WO2022115909A1

WO2022115909A1 - Twist drill for shallow angle drilling

Info

Publication number: WO2022115909A1
Application number: PCT/AU2021/051436
Authority: WO
Inventors: Patrick Thornton
Original assignee: Loggo Ip Pty Ltd
Priority date: 2020-12-04
Filing date: 2021-12-02
Publication date: 2022-06-09

Abstract

The present invention relates generally to a twist drill useful for boring holes into wood, wood composites and other lignin-based materials. In particular, the invention relates in one form to twist drill having a rotational axis and comprising: a body portion having a flute running helically at a helix angle therealong, and a tip portion having a point, the point having a point angle, wherein the helix angle and point angle are both determined by reference to rotational axis, and the point angle is about equal to or less than the helix angle.

Description

TWIST DRILL FOR SHALLOW ANGLE DRILLING

5 FIELD OF THE INVENTION

[001]. The present invention relates generally to a twist drill useful for boring holes into wood, wood composites and other lignin-based materials. In particular, the invention relates to a twist drill useful for boring holes at shallow angles. 0

BACKGROUND TO THE INVENTION

[002]. Advances in the engineering of wood products have allowed for the production of composite timber members capable of use in structural applications such as beams, joists, columns, roof trusses, lintels, framing members, and the like.

[003]. In the manufacture of some composite timber structural members it is necessary to laminate together two of more elongate members of a relatively small cross-sectional area to produce a member of large cross-sectional area. In this way, lower value timbers such as rounds and peeler cores may be exploited to produce high value engineered timber0 structural members.

[004]. In the manufacture of some composite timber structural members, the elongate smaller members are aligned longitudinally and metal rods are inserted through each of the smaller members to improve load bearing capacity. Multiple rods may be inserted along5 the central axis of composite member.

[005]. The rods may be angled into the composite member forming a repeating “V” pattern comprising alternately acutely and obtusely angled rods. In this way, a trussing effect is provided with load exerted in the central region of the composite member being distributed0 to the termini. The termini of composite member are typically supported, and thus load is transferred to the supports. [006]. Typically, rods are inserted into pre -drilled boreholes of appropriate diameter and length. An adhesive may be used to increase engagement between a rods and the borehole wall.

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[007]. Particularly where three or more smaller members are laminated together, it is sometimes necessary to insert rods at shallow angles. In some circumstances, angles of between 20° and 40° are used. Accordingly, boreholes to accept the rods must be drilled at shallow angles to the surface where the drill bit first penetrates. A problem presents in0 that the drill bit tip may not directly enter the wood, and instead skip across the surface or judder against the surface leading to damage of the wood. In addition or alternatively, the drill bit may enter the wood but not at the required angle, or may enter the wood at multiple positions.

[008]. In applications requiring the borehole to be of an extended length, a relatively long drill bit is required. Longer drill bits are more difficult to control, to the extent that the tip has a greater propensity to deviate from a desired central point during rotation of the bit. This undesirable deviation is facilitated by contact of the drill bit tip on the wood surface, given that the pressure occasioned leads to a slight flexing of the bit. The rapid axial0 rotation of the drill bit amplifies the deviation, thereby leading to the aforementioned problems.

[009]. The prior art addresses these problems by teaching the drilling of a relatively small pilot hole with a first drill bit. The first drill bit is removed, and a second main drill bit is5 seated using the pilot hole and then drilling to the required depth is carried out. While this approach can be effective, complication is added by the need for a pilot hole drilling step and the associated additional hardware. For the large scale automated production of composite structural members, the addition of steps and hardware adds significantly to cost. 0 [010]. Another approach of the prior art is to use a jig of some description to hold the motor housing of a drill such that the bit extends at the required angle to the wood surface. That approach may be effective where the drill bit is short, it is much less effective where longer bits are used to form deep boreholes. Longer bits are more liable to flex, and the tip is therefore more likely to deviate from its preferred central position. A jig is unable to control deviation of the tip leaving open the possibility for skipping and juddering.

[Oi l]. It is an aspect of the present invention to provide an improvement to prior art drill bits so as to be useful or more useful in drilling holes at shallow angles, and without any skipping. It is a further aspect of the present invention to provide a useful alternative to prior art drill bits.

[012]. The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

SUMMARY OF THE INVENTION

[013]. In a first aspect, but not necessarily the broadest aspect, the present invention provides a twist drill for drilling a borehole into a lignin-based material, the twist drill having a rotational axis and comprising: a body portion having a flute running helically at a helix angle therealong, and a tip portion having a point, the point having a point angle, wherein the helix angle and point angle are both determined by reference to rotational axis, and the point angle is about equal to or less than the helix angle.

[014]. In one embodiment of the first aspect, the point comprises two cutting lips, and the point angle is determined by reference to the cutting lip of one of the two cutting lips. [015]. In one embodiment of the first aspect, the helix angle is determined by reference to the angle made with a flute edge.

[016]. In one embodiment of the first aspect, the flute edge is configured as a secondary cutting edge.

[017]. In one embodiment of the first aspect, the twist drill comprises two cutting lips and two flutes.

[018]. In one embodiment of the first aspect, the point angle is about 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, or 30% of the helix angle.

[019]. In one embodiment of the first aspect, the point angle is between about 50% and about 80% of the helix angle.

[020]. In one embodiment of the first aspect, the point angle is between about 60% and about 70% of the helix angle.

[021]. In one embodiment of the first aspect, the helix angle is between about 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0-fold that of the point angle.

[022]. In one embodiment of the first aspect, wherein the helix angle is between about 1.3 and about 1.7-fold that of the point angle.

[023]. In one embodiment of the first aspect, the helix angle is between about 1.4 and about 1.6 - fold that of the point angle.

[024]. In one embodiment of the first aspect, the point angle is less than about 50°, 45°, 40°, 35°, 30°, 25°, 20°, 15°, or 10°.

[025]. In one embodiment of the first aspect, the point angle is between about 30° and about 10°.

[026], In one embodiment of the first aspect, the point angle is between about 25° and about 15°. [027]. In one embodiment of the first aspect, the tip portion has a length of at least about 3mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, or 13 mm, the length being measured along the rotational axis

[028]. In one embodiment of the first aspect, the cutting lip of the point portion is continuous with a flute edge,

[029]. In one embodiment of the first aspect, the twist drill comprises a helical land, wherein the cutting lip of the point portion is continuous with the helical land.

[030]. In one embodiment of the first aspect, wherein the tip portion transitions directly to the outer circumference of the body portion

[031]. In one embodiment of the first aspect, the tip portion is not a barb, or a spur, or a feed screw.

[032]. In one embodiment of the first aspect, the twist drill is devoid of a barb, or a spur, or a feed screw.

[033]. In one embodiment of the first aspect, the twist drill is not configured as a self-feed drill.

[034]. In one embodiment of the first aspect, the twist drill is not configured as an auger drill, or a Brad point drill, or a spade drill.

[035]. In one embodiment of the first aspect, the tip portion has an apex region.

[036]. In one embodiment of the first aspect, the twist drill comprises a barb extending from the apex region.

[037]. In one embodiment of the first aspect, the barb has a length of between about 1 mm and 3 mm, the length being measured along the rotational axis

[038]. In one embodiment of the first aspect, the twist drill comprises a shank portion connected to the body portion. [039]. In one embodiment of the first aspect, the length of body portion, or the combined length of the body portion and shank portion is at least about 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm or 100 cm.

[040]. In one embodiment of the first aspect, the twist drill is configured as a drill bit.

[041]. In a second aspect, the present invention provides a method of drilling a borehole into a lignin-based material at a desired angle, the method comprising: providing the twist drill of any embodiment of the first aspect, holding the twist drill such that its rotational axis is at a desired angle to the surface of, or an axis of, the lignin-based material, contacting the tip portion of the twist drill with the lignin-based material, rotating the twist drill about its rotational axis, and maintaining the twist drill at the desired angle and urging the twist drill into the ligninbased material.

[042]. In one embodiment of the second aspect, the desired angle is less than about 45°, 40°, 35°, 30°, 25°, 20° or 15°.

BRIEF DESCRIPTION OF THE FIGURES

[043]. FIG. 1 A illustrates a typical prior art drill bit in lateral view.

[044]. FIG. IB is a magnification of the tip portion of the drill bit illustrated in FIG. 1, showing the cutting lips and the angle formed by the cutting lip #1 with the rotational axis of the drill bit.

[045]. FIG. 2A illustrates a preferred drill bit of the present invention in lateral view.

[046]. FIG. 2B is a magnification of the tip portion of the drill bit illustrated in FIG. 2, showing the cutting lips and the angle formed by the cutting lip #1 with the rotational axis of the drill bit. [047]. FIG. 3A illustrates the tip portion of a drill bit of the present invention, having a barb extending from the apex region thereof.

5 [048]. FIG. 3B illustrates the tip portion of a drill bit of the present invention, having a threaded part of the tip portion, as for an auger bit.

[049]. FIG. 4 illustrates two boreholes drilled at equal but opposite angles into a composite timber structural member. The angles are shallow, and the holes may be bored by a drill0 bit of the present invention.

[050]. Unless otherwise indicated herein, features of the drawings labelled with the same numeral are taken to be the same features, or at least functionally similar features, when used across different drawings.

[051]. The drawings are not prepared to any particular scale or dimension and are not presented as being a completely accurate presentation of the various embodiments. 0 DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF

[052]. After considering this description it will be apparent to one skilled in the art how the invention is implemented in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be5 described herein, it is understood that these embodiments are presented by way of example only, and not limitation. As such, this description of various alternative embodiments should not be construed to limit the scope or breadth of the present invention. Furthermore, statements of advantages or other aspects apply to specific exemplary embodiments, and not necessarily to all embodiments, or indeed any embodiment covered by the claims. 0 [053]. Throughout the description and the claims of this specification the word "comprise" and variations of the word, such as "comprising" and "comprises" is not intended to exclude other additives, components, integers or steps.

5 [054]. Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but0 may.

[055]. The present invention is predicated at least in part on the inventor’s discovery that improved or alternative drilling into wood members at shallow angles is provided by the use of a twist drill having a point angle that is less than the helical angle of the flutes. Reference is made to FIG. 1A and FIG. IB which illustrate a typical fluted wood drill bit of the prior art, labelled using terminology common in the art. It will be noted that the point angle is greater than the helix angle, both angles being the smallest angle measured from the rotational axis. . 0 [056]. By comparison, and in reference to FIG. 2A and FIG. 2B the twist drill of the present invention has a point angle that is less than the helix angle. As shown in FIG. 2 A the twist drill (10) of the present invention shares features with prior art twist drills, both having a shank portion (15), a body portion (20) and a tip portion (25). The body portion (20) has prominent helical flutes (30) which function (as in the prior art) to convey the5 wood removed in the course of drilling (swarf) to the surface of the borehole. The flutes (30) are abutted by the land (35). At the juncture between the flute (30) and land (35) there is a flute edge (40) which is overlayed by the dashed line (45) to define the helix angle (50). The helix angle (50) is determined by measuring the angled formed by the dashed line (45) with the rotational axis. 0 [057]. Considering the magnified drawing of the tip portion in FIG. 2B, the two cutting lips (55) (60) are clearly shown. As for prior art drill bits, the cutting lips (55) (60) act to remove wood material to form the borehole as the bit is advanced into the wood. The point angle (65) is measured as the angle made by the rotational axis and the dashed line (70)

5 overlayed on the cutting lip (55). The point angle is clearly smaller than that for a prior art twist drill shown in FIG. 1A and FIG. IB.

[058]. It will be noted that in the present invention as shown in FIG. 2A and FIG. 2B, the tip portion of the drill bit is notably longer (axially) as compared with the prior art drill bit0 illustrated in FIG. 1A and FIG. IB. The longer tip is associated with the decreased point angle as required by the present invention. The diameter of the drill bit (10) is fixed according to the diameter of borehole required, and in order to reduce the point angle the tip is elongated. An advantage of the elongate tip portion is that it acts to drill an elongate pilot hole of sorts, preparing for the body of the drill bit to enter as the drill bit is advanced into the wood. Furthermore, the elongate tip tends to remain within the just formed relatively deep hole thereby inhibiting lateral or outward axial movement of the drill bit, which in turn limits the opportunity for the drill bit to exit the borehole and/or skip across the surface. A prior art drill bit having a shorter and broader tip portion is unable to bore deeply before the full diameter of the body portion contacts the wood, and accordingly is0 more liable to exit the shallow hole formed by the tip.

[059]. Furthermore, a prior art drill bit contacting a wood surface at a shallow angle may not even allow the tip region to contact the surface given its short and broad dimensions. When the bit rotates, the body portion cuts at the wood surface each time one of the flute5 edges pass over it. As will be understood, the rotating body portion contacts the wood surface alternately with the smooth surface of the land, and then with the flute edge leading to juddering of the bit. By contrast, the tip portion of the present twist drill is more tightly angled, slender, and elongate allowing for the tip to enter to a greater depth in the wood before the body portion contacts the wood surface. 0 [060]. Applicant conceived the true nature of the problem of drill bits skipping across surfaces being drilled at a shallow angle, and devised the present twist drill to overcome that problem. The problem does not routinely arise with prior art drill bits used at more steep angles given that the bit is being urged generally toward a central region of the wood

5 and is therefore unlikely to skip or judder. It is only due to the need to improve drilling at shallow angles in the course of manufacturing engineered timber structural members. Reference is made to FIG. 4 showing such an application, being the manufacture of a structural member (100) being formed compositely from three sub-members (105) (110) (115). Two drilled boreholes (120) (125) are shown, each may be formed by a twist drill0 of the present invention so as to avoid or limit any of the problems identified herein in drilling at shallow angles. As a further step in manufacture, steel rods are inserted into the boreholes (120) (125) to reinforce the structural member (100).

[061]. Turning back now to FIG. 2B it should be noted that in the preferred drawn embodiment the cutting lip of the tip is continuous with a flute edge, providing for an uninterrupted and smooth transition to the body portion. This is very different to a prior art auger drill bit, for example, whereby the tip forms a discrete structure to the body portion. Accordingly, when an auger bit is urged past the tip portion, the rapid change in dimension from the tip to the body acts to destabilise the bit, especially at very shallow0 angles of entry.

[062]. Arranging the cutting lip of the tip continuous with a flute edge provides the further advantage that swarf removed by the cutting lip is immediately conveyed away by the associated flute and not left on surface. Applicant has found that swarf left on the surface5 can facilitate the bit skipping over the surface by inhibiting direct contact of the bit with the surface. Keeping the helix angle at around prior art angles facilitates the removal of swarf, but decreasing the point angle relative to the helix angle provides the advantages described herein. 0 [063]. The point angle may be selected according to a particular application. Lower point angles are generally preferred for more shallow drilling angles. The lower angles provided for a highly elongate and slender tip thereby providing for greater engagement with the wood when drilling at first. High drilling angles are associated with a higher propensity for juddering and skipping, and accordingly greater levels of engagement between bit and wood are required to prevent or inhibit same.

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[064]. The present twist drill may be fabricated by modifying a prior art fluted twist drill. Material is ground away from the existing tip region, and also the adjacent body region to elongate the tip region and provide a point angle that is greater than the helix angle. The grinding provides two cutting lips, each of which is longer than those of the prior art0 starting twist drill. Each of the cutting lips is preferably ground to form a sharp edge to facilitate progressive cutting of wood to form the borehole. If removed in the course of modification, a new chisel edge may be ground at the junction of the two cutting lips to form a sharp apex on the tip portion.

[065]. Alternatively, the twist drill of the present invention may be formed de novo, by exploiting prior art methods of twist drill fabrication although modified so as to provide a point angle being less than the helix angle.

[066]. Referring now to FIG. 3A there is shown an embodiment whereby the apex region0 of the tip (200) has a barb (205) extending therefrom. The barb is in this embodiment of generally planar construction, being fabricated from a sufficiently hard metal and formed with a point at the terminus. The barb (205) may be formed separately from metal plate and welded to the tip (200) apex region. 5 [067]. The barb may be urged into the wood before rotation of the drill commences so as to further lessen the possibility of any skipping or juddering when the drill bit (10) is rotated. Alternatively, the barb (205) may first contact the wood when the drill bit (10) is already rotating, and in which case it forms an initial very small borehole with very little risk of any skipping or juddering. The stabilisation provided by the very small borehole0 assists in ensuring the following tip portion enters the wood cleanly and at the desired angle. The further stabilisation provided borehole formed by the tip in turn assists in ensuring the following body portion enters the wood cleanly and at the desired angle.

[068]. The embodiment shown in FIG. 3B has a threaded section (210) on the tip portion. The function of the threaded section (210) is analogous to the threaded tip of an auger drill bit which acts to assist in starting a bore hole and maintaining the tip in place on the wood surface. It should be noted that this embodiment is distinguished from a prior art auger drill bit given the presence of the specially configured and angled tip portion.

[069]. The present twist drill may be utilised as a pilot bit (also known as a leader bit) in the context of a hole saw. Accordingly, in one aspect the present invention provides a hole saw comprising a twist drill of any embodiment described herein, the twist drill being configured as a pilot bit.

[070]. Those skilled in the art will appreciate that the invention described herein is susceptible to further variations and modifications other than those specifically described. It is understood that the invention comprises all such variations and modifications which fall within the spirit and scope of the present invention.

[071]. While the invention has been disclosed in connection with the preferred embodiments shown and described in detail, various modifications and improvements thereon will become readily apparent to those skilled in the art.

[072]. Accordingly, the spirit and scope of the present invention is not to be limited by the foregoing examples, but is to be understood in the broadest sense allowable by law.

Claims

CLAIMS:

1. A twist drill for drilling a borehole into a lignin -based material, the twist drill having a rotational axis and comprising: a body portion having a flute running helically at a helix angle therealong, and a tip portion having a point, the point having a point angle, wherein the helix angle and point angle are both determined by reference to rotational axis, and the point angle is about equal to or less than the helix angle.

2. The twist drill of claim 1 , wherein the point comprises two cutting lips, and the point angle is determined by reference to the cutting lip of one of the two cutting lips.

3. The twist drill of claim 1 or claim 2, wherein the helix angle is determined by reference to the angle made with a flute edge.

4. The twist drill of claim 3, wherein the flute edge is configured as a secondary cutting edge

5. The twist drill of any one of claims 2 to 4 comprising two cutting lips and two flutes.

6. The twist drill of any one of claims 1 to 5, wherein the point angle is about 95%, 90%, 85%, 80%,

75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, or 30% of the helix angle.

7. The twist drill of any one of claims 1 to 5, wherein the point angle is between about 50% and about 80% of the helix angle.

8. The twist drill of any one of claims 1 to 5, wherein the point angle is between about 60% and about 70% of the helix angle.

9. The twist drill of any one of claims 1 to 8, wherein the helix angle is between about 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0-fold that of the point angle.

10. The twist drill of any one of claims 1 to 8, wherein the helix angle is between about 1.3 and about 1.7-fold that of the point angle.

11. The twist drill of any one of claims 1 to 8, wherein the helix angle is between about 1.4 and about 1.6 -fold that of the point angle.

12. The twist drill of any one of claims to 11 , wherein the point angle is less than about 50°, 45°, 40°, 35°, 30°, 25°, 20°, 15°, or 10°.

13. The twist drill of any one of claims 1 to 11, wherein the point angle is between about 30° and about 10°.

14. The twist drill of any one of claims 1 to 11, wherein the point angle is between about 25° and about 15°.

15. The twist drill of any one of claims 1 to 14, wherein the tip portion has a length of at least about 3mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, or 13 mm, the length being measured along the rotational axis

16. The twist drill of any one of claims 1 to 15, wherein the cutting lip of the point portion is continuous with a flute edge,

17. The twist drill of any one of claims 1 to 16 comprising a helical land, wherein the cutting lip of the point portion is continuous with the helical land.

18. The twist drill of any one of claims 1 to 17, wherein the tip portion transitions directly to the outer circumference of the body portion

19. The twist drill of any one of claims 1 to 18, wherein the tip portion is not a barb, or a spur, or a feed screw.

20. The twist drill of any one of claims 1 to 19, that is devoid of a barb, or a spur, or a feed screw.

21. The twist drill of any one of claims 1 to 20 that is not configured as a self- feed drill.

22. The twist drill of any one of claims 1 to 20 that is not configured as an auger drill, or a Brad point drill, or a spade drill.

23. The twist drill of any one of claims 1 to 22, wherein the tip portion has an apex region.

24. The twist drill of any one of claims 1 to 23 comprising a barb extending from the apex region.

25. The twist drill of claim 24, wherein the barb has a length of between about 1 mm and 3 mm, the length being measured along the rotational axis

26. The twist drill of any one of claims 1 to 25 comprising a shank portion connected to the body portion.

27. The twist drill of claim 26, wherein the length of body portion, or the combined length of the body portion and shank portion is at least about 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm or 100 cm.

28. The twist drill of any one of claims 1 to 27 configured as a drill bit.

29. A method of drilling a borehole into a lignin-based material at a desired angle, the method comprising: providing the twist drill of any one of claims 1 to 28, holding the twist drill such that its rotational axis is at a desired angle to the surface of, or an axis of, the lignin -based material, contacting the tip portion of the twist drill with the lignin-based material, rotating the twist drill about its rotational axis, and maintaining the twist drill at the desired angle and urging the twist drill into the lignin-based material.

30. The method of claim 29, wherein the desired angle is less than about 45°, 40°, 35°, 30°, 25°, 20 or 15°.

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