US2710172A

US2710172A - Expansible drill bits for enlarging well bores

Info

Publication number: US2710172A
Application number: US393772A
Authority: US
Inventors: Jr Archer W Kammerer
Original assignee: Rotary Oil Tool Co
Current assignee: Rotary Oil Tool Co
Priority date: 1953-11-23
Filing date: 1953-11-23
Publication date: 1955-06-07
Anticipated expiration: 1972-06-07

Description

June 1955 A. w. KAMMERER, JR 2,710,172

EXPANSIBLE DRILL BITS OR ENLARGING WELL BORES 2 Sheds-Sheet 1 jg I.

I c I 3.

Filed Nov. 25. 1953' IN V EN TOR.-

4420/52 7V: KAMMEPEE, (IQ.

A TTQEA/EY- June 7, 1955 w. KAMMERER, JR 2,710,172

EXPANSIBLE DRILL BITS FOR ENLARGING WELL BORES Filed Nov. 25, 1953 2 Sheets-Sheet 2 INVENTOR. APCHEE KAMMEEEE, :19.

BY I

4 T TOQNEY- United States Patent EXPANSIBLE DRILL BITS FOR ENLARGING WELL BORES Archer W. Kammerer, Jr., Fullerton, Califi, assignor, by

direct and mesne assignments, to Rotary Oil Tool Company, Huntington Park, Califi, a corporation of California Application November 23, 1953, Serial No. 393,772

18 Claims. (Cl. 255-76) The present invention relates to rotary drill bits of the expansible type for drilling or enlarging well bores below well casing to a larger diameter than the inside diameter of the well casing itself.

Expansible drill bits are known in which the cutters are expanded laterally outward and locked in such expanded position through the medium of a mandrel telescopically arranged in the body of the drill bit. It is necessary to move the mandrel down relative to the body to lock the cutters in an outward position. Elevation of the mandrel with respect to the body releases the cutters from their locked condition, enabling them to move inwardly toward retracted position. 7

Certain disadvantages are associated with bits of th above type, in that a downward force must be maintained on the mandrel to hold it in its locked position, for the purpose of securing the cutters in their expanded position. Elimination of this downward force, which may occur as a result of the cutters no longer engaging a formation shoulder, permits the body and cutters to move or drop down with respect to the mandrel, thereby, in effect, producing relative elevation of the mandrel within the body and shifting of the mandrel to an unlocked position that could allow the cutters to retract, at least partially. It then becomes necessary to reshift the mandrel downwardly of the body, to again lock the cutters in their fully expanded position.

It is an object of the present invention to provide an expansible type of rotary drill bit in which the cutters are locked automatically in their fully expanded position Without the necessity for moving a mandrel, telescopically arranged in the bit body, downwardly of the body. The locking action occurs as a result of structure embodiedin the bit itself, and without the need for-imposing any external forces on the bit.

Another object of the invention is to provide an expans ible rotary drill bit of the type having a mandrel connectible to a drill string telescopically arranged in the bit body, in which the cutters are locked automatically in their maximum outwardly expanded position without the necessity for imposing drilling weight on the cutter'spor for moving the mandrel with respect to the body.

A further object of the invention is to provide an expansiole rotary drill bit in which the cutters can be locked in their outwardly expanded position by a combination of spring force, hydraulic force and drilling weight imposed 1 on the cutters, or by one or more of theforegoing.

Another object of the invention is to provide an expansible rotary drill bit, in which the cutters are locked automatically in their fully expanded position without the necessity for telescoping the mandrel with respect tocompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

. Figure l is a longitudinal section through an embodiment of the invention disposed in a well bore, with the cutters and other parts in their initial retracted position;

Fig. 2 is a longitudinal section, similar to'Fig. 1, disclosing the cutters locked in their fully expanded position prior to the imposition of drilling weight on the cutters;

Fig. 3 is a longitudinal section, similar to Fig. 1,disclosing the cutters locked in their outwardly expanded position and with downward or drilling weightbeing imposed on the cutters;

Fig. 4 is a longitudinal section, similar to Fig. 1, disclosing the locking portion of the device shifted to a retracted position to enable the cutter mechanism to be returned to its retracted position Within a well casing.

The expansible drill bit A disclosed in the drawings is of the general type shown in the patent to Archer W. Kammerer, Patent No. 2,545,036, to which attention is invited. The rotary drill bit is attached to a string of drill pipe 13, by means of which it is lowered through a well casing C in a well bore D to a point below the casing shoe E at which the diameter of the bore hole is to be enlarged. The drill bit may have a pilot bit 10 at its lower end for centering the tool in a hole that may have already been drilled, or for drilling the central portion pander 23 beats.

of a compressed coil spring, is received within a retainer. pocket 24 in the body and exerts its force against the of a new hole, in the absence of a pre-existing hole. The main portion of the bit is capable of enlarging the bore hole by producing and operating upon a formation shoulder F, as hereinafter described.

The main body 11 of the bit has a plurality of expansible parts mounted on it, comprising cutter supporting members 12 pivotally mounted in body slots 13 on hinge pins 14 suitably welded to the body. Each cuttersup porting member consists of a depending leg 15 having a bearing supporting pin 16 inclined inwardly and down-' wardly and on which a roller side cutter 17 is rotatably mounted. Anti-friction roller and

ball bearing elements

18, 19 are preferably placed between each cutter and bearing pin, the roller bearings 18 transmitting radial thrusts and the ball bearings 19 both radial and axial thrusts. The ball bearings also retain each cutter on a pin 16, being inserted in place through a passage 20 in the bearing support, which is then closed by a plug 21 welded to the pin. The plug 21 depends from the passage andis used to hold the cutters 17 in retracted position, as explained below.

Each cutter supporting member 12 also includes an upwardly extending arm 22 against which an elastic ex- This expander, which 'is in the form arm 21, tending to swing the latter inwardly and thus urge the cutter 17 on 'the'other side of the fulcrum pin 14 in an outward direction. The extent of this outward movement is limited by engagement of a suitable stop shoulder 25' on each cutter supporting member 12 with acooperable stop portion 26 on the body 11. 7

After the cutters 17 have been expanded outwardly by the springs 23 to a maximum extent, they can be locked in this position by a tubular member 27 of a composite lar member 27 is provided with a lock portion 31 at its lower region movable from an upper position in transverse alignment with inner supporting member recesses 32, which allow retraction of the cutters 17, to a lower position opposite lugs 33 formed on and projecting inwardly from the cutter supporting legs 15, which prevents retraction of the cutters.

As stated above, the tubular member 27 is telescopically arranged within the Kelly portion of the mandrel, the member 27 and Kelly 30 being capable of partaking of relative longitudinal movement. The upper portion 30a of the Kelly has an upper threaded pin 34 connected to a collar 35 threadedly secured to the lower end of the string of drill pipe B extending to the top of the well bore.

A lower Kelly member 30b is threadedly attached to the upper Kelly member 30a, being disposed within the upper portion of the body 11 and slidably splined to the latter. Such slidable splining is secured by making the ex terior 36 of the Kelly of non-circular or hexagonal shape, which is telescopically received in a companion non-circular or hexagonal socket 37 formed in the body. The Kelly 30 has a limited range of movement within the body. Its upward movement is restrained by the engagement of an external shoulder 38 on the lower Kelly portion 30b, disposed within a counterbore 39 in the body, with the lower end of a yieldable stop and body supporting spring 40, the upper end of which engages a retainer ring 41 at the upper end of the body 11 which may be secured to the latter, as by the use of welding material 42.

The body supporting spring causes the Kelly 30 to yieldably support the bit body 11 and the cutter mechanism carried thereby in an intermediate position with respect to the Kelly. However, the Kelly 30 is still movable upwardly, as explained hereinbelow, with respect to the body, such relative upward movement being permitted by the compression of the spring 40. The Kelly is also capable of movement downwardly of the body to a limited extent, determined by the engagement of the lower end 43 of the lower Kelly portion 30b with the connecting flange 44 of a spring housing 45 which rests upon a body shoulder 46. This spring housing 45 is secured to the body by one or more screws 47 threaded transversely through the body and disposed within a pcripheral groove 48 in the connecting flange 44.

In the specific tool disclosed in the drawings, the tubular member 27 cannot move downwardly to dispose its lock .ring 31 behind the supporting member lugs 33 until the supporting members 12 and their cutters 17 have been expanded outwardly to their maximum extent. The member 27 is prevented from moving downwardly until this condition occurs by virtue of the fact that the lower end of the lock ring 31 rests upon the upper portions of the lugs 33 (.Fig. 1). After the cutter supporting members and cutters have been expanded outwardly to their maximum extent, the lock ring 31 of the tubular member is automatically shifted downwardly, to be disposed behind the lugs 33 independently of the movement of the Kelly 30. A spring force is availed of for accomplishing this purpose. Thus, the spring housing 45 extends upwardly around the tubular mandrel member 27 and has a thrust head or upper spring seat 49 extending inwardly toward the tubular member. A helical compression spring 59 encompasses the member 27, its upper nd engaging the upper thrust head 49 and its lower end alower mandrel head or spring seat 51, so that the compression spring 50 tends to move the tubular member 27 in a downward direction. Such downward movement can occur after the cutters 17 have been expanded outwardly to the maximum position, inasmuch as an upperhead '52 on the tubular member is spaced initially a sufficient distance above the upper end of the spring housing head 49 and the tubular member head 52 is also disposed a suflicient distance above an inwardly extending release shoulder 53 iii) formed on the lower Kelly portion 30!). After the cutter supporting members 12 and cutters 17 have been expanded outwardly to the maximum extent, the spring 50 can expand, to shift the tubular member 27 downwardly and dispose the lock ring 51 in its locking position behind the supporting member lugs 33. This position is definitely located by the engagement of the lower surface 54 of the tubular member head 52 with the upper end of the spring housing 45, as disclosed in Fig. 2.

If desired, the tubular member head 52 may be constituted as a piston slidable along an inner cylindrical wall 55 of the lower Kelly member 30b. Leakage of fluid between the piston and cylindrical wall in a downward direction may be prevented by providing a suitable piston ring 56, such as a rubber O ring, in a ring groove 56 in the piston which slidably and sealingly engages the cylindrical wall 55. If need be or desired, the mandrel member 27 may be moved downwardly hydraulically by the application of hydraulic pressure to the upper surface of the piston 52, urging it and its tubular member 27 downwardly, to dispose the lock portion or ring 31 behind the supporting member lugs 33.

The compression spring Si) is constantly urging the tubu lar member 27 in a downward direction toward its locking position behind the lugs. However, such downward movement is initially prevented by holding the cutters 17 and their supporting members 12 positively in an inward direction, so that the lower end of the lock portion 31 rests upon upper portions of the lugs 33. As disclosed in the drawings, a hydraulically releasable latch or holding device is employed. This holding device includes a holding member 57 secured to the lower end oi a central rod 58 whose upper end projects into a passage 59 extending completely through the tubular member 27. This passage communicates with a central passage 60 extending upwardly through the Kelly portion 30 of the tubular mandrel 28. The passage 59 through the tubular member 27 is substantially smaller in diameter than the passage 60 through the Kelly. A head 61 is secured to the upper end of the rod 58, having substantial clearance in the passage 59 to allow fluid to pass upwardly into the central passages 59, 6t) and into the drill string B. The holding member 57 has spaced holes 62 in its outer portion for receiving the lower ends of the bearing plugs 21.

When the holding device 57 is disposed over the plugs 21, the cutter supporting members 12 are prevented from expanding under the influence of the springs 23, thereby holding the cutters 17 in retracted position. Such retr-acted condition of the cutter supporting members 12 prevents the helical compression spring 50 from shifting the tubular member 27 downwardly to its locking position. The holding member 57 can be released from the plugs 21 as a result of fluid pressure acting downwardly F on a ball 63, which can be disposed in the passage 59 and which will come to rest on the head 61, the ball having substantially the .same diameter as the diameter of thepassage 59, to allow fluid pressure to be built up thereabove. When fluid pressure is applied to the fluid in the drill pipe B and the

mandrel passages

60, 59, it can shift the ball 63, rod 58 and holding member 57 downwardly, to free the latter from the plugs 21 and allow the .springs .23 to move the arms 21 inwardly and the cutters 17 outwardly. The drill pipe B and drill bit A are rotated, the springs 23 urging the cutters 17 outwardly until they are in their fully expanded position and have produced a formation shoulder F in the wall of the well bore D. Thereafter, the compression spring 50 is effective to shift the tubular member 27 downwardly automatically, to place its lock portion 31 behind the sup 5i porting member lugs 33, to positively hold the cutters in the drill pipe B downwardly, which shifts the Kelly portion of the mandrel in a downward direction to the extent determined by engagement of its lower end 43 on with the connecting flange 44 of the spring housing 45. When such engagement occurs, the lower end 64 of the upper Kelly section 30a is preferably disposed contiguous the upper end of the tubular member head or piston 52, which provides a positive stop limiting upward movement of the tubular member 27 with respect to the body 11 (Fig. 3).

In the operation of the drill bit in a well bore, the cutters 17 and their supporting members 12 are locked in their retracted position by the hydraulically releasable latch device 57, the parts occupying the position disclosed in Fig. l. The tubular member 27 is in its upward position, its lock portion 31 engaging the upper portions of the supporting member lugs 33, with the tubular member head or piston 52 disposed adjacent the lower end 64 of the upper Kelly section 33a and substantially above the upper end of the spring housing 45 and the release shoulder 53 on the lower Kelly section 30b. The yieldable body supporting spring is holding the body of the tool and the other parts in a desired upper position with respect to the mandrel 28, so as to appropriately locate the parts in the position shown in Fig. l, with the lower end 43 of Kelly 30 an appropriate distance above the flange 44.

The apparatus is lowered through the casing C to the open well bore D therebelow, and, when the region in the latter is reached at which the hole enlarging operation is to occur, pressure is applied to the fluid in the drill pipe B, to move the ball 63 into the tubular member passage 59 and into engagement with the rod head 61 of the latch mechanism. The application of sufiicient pressure on this ball 63 moves it and the latch 57 downwardly, to shift the latter oif the plugs 21 secured to the cutter supporting members 12. When such release occurs, the tubular string B can be rotated, the springs 23 urging the arms 21 inwardly and forcing the cutters 17 outwardly into engagement with the wall of the well bore D. Rotation of the drill pipe B rotates the Kelly portion 30 of the mandrel 28, and, through the

splined connection

36, 37, the body 11 of the tool, the cutters 17 beginning to dig into the wall of the well bore. During such rotation, no drilling weight is imposed on the tool, so that the mandrel portion 28 of the apparatus still occupies essentially the position disclosed in Fig. 1. When the springs 23 have expanded the cutters 17 outwardly to their maximum extent, the mandrel compression spring 50 is then effective to immediately shift the tubular member 27 downwardly, to dispose its lock portion 31 behind the lugs 33, the tubular member head 52 engaging the upper end of the cylindrical housing (Fig. 2).

Inasmuch as the drilling mud is usually being pumped down the drill pipe B and through the tool A at this time, for the purpose of removing the cuttings to the top of the well bore, a hydraulic force is also available, acting on the tubular member head or piston 52, to urge the latter in a downward direction, in view of the throttling effect of the fluid as it enters the smaller diameter passage 59 through the tubular member 27. Accordingly, should the spring 50, for some reason, be incapable of shifting the tubular member 27 downwardly to its fullest extent, then a hydraulic force is available to insure the shifting of the tubular member downwardly to its locked position. Accordingly, it is evident that the force of the compression spring 56 is supplemented by a hydraulic force acting on the piston 52, to insure the disposition of the lock portion 31 behind the lugs 33.

It is to be noted that the tubular member 27 has moved downwardly to its locked position behind the cutter supporting members ,IZautomatically after the.

latter have been expanded outwardly to their maximum extent. It is unnecessary for the operator to partake of any other action. After the formation shoulder F has been produced and it is desired to drill away the hole to the enlarged diameter, downweight is imposed on the drill pipe B, which will shift the Kelly portion 30 of the composite mandrel 28 downwardly of the body 11 and of the spring housing 45, to the extent limited by engagement of the lower end 43 of the Kelly 30 with the spring housing flange 44. The drilling weight is then transferred directly from the Kelly 30 to the body 11, and from the latter to the cutter supporting members 12 and cutters 17. This position of the parts is disclosed in Fig. 3, from which it will be noted that the lower end 64 of the upper portion 30a of the Kelly has now been disposed immediately above the tubular member head or piston 52, which will further insure the retention of the tubular member 27 in its downward locked position behind the cutter supporting members 12.

Drilling will proceed to the desired extent, with the cutters 17 locked in their outward position. Should the apparatus be elevated, to raise the cutters above the formation shoulder F, then the tubular member 27 will still remain in its locked position, inasmuch as the spring is effective to hold the mandrel member 27 in its downward postition, the force of this spring being supplemented by the action of the fluid pressure acting on the upper surface of the piston 52, assuming that the pumping of the drilling fluid through the apparatus continues. Accordingly, it is evident that the parts remain in their outward locked position, regardless of the elevation or lowering of the drill string. Moreover, it is to be noted that it is unnecessary for the cutters 17 to remain in engagement with the formation shoulder F, or the like, and for drilling weight to be imposed on the cutters, for the purpose of holding them locked in their outwardly expanded position.

When it is desired to retrieve the expansible drill bit A from the well bore, the drilling fluid is no longer pumped through the tool and the drill pipe B is elevated, the tool being moved up the hole until a smaller diameter portion or the casing shoe E is reached. When this occurs, the outer surfaces of the cutter supporting members 12 engage the lower end of the shoe E and tend to prevent upward movement of the bit body 11. An upward strain can then be taken on the drill pipe B and on the kelly 30 of the tool, the releasing shoulder 53 on the lower kelly portion 30b engaging the underside of the tubular member head or piston 52, to forcibly pull the tubular member 27 in an upward direction against the action of the compression spring 50 surrounding the tubular member. The tubular member 27 is thus pulled upwardly, to relocate its locking portion 31 in alignment with the supporting member recesses 32 and above the lugs 33, which then allows the casing shoe E to urge the cutter sup porting legs 15 and cutters 17 in an inward direction, disposing the lugs 33 under the lock portion 31 and thereby preventing the compression spring 50 from re-- shifting the tubular member 27 in a downward direction into its lock-ed position behind the lugs- The upward movement of the kelly portion 30, for the purpose of forcibly moving the tubular member 27 upwardly to its released position is permitted, since the body supporting spring 46 will merely be compressed to a further extent. as the release shoulder 53 carries the tubular memberv head 52 upwardly to its initial position above the upper end of the spring housing 45 (Fig. 4). After the cutter supporting members 12 have been shifted inwardly by the casing shoe E, they are held inwardly by the wall of the well casing C, to secure the lugs 33 under the lock portion 31 of the tubular mandrel member 27 When this occurs, it is immaterial whether the kelly portion 30 of the tool is lowered with respect to the body 11, since the compression spring 50 is then incapable of reshifting the tubular member 27 back to its locked position within and behind the supporting member lugs 33.

The tool A may now be elevated in the well casing C and withdrawn completely from the well bore.

It is, accordingly, apparent that an expansible rotary drill bit has been provided in which the cutters 17 and their supporting members 12 are positively locked in their outward position automatically, regardless of the downward movement of the Kelly portion 30 of the mandrel with respect to the body 11 of the tool. The lock device 31 is shifted to and held in its locked position behind the cutter supporting member lugs 33 by the force being exerted constantly by the compression spring 5%. This force may be supplemented, if desired, by the pressure of the fluid being pumped through the apparatus and acting on the upper piston 52. Of course, it is not necessary that the upper piston 52 be used at all. The upper member 52 may merely constitute a guide head for the tubular member 27, to insure its proper longitudinal movement with respect to the other parts. In addition to the presence of the spring force and the hydraulic force to hold the lock member 31 behind the supporting member lugs 33, the imposition of downweight on the up paratus provides an additional mechanical holding device by locating the Kelly portion 3% of the tool immediately above the tubular member head 52, which further prevents the lock portion of the mandrel from being retracted from its locking position behind the supporting member lugs.

In the event that the application of drilling weight to the cutters is discontinued, as through elevation of the Kelly portion 30 of the mandrel within the body, the tubular member 27 will still remain in its locked position behind the cutter supporting members 12, such result be ing produced by the compression spring 59 and by the hydraulic force of the drilling fiuid acting on the piston 52, if a piston is provided in the apparatus. Regardless of such retention of the tubular mandrel member 27 in its locked position, it is still capable of being forcibly released from such locked position upon elevation of the apparatus in the well bore, and particularly into the casing string C.

The inventor claims:

1. A rotary well drilling bit, including a main body,

having'a connection for securing said mandrel member directly to a drill string, said mandrel member being slidably splined to said body, a second mandrel member telescopically related to said first mandrel member and movable relatively downward of said body to hold said cutter means laterally outward, and means operatively $1.

engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member.

2. A rotary well drilling bit, including a main body, cutter means mounted on said body for expansion laterally outward of said body, means for expanding and holding said cutter means laterally outward, said expanding and holding means comprising a first mandrel member having a connection for securing said mandrel member directly to a drill string, said mandrel member being slidably splined to said body, a second mandrel member movable longitudinally with respect to said body and first mandrel member in one direction to hold said cutter means laterally outward, and means operatively engaging said body and second mandrel member to urge said second mandrel member in said one longitudinal direction relative to said body and first mandrel member.

3. A rotary well drilling bit, including a main body, cutter means mounted on said body for expansion laterally outward of said body, means for expanding holding said cutter means laterally outward, said expanding and holding means comprising a first mandrel member connec'tible to a drill string and slidably splined to said body, a second mandrel. member movable longitudinally with respect to said body and first mandrel Lil member in one direction to hold said cutter means later ally outward, and means operatively engaging said body and second mandrel member to urge said second mandrel member in said one longitudinal direction relative to said body and first mandrel member, said first mandrel member being movable in said one longitudinal direction with respect to said body into juxtaposed relation to said second mandrel member to prevent longitudinal movement of said second mandrel member in the opposite longitudinal direction.

4. A rotary well drilling bit, including a main body, cutter means mounted on said body for expansion laterally outward of said body, means for expanding and holding said cutter means laterally outward, said expanding and holding means comprising a first mandrel member connectihle to a drill string and slidably splined to said body, a second mandrel member telescopically related to said first mandrel member and movable relatively downward cl said body to hold said cutter means laterally outward, and means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member, said first mandrel member being moved downwardly with respect to said body into juxtaposed relation to said second mandrel member to prevent upward movement of said second mandrel member out of its position holding said cutter means laterally outward.

5. A rotary well drilling bit, including a main body, cutter means mounted on said body for expansion laterally outward cf said body, means for expanding and holding said cutter means laterally outward, said expanding and holding means comprising a first mandrel member having a connection for securing said mandrel member directly to a drill string, said mandrel member being slidably splined to said body, a second mandrel member movable longitudinally with respect to said body and first mandrel member in one direction to hold said cutter means laterally outward, means operatively engaging said body and second mandrel member to urge said second mandrel member in said one longitudinal direction relative to said body and first mandrel member, and means on said first mandrel member engageable with said second mandrel member to shift said second mandrel member in the opposite longitudinal direction out of holding relation to said cutter means.

6. A rotary well drilling bit, including a main body,

cutter means mounted on said body for expansion laterally outward of said body, means for expanding and holding said cutter means laterally outward, said expanding and holding means comprising a first mandrel member having a connection for securing said mandrel member directly to a drill string, said mandrel member being slidably splined to said body, a second mandrel member telescopically related to said first mandrel member and movable relatively downward of said body to hold said cutter means laterally outward, means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member, and means on said first mandrel member engageable with said second mandrel member to shift said second mandrel member upwardly out of holding relation to said cutter means.

7. A rotary well drilling bit, including a main body, cutter means mounted on said body for expansion laterally outward of said body, means for expanding and holding said cutter means laterally outward, said expanding and holding means comprising a first mandrel member connectible to a drill string and slidably splined to said body, a second mandrel member movable longitudinally with respect to said body and first mandrel member in one direction to hold said cutter means laterally outward, means operatively engaging said body and second mandrel member to urge said second mandrel member in said one longitudinal direction relative to said body and first mandrel member, said first mandrel member being movable in said one longitudinal direction with respect to said body into juxtaposed relation to said second mandrel member to prevent longitudinal movement of said mandrel member in the opposite longitudinal direction, and means on said first mandrel member engageable with said second mandrel member to shift said second mandrel member in the opposite longitudinal direction out of holding relation to said cutter means.

8. A rotary well drilling bit, including a main body, cutter means mounted on said body for expansion laterally outward of said body, means for expanding and holding said cutter means laterally outward, said expanding and holding means comprising a first mandrel member connectible to a drill string and slidably splined to said body, a second mandrel member telescopically related to said first mandrel member and movable relatively downward of said body to hold said cutter means laterally outward, means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member, said first mandrel member being moved downwardly with respect to said body into juxtaposed relation to said second mandrel member to prevent upward movement of said second mandrel member out of its position holding said cutter means laterally outward, and means on said first mandrel member engageable with said second mandrel member to shift said second mandrel member upwardly out of holding relation to said cutter means.

9. A rotary well drilling bit, including a main body, cutter means mounted on said body, means engaging said cutter means for expanding said cutter means laterally outward of said body, a first mandrel member having a connection for securing said mandrel member directly to a drill string, said mandrel member being slidably splined to said body, a second mandrel member movable relatively downward of said body to hold said cutter means laterally outward, and means operatively engaging said body and second'mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member.

10. A rotary well drilling bit, including a main body, cutter means mounted on said body, means engaging said cutter means for expanding said cutter means laterally outward of said body, a first mandrel member connectible to a drill string and slidably splined to said body, a second mandrel member movable relatively downward of said body to hold said cutter means laterally outward, and means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member, said first mandrel member being movable downwardly with respect to said body into juxtaposed relation to said second mandrel member after said second mandrel member has been shifted into holding relation to said cutter means to prevent upward movement of said second mandrel member out of holding relation to said cutter means.

11. A rotary well drilling bit, including a main body, cutter means mounted on said body, means engaging said cutter means for expanding said cutter means laterally outward of said body, a first mandrel member connectible to a drill string and slidably splined to said body, a second mandrel member movable relatively downward of said body to hold said cutter means laterally outward, means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member, said first mandrel member being movable downwardly with respect to said body into juxtaposed relation to said second mandrel member after said second mandrel member has been shifted into holding relation to said cutter means to prevent upward movement of said second mandrel member out of holding relation to said cutter means, and means on said first mandrel member engageable with said second mandrel member to shift said second mandrel member upwardly out of holding relation to said cutter means.

12. A rotary well drilling bit, including a main body, cutter means mounted on said body for expansion laterally outward of said body, means for expanding and hold ing said cutter means laterally outward, said expanding and holding means comprising a first mandrel member having a connection for securing said mandrel member directly to a drill string, said mandrel member being slidably splined to said body, a second mandrel member telescopically related to said first mandrel member and movable relatively downward of said body to hold said cutter means laterally outward, and spring means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member.

13. A rotary Well drilling bit, including a main body,

downward of said body to hold said cutter means laterally outward, spring means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrelmember, and hydraulic means connected to said second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member in response to fluid pressure in the drill string.

14. A rotary well drilling bit, including a main body, cutter means mounted on said body for expansion laterally outward of said body, means for expanding and holding said cutter means laterally outward, said expanding and holding means comprising a first mandrel member connectible to a drill string and slidably splined to said body, a second mandrel member telescopically related to said first mandrel member and movable relatively downward of said body to hold said cutter means laterally outward, and spring means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member, said first mandrel member being movable downwardly with respect to said body into juxtaposed relation to said second mandrel member to prevent upward movement of said second mandrel member out of holding relation to said cutter means.

15. A rotary well. drilling bit, including a main body, cutter means mounted on said body for expansion laterally outward of said body, means for expanding and holding said cutter means laterally outward, said expanding and holding means comprising a first mandrel member connectible to a drill string and slidably splined to said body, a second mandrel member telescopically relative to said first mandrel member and movable relatively downward of said body to hold said cutter means laterally outward, spring means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member, said first mandrel member being movable downwardly with respect to said body into juxtaposed relation to said second mandrel member to prevent upward movement of said second mandrel member out of holding relation to said cutter means, and means on said first mandrel member engageable with said second mandrel member to shift said second mandrel member upwardly out of holding relation to said cutter means.

16. A rotary well drilling bit, including a main body, cutter means mounted on said body, means engaging said cutter means for expanding said cutter means laterally outward of said body, a first mandrel member having a connection for securing said mandrel member directly to a drill string, said mandrel member being slidably splined to said body, a second mandrel member movable relatively downward of said body to hold said cutter means laterally outward, and spring means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member.

17. A 'rotar well drillin bit, including a main body,

cutter means mounted on said body, means engaging said cutter means for expanding said cutter means laterally outward of said body, a first mandrel member connectible to a drill string and slidably splined to said body, a second mandrel member movable relatively downward or": said body to hold said cutter means laterally outward, spring means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member, said first mandrel member being movable downwardly with respect to said body into juxtaposed relation to said second mandrel member after said second mandrel member has been shifted into holding relation to said cutter means to prevent upward movement of said second mandrel member out of holding relation to said cutter means, and means on said first mandrel member engageable with said second mandrel member to shift said second mandrel member upwardly out of bold ing relation to said cutter means.

18. A rotary well drilling bit, including a main body, cutter means mounted on said body, means engaging said cutter means for expanding said cutter means laterally outward. of said body, a first mandrel member connectible to a drill string and slidably splined to said body, a second mandrel member movable relatively downward of said body to hold said cutter means laterally outward, spring means operatively engaging said body and second mandrel member to urge said second mandrel member relatively downward of said body and first mandrel member, said first mandrel member being movable downwardly with respect to said body into juxtaposed relation to said second mandrel member after said second mandrel member has been shifted into holding relation to said cutter means to prevent upward movement of said second mandrel member out of holding relation to said cutter means, means on said first mandrel member engageable with said second mandrel member to shift said second mandrel member upwardly out of holding relation to said cutter means, and hydraulic means connected to said second mandrel member and shiftable by fluid pressure in the drill string for urging said second mandrel member relatively downward of said body and first mandrel member.

References (Iitetr in the file of this patent UNZTED S ATES PATENTS 473,909 Bullock May 3, 1892 1,708,932 Brown Apr. 16, 1929 FOREIGN PATENTS 21,696 Great Britain 1901