Hole boring apparatus

Abstract

A hole boring apparatus and method for boring holes in earth is disclosed that includes, a support frame including an earth engaging member and an upright tubular portion adjacent to the earth engaging member so as to provide a passageway therethrough from a top of the tubular portion through the earth engaging member. Also included is a boring member, including a shaft comprising a shaft lower end and a shaft upper end, a blade adjacent to the shaft lower end, a handle adjacent to the shaft upper end, the shaft being located within the passageway of the tubular portion to allow rotation of the shaft, the handle is operational for initiating rotation of the shaft.

Description

TECHNICAL FIELD

[0001] This invention relates to apparatus for boring holes suitable for transplanting plants from pots into the earth.

BACKGROUND OF INVENTION

[0002] The transplanting of plants from small pots of diameter in the range 50 to 250 mm normally requires a hole to be bored or dug in the earth of slightly greater diameter than that of the pot and up to a depth of 250 mm. In a domestic situation the number of plantings required are relatively few and normally the holes are dug by means of a shovel or spade. If the earth is particularly difficulty to dig because of stones or the earth composition or condition, a pick, mattock or crow bar may be necessary to form the hole. This can be inconvenient and an apparatus that can form holes in such difficult earths would be desirable. Furthermore, when plantings are undertaken on a larger commercial scale as in the forestry industry, more convenient hole digging apparatus are desirable.

[0003] One known type of hole digging apparatus is auger type equipment. These involve a helical fluted blade arranged around a central shaft. The auger is usually operated by rotating the shaft by powered means, such as a power drive attachment to a tractor. This equipment is often used for digging postholes and the rotation of the helical flukes causes the earth to be transported to the top of the hole. However, these auger type hole diggers are not convenient for digging the relatively shallow holes required for transplanting plants. Furthermore, the normal requirement for other than manual operation renders this type of equipment unsuitable for areas where powered drives are not available. Manually operated auger type hole diggers are difficult to operate in hard clay or rocky earths.

[0004] A further posthole digger is disclosed in U.S. Pat. No. 5,669,648. The apparatus of this invention involves the downward driving of sharpened shovel blades. It requires the use of considerable downward force from either a sledgehammer or the weight of the operator when jumping. A posthole digger is also disclosed in U.S. Pat. No. 5,209,534. However, the digger of that invention is not suitable for use in hard earths unless the earth is moistened with water before the hole is dug.

SUMMARY OF INVENTION

[0005] The present invention of a hole boring apparatus provides in one form a hole boring apparatus for boring holes in earth for the purpose of placing plantings into the bored holes. The hole boring apparatus includes, a support frame comprising an earth-engaging member and an upright tubular portion joined or adjacent to the earth-engaging member so as to provide a cylindrical passageway from the top of the tubular portion through the earth engaging member therethrough. The hole boring apparatus also includes, a boring member including a shaft comprising a shaft lower end and a shaft upper end, a blade adjacent to the shaft lower end, and a handle adjacent to the shaft upper end, with the handle being operational to facilitate rotation of the shaft. The shaft is located within the passageway of the tubular portion to allow rotation of the shaft.

[0006] Preferably the earth engaging member includes two foot portions located either side of the tubular portion and adapted for locating the soles of an operator's feet. Also preferably, the earth engaging member further includes downwardly directed earth piercing spikes to locate the hole boring apparatus in the surface of the earth.

[0007] In addition, it is preferred that the earth engaging member is in the form of an elongate strip with the foot portions swept back and angled, in use, towards the operator. Preferably, the foot portions are lower than a central portion of the elongate strip so that when the foot portions are in contact with the earth surface the blade is able to rotate without contacting the earth surface.

[0008] Preferably the handle is in the form of a T-bar.

[0009] Preferably the shaft is 100 200 mm longer than the tubular portion.

[0010] Preferably the blade is a pair of blades with working edges angled towards the direction of rotation and shaped to provide a downward cutting action on the earth.

[0011] In an alternative embodiment, the apparatus includes resilient urging means to apply, in use, downward force on the blade. Preferably, the urging means is a helical spring mounted around the shaft and the upper portion of the spring is located within a recess formed between the elongate strip and the upright tubular portion. In another alternative embodiment, the apparatus includes an annular section adjacent to the blade ends for use in moist or plastic earths, wherein the annular section causes the earth to be removed in the form of a plug of earth from the hole.

BRIEF DESCRIPTION OF DRAWINGS

[0012] FIG. 1 is a perspective view of a hole boring apparatus assembly;

[0013] FIG. 2 is a cross-sectional view of an alternative embodiment of the hole boring apparatus utilizing a means for applying resilient urging force on the blade;

[0014] FIG. 3 is an expanded perspective view of another alternative embodiment of the hole boring apparatus utilizing an annular section adjacent to the ends of the blade;

[0015] FIG. 4 is a perspective view of the hole boring apparatus assembly utilizing the annular section adjacent to the ends of the blade;

[0016] FIG. 5 shows a perspective view of a core blade;

[0017] FIG. 6 shows a perspective view of an angle blade;

[0018] FIG. 7 shows a side view of an angle blade;

[0019] FIG. 8 shows an end view of an angle blade;

[0020] FIG. 9 shows a perspective view of a helical blade;

[0021] FIG. 10 shows a side view of a spear blade;

[0022] FIG. 11 shows a side view of an offset blade;

[0023] FIG. 12 shows a perspective view of an arch blade;

[0024] FIG. 13 shows a perspective view of a slide blade mount with a twist blade;

[0025] FIG. 14 shows a perspective view of a cross blade mount with a crossover blade;

[0026] FIG. 15 shows a perspective view of a flat blade mount;

[0027] FIG. 16 shows a perspective view of a fold up handle mount;

[0028] FIG. 17 shows a side view of the fold up handle mount;

[0029] FIG. 18 shows a perspective view of a flat handle mount;

[0030] FIG. 19 shows a perspective view of a circular handle;

[0031] FIG. 20 shows a perspective view of a slide in receptacle mount for an earth-engaging member;

[0032] FIG. 21 shows a perspective view of a hook receptacle mount for a separable earth-engaging member;

[0033] FIG. 22 shows a perspective view of the hook receptacle mount and separable earth-engaging member assembled;

[0034] FIG. 23 is a perspective view of the hole boring apparatus in use;

[0035] FIG. 24 is a perspective view of the hole boring apparatus in use utilizing the annular section adjacent to the ends of the blade; and

[0036] FIG. 25 is a perspective view of a cam lock safety device attached to the upright tubular portion.

REFERENCE NUMBERS IN DRAWINGS

[0037] 30 Hole Boring Apparatus Assembly

[0038] 31 Alternative embodiment of the Hole Boring Apparatus Assembly utilizing the means for applying resilient urging force on the blade

[0039] 32 Support frame

[0040] 33 Another alternative embodiment of the Hole Boring Apparatus Assembly utilizing the annular section adjacent to the ends of the blade

[0041] 34 Upright tubular portion

[0042] 36 Earth engaging member

[0043] 38 Mild steel bar

[0044] 40 Bar central portion

[0045] 42 Bar foot portion

[0046] 43 Kneepads

[0047] 44 Bar earth piercing spikes

[0048] 46 Blade

[0049] 47 Shaft upper end

[0050] 48 Shaft lower end

[0051] 49 Blade ends

[0052] 50 Annular section

[0053] 51 Annular section weld

[0054] 52 Earth cylindrical plug

[0055] 53 Annular section depth

[0056] 54 Hole, bored

[0057] 55 Hole, depth

[0058] 56 Handle

[0059] 58 Operator

[0060] 59 Operator hand

[0061] 60 Operator foot sole

[0062] 62 Handle clockwise rotation force

[0063] 64 Downward force

[0064] 66 Earth

[0065] 67 Earth surface

[0066] 68 Helical spring

[0067] 70 Recess

[0068] 72 Flange

[0069] 74 Core blade

[0070] 76 Angle blade

[0071] 78 Helical blade

[0072] 80 Spear blade

[0073] 82 Offset blade

[0074] 84 Arch blade

[0075] 86 Twist blade

[0076] 88 Female slide blade mount

[0077] 90 Male slide blade mount

[0078] 92 Setscrew

[0079] 94 Crossover blade

[0080] 96 Female cross blade receptacle

[0081] 98 Male cross blade insert

[0082] 100 Female drive flat blade receptacle

[0083] 102 Male drive flat blade insert

[0084] 104 Handle attachment screw

[0085] 106 Folding handle base

[0086] 108 Folding handle

[0087] 110 Folding handle pivot

[0088] 112 Male drive flat for shaft upper end

[0089] 114 Female drive flat for shaft upper end

[0090] 116 Circular handle

[0091] 118 Earth engaging member attachment screw

[0092] 120 Female slide in receptacle for earth engaging member

[0093] 122 Separable earth engaging member

[0094] 124 Hook receptacle for separable earth engaging member

[0095] 126 Cam lock safety device

[0096] 128 Cam lock arm movement

[0097] 130 Cam lock arm

DETAILED DESCRIPTION

[0098] While the hole boring apparatus of the present invention may take many different forms, the particularly preferred embodiments and use of the invention are detailed with reference to FIGS. 1 through 25.

[0099] Referring initially to FIGS. 1, 2, 3, and 4, the hole boring apparatus 30, 31, or 33 includes a support frame 32, which is constructed from an upright tubular portion 34 and an earth-engaging member 36. The tubular portion 34 is preferably formed from approximately 16 mm inside diameter, approximately 20 mm outside diameter, mild steel pipe with length of about 600 mm. These diameters and length may be varied to accommodate a range of types of applications. This tubular portion 34 is adjacent to the earth-engaging member 36 to provide an internal preferably cylindrical passageway therethrough. The attachment of the tubular portion 34 and earth engaging member 36 is preferably a permanent attachment by welding, or in the alternative a shrink fit interface, however, removable attachment by threads, bolting, a slide in receptacle 120 with retention screws 118, or a hook receptacle 124 mating with a separable earth engaging member 122 and the like as shown in FIGS. 20, 21, and 22 respectively would also be acceptable. An additional form of separable attachment would be through the use of a setscrew 92 in the upright tubular portion 34 as shown in FIG. 21. The earth-engaging member 36 is preferably constructed of a mild steel bar 28, 32 mm in width, 5 mm thick, and having a length of about 700 mm. The bar 38 is configured to adopt the shape shown, but could assume different widths, thicknesses, and lengths as different uses require. A central portion 40 extends about 75 mm either side of where the tubular portion 34 is adjacent. The bar 38 then is angled at about 45° downward from the horizontal for approximately 70 mm. Foot portions 42 that are generally coplanar with the central portion 40 are each angled inwardly at about 30°. Other angles may be used, especially if instead of feet, knees were used to apply downward pressure. A particularly suitable angle when knees are used is 45°. When the apparatus is used by kneeling, kneepads 43 of a resilient type material can be used on the foot portions 42. In this modified form of the apparatus suitable for kneeling use, the tubular portion 34 is approximately 150 mm in length and the total height of the apparatus 30, 31, or 33 is approximately 400 mm. Generally vertical earth 66 piercing spikes 44 are located at the lower ends of the earth-engaging member 36. The earth engaging member 36 can optionally have an additional pivoted fold out stand that pivots at each piercing spike 44 adjacent to the bar foot portion 42 with the stand adjacent to the earth surface 67 for added support of the earth engaging member 36 of the earth surface 67. Another option for the earth engaging member 36 would be to have a pivotal connection at the interface of the bar central portion 40 and the foot portion 42 to save space while transporting the apparatus 30, 31, or 33. An additional option for the earth-engaging member would be to have one earth-piercing spike 44 on one end and a large area foot platform resting on the earth surface 67 on the other end to more easily engage the earth-engaging member 36 into the earth surface 67.

[0100] An optional safety feature is the addition of a means for restricting relative movement between the upright tubular portion 34 and the shaft upper end 47. Preferably the means for restricting relative movement between the upright tubular portion 34 and the shaft upper end 47 is a cam lock safety device 126 as shown in FIG. 25 that is secured between the interface of the tubular portion 34 and the shaft upper end 47. The purpose of the cam lock safety device 126 is to prevent the shaft upper end 47 and the adjacent handle element 56 from making a hard contact with each other possibly resulting in pinching or injuring the operator hand 59 when the hole boring 54 is complete and the operator 58 lifts the hole boring apparatus 30, 31, or 33 from the earth surface 67. The cam lock safety device 126 is operated by closing the cam lock arm 130 in a movement 128 as shown in FIG. 25 thereby placing the cam lock safety device 126 into a locked state causing the relative movement between the upright tubular portion 34 and the shaft upper end 47 to be restricted. Conversely, when the operator 48 wants to bore a hole 54 making the hole boring apparatus 30, 31, or 33 operational, the cam lock arm 130 is moved in a direction opposite from movement 128 placing the cam lock safety device into an unlocked state thus allowing unrestricted relative movement between the upright tubular portion 34 and the shaft upper end 47. Other means for restricting movement between the upright tubular portion 34 and the shaft upper end 47 in the aforementioned manner would be acceptable such as a collet, or a resilient grommet, and the like.

[0101] A blade element is adjacent to the lower end of the shaft 48. The blade element can have many different configurations that can depend upon the condition of the earth 66. The blade element is meant to include any type of blade configuration that may be required, however, not limited to the following blade elements disclosed. Options for the blade element configuration could include a core blade 74 as shown in FIG. 5, an angle blade 76 as shown in FIGS. 6, 7, and 8. Other blade element configurations include, a helical blade 78 as shown in FIG. 9, a spear blade 80 as shown in FIG. 10, an offset blade 82 as shown in FIG. 11, and an arch blade 84 as shown in FIG. 12. Additionally, a longitudinal blade 46 can be used as shown in FIGS. 1, 2, 3, and 4. The blade element can be removable or permanently attached to the shaft lower end 48. The blade element can be removable by threads or bolting. Also, to make the blade element removable, a female slide blade mount 88 mating with a male slide blade mount 90, secured by a set screw 92, with the female slide blade mount 88 attached to the shaft lower end 48 and the male slide blade mount 90 attached to the blade element or as shown in FIG. 13 with the twist blade 86. Other blade element and shaft lower end 48 attachment options are utilizing a male cross blade insert 98 mating with a female cross blade receptacle 96 secured by set screw 92 as shown in FIG. 14. Note that the crossover blade 94 is shown, however, any blade element configuration could be used. Another blade element and shaft lower end 48 attachment option utilizes a male drive flat blade insert 102 attached to the shaft lower end 48 that mates with a female drive flat blade receptacle 100 being attached to the blade element, with the male drive flat blade insert 102 and female drive flat blade receptacle 100 secured by set screws 92 as shown in FIG. 15. For permanently attaching the blade element and shaft lower end 48, this is preferably accomplished by welding or a shrink fit directly to the termination of the shaft lower end 48. The shaft upper end 47 and shaft lower end 48 that comprise the shaft are preferably constructed of a 15 mm diameter mild steel rod. The combined length of both the shaft upper end 47 and shaft lower end 48 is about 900 mm. The diameter of the blade element corresponds to the diameter of the hole to be bored. It will thus usually range in diameter from 50 to 250 mm. However, longer or shorter diameters of the blade element may be used.

[0102] The shaft has a shaft upper end 47 is adjacent to a handle element. The handle element can assume a number of configurations as required for the earth 66 conditions and storage space available. These handle element configurations could include but not be limited to a T bar 56 as shown in FIGS. 1, 2, 4, 23, and 24. Additionally, the handle element could be a circular type 116 as shown in FIG. 19, or a fold up type 108 utilizing a folding handle base 106 with pivotal connections 110 as shown in FIG. 16. The handle element is preferably about 350 mm across in diameter or length, however, other diameters or lengths may be required for different earth 66 conditions, hole bore sizes 54, and hole depths 55. Attachment of the handle element to the upper shaft end 47 may be permanent or removable. Preferable permanent attachment of the handle element to the shaft upper end 47 would be by welding or alternatively a shrink fit. The removable handle element to shaft upper end 47 attachment would be preferably be by a bolt 104 as shown in FIG. 16, or alternatively, setscrews, brackets, a releasable cam lock, and the like. Also, a male drive flat 112 attached to the shaft upper end 47 could mate with a female drive flat 114 attached to the handle element being a T bar handle 56 as shown in FIG. 18. Setscrews 92 would secure the male drive flat 112 and female drive flat 114 together. Optionally, a ratchet type of arrangement could be utilized between the handle element and the shaft upper end 47 with either the permanent or removable attachment. The shaft element, which includes the shaft upper end 47 and shaft lower end 48, residing in the passageway that is internal to the upright tubular portion 34 is circular in cross-section and this is the preferred arrangement as this provides maximum bearing surfaces. However, other cross-sectional shapes can be used provided they allow rotation of the shaft element within the passageway that is internal and therethrough to the upright tubular portion 34 and the earth engaging member 36. For example, the tubular portion 34 could be a square section and the shaft element a cylindrical rod and vice versa. The blade element is preferably made of roll hardened spring steel and has a rake of about 45° towards the direction of rotation; however, other rake angles would be acceptable depending upon the earth 66 conditions. The tensile strength of the steel in the blade element is preferably 550 720 MPs. The blade is normally made from flat bar stock. The blade element may be fabricated from multiple pieces or from one piece. The blade need not have a cutting edge along its entire length. Cutting teeth may be used and these are of advantage in particularly hard earth 66. The shaft element, including the upper 47 and lower 48 ends and handle element are preferably manufactured from any suitable pipe that has the requisite strength characteristics, however, other material would be acceptable provided the strength requirements are complied with.

[0103] In an alternative embodiment the hole boring apparatus assembly 31, is shown in referring to FIG. 2, where a means for applying resilient urgent downward force 64 is preferably a helical spring 68 that is located within a recess 70. The end of the spring 68 adjacent the blade 46 and is retained by a flange 72 welded to the steel shaft lower end 48.

[0104] In another alternative embodiment the hole boring apparatus 33 is shown referring specifically to FIGS. 3, 4, and 24, where the apparatus 33 is intended for use in moist or plastic earths it is convenient to have an annular section 50 of depth 53 being approximately 15 mm that is welded 51 to the upper ends 49 of the blade 46. This annular section 50 or ring causes the earth 66 to be removed as a plug 52, facilitating the removal of the earth 66 from the hole 54.

[0105] Method of Use

[0106] The following method of use applies to all the disclosed embodiments of the hole boring apparatus 30, 31, or 33 including any type of blade or handle elements and attachment methods, referring specifically to the use FIGS. 23 and 24. Once the hole boring apparatus 30, 31, or 33 is provided, the operator 58 locates the blade 46 on the earth surface 67 where a bored hole 54 is desired, and thus the operator 58 has located the hole boring apparatus assembly 30, 31, or 33 on the earth surface 67. Next, in typical use, the operator 58 places his foot sole 60 on the foot portion 42 of the earth engaging member 36 and applies downward force on the earth engaging member 36 and causes the earth piercing spikes 44 to engage the earth engaging member 36 in the earth surface 67 thus engaging the apparatus 30, 31, or 33 into the earth surface 67. The operator 58 then grasps the handle 56 and applies by hand 59 a lateral force upon the handle 56 to force the shaft upper end 47 and shaft lower end 48 to rotate in a clockwise 62 direction while at the same time the operator 58 is applying downward force 64 upon the handle 56. This downward force 64 and lateral force 62 on the handle 56 from the operator's hand 59 causes the blade 46 to pare or cut the earth 66 and form a cylindrical hole 54. Note that the aforementioned downward pressure 64 on the handle 56 by the operators hand 59 is not required for the hole boring apparatus 31 as shown in FIG. 2 that includes the means for applying a resilient urgent downward force on the blade 46. This aforementioned process is continued until the desired bored hole depth 55 is achieved. At this point the hole boring apparatus 30, 31, or 33 is removed from the desired bored hole depth 55 and loosened earth 66 may be removed by hand 59 after part or all of the hole 54 has been formed. Further earth 66 may be removed after the apparatus 30, 31, or 33 has been removed after the required depth 55 has been reached. The depth 55 can be gauged by the relative position of the handle 56 to the upper end of the tubular portion 34.

[0107] Since modifications within the spirit and scope of the invention may be readily effected by persons skilled in the art, it is to be understood that the invention is not limited to the particular embodiment described, by way of example, hereinabove.

Claims

1. A hole boring apparatus for boring holes in earth, comprising:

(a) a support frame including an earth engaging member and an upright tubular portion adjacent to said earth engaging member so as to provide a passageway therethrough from a top of said tubular portion through said earth engaging member; and

(b) a boring member including a shaft comprising a shaft lower end and a shaft upper end, a blade adjacent to said shaft lower end, a handle adjacent to said shaft upper end, said shaft being located within said passageway of said tubular portion to allow rotation of said shaft, said handle is operational for initiating rotation of said shaft.

2. A hole boring apparatus as defined in claim 1 wherein said earth-engaging member includes a foot portion located on a side of said tubular portion and adapted for locating a sole of an operator's foot.

3. A hole boring apparatus as defined in claimed 2 wherein said earth engaging member further includes a downwardly directed earth piercing spike to locate said hole boring apparatus on an earth surface.

4. A hole boring apparatus as defined in any one of claims 2 to 3 wherein said earth-engaging member is in the form of an elongate strip with said foot portion swept back and angled, in use, towards the operator.

5. A hole boring apparatus as defined in claim 4 wherein said foot portion is lower than a central portion of said elongate strip so that when said foot portion is in contact with the earth surface said blade is able to rotate without contacting the earth surface.

6. A hole boring apparatus as defined in any one of claims 1 to 5 wherein said handle is in the form of a T-bar.

7. A hole boring apparatus as defined in any one of claims 1 to 6 wherein said shaft is 100 200 mm longer than said tubular portion.

8. A hole boring apparatus as defined in any one of claims 1 to 7 wherein said blade is a pair of blades with working edges angled towards the direction of rotation and shaped to provide a downward cutting action on the earth.

9. A hole boring apparatus as defined in any one of claims 1 to 8 wherein said apparatus further includes a means to apply a resilient urgent downward force on said blade.

10. A hole boring apparatus as defined in claim 9 wherein said urging means is a helical spring mounted around said shaft and an upper portion of said spring is located within a recess formed between said ground engaging member and said upright tubular portion.

11. A hole boring apparatus as defined in claim 1 further including an annular section adjacent to said blade ends, said annular section is operational to cause the earth removed from the hole to be removed as a cylindrical plug.

12. A hole boring apparatus as defined in claim 1 further including a means for restricting relative movement between said upright tubular portion and said shaft upper end, said means for restricting relative movement between said upright tubular portion and said shaft upper end is operational to restrict relative movement between said upright tubular portion and said shaft upper end when in a locked state and to allow unrestricted relative movement between said upright tubular portion and said shaft upper end when in an unlocked state.

13. A method for manually boring a hole in an earth surface utilizing a hole boring apparatus with an operator with a foot and a hand, comprising the steps of:

(a) providing a support frame including an earth engaging member and an upright tubular portion adjacent to said earth engaging member so as to provide a passageway from a top of said tubular portion through said earth engaging member therethrough, a boring member including a shaft comprising a shaft lower end and a shaft upper end, a blade adjacent to said shaft lower end, a handle adjacent to said shaft upper end, said shaft being located within said passageway of said tubular portion to allow rotation of said shaft, said handle is operational for initiating rotation of said shaft;

(b) locating said blade on the earth surface wherein a bored hole is desired thus locating said hole-boring apparatus;

(c) placing the foot on said earth engaging member to engage said earth-engaging member into the earth surface;

(d) grasping said handle with the hand;

(e) applying lateral and downward force to said handle for the purpose of rotating said shaft upper and lower ends to engage said blade into the earth surface;

(f) continuing step (e) until a desired bored hole depth is achieved;

(g) removing said hole boring apparatus from the desired bored hole depth; and

(h) removing earth from the desired bored hole depth.

14. A method for manually boring a hole in an earth surface utilizing a hole boring apparatus with an operator with a foot and a hand, comprising the steps of:

(a) providing a support frame including an earth engaging member and an upright tubular portion adjacent to said earth engaging member so as to provide a passageway from a top of said tubular portion through said earth engaging member therethrough, a boring member including a shaft comprising a shaft lower end and a shaft upper end, a blade adjacent to said shaft lower end, a resilient urgent means to apply a downward force on said blade, a handle adjacent to said shaft upper end, said shaft being located within said passageway of said tubular portion to allow rotation of said shaft, said handle is operational for initiating rotation of said shaft;

(b) locating said blade on the earth surface wherein a bored hole is desired thus locating said hole-boring apparatus;

(c) placing the foot on said earth engaging member to engage said earth-engaging member into the earth surface;

(d) grasping said handle with the hand;

(e) applying lateral force to said handle for the purpose of rotating said shaft upper and lower ends to engage said blade into the earth surface;

(f) continuing step (e) until a desired bored hole depth is achieved;

(g) removing said hole boring apparatus from the desired bored hole depth; and

(h) removing earth from the desired bored hole depth.