have been optimized for use with a cordless power tool in order to maximize power tool runtime (i.e., the number of holes that can be drilled per battery charge), while maintaining adequate speed and quality of hole formation. In certain embodiments, it has been discovered that power tool runtime can be substantially increased (even more than expected) by using a holesaw assembly having the following combination of features: a hook angle α of the cutting inserts  30  between approximately −10° and approximately +10°; a width W of the paddle  64  of the pilot bit  16  between approximately 7 mm and approximately 13 mm, and a thread pitch P of the threads  85  on the tip  82  of between approximately 1.0 mm and approximately 2.5 mm. 
     As shown in the below table, in an experiment, several prototype designs of 2 9/16 inch holesaws having different carbide cutting insert hook angles and pilot bits having tips with different thread pitch were compared to the Milwaukee® 49-56-9010 2 9/16″ Big Hawg® Hole Cutter. The experiments were performed using a DEWALT 60V MAX* cordless right angle drill and making holes in 2-inch thick SPF board, with no axial bias applied to the tool. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
               
                   
                 Carbide 
                   
                   
                 Average 
                 Improve- 
               
               
                   
                 Insert 
                   
                 Tip 
                 Holes 
                 ment vs. 
               
               
                   
                 Hook 
                 Spade 
                 Thread 
                 Per 
                 Milwau- 
               
               
                 Sample 
                 Angle 
                 Width 
                 Pitch 
                 Charge 
                 kee ® 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Milwaukee ® 
                  0° 
                 9.52 mm 
                 None 
                 40.0 
                 N/A 
               
               
                 49-56-9010 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Prototype 1 
                  0° 
                 7.94 mm 
                 2.0 
                 mm 
                 78.6 
                  96% 
               
               
                 Prototype 2 
                  0° 
                 7.94 mm 
                 1.5 
                 mm* 
                 82.7 
                 107% 
               
               
                 Prototype 3 
                 −5° 
                 7.94 mm 
                 2.0 
                 mm 
                 96.9 
                 142% 
               
               
                 Prototype 4 
                 −5° 
                 7.94 mm 
                 1.5 
                 mm* 
                 104.9 
                 162% 
               
               
                 Prototype 5 
                 +5° 
                 7.94 mm 
                 2.0 
                 mm 
                 80.4 
                 101% 
               
               
                 Prototype 6 
                 +5° 
                 7.94 mm 
                 1.5 
                 mm* 
                 85.7 
                 114% 
               
               
                   
               
               
                 *Tip modified to have flats (as in FIG. 4D) 
               
            
           
         
       
     
     In each of the designs according to the present disclosure, the number of holes per charge unexpectedly and greatly exceeded the number of holes per charge achievable without the pilot bit with the at least partially threaded tip, e.g., by approximately 96% to approximately 162%. In addition, the inventors expected the holesaw with the more aggressive (higher) thread pitch and the more aggressive (positive) hook angle to cut faster and, therefore, to have a greater number of holes per charge. However, contrary to expectations, in this experiment, the greatest improvement was discovered with a holesaw having a negative hook angle (e.g., negative 5°) and a less aggressive (smaller) thread pitch (e.g., 1.5 mm). Moreover, it was discovered that the threaded tip that has been modified to have flats has even greater improvement. 
     In addition, the designs of the present disclosure also have markedly, and unexpectedly, increased drill speed (which correlates with increased cordless efficiency and runtime) as compared with existing bi-metal holesaws. For example, three diameters of holesaw assemblies having a holesaw constructed in accordance with the embodiment of  FIGS. 3C and 3E  and a pilot bit constructed in accordance with the embodiment of  FIGS. 4E-4G  were compared to similar diameters of DEWALT D180041 bi-metal holesaws with a ¼″ twist drill pilot bit. The experiments were performed using a DEWALT 60V MAX* cordless right angle drill, making holes in 2-inch thick SPF board, with 15 pounds of axial bias applied to the tool. In the below table, cutting speed refers to the average number of seconds needed to form a single hole, with a lower number indicating a faster cutting speed. 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                   
                 Avg. Cutting Speed 
                 Avg. Cutting Speed 
                   
               
               
                   
                 D180041 Bi-Metal 
                 Holesaw of Present 
               
               
                 Diameter 
                 Holesaw (sec) 
                 Application (sec) 
                 Improvement 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 2 9/16″ 
                 47.9 
                 11.7 
                 76% 
               
               
                 1⅜″ 
                 36.1 
                 2.4 
                 93% 
               
               
                 4¼″ 
                 134.0 
                 40.0 
                 70% 
               
               
                   
               
            
           
         
       
     
     In each of the designs according to the present disclosure, the cutting speed (and thus the expected efficiency and number of holes per charge) greatly exceeded the cutting speed of a comparably sized bi-metal holesaw, e.g., by approximately 70% to approximately 93%. 
     Referring to  FIGS. 5A and 5B , in another embodiment, a holesaw assembly  510  includes a holesaw  512  similar to the holesaw  12  described above, an arbor  514  similar to the arbor  14  described above, and an auger bit  516  with an at least partially threaded tip  582 . The auger bit  516  includes a shank  560 , an intermediate shaft  562 , and a cutting head  564  extending along a center axis X. The shank  560  is generally cylindrical with one or more flats  566 . The shank  560  is receivable in a central opening of the holesaw  512  and is removably mountable in a central bore in the arbor  514 . The intermediate shaft  562  includes a generally cylindrical core  561  and one or more helical threads  563 . The cutting head  564  includes a pair of radially extending cutting edges  566  (one of which is shown) generally perpendicular to the center axis X terminating in a pair of axially forwardly projecting cutting teeth  568  (one of which is shown) extending forward of the cutting edges  566  as an extension of the threads  563 . The cutting head  564  has the same outer diameter as the helical threads  563 . Extending axially forward of the cutting head  564  along the center axis X is the least partially threaded tip  582 , which may be similar to one of the tips  82  and  82 ′ described above. 
       FIGS. 6 and 7  illustrate two alternative embodiments of holesaw assemblies  610  and  710 . The holesaw assemblies each include a holesaw  612 ,  712 , an arbor  614 ,  714 , and a pilot bit  616 ,  716 , similar to the holesaw  12 , arbor  14 , and pilot bit  16  of the holesaw assembly  10  described above. The holesaw assemblies  610 ,  710  differ from the holesaw assembly  10  insofar as the holesaws  612 ,  712  have a height H 2 , H 3  that is approximately twice a height H 1  of the holesaw  12 . This enables the holesaws  612 ,  712  to be used to form holes in materials that are approximately twice as thick. For example, the holesaw  12  may be sized to form holes in a 2″ thick piece of material, while the holesaws  612 ,  712  may be sized to form holes in 4″ thick piece of material. In addition, the holesaw  612  has a plurality of elongated slots  632  open to a peripheral edge  624  and that extend over a majority of the height H 2  of the holesaw  612  to facilitate removal of a plug of waste material from the holesaw  612 . The holesaw  712  has a plurality of open elongated slots  732  that are open to a peripheral edge  724  of the holesaw  712 , and plurality of fully enclosed elongated slots  733  axially aligned with and behind the open slots  732 . Each of the slots  732 ,  733  extends over less than half the height H 3  of the holesaw  712  and facilitate removal of a plug of waste material from the holesaw  712 . 
     Terns of degree such as “generally,” “substantially,” “approximately,” and “about” may be used herein when describing the relative positions, sizes, dimensions, or values of various elements, components, regions, layers and/or sections. These terms mean that such relative positions, sizes, dimensions, or values are within the defined range or comparison (e.g., equal or close to equal) with sufficient precision as would be understood by one of ordinary skill in the art in the context of the various elements, components, regions, layers and/or sections being described. 
     Numerous modifications may be made to the exemplary implementations described above. These and other implementations are within the scope of this application.