US3190369A

US3190369A - Rotary percussion rock drilling apparatus

Info

Publication number: US3190369A
Application number: US255424A
Authority: US
Inventors: Harley G Pyles
Original assignee: GALIS Manufacturing CO
Current assignee: GALIS Manufacturing CO
Priority date: 1963-01-24
Filing date: 1963-01-24
Publication date: 1965-06-22
Anticipated expiration: 1982-06-22

Description

June 22, 41965 H. G. PYLEs ROTARY PERCUSSION ROCK DRILLING APPARATUS 5 Sheets-Sheet 1 Filed Jan. 24, 1963 ATTORNEYS June 22 1965 H. G. PYLES 3,190,369

ROTARY PERCUSSION ROCK DRILLING APPARATUS Filed Jan. 24, 1963 5 Sheets-Sheet 2- INVENTOR ATTORNEYS June 22, 1965 H. G. PYLES ROTARY PERCUSSION ROCK DRILLING APPARATUS 5 Sheets-Sheet 5 Filed Jan. 24, 1963 ATTORNEYS R m N w m June 22, 1965 H. G. PYLES ROTARY PERCUSSION ROCK DRILLING APPARATUS 5 Sheets-Sheet 4 Filed Jan. 24, 1963 June 22, 1965 H. G. PYLES ROTARY PERCUSSION ROCK DRILLING APPARATUS 5 Sheets-Sheet 5 Filed Jan. 24, 1963 l United States This application is a continuation-in-part of my prior application Serial No. 835,880, filed August 25, 1959, now abandoned, entitled Rotary Percussion Rock Drilling Apparatus.

rIbis invention relates generally to drills, and particularly to drills 'utilizing a combination of forces acting upon the drill bit to produce a tool, or machine, peculiarly adapted for, but not limited to, rock drilling, such as is necessary to form openings in mine roofs, iloors, etc.

In rock drilling, different drilling operations are necessary for best results in rock of different characteristics. In soft rock rotary drilling may prove quite effective, while in hard rock a rotary drill may have little effect and percussive drilling may be required. ln the wide range between these extremes, the operation has been to select the one drilling operation thought best suited to the particular job at hand.

lt has been proposed to combine rotary and percussive action in a single drill. Efforts in this direction have included means to impart rotary movement to .the drill to change its orientation relative to the hole between percussive impacts, and devices in which means to rotate a drill are used also to actuate a hammer to deliver successive blows to the drilling tool.

The general object of the present invention is to provide drilling apparatus which includes independently controllable means to rotate the drill and to deliver repeated driving impulses to the drill, so that rotary drilling, percussive type drilling, or graduated combinations of the two may be achieved at the desire of the operator.

Another object is to provide a drill having means to deliver repeated driving impulses in the direction of the longitudinal axis of the drill bit without actual contact impact, and without the use of a hammer, or other striking means, to deliver a blow to the drill, or to the structure connected to the drill.

A further object is to provide a drill having means to provide for rotation of the drill and for driving impulses to the drill, in which the relative speed of rotation and rapidity of driving impulses, as well as the force of the driving impulses, may be varied at the will of the operator, either before or during a drilling operation, and Without need for stopping the operation.

Still another object of the invention is to provide drilling apparatus wherein a predetermined fixed force is applied to the drill in the direction the hole is to be made, and a second forcewhich oscillates axially of the drill, is applied to the apparatus in such manner that the oscillation of the second torce opposite to the drilling direction counteracted by the fixed force and the oscillation in the drilling direction is added to the fixed force to provide a driving force upon the drill.

A more specific object of the invention is to provide drilling apparatus in which an oscillator, or vibrator, is used as a means for supplying a pulsating driving force for the drill.

Yet a further object of the invention is to provide a mine drilling machine having drilling means as set out above and including means to impose a fixed force iupon the drill in the drilling direction, to overcome that force component of the oscillator which acts opposite to the drilling direction.

Other objects of the invention will become apparent arent G M lgg Patented ,lune 22, 1965 from the following description of one practical embodiment thereof, when taken in conjunction with the drawings which accompany, and form part of, this specification.

In the drawings:

FIGURE l is a side elevation of a mine drilling machine which embodies the principles of the present invention;

FGURE 2 is a transverse section through the oscillator, or vibrator, which provides the pulsating driving force to be imposed upon the drill, and is taken on the line 2-2 of FIGURE 1 and line 2 2 of FIGURE 3;

FIGURE 3 is a horizontal section through the oscillator, taken on the line 3 3 of FIGURE 2;

FGURE 4 is a schematic perspective View illustrating an adjusted position of the weights of the oscillator;

FIGURE '5 is a view similar to FIGURE d showing the weights in still another position;

FGURE 6 is a detail view showing the drill pot in section, and the drive means for rotating the drill;

FGURE 7 is a graph illustrating the forces which will act upon the drill and their direction of application;

FIGURE 8 is a side view of a drilling machine of slightly modified construction;

FlGURE 9 is a top plan view of the machine shown in FlGURE S; and

FIGURES l() and 1l are schematic side elevations showing thrust forces in drilling upwardly and downwardly.

In general, the invention consists in drilling apparatus in which means to rotate the drill is provided, and an oscillator, or vibrator, is used to impart a driving force to the drill. The speed of rotation and the speed of the oscillator are variable, and the oscillator force is variable to permit wide variation in the `actions of the two drill operating means. The drilling apparatus is incorporated in a machine for use in mines, and the drill-supporting boom of the machine is used as a means for exerting pressure uponA the drill in a drilling direction, to amplify the driving thrust of the oscillator and to nullify, or overcome, its opposite, or reverse, thrust.

Referring to the drawings in detail, and first to that form of the invention shown in FIGURES 1 to 6, the invention is illustrated in conjunction with a mine drilling machine of the type disclosed in my co-pending application Serial No. 827,317, led July 15, 1959, now abancloned. Only enough of the machine to show its operative association with the drill has been shown.

The machine includes a frame ll, supported by wheels Z, with boom-supporting rails 3 carried by, and extending longitudinally of, the frame. Sleeves 4 are slidably mounted on the rails, and a boom 5 is pivotally connected at its lower end to the sleeves 4, so that it may move forwardly and backwardly, and tilt vertically, relative to the frame. The boom is connected intermediate its ends to a lever 6 which has its opposite end pivotally attached to the machine frame, as at 7. A boom jack 3, in the form of a hydraulic cylinder assembly, has its piston rod 9 pivotally mounted on the machine frame, and the cylinder ll) is pivotally connected to the boom lever 6 at a point between the lever ends. It will be obvious that operation of the boom jack 8 will cause lever 6 to swing about its pivot 7 and raise and lower the boom. Due to the fact that the connection between the lever and the boom will be caused to move in an arc, the lower end of the boom will slide along the rails 3 and a drill 11, carried at the upper, or outer, end of the boom will be moved along a straight, vertical line. The drill assembly is pivotally attached to the outer end of the boom, as at 12, and a levelling linkage 13 is interposed between the frame and the drill assembly to maintain the drill vertical during raising and lowering of the boom. These movements and mechanism are disclosed in detail inthe above-mentioned Y application.

The drill assembly consists of a drill pot 14, which carries the pivots 12 for connection tothe boom. An

oscillator 15 is mounted on the drill pot opposite to the drill 11. The drill'pot is the same as that illustratedin Oscillator 15 may be of anyy known type which will produce an oscillating force directed along a straight line. An oscillator having a pair of parallel shafts with eccentric weightsv mounted upon the shafts in opposite phase, and the shafts rotated in opposite directions has been shown.

If the shafts are arranged and spaced horizontally, the side thrusts developed by the oppositely `rotating weights will cancel one another and only the upward and downward components of force will be effective.

The oscillator illustrated' (see FIGURES 2 and 3) is mounted in a housing 24 attached to the bottom of the drill pot. v A'pair of

shafts

25 and 26 lie in spaced, parallel relation in the housing and are journalled in the of the drill, this force will act first in'a direction toward the drill and then equally in a Y,direction away from the drill. If the oscillator is permitted to Voperate freely inl this manner, no drilling would result. If, however, the force operating to withdraw the drill from the hole can be.counter,acted,rthe full effect of the oscillator force acting toward the drill plus the counteracting force will be utilized as laV driving forcev for4 the drill.

In the embodiment of the drill in a mine drilling machine, as shown,`the boom may be utilized to exert a force upon the drill in a drilling direction to counteract the opposite force componentof the oscillator. If, for example, in drilling into a mine roof the oscillator operates to deliver an alternating force of 1800 pounds in each direction, the boom jack of the machine maybe operated to cause the boom to exert a steady` upward force of 1800 pounds upon the drill and cancel, or negative' the 1800 pound downward component of the oscillator. The upward component of the oscillator action, however, will be added to the upward thrust of the boom, so that a force of 3600 pounds will be exerted upon the drill in a drilling direction. Due to the reversal of force by the oscillator, the full upward4 thrust upon the drill will be delivered as an impact. As the movement of the eccentric weightsV of the'oscillato'r is a rotary'one, the impactrrate may be' very'high, as no direction change' of moving parts isinvolved. i

FIGURE 7 of the drawings shows -diagrammatically Y the forces which will cut upon the apparatus and the net housing end walls. Shaft 251i's coupled tothe drive shaft 27 of a hydraulic motor 28. YMotor 28 will also be a variable speed motor and can `be controlled from the machinev by suitable, conventional controls (not shown). The shafts are interconnected by means of meshing spur gears, gear 29being mounted upon'shaftZSv and gear 30' upon shaft 26'. The gears are identical so that the .shafts will have equal' and opposite movement. The shafts carryeccentric weights which,rin order to permit adjustment, are divided. By this is meant that the total weight to be carried by a shaft is divided in two, and two weights, each one-half the totalweight, are used on eachr shaft. Thus, shaftk 25 carries

weights

31 and 32, and shaft 26 Y Weights 33 and34.` Weights 3.1 andl 33 are fixed relative to their respective shafts, and

weights

32 and 34 are fixed to sleeves 35 and 36fwhich are rotatably mounted upon the

shafts

25 and 26 so that the effective force of the force upon the drill. Line `48, at the y1800 pound level,

`represents the steady unidirectional force exerted bythe boom in an upward direction. The dotted. line 49 shows the alternating vibratory, or oscillating,force generated by the oscillator. This force will be developed equally on opposite directions building up from zero. If the thrust of the boom is equal to the alternating component of the oscillator,` the downward thrust of the oscillator will be exactly oounteracted so that the thrust upon the drill will be zero. During the upward movement of the oscillator, ther lwill be two forces acting upon the drill in a driving direction, and the total impact'will beequal to the sum of the two. Thus, the actual force upon the drill may be represented by the sinusoidal curve 50,- alternating from zero to 3600 pounds. It will be understood that the boom thrust need not exactly equal Vthe downward force of the oscillator. The boom thrust should never be lower than that needed to cancel out the oscillator downward combined eccentric weights on each shaft can be varied.

The sleevesV 35 andu 36 carry meshing spur gears 37 andY 38 tov intercouple the adjustable weights for similar operative movement and similar adjustment. In yorder to' adjust the weights, shaft 26 is formed in two parts, an outer hollow shaft 39 whichfcarries tl'ie` gear 30 and anv inner shaft 40 keyed to, and-telescopically slidable in the hollow. shaf-t39s Inner shaft t0-carries the sleeve 36, and isprovided'with aspiral groove 411in whicha pin 42, carried bysleeve 36, rides. The hollow shaft 39 and sleeve 36= are in: end'.= abutment and heldagainst end movement by the end bearings in the .housing Axial movement of' the inner shaft;40 willcauseipin'42j to ride in` groove 411 force, for most effective operation, but it may be greater.

If it is found that the oscillator operation creates excessive vibration in the boom, an accumulator 51 may be interposed in the fluid line 52 to the boom jack so as to dampen the vibration and prevent its transmission to the machine. The accummator may be any suitable type. The one shown consists of a fluid chamber 53 communieating with the fluid'line, in which a flexible gas bag 54 is located. Pressure differential in the fluid line will be smoothed `out by compressori and expansion of the gas bag.

It will be seen that the drillingy apparatus disclosed is y capable of operation under wide variation of control. It

andsleeve 36 tor rotaterelativeto the inner shaft 40'and -Y hollow shaftr39'. Thus;` weight 3.4 will be caused to shift arcuately relative to weight 33 and, ,through gears 37 and 38; weight 32 will be shifted in an equal'and opposite amountrelative to weight 31. Movement of inner. shaft 40j in an Vaxial directionmay be effected in an appropriate manner. For examplean adjusting screw 43 may `be threaded into the oscillator housing and" coupled to the shaft by means-cfa yoke 44,'engaginga groove 45 inkan` may be operated as a rotarydrill; it may be operated as a percussive drill; or,it may be operated as a rotary and percussive drill in any desired ratioof rotary and impact speeds. The rimpact force may be varied at will to increase or reduce the force applied to the tool. vThis permits a single drilling apparatus to function wherever needed, irrespective ofthe 'character ofrock formation encountered. The change from rotary to percussion drilling, or to a combination of the two inany desired ratio, or a change in the percussive force applied may be made while the toolis in operation in drilling a single hole. The change from rotary to percussive drilling or to a combination of the two may be accomplished-by selective operation of thefmotors 16 `and 28. A change in oscillator thrust'may be made by manipulating the adjustment screw 43 of the oscillators to vary to arcuate relationship of the escasas E eccentric weights to and from concentricity axially of their respective shafts. If the Weight-s are aligned on their shafts, as shown in FIGURE 4, maximum thrust will be obtained. If the movable weights are displaced through an angle of 90, as seen in FIGURE 2, the oscillating thrust will be less, and it the Weights are displaced at 120, as seen in FIGURE 5, the force is further reduced. When the oscillator is adjusted to change its thrust force, the boom thrust may be also be regulated.

In FIGURES 8 and 9, a drilling machine is shown having means to counteract the drilling thrust to increase the forces which can be used. As the machine is the same as that previously described except for the addition of forceresisting jacks, the parts of the machine are indicated by the same reference characters used in connection with that form of the machine shown in FIGURES 1 and 6.

T he drilling machine shown in FIGURES 8 and 9 has a iloor, or ground, engaging jack 55 mounted at the center of the front of the frame. Two additional floor engaging jacks 56 are fixed to the rear of the frame, one on each side of the machine. A roof engaging jack S7 is connected to the frame immediately behind jack 55 for vertical movement between the spaced arms or" boom 5. These jacks may be hydraulically operated by suitable connection 58 to a pump 59 and a supply of fluid, and independently controlled by valves 60 mounted conveniently to an operators position 6I. By operation ot the proper valves, the several jacks may be raised, lowered and held iixed in ground, or roof, engaging position by hydraulic pressure.

The

jacks

55 and 56 will require little piston movement to bring the Hoor-engaging

plates

62 and 63 to and from operative positions. Roof jack 57, however, may have its plunger 64 some distance below the roof of the area in which the machine is working. In order to reduce the movement to a minimum, and to keep the plunger short so that it need not project above the machine frame when retracted, the plunger may have a socket 65 in its upper end, and a length of pipe 66 may be seated in the socket as a plunger extension (see FIGURE 11). Different length pipe extensions can be provided for different height tunnels, or chambers.

Referring now to FIGURE 10, the machine is set up for roof drilling by arranging the drill pot with its bitreceiving chuck upwardly, and inserting a proper bit, or auger 11. Jack 55 is operated to lower its plate 62 to ground contact, and held there by hydraulic pressure. The oscillator and the bit rotating means are started, with the oscillator set to deliver the selected percussive thrust to the bit and the rotating means set for the desired speed for the drilling job to be done. The boom jack 8 is then actuated to raise the bit to drilling position against the roof and to canse the boom to exert an upward force upon the drill at least equal to the downward component of the oscillator. Thus, the drill will be held against the hole bottom, and the boom thrust will be added to the oscillator force in the drilling direction to deliver percussive blows to the drill.

The maximum driving thrust which can be imposed upon the drill in any given instance is determined by the machine weight, the distance of the mach-ine center of gravity from the jack S5, and the distance of the projected drill axis from jack 55. These distances, or lever arm lengths, are indicated schematically on FIGURE 10, with the distance of the machine center of gravity from the jack 55 being indicated as a and the distance from the jack t-o the drill axis being shown :as b. As the weight of the machine is known, and the distances a and b are known, the maximum thrust can be found by -substit-uting the known quantities in the equation, a machine weight=b thrust- If, for example, it is found that a thrust of 10,000 pounds can be used, and it is known that the oscillator developes a thrust of 2,000 pounds in both directions vertically, it will be possible theoretically to set the boom jack to cause the boom 'to exert an upward torce upon the drill pot up to ti 8,000 pounds. This of course is far more than is necessary to offset the downward -force component of the oscillatory under the given circumstances.

When the machine is to be used for downward drilling, the leveling linkage 13 is disconnected from the drill pot, and the drill pot rotated to orient the drill vertically downward. The linkage 13 will be reconnected and the movement of the drill will then be along a vertical line. For downward drilling, the forward jack 5S is not in use. The lrear ground-engaging jacks 5d are lowered, and the jack 57 is raised into contact with the roof. The boom jack is then operated to lower the boom and exert the desired thrust upon the drill assembly (see FIGURE 11). In this case, the thrust on the drill times the distance b will be equal to the distance a times the `force of jacks 51's. The force exerted upon roof jack 57 will be equal to the drill thrust plus the jack 56 torce.

In drilling either up or down, with any of the structural forms of the invention disclosed, the percussive drilling thrust is the oscillator force in the drilling direction plus the force applied through the boom. The boom force is obtained by maintaining a constant hydraulic pressure upon the boom jack. This will cause some deflection ofthe boom, but the amplitude of movement caused by the oscillator is very slight, and the amount of deflection will depend upon the force applied.

So long as the force is applied to lthe drill pot and oscillator .assembly acting in the direction of longitudinal extension of the drill and at least equal to the thrust of the oscillator in an opposite direction, effective drilling is possible irrespective whether the drilling is done upwardly or downwardly.

While in the above practical embodiments of the invention have been disclosed, it will be understood that the structural details described and .shown are merely by way of illustration, and the invention may take other `forms within the scope of the appended claims.

What is claimed is:

I. Rotary percussion rock drilling apparatus comprising, a wheeled frame, a drill pot having means to receive a drill bit in longitudinal extension therefrom, means to rotate the drill bit mounted in the drill pot, an oscillator of the type developing thrust alternately in opposite linear directions connected to the drill pot, means for driving the oscillator and producing a linear thrust in opposite directions parallel to the longitudinal axis of the drill bit, a boom supporting at one end the drill pot and mounted at the other end on the trame for swinging movement of the drill pot supporting end to move the drill pot along straight lines, .and means interposed between the trame `and the boom to swing the boom and move the drill pot and impose a continuing selected force through the boom upon the drill pot in the direction of extension of the drill bit from the drill pot.

2. Rotary percussion rock drilling apparatus as claimed in claim 1 wherein, the end of the boom supporting the drill pot is adjacent one end of the frame, and there is a ground engaging jack xed to said one end of the frame to counteract the thrust of the oscillator and the force imposed through the boom upon the drill pot when drilling in an upward direction.

3. Rotary percussion rock drilling apparatus as claimed in claim 1 wherein, the end of the boom `supporting the drill pot projects beyond one end of the frame, and there is a roof-engaging jack fixed to said one end of the frame and a ground-engaging jack fixed to the opposite end of the trame, said jacks when in engaging position counteracting the thrust of the oscillator and the force imposed through the boom upon the drill pot when drilling in a downward direction.

4. Rotary percussion rock drilling apparatus as claimed in claim 1 wherein, the end of the boom supporting the drill pot projects beyond one end of the frame, groundengaging and roof-engaging jacks mounted on said one end of the frame for use alternately when drilling in oppo- 7. site vertical directions tocounteract Ioscillator` thrust and the force imposed through the boom upon the drill pot, .and a ground-engaging jack mounted on the; end ffthe frame opposite the said one end for use in conjunction with the rooflengaging jack. y5.Y Rotary percussion rock drilling apparatus as claimed lin claim 4Wherein, the means toyimpose a 4for-ce Vthrough the boom -upon the drill pot is a hydraulic jack.

6. Rotary percussion rock drilling apparatus as claimed in claim 1 wherein, the means to impose a force thro-ugh the boom upon the drill pot is a hydraulic jack.

7. Rotary percussion rock drilling apparatus compris-V ing, a frame, a drill pot having means to receive a drill bit in longitudinal extension therefrom, a drill bit in the drill bit-receiving means, means to rotate the drill bit mounted in the drillV pot, an oscillator having at least a pair of eccentric weighted shafts mounted in rparallel relation, means to drive the weighted shafts in opposite phase to produce a lineal thrust in opposite directions nr'r'rial Vto a plane including lthe aXes of the shafts, the! oscillator mounted on the drill pot with the weighted shafts at right angles to the longitudinal extent of Vthe drill bit, whereby the lineal thrust of the oscillator willY b'eparallel to the longitudinal axis of the drill bit, a boom'supporting at one end the drill pot and pivotally mounted at the other end on the frame, the boom including means to cause straight-linemovement'of the drill when the boornV is' ground engaging jack fixed to. said one end ofthe frame v to counteract the thrust of the oscillator and the force imposed through the boom upon the drill pot whenY drilling in an upward direction.

9. Rotary percussion rock drillingapparatus;V as clairrred in claim 7` wherein, the endof the boom supporting the drill pot projects beyond one end' of the frame, and there is a roof-engaging jack fixed to said one end of the frame` and a ground-engaging jack xed'to the opposite end of acting thethrust of the oscillator arid thevforce imposed through theboom upon the drill lpot when drilling in a downward'direction. y

10. Rotary percussiorock drillingapparatus as claimed in claim 7 whereinfthe position'of thev drill pot in the bot'urt` is reversible to permit drilling inopposite directions, theend ofthe boom supporting the drill pot projects beyo'nd one end of the traine, ground-engaging and roof; engaging jacksrnounted on said one end of the frame for use alternately when drilling in ppo'vsite vertical directions 4to counteract oscillator' thrust and 'the' force `imposed tl'l'ro'ugh the boo-'m upon the drillfpot, anda ground-en-v gaging jack mounted o'n the end of the fram'efoppoi'ste the Said one end for use in conjunction with therooflengaging jack.l y

v, 11. Rotary percss'ion'ro'ck drillingl apparatusY as claimed claim I0 wherein, the means to impose a force through the boomupon the drill pot is a hydraulic jack. y n

12. Rotary percussion rock drilling apparatus as claimed in cl'aini7 wherein, the Ymeans to impose a force through theyboom upon the drill pot isa hydraulic jack.

1:3. Rotary percussion rock drilling apparatus as vclaimed inrclaim'7 wherein, there are separate control means for the means to rotate the drill bit and the oscillator so that independent and lcombined drill rotation and oscillator thrust can b'e obtained, and Vmeans to vary the speed of drill rotation and the thrust developed bytheoscillator.

14. Rotary percussion rock drilling apparatus as claimed in claim 7 wherein, there is'means to Vabsorb vibration' communicated to the'hoom.v

` y'References Cited -by the Examiner vUNITED STATES PATENTS 2,102,603. '1'2/371 raamtl 1 173-49 2,698,735v .1p/5,5, Lehner i 173-160 V2,745,637 5-/56 B au i s 173-23 2,776,113 1757.1@ 173-49 2,942,849 6/60 Y Bodin@ 4ms-; 173-49 Y roRfEI'GN4 PATENTS 798,508 5736 France.

BROUGvI-FFON'G.l DURHAM@ Primary Examiner.

Claims

1. ROTARY PERCUSSION ROCK DRILLING APPARATUS COMPRISING, A WHEELED FRAME, A DRILL POT HAVING MEANS TO RECEIVE A DRILL BIT IN LONGITUDINAL EXTENSION THEREFROM, MEANS TO ROTATE THE DRILL BIT MOUNTED IN THE DRILL POT, AN OSCILLATOR OF THE TYPE DEVELOPING THRUST ALTERNATELY IN OPPOSITE LINEAR DIRECTIONS CONNECTED TO THE DRILL POT, MEANS FOR DRIVING THE OSCILLATOR AND PRODUCING A LINEAR THRUST IN OPPOSITE DIRECTIONS PARALLEL TO THE LONGITUDINAL AXIS OF THE DRILL BIT, A BOOM SUPPORTING AT ONE END THE DRILL POT AND MOUNTED AT THE OTHER END ON THE FRAME FOR SWINGING MOVEMENT OF THE DRILL POT SUPPORTING END TO MOVE THE DRILL POT ALONG STRAIGHT LINES, AND MEANS INTERPOSED BETWEEN THE FRAME AND THE BOOM TO SWING THE BOOM AND MOVE THE DRILL POT AND IMPOSE A CONTINUING SELECTED FORCE THROUGH THE BOOM UPON THE DRILL POT IN THE DIRECTION OF EXTENSION OF THE DRILL BIT FROM TE DRILL POT.