Auger

An auger includes a body with a first end, a second end opposite the first end, a stem that extends from the first end to the second end and defines an axis of rotation, and a flute helically wrapped around the stem. The auger further includes a shank at the first end of the body configured to be received by a power tool and a cutting head at the second end of the body. The cutting head includes a cutting edge, a spur, and a feed screw with a thread. The thread has a pitch and a nonsymmetrical thread profile. The pitch of the thread is at least 2.5 mm.

BACKGROUND

The present invention relates to augers and, in particular, to augers for cutting holes in workpieces.

Augers are typically used with power tools, such as, for example, a drill, a driver drill, an impact driver, and the like to cut or carve holes into a material or surface, such as, for example, wood, composites, and the like. It is desired for augers to cut at faster speeds to minimize the amount of time drilling into a workpiece. In addition, rotating at faster speeds produces a cleaner cutting hole.

SUMMARY

In one embodiment, the invention provides an auger including a body with a first end, a second end opposite the first end, a stem that extends from the first end to the second end and defines an axis of rotation, and a flute helically wrapped around the stem. The auger further includes a shank at the first end of the body configured to be received by a power tool and a cutting head at the second end of the body. The cutting head includes a cutting edge, a spur, and a feed screw with a thread. The thread has a pitch and a nonsymmetrical thread profile. The pitch of the thread is at least 2.5 mm.

In another embodiment, the invention provides an auger including a body with a first end, a second end opposite the first end, a stem that extends from the first end to the second end and defines an axis of rotation, and a flute helically wrapped around the stem. The auger further includes a shank at the first end of the body configured to be received by a power tool and a cutting head at the second end of the body. The cutting head includes a cutting edge, a cutting face adjacent the cutting edge, a spur, and a feed screw with a thread. The cutting face includes a first surface portion extending from the cutting edge toward the flute and a second surface portion extending from the first surface portion to the flute. A primary angle measured between the first surface portion and a plane defined by the cutting edge and the axis of rotation is greater than a secondary angle measured between the second surface portion and the plane. The flute has a pitch in a range between 30 mm and 70 mm and a width measured in a direction parallel to the axis of rotation in a range between 25 mm and 50 mm.

In another embodiment, the invention provides an auger including a body with a first end, a second end opposite the first end, a stem that extends from the first end to the second end and defines an axis of rotation, and a flute helically wrapped around the stem. The auger further includes a shank at the first end of the body configured to be received by a power tool and a cutting head at the second end of the body. The cutting head includes a cutting edge formed on an edge of the flute at the second end of the body, a spur extending from the second end of the body on a diametrically opposite side of the axis of rotation from the cutting edge, and a feed screw positioned between the cutting edge and the spur. The feed screw includes a base connected to the stem, a tip opposite the base, and a thread. The spur extends from the flute past the base of the feed screw. The spur extends axially past the cutting edge a distance equal to at half a pitch of the thread of the feed screw.

DETAILED DESCRIPTION

FIGS. 1-7illustrate an auger10for use with a power tool, such as, for example, a drill, a driver drill, an impact driver, and the like. The auger10may be used to cut holes or drill into a workpiece such as wood and the like. In some particular applications, the workpiece can be a power utility pole. The illustrated auger10comes in a variety of sizes that correspond to the diameter of a hole to be created in a workpiece. For example, possible sizes of the auger10may be ⅜″, ½″, 9/16″, ⅝″, 11/16″, ¾″, 13/16″, ⅞″, 15/16″, 1 1/16″, 1⅛″, and 1¼″. In other embodiments, the auger10may be other sizes.

With reference toFIG. 1, the auger10includes a body14having a first or workpiece-engaging end18, a second or rearward end22configured to be received in a tool holder or chuck of a power tool, a stem26extending from the first end18to the second end22, and a flute30. The auger10may come in a variety of different lengths defined between the first and second ends18,22. In some embodiments, the length of the auger may be 18″,24″ or 30″ although other lengths are possible. The stem26defines an axis of rotation34that the auger10rotates about during a drilling operation. The flute30is helically wrapped around the stem26and extends the full length of the body14. In the illustrated embodiment, the auger10includes a single flute30. In other embodiments, the auger10may include multiple flutes30. In further embodiments, the auger10may not include a flute30.

With continued reference toFIG. 1, the second end22of the auger10includes a hex-shaped shaft or shank38that is configured to be coupled to the power tool. The shank38is approximately one sixth to one tenth the total length of the auger10. An indication band42is located adjacent the shank38on the second end22of the auger10. The indication band42may indicate to a user the size of the auger10. The indication band42may be a variety of colors such as red, green, blue, purple, orange, yellow, etc.

With reference toFIG. 2, a cutting head46is located at the second end22of the body14. The cutting head46includes a feed screw50, a cutting edge54, and a spur58. The feed screw50extends from the stem26and includes a tip62at the furthest point of the feed screw50, a base66opposite the tip62and adjacent the stem26, a feed screw surface70, and a thread74that is helically wrapped around the feed screw surface70from the base66to the tip62. In the illustrated embodiment, the feed screw50includes a single thread74. In other embodiments, the feed screw50may include more than one thread74. In further embodiments, the base66of the feed screw50has a diameter between 6 mm and 8 mm and the length of the feed screw is between 10 mm and 16 mm. The thread74includes a top surface78facing away from the body14and a bottom surface82facing the body14. The top and bottom surfaces78,82define a nonsymmetrical profile for the thread74. In other words, the top surface78and bottom surface82extend from the feed screw50at different angles. The top surface78extends obliquely from the feed screw50, and the bottom surface82extends substantially flat from the feed screw50. The bottom surface82of the thread74defines an angle86with the axis of rotation34. The substantially flat bottom surface82inhibits the thread74from losing engagement from a workpiece during a drilling operation. The thread74also includes a peak angle90defined between the top and bottom surfaces78,82of the thread74. The peak angle90is generally an acute angle and may be within a range between 50 degrees and 70 degrees. The thread74includes a depth94measured in a direction perpendicular to the axis of rotation34from the feed screw surface70to a point where the bottom and top surfaces78,82meet. As shown in Table 1 below, the depth94of the thread74may vary depending on the size of the auger10.

In addition, the pitch of the thread74is larger than the depth94of the thread. As shown in Table 2 below, the pitch of the thread74may vary depending on the size of the auger10. In some embodiments, the pitch of the thread may be at least 2.5 mm. In other embodiments, the pitch of the thread is in a range between 2.5 mm and 3 mm.

The high pitch of the thread74increases the speed of the auger10during a drilling operation on a workpiece. The high pitch of the thread74also allows for the depth94to be increased. Overall, the feed screw50of the auger10increases the speed of a drilling operation in a workpiece and reduces chipping around the edge of the hole being drilled.

With reference toFIG. 3, the cutting edge54is positioned on an end of the flute30at the second end22of the body14. In some embodiments, the distance between the cutting edge54and the base of the feed screw66is less than 3 mm. Adjacent the cutting edge54is a cutting face98that extends from the cutting edge54towards the first end18of the body14. The cutting face98includes a first surface portion102extending from the cutting edge54towards the flute30and a second surface portion106extending from the first surface portion102to the flute30. The first surface portion102defines a primary cutting angle110measured between the first surface portion102and a plane defined by the cutting edge and the axis of rotation34. The primary cutting angle110can be about 31 degrees to about 39 with some embodiments being about 35 degrees. The first surface portion102includes a height114measured in a direction parallel to the axis of rotation34. The height114of the cutting edge54is thin to reduce drag while drilling, but remains durable. The second surface portion106provides a smooth transition between the sharp cutting edge54and the flute30. The second surface portion106defines a secondary cutting angle118measured between the second surface portion106and the plane. The secondary cutting angle118is at an angle that is approximately twice as big as the primary cutting angle110. As shown in Table 3 below, the secondary cutting angle118may vary depending on the size of the auger10.

With continued reference toFIG. 3, the cutting head46includes a back taper surface122extending from the cutting edge54in a direction opposite the cutting face98along the flute30. The back taper surface122defines a back taper angle126between an axis perpendicular to the axis of rotation34and the back taper surface122. The back taper angle126is a relatively small non-zero angle. In some embodiments, the minimum back taper angle126matches the angle of the feed screw pitch. In other embodiments, the back taper angle126is greater than the angle of the feed screw pitch. In some embodiments, the minimum distance between the back taper surface122and the second surface portion106is 3.5 mm. As shown in Table 4 below, the back taper angle126may vary depending on the size of the auger10.

Now referring toFIG. 4, the spur58extends from the cutting head46away from the body14on a generally diametrically opposite side of the axis of rotation34from the cutting edge54. The spur58is designed to create a clean cutting hole by scoring the hole before the cutting edge54begins to remove material. The spur58includes a bottom130adjacent the cutting head46and a top134opposite the bottom130. The top134of the spur58extends past the cutting edge54away from the body14in a direction parallel to the axis of rotation34by a first distance138. The first distance138is equal to or greater than half of the pitch of the thread74of the feed screw50. In some embodiments, the first distance138is in a range of 1 mm to 2 mm. The top134of the spur58also extends past the base66of the feed screw50a second distance142to reduce the force required for the auger10to exit a workpiece during a drilling operation. A third distance146between the bottom130of the spur58and the base66of the feed screw50is larger than the pitch of the thread74of the feed screw50to inhibit chips from the workpiece getting stuck during a drilling operation.

The spur58also has a height150between the bottom130of the spur58and the top134of the spur58in a direction parallel to the axis of rotation34. As shown in Table 5 below, the height150of the spur58may vary depending on the size of the auger10.

With reference toFIG. 5, the cutting head46of the auger10defines a stepped region154that provides stability during a drilling operation. The stepped region154has a maximum diameter that is greater than a maximum diameter of the body14. In some embodiments, the minimum difference between the maximum diameter of the stepped region154and the maximum diameter of the body14is 0.5 mm. The stepped region154includes a step158where the body14transitions to the cutting head46. The step158extends in a direction perpendicular to the axis of rotation34on the peripheral of the flute30. A length162of the step158is measured between the step158and the tip134of the spur58. A ratio of the outside diameter of the body14to the length162of the step158is between about 0.5 and about 1.5. In particular, for augers10having an outside diameter of the body14between ⅜″ and ⅝″, a ratio of the outside diameter of the body14to the length162of the step158is between 0.45 and 1; for augers10having an outside dimeter of the body14between 11/16″ and ⅞″, a ratio of the outside diameter of the body14to the length162of the step158is between 0.77 and 0.95; and for augers10having an outside diameter of the body14between 15/16″ and 1¼″, a ratio of the outside diameter of the body14to the length162of the step158is between 0.92 and 1.55. As shown in Table 6 below, the maximum diameter of the stepped region154, the maximum diameter of the body14, and the length162of the step158may vary depending on the size of the auger10.

With reference toFIG. 7, the flute30is designed to have a maximum flute volume that facilitates chip removal. The pitch of the flute30is larger than previous augers to reduce the time the chips are in the flute30. The flute30has a width166measured in a direction parallel to the axis of rotation34. The width166of the flute is larger than previous augers to avoid chips becoming stuck and clogging the flute30. The larger width166and pitch of the flute30reduce the weight of the auger10to reduce user fatigue. A distance168defined between parallel surfaces of the wraps of the flute is between a range of 8 mm and 25 mm. As shown in Table 7 below, the pitch and width166of the flute30may vary depending on the size of the auger10.

In some embodiments, the auger10may include several coatings. For example, a top coating of a general purpose low-friction dry film lubricant may be applied to reduce friction during a drilling operation of the auger10. In addition, a low-friction, internally reinforced coating improves abrasion resistance of the auger10. Further, black phosphate may be used as a transition coating for improved coating adhesion to the auger10. The coatings reduce drilling time, reduce the force needed to remove the auger10from a workpiece, and help wood chips eject through the flute30.

As discussed above, the auger10is meant for use with a rotary tool. The rearward end22of the auger10is received in a chuck of the rotary tool. The rotary tool rotates the auger10clockwise towards a workpiece. When a user engages the workpiece with the auger10, the feed screw50first engages the workpiece to create a pilot hole for the cutting head46to easily follow into. The thread74grasps the workpiece to provide stability during drilling. Once the feed screw50is engaged, the spur58scores a hole in the workpiece ahead of the cutting edge54to inhibit the edges of the hole from chipping. During drilling, the cutting edge54cuts (e.g., break up) material from the workpiece and directs the cut material to the flute30of the auger10. As the auger10advances through the workpiece, the spur58continues to score a path for the cutting edge54and the cutting face98directs the cut material to the flute30for exit. Once the hole is complete, the user may retract the auger10from the hole and repeat as necessary.

Accordingly, providing an auger10with a feed screw50with an aggressive pitch and nonsymmetrical thread74increases the rotational speed of the auger10so a user may quickly cut holes in a workpiece while reducing the chance of the feed screw50from disengaging from the workpiece. Additionally, providing an auger10with a cutting edge54that has a cutting face98with a sharp primary cutting angle110reduces drag on the auger10to increase the rotational speed more. Further, an auger10with a spur58that extends past a cutting edge54allows the auger10to produce a clean drilling hole in a workpiece.