HOLESAW AND PILOT BIT WITH THREADED TIP

Abstract

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.

Claims

1. A holesaw assembly comprising: a holesaw comprising a hollow cup defining a center axis, the cup having 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; and a spade bit received in the holesaw along the center axis, the spade bit having 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 cutting head, wherein the holesaw is free of any radial cutting elements disposed inside the cup between the spade bit and the peripheral wall of the cup, and wherein the peripheral edge has one or more hard metal cutting inserts, each cutting insert having a cutting edge and a rake face disposed at a hook angle relative to a line parallel to the center axis, the hook angle being between approximately 5 and approximately +5.

2. The holesaw assembly of claim 1, wherein the at least partially threaded tip has a thread pitch of approximately 1.0 mm to approximately 2.5 mm.

3. The holesaw assembly of claim 1, wherein each cutting insert has a rectangular or trapezoidal cross-sectional shape and the cutting edge is straight.

4. The holesaw assembly of claim 1, wherein each cutting insert includes 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.

5. The holesaw assembly of claim 1, wherein the plate-like body includes first and second side faces extending radially outward from center axis and first and second cutting edges extending radially outward from center axis.

6. The holesaw assembly of claim 1, wherein the plate-like body has a width of approximately 7 mm to approximately 13 mm.

7. The holesaw assembly of claim 1, wherein the plate-like body includes 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.

8. The holesaw assembly of claim 7, wherein the radial faces taper radially inwardly to cut out regions in an axially rearward direction from the threaded tip.

9. The holesaw assembly of claim 1, wherein the threaded tip has a conical shape with a thread.

10. The holesaw assembly of claim 9, wherein a portion of the threaded tip includes at least one flat surface.

11. A holesaw assembly comprising: a holesaw comprising a hollow cup defining a center axis, the cup having 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; and a spade bit received in the holesaw along the center axis, the spade bit having 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 cutting head, wherein the holesaw is configured to form and remove a generally cylindrical plug of material from a workpiece, and wherein the peripheral edge has one or more hard metal cutting inserts, each cutting insert having a cutting edge and a rake face disposed at a hook angle relative to a line parallel to the center axis, the hook angle being between approximately 5 and approximately +5.

12. The holesaw assembly of claim 11, wherein the at least partially threaded tip has a thread pitch of approximately 1.0 mm to approximately 2.5 mm.

13. The holesaw assembly of claim 11, wherein each cutting insert has a rectangular or trapezoidal cross-sectional shape and the cutting edge is straight.

14. The holesaw assembly of claim 11, wherein each cutting insert includes 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.

15. The holesaw assembly of claim 11, wherein the plate-like body includes first and second side faces extending radially outward from center axis and first and second cutting edges extending radially outward from center axis.

16. The holesaw assembly of claim 11, wherein the plate-like body includes 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.

17. The holesaw assembly of claim 17, wherein the radial faces taper radially inwardly to cut out regions in an axially rearward direction from the threaded tip.

18. The holesaw assembly of claim 11, wherein the threaded tip has a conical shape with a thread.

19. The holesaw assembly of claim 18, wherein a portion of the threaded tip includes at least one flat surface.

20. A holesaw assembly comprising: a holesaw comprising a hollow cup defining a center axis, the cup having 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 including a straight 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 5 and approximately +5; and a spade bit received in the holesaw along the center axis, the spade bit having 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 including 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 tapering radially inwardly in a circumferential direction from the cutting edge to a trailing edge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is a perspective view of a first embodiment of a holesaw assembly.

[0022] FIG. 2A is an exploded perspective view of the holesaw assembly of FIG. 1.

[0023] FIG. 2B is a side view of the holesaw assembly of FIG. 1 with the collar on the arbor retracted.

[0024] FIG. 3A is a perspective view of a holesaw of the holesaw assembly of FIG. 1.

[0025] FIGS. 3B and 3C are close up perspective views of two alternative embodiments of a cutting tooth for the holesaw of FIG. 3A.

[0026] FIG. 3D is a front view along line 3D-3D of the two embodiments of a cutting tooth in FIGS. 3B and 3C.

[0027] FIG. 3E is a top view along line 3E-3E of the two embodiments of a cutting tooth in FIGS. 3B and 3C.

[0028] FIG. 4A is a front view of a first embodiment of a pilot bit for use with the holesaw assembly of FIG. 1.

[0029] FIG. 4B is a perspective view of the pilot bit of FIG. 4A.

[0030] FIG. 4C is a close up side view of the pilot bit of FIG. 4A assembled with the holesaw of FIG. 1.

[0031] 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.

[0032] 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.

[0033] FIG. 4F is a front end view of the pilot bit of FIG. 4E.

[0034] 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.

[0035] FIG. 5A is a side view of a second embodiment of a holesaw assembly.

[0036] FIG. 5B is a side view of a pilot bit of the holesaw assembly of FIG. 5A.

[0037] FIG. 6 is a perspective view of a third embodiment of a holesaw assembly.

[0038] FIG. 7 is a perspective view of a fourth embodiment of a holesaw assembly.

DETAILED DESCRIPTION

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 31A and an inner side face 31B extending generally axially downward from the relief face 35. The outer side face 31A intersects relief face 37 at an outer top edge 39A and the inner side face 31B intersects the relief face 37 at an inner top edge 39B. The rake face 37 lies in a plane that is at a hook angle to a line L that is generally parallel to the center axis X. The hook angle 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 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.

[0043] Referring also to FIG. 3D, when viewed in a circumferential direction opposite to the direction of rotation R (as indicated by arrow 3D-3D 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 39A to the inner top edge 39B at a top bevel angle relative to horizontal H. The top bevel angle improves cordless runtime as discussed in more detail below.

[0044] The outer side surface 32A is angled radially outward in an axially forward direction F by an outer offset angle A so that the outer top edge 39A 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 32B is angled radially outward in an axially forward direction F by an inner offset angle B so that the inner top edge 39B 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 B are greater than the outer offset distance Da and the outer offset angle A. In one implantation, the top bevel angle is approximately 5 to 15 (e.g., approximately 10), the outer offset angle A is approximately 2 to 8 (e.g., approximately 5), the inner offset angle B 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 B and offset distance Da of the inner side surface 32B 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.

[0045] Referring also to FIG. 3E, when viewed from an axially forward end of the holesaw (as indicated by arrow 3E-3E in FIGS. 3B and 3C), the outer side surface 31A and the inner side surface 31B taper inwardly toward each other from the rake face 37 toward a trailing face 41 by angles A and B, respectively, relative to a lines Ya and Yb perpendicular to the cutting edge 33. The outer taper angle A may be greater than the inner taper angle B. In one implementation, the outer taper angle A may be approximately 9 to 13 (e.g., approximately) 11 and the inner taper angle B may be approximately 8 to 12 (e.g., approximately 10). The taper angles improve cordless runtime and plug removal discussed in more detail below.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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 to a line A that is generally perpendicular to the center axis X. In one embodiment, angle 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 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.

[0052] 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.

[0053] 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.

[0054] 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 W1 of approximately 7 mm to approximately 13 mm (e.g., approximately 9.5 mm).

[0055] 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.

[0056] 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 to a line A that is generally perpendicular to the center axis X. In the embodiment depicted, angle 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 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.

[0057] 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 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 r1 that is larger than a second radius r2 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 W2 (e.g., approximately 5 mm to 8 mm) that is less than the first width W1. Finally, the radial faces 176, 178 are tapered radially inwardly in an axial direction rearward of the cutting tip 182 at an angle , e.g., approximately 1 to 20. The combination of the tapering of the radial faces 176m 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.

[0058] 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.

[0059] 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.

[0060] 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 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.

[0061] 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.

TABLE-US-00001 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)

[0062] 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.

[0063] 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 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.

TABLE-US-00002 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% 1 36.1 2.4 93% 4 134.0 40.0 70%

[0064] 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%.

[0065] 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.

[0066] 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 H2, H3 that is approximately twice a height H1 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 H2 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 H3 of the holesaw 712 and facilitate removal of a plug of waste material from the holesaw 712.

[0067] 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.

[0068] Numerous modifications may be made to the exemplary implementations described above. These and other implementations are within the scope of this application.