US3180439A

US3180439A - Rotary, expansible bore hole reamers with improved safety features

Info

Publication number: US3180439A
Application number: US164787A
Authority: US
Inventors: Carroll L Deely
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-01-08
Filing date: 1962-01-08
Publication date: 1965-04-27
Anticipated expiration: 1982-04-27

Description

April 27,1965 c. L. DEELY 3,180,439

ROTARY, EXPANSIBLE BORE HOLE REAMERS WITH IMPROVED SAFETY FEATURES 2 Sheets-Sheet 1 Filed Jan. 8, 1962 12 M g H. n M M \M M 5 m 18 4 April 27, 1965 c. L. DEELY ROTARY, EXPANSIBLE BORE HOLE REAMERS WITH IMPROVED SAFETY FEATURES 2 Sheets-Sheet 2 Filed Jan. 8, 1962 LHHHULL L. .DE'EZ Y -INVENTOR.

United States Patent 3,189,439 ROTARY, EXPANSIBLE BgltE HOLE REAE'EERS Wil'll-I lMPROVEl) SAFETY FEATURES Carroll L. Deely, 621% N. Central Expressway, Dallas, Tex. Filed Jan. 8, E62, Ser. No. 164,787 8 Claims. (1. 17 286) This invention relates to bore hole rearner for use with rotary well drilling equipment and more particularly to an expansible bore hole manner for reaming the bore hole being drilled by a rotary drill bit, wherein locking means is provided for the reamer assembly to retain the same in assembled condition while the reamer is being used in the bore hole. This patent application contains certain improved features over my co-pending application, Ser. No. 29,847, tiled May 18, 1960, for Reamer, now United States Patent No. 3,051,255, issued August 28, 1962.

An object of this invention is to provide a re-amer for a bore hole, the blades of which ream-er will be positively expanded when the Weight of the drill stem is placed thereon so as to ream the hole to a larger diameter than the diameter of the drill bit, and wherein the reamer elements will be positively held together to prevent disassembly while in the bore hole.

Another obiect of the invention is to provide a locking arrangement for the reamer elements of the bore hole reamer, which elements are connected together so as to maintain the reamer elements in assembled relation while in the bore hole.

Still another object of the invention is to provide a locking arrangement to retain the various elements of the bore hole reamer together, which is simple in construction, easy to assemble and disassemble, and which is safe to operate in wells under all conditions.

Yet another object of the invention is to provide a lubrication arrangement to lubricate the relatively movable parts of the bore hole reamer while the reamer is being operated within a well, and to retain the lubricant within the reamer and to exclude foreign matter therefrom.

With these objects in mind and others which vw'll be come manifest as the description proceeds, reference is to be had to the accompanying drawings in which like reference characters designate like parts in the several 7 views thereof, in which:

FIG. 1 is m elevational view of a reamer body in a well with parts being broken away and with parts shown in section to bring out the details of construction;

FlG. 2 is a sectional View taken on the line Z2 of FIG. 1, looking in the direction indicated by the arrows;

FIG. 3 is a fragmentary, longitudinal sectional view through a portion of the re ainer body, showing a ball locking arrangement therein, and balls thereof in re tracted position;

FIG. 4 is a cross-sectional view taken on the line 4-4 of FIG. 1, looking in [the direction indicated by the arrows, showing parts in elevation and with parts being broken away to bring out the details of construction;

FIG. 5 is an enlarged, fragmentary, elevational view, with parts shown in section, of the lower portion of the reamer body and the locking screws therefor, as shown in FIG. 1;

FIG. 6 is a view showing a modified form of locking arrangement, which is an alternate form with respect to the forms shown in FIGS. 4 and 5;

FIG. 7 is an enlarged fragmentary view similar to FIG. 5, but of the alternate form of invention;

FIG. 3 is a sectional view taken on the line S% of FIG. 1, looking in the direction indicated by the arrows;

3,13,43d Patented Apr. 2?, 1%65 FIG. 9 is an enlarged fragmentary view of the upper portion of the reamer body;

FIG. 10 is an enlarged fragmentary view of the lower portion of the reamer body, showing the blades and the tapered mandrel in expanded condition, in full outline, and showing the retracted position of the blades in dashed outline with the tapered mandrel being shown in raised position in dashed outline;

FIG. 11 is a view similar to FIG. 9, but showing a floating piston in the lubrication chamber in another position; and

FIG. 12 is a transverse sectional view taken on the line l212 of FIG. 1, looking in the direction indicated by the arrows.

With more detailed reference to the drawing, the numeral 1 designates the bore hole of a well after it has been reamed, and the numeral 2 designates the bore hole of the well before it has been reamed. A drill bit E, shown in dashed outline, is mounted on the lower end of the reamer, which reamer is designated generally by the numeral 4. A mandrel 6 connects to the lower end of a drill stem 8, so as to lower the reamer 4 into the bore hole 1 of the well. The mandrel 6 has an internally threaded collar 12 telescoped thereover, which collar threadably engages the upper end of the shell 14, as will best be seen in FIGS. 1, 9 and 11. The mandrel 6 has a cylindrical portion it adjacent the upper end thereof, with a raised spliced portion 16 therebelow. Below the splined portion 16 the mandrel 6 tapers inwardly and downwardly, as will best be seen in FIGS. 1 and 10. The shell 14 has radial slots 15, in the present instance four, formed therein, which slots 15 are of a width to receive reamer blades 15a therethrough. The top and bottom ends of the respective slots 15 each converge outwardly so as to form a complementary seat with the tapered end surface of the respective reamer blades 15:; when the blades are in the extreme outermost position. However, the taper on each end of each slot is such as to permit each blade 15a to move inward from the position as shown in full outline in FIG. 10 to the dashed outline position shown therein, upon upward movement of tapered portion 6a of mandrel 6.

The tapered portion on on mandrel 6 is a relatively steep taper which forms a complementary wedging action with the inner tapered bore 14a of shell 14 and complementally engages the respective inner faces of blades 15a. The wedging engagement of tapered portion 6a of mandrel 6 with the tapered bore 14a of shell 14 exerts a friction hold to augment the holding action between the splined portion 16 on mandrel 6 and the complementary splines 14b within shell 14, thereby enabling greater torque to be transmitted through drill stem 8 to mandrel 6 and through shell 14 to reamer blades lSa. The lower peripheral face portion of the respective reamer blades 15a are inset with abrading elements 151) which abrading elements project outward from the surfaces thereof. However, the upper portions of the blades ls'cz are inset with abrading elements which are embedded within the respective faces of the reamer blades, as will best be seen in FIGS. 1, 8 and 10. Further abrading elements 15d are embedded within the leading side of each of the reamer blades 150 along the leading edge thereof and a spaced distance inward thereform, as will best be seen in FiGS. 1 and 8.

The internally threaded collar 12 is counterbored, as indicated at lit, near the upper end thereof to receive piston 17 therein between the collar 12 and a down wardly extending sleeve 12a formed on the lower end of spanner nut 12.), which spanner nut threadably engages the upper end of internally threaded collar 12. The floating piston 17 is located in counterbore 19 0f collar 12 and has an O-ring 17:; on the piston 17 to be in drel 6,

fluid on the upper face of piston 17 will cause the piston the shear .pins.

wardly extending sleeve 12a, which sleeve 12:: is fitted in close sliding relation with the cylinderical portion 10 of mandrel 6, The collar 12 has an inwardly extending annular boss 13 to form an abutment at the lower end of the counterbo're 19 to limit the downward movement of piston 17, as will best be seen in FIG. 11. The internally threaded collar 12 has one or more vent holes 12cformed therein, as will best be seen in FIGS. 1, 9, '11

I and 12.

Normally, before the spanner nut 12b and piston 17 are assembled on the mandrel 6 and fitted onto collar 12, the annular space formed between the collar 12 and the mandrel 6, as is best seen in FIGS. 1 and 9, is at least partially filled with lubricant. The floating piston 17 is positioned'in the chamber 19a of counterbore 19, which chamber, below the piston 17, is partially filled with lubricant. The holes 12c provide communication between the bore hole of the Well, containing the drilling fluid under pressure, and the chamber 19a to exert a pressure on the upper face of floating piston 17. The sleeve 12a has holes 12d formed therein, near the lower end thereof, which holes interconnect lubricant chamber 19a 'with the space between the inner bore of sleeve 12a and the outer diameter of the cylindrical portion 10 of man- In this manner the pressure exerted by. the drilling 17 to move downward Within chamber 19a, which causes the lubricant in chamber 19a below piston 17 to be forced through holes 12d in sleeve 12a, thereby maintaining an oil film between the working surfaces at a pressure which will prevent entrance of foreign matter between the nut 12b and the cylindrical portion 10 of the mandrel 6. Due

to the arrangement of the floating piston 17, pressure may be held thereon so that the lubricant will be discharged to prevent entrance of foreign matter to certain interior' parts of the reamer.

The spanner nut 12b has O-ring grooves formed therein near the upper end of the bore thereof to receive elastomer 'O-rings 18 therein for sealing relation between the bore of the spanner nut 12b and the cylindrical portion 10 of mandrel 6. The pressure onO-rings 18 is substantially equalized and the O-rings prevent entrance of foreign matter and will prevent the escape of lubricant in any appreciable quantities.

. The shell 14 has annular grooves intermediate the up per end thereof and the reamer. blades a,'in which groovesO-rings 20 are positioned, which rings are adapted 'to form a seal with the cylindrical portion 10 of the mandrel 6 below the splined portion 16, so as 'to form a substantially fluid tight chamber between the O-

rings

18 and 20. A lubricant fitting 22 is fitted within a recess 24 in the shell 14, so the annular space and'the work-, 1 ing elements between O-

rings

18 and 20 may be lubricated was to enablea tool to be inserted into contact relation with shear pins 26, after the pins have been sheared, to enable the ready removal ofthe remaining portion of The semi-cylindrical ring segments 28, connected to mandrel 6 by shear pin 26, maintain the mandrel lin'fixed relation to shell 14 so long as the shear pins 26are not sheared. The semi-cylindrical ring members 28 form an abutment for splined portion 16 when the mandrel is in the uppermost position.

Difiiculty has heretofore been experienced with the threaded elements of reamers becoming separated within the bore hole of a well, and it is to this end that certain safety and precautionary devices have been provided in the present reamer, thereby to prevent the separation of one threaded part from another threaded part, the separation of which threaded elements frequently re- 7 sults in delay in the completion of a well, and possible loss of the well.

The present reamer provides a particular manner of locking the collar 12 in place so that, as long as the reamer is being used for reaming, the collar 12 and mandrel 6 will be moved to the position as shown in full outline in FIG. 10, which will shear pins2'6, whereupon, steel balls'29, positioned in the respective'holes 36a formed in the wall of the shell 14 intermediate mandrel 6 and internally screw threaded collar 12, will be moved from the position as shown in FIG. 3, into the annular recess 31 in collar712, as shown in FIG. 2, with the distance between the mandrel 6 and the root diameter of the recess 31 being less than the opening between the mandrel 6 and 'to receive the dog points 42 of set screws 41, which are screw threaded through shell 14,'with the dog'points 42 of the set screws 41 extending into annular groove 38, so upon movement of the mandrel 6, the shell 14 will remain stationary unit1 the upper end of the splined portion 16 abuts with the semi-cylinder ring segments 28 in coll'ar 12, which will move the dog points 42 of set screws 41 to within a short distance of the lower shoulder 40 of mandrel 6, so that the dog points 42 will extend into bore 46 of shell14 between

shoulders

40 and 43 of mandrel 6 andwill normally be spaced above the shoulder 41) so long as the collar 12 is screw threaded in place. However, should the threaded collar 12 become loosened and the shell 14 be moved relative to the collar 12, the dog points 42' of the set screws 41 will rest upon shoulder 40 and lift the shell 14 to the surface of the well.

tight seal with the inner bore of the lower end of shell 14. V

The set screws 41 are ofthe self-locking type, which resist being unscrewed once they are screwed in place. Such screws are well known in commerce, and no claim is directed to the locking feature of the screws per se, as screws produced and sold byvarious companies possess this self-locking feature.

Modified form of invention An alternate form of locking arrangement for securing the mandrel 6 against becoming disconnected from the shell 14 is provided, which is shown in the form of the invention disclosed in FIGS. 6'an'd 7, wherein an annular groove 51 is provided. around the mandrel 6, near the a lower end thereof, and wherein a series of holes 52 are drilled upwardly within shell 14, which holes converge inwardly and'are of such size as to receive balls 54 respectively therethrough,,one-half the diameter of each,

ball being the depth of the annular groove 51. The holes 52 aredrilled in such manner as to form the respective seats 53 in the shell 14, at the respective upper ends of the holes. A spring 56 is positioned below each ball '54,

, to urge-the respective balls 54 upward against the respective seats 53, and into contact relation with the bottom of annular 'groove'Sl. 'A screwthreaded plug '58 is fitted into the lower end of each hole 52 to retain the respective sp rin'gs56 in place, and to apply the correct pressure to the v -O-rings 44 are provided within annular grooves formed in the lower end'of mandrel 6, so as to form a fluid springs to urge the respective balls 54 upward into seating relation with the respective seats 53 and the outer diameter of mandrel 6 within annular groove 51.

With the collar 12 screw threaded into place on shell 14, and with mandrel d slidably fitted therein, the mandrel 6 will be permitted to move a limited distance, however, the lower face 69 of annular groove 51 will not normally abut with balls 54. However, upon screw threads 34 becoming loosened or disengaged, the balls 54 will seat on face 6%) of groove 51, and will sustain and support the shell 14 thereon until the reamer can be removed from the bore hole of the well.

The present form of the invention is for the same purpose and performs the same operation as the reamer disclosed in my co-pending application Ser. No. 29,847, Reamer, as set out above. The safety features, as de scribed herein, then to make the reamer elements, as set out in the aforementioned application, relatively free from accidental separation within the bore hole of a well, while the reamer is in use.

The feature of providing lubricant within chambers 19:! and 6b lubricates the interior working surfaces of the reamer, which lubricant is under pressure, also normally prevents entrance of foreign matter, such as dirt, sand, and the like, from entering the interior portions of the reamer.

Having thus clearly shown and described the invention, what is claimed as new and desired to be secured by Letters Patent is:

l. A safety device for a multi-blade bore hole reamer, comprising:

(a) a shell,

(1) the upper end of said shell being screw threaded,

(2) splines within said shell within the length thereof,

(b) a mandrel,

(1) a raised splined portion formed on said mandrel intermediate the length thereof, and being in complementary, longitudinal sliding relation with said splines within said shell, and being in relative non-rotatable relation with respect thereto,

(c) an internall screw threaded collar complementally engaging the screw threads on the upper end of said shell,

(42) an inwardly extending, annular boss within said threaded collar intermediate the length thereof,

(6) an abutment fitted within the bore of said collar immediately below and in abutting relation with said inwardly extending, annular boss in said threaded collar and being adapted to complementally abut the upper end of said raised spline portion of said mandrel when said mandrel is in the uppermost position,

(f) the wall of sa d shell having a hole formed therethrough within the length of the complementally engaging portions of said screw threaded collar and said shell,

(g) said mandrel having an annular recess formed within the length of said splined portion thereof,

(1) said threaded collar having a recess formed therein, which recess is complementary to said hole in the wall of said shell when said screw threaded portions of said collar and said shell are in fully engaged relation,

([1) a ball fitted within said hole in the wall of said shell,

(1) said ball being or a diameter greater than the depth of said hole in the wall of said shell and of less diameter than the combined depth of either of said recesses and said hole in the wall of said shell, so when said mandrel is moved into a position intermediate the length of travel thereof, the annular recess therein will be in register with said hole in the wall of said shell, whereupon said screw threaded collar will threadably disengage from said threads of said shell,

(2) when said mandrel is in a lowered position said ball within said hole in the wall of said shell will extend into said recess in said screw threaded collar to prevent disengagement of said screw threaded collar from the screw threads on said shell,

(1') the lower end of said mandrel being tapered downwardly and inwardly,

(i) said shell having a plurality of elongated, longitudinally extending slots formed therein,

(It) said shell having the bore thereof tapered to com plementally fit the downwardly and inwardly tapered portion of said mandrel,

(Z) reamer blades complementally fitted within said elongated, longitudinally extending slots in said shell,

(1) said reamer blades having faces thereof adjacent said mandrel tapered to complementally engage said mandrel,

(2) said reamer blades being of greater length within said shell than exterior of said shell,

(in) said shell having screw threads on the lower end thereof for complementary attachment of a screw threaded drill bit, and

(. 2) said mandrel having an axial opening formed therethrough.

2. A safety device for a multi-blade bore hole reamer as defined in claim 1; wherein (a) said recess formed within said threaded collar is an annular recess.

3. A safety device for a multi-hlade bore hole reamer as defined in claim 1, wherein (a) Q-ring seals are fitted within the bore of said shell and which O-ring seals are in complementary sealing relation with said mandrel.

4. A safety device for a multi-hlade bore hole reamer as der'ined in claim 1; wherein (a) said mandrel has a recess formed therein,

(1) which groove has a length of at least the length of the longitudinal movement of said mandrel slidahly mounted within said shell,

(1;) at least one projection extending through said shell and into said groove in said mandrel in such position as to normally allow full relative sliding movement between said mandrel and said shell,

(1) which projection is engageable with a shoulder of said groove upon said mandrel moving longitudinally relative to said shell a distance greater than the normal relative travel of said mandrel.

5. A safety device for a multi-blade bore hole reamer as defined in claim 4, wherein (a) said projection is a set screw threadably engaging said shell, and

(b) said set screw has a dog point on the inner end thereof, which dog point is the portion of said projection which extends into said groove.

6. A safety device for a multi-blade bore hole reamer as defined in claim 4, wherein (a) said projection which extends into said groove is a spring pressed ball.

7. A safety device for a multi-blade bore hole reamcr for wells, comprising:

(a) a shell,

(1) the upper end of said shell being exteriorly screw threaded,

(2) said shell having splines formed interiorly thereof within the length thereof,

(b) a mandrel,

(l) a raised splined portion formed exteriorly on said mandrel intermediate the length thereof, and being in complementary, longitudinal sliding relation with said splines within said shell, and being in relative non-rotatable relation with respect thereto,

(c an internally screw threaded collar com'plementally engaging the screw-threads on the upper end of said shell,

V (d) an inwardly extending, annular boss within said threaded collar intermediate the length thereof,

(a) an abutment fitted within the bore of said collar '(f) the wall of said shell having a hole formed therethrough within the length of the complementally engaging portions of said screw threaded collar and said shell, V

(1) said threaded collar havingan annular recess formed therein, which recess is complementary to said-hole in the wall of said shell when said screw'threaded portions of said collar and said shell are in fully engaged relation,

(h) a ball fitted within said hole in the wall of said shell,

(1) said ball being of a diameter greater than the depth of said hole in the wall of said shell and of lessdiameter than the combined depth of either of said recesses and said hole in the wall of said shell, so when said mandrel is moved into a position intermediate the length of travel thereof V the annular recess will be in register with said holein the wall of said shell,whereupon said screw threaded collar will threadably disengage from said threads of said shell,

(2) when said mandrel is in the lowermost position said ball within said hole in the wall of said shell will extend into said annular recess in said collar to form ablock to prevent disengagement of said screw threaded collar from the screw threads on said shell, 7

(i) said mandrel having an annular groove formed therein/of at least the length of the longitudinal sliding movement of said mandrel in said shell,

(j) a plurality of projections extending through said shell into said annular groove in said mandrel in such manner as to normally allow full relative sliding movement between said mandrel and said shell,

o (1) said projections being engageable with shoulder of said groove upon saidmandrel moving longitudinally relative to said shell a distance greater than the relative normal travel of the mandrel with respect thereto,

(k) the lower end of said mandrel being tapered downwardly and inwardly,

(I) said shell having a plurality of elongated longitudinally extending slots formed therein,

(m) said shell having the bore thereof tapered to complementally fit the downwardly and inwardly tapered portion of said mandrel,

(n) reamer blades complementally fitted within said elongated, longitudinally extending slots in said shell,

(1) said reamer blades'having faces thereof adjacent said mandrel tapered to complementally engage said mandrel,

(0) said shell having screw threads on the lower end thereof for complementaiy attachment of'a screw threaded drill bit, and

(p) said, mandrel having an axial opening formed therethrough.

8. A safetydevice for a multi-blade-bore hole reamer as defined in clairn 7, wherein v j (a) said plurality of projections are set screws, which set screws threadably engage said shell, and

(1)) each said set screw has a dog point on the inner end thereof, which dog point is the portion of said 'set screws which extends into said groove.

fieferenees' Cited by the Examiner UNITED STATES PATENTS 1,639,017 8/27 Woodrufi 1s4 39 2,401,119 5/46 Taylor 166237 X 2,409,811 10/46 Taylor, et al; '166--125 2,447,545 8/48 Spencer 166--237 X 2,450,527 10/48 Smithet al 285 2,637,402 5/53 Baker et a1. a 166 2,684,860 7/54 Rafferty 285-85 2,828,944 4/58 Udry 184-39 X 3,010,539 11/61 Goof et a1 18439 CHARLES E. O CONNELL, Primary Examiner.

Claims

1. A SAFETY OF DEVICE FOR A MULTI-BLADE BORE HOLE REAMER, COMPRISING: (A) A SHELL, (1) THE UPPER END OF SAID SHELL BEING SCREW THREADED, (2) SPLINES WITHIN SAID SHELL WITHIN THE LENGTH THEREOF, (B) A MANDREL, (1) A RAISED SPLINED PORTION FORMED ON SAID MANDREL INTERMEDIATE THE LENGTH THEREOF, AND BEING IN COMPLEMENTARY, LONGITUDINAL SLIDING RELATION WITH SAID SPLINES WITHIN SAID SHELL, AND BEING IN RELATIVE NON-ROTATABLE RELATION WITH RESPECT THERETO, (C) AN INTERNALLY SCREW THREADED COLLAR COMPLEMENTALLY ENGAGING THE SCREW THREADS ON THE UPPER END OF SAID SHELL, (D) AN INWARDLY EXTENDING, ANNULAR BOSS WITHIN SAID THREADED COLLAR INTERMEDIATE THE LENGTH THEREOF, (E) AN ABUTMENT FITTED WITHIN THE BORE OF SAID COLLAR IMMEDIATELY BELOW AND IN ABUTTING RELATION WITH SAID INWARDLY EXTENDING, ANNULAR BOSS IN SAID THREADED COLLAR AND BEING ADAPTED TO COMPLEMENTALLY ABUT THE UPPER END OF SAID RAISED SPLINE PORTION OF SAID MANDREL WHEN SAID MANDREL IS IN THE UPPERMOST POSITION, (F) THE WALL OF THE SHELL HAVING A HOLE FORMED THERETHROUGH WITHIN THE LENGTH OF THE COMPLEMENTALLY ENGAGING PORTIONS OF SAID SCREW THREADED COLLAR AND SAID SHELL, (G) SAID MANDREL HAVING AN ANNULAR RECESS FORMED WITHIN THE LENGTH OF SAID SPLINED PORTION THEREOF, (1) SAID THREADED COLLAR HAVING A RECESS FORMED THEREIN, WHICH RECESS IS COMPLEMENTARY TO SAID HOLE IN THE WALL OF SAID COLLAR AND SAID SHELL THREADED PORTIONS OF SAID COLLAR AND SAID SHELL ARE IN FULLY ENGAGED RELATION, (H) A BALL FITTED WITHIN SAID HOLE IN THE WALL OF SAID SHELL, (1) SAID BALL BEING OF A DIAMETER GREATER THAN THE DEPTH OF SAID HOLE IN THE WALL OF SAID SHELL AND OF LESS DIAMETER THAN THE COMBINED DEPTH OF EITHER OF SAID RECESSES AND SAID HOLE IN THE WALL OF SAID SHELL, SO WHEN SAID MANDREL IS MOVED INTO A POSITION INTERMEDIATE THE LENGTH OF TRAVEL THEREOF, THE ANNULAR RECESS THEREIN WILL BE IN REGISTER WITH SAID HOLE IN THE WALL OF THE SAID SHELL, WHEREUPON SAID SCREW THREADED COLLAR WILL THREADABLY DISENGAGE FROM SAID THREADS OF SAID SHELL, (2) WHEN SAID MANDREL IS IN A LOWERED POSITION SAID BALL WITHIN SAID HOLE IN THE WALL OF SAID SHELL WILL EXTEND INTO SAID RECESS IN SAID SCREW THREADED COLLAR TO PREVENT DISENGAGEMENT OF SAID SCREW THREADED COLLAR FROM THE SCREW THREADS ON SAID SHELL, (I) THE LOWER END OF SAID MANDREL BEING TAPERED DOWNWARDLY AND INWARDLY, (J) SAID SHELL HAVING A PLURALITY OF ELONGATED, LONGITUDINALLY EXTENDING SLOTS FORMED THEREIN, (K) SAID SHELL HAVING THE BORE THEREOF TAPERED TO COMPLEMENTALLY FIT THE DOWNWARDLY AND INWARDLY TAPERED PORTION OF SAID MANDREL, (L) REAMER BLADES COMPLEMENTALLY FITTED WITHIN SAID ELONGATED, LONGITUDINALLY EXTENDING SLOTS IN SAID SHELL, (1) SAID REAMER BLADES HAVING FACES THEREOF ADJACENT SAID MANDREL TAPERED TO COMPLEMENTALLY ENGAGE SAID MANDREL, (2) SAID REAMER BLADES BEING OF GREATER LENGTH WITHIN SAID SHELL THAN EXTERIOR OF SAID SHELL, (M) SAID SHELL HAVING SCREW THREADS ON THE LOWER END THEREOF FOR COMPLEMENTARY ATTACHMENT OF A SCREW THREADED DRILL BIT, AND (N) SAID MANDREL HAVING AN AXIAL OPENING FORMED THERETHROUGH.