US 3118511 A
Description (OCR text may contain errors)
Jan. 21, 1964 C. T. KAY
ROTARY DRILL BITS Filed Sept. 29, 1960 3 Sheets-Sheet 1 I0 F g. 3 l5 m ,i 38 W W 3a A .9 la 2/ B 2 3 25 2 a 3 a; 3.; 32 V7 ig .73 32 Hg 4 INVENTOR Cas/mir I Kay 20 ATTORNEYS Jan. 21, 1964 Filed Sept. 29, 1960 ROTARY DRILL BITS 3 Sheets-Sheet 2 I/II ATTORNEYS Jan. .21, 1964 C. T. KAY
ROTARY DRILL BITS 3 Sheets-Sheet 3 Q /5 a 'lb .7/ 2a IN "WIN 32 .4 20 2/ Flag 32 1a 27 m /7 24 MP [W l? 33 32 k7 ENTOR mv F g9 32 Cos/mir I Kay ATTORNEYS United States Patent 3,118,511 RQTARY DRILL BKTS Casimir T. Kay, 4135 W. 7th St, Dallas, Tex. Filed Sept. 29, 1960, Ser. No. 59,301 2 Claims. (Cl. 175'-397) This invention relates to new and useful improvements in rotary drill bits.
The invention is specifically concerned with drill bits of the type having no revolving cutter cones or rollers, the invention being especially useful in relatively small and medium-sized drill bits.
An important object of the invention is to provide an improved rotary drill bit in which the cutting faces, and particularly the hard tipping thereof, are concentrated in the outer portions of the formation face being drilled, with lesser areas of the cutting faces being positioned for drilling or cutting of the inner portions of the formation face. A rotary drill bit cuts or drills a more or less circular hole, and the formation face against which the drill is operating is in the configuration of a circle. It is quite apparent that there is less of the formation to be drilled or cut in the inner or central portions of the formation face, and considerably greater areas in the outer portions of the formation face being drilled. By concentrating the cutting or drilling faces and especially the hard metal inserts carried thereby, in the proper positions so as to drill predominantly upon the outer portions of the formation face, increased cutting action over this principal area is made possible. In addition to which, in a given bit of a given size and containing a given quantity of hard metal, such as tungsten carbide, the hard metal may be concentrated so as to function predominantly upon the outer portions of the formation face, and accordingly, hard metal inserts of greater thickness may be employed in the bit without increased cost but with increased wearing life and faster drilling.
Another object of the invention is to provide an improved rotary bit having several blades, and in which the blades are not equidistantly or equi-angularly dis posed, with the result that the bit runs more smoothly and the tendency of the bit to chatter as it revolves and drills is largely eliminated.
A still further object of the invention is to provide an improved rotary bit having several cutting blades with cutting points thereon and in which the cutting points of the several blades are not rotationally alined so that the cutting points do not track one another, but instead, travel in slightly different annular paths whereby faster and more effective drilling or cutting is achieved.
A still further object of the invention is to provide an improved rotary bit having several cutting blades in which the cutting faces of the blades are swept back both longitudinally as well as transversely or laterally to cause the blades to drag over the formation, to help hold the hard metal inserts in place in the cutting faces of the blades, and also to provide an increased or greater wearing area on the hard rnetal inserts.
An additional object of the invention is to provide an improved rotary drill bit having reduced blade area and cutting face area to cause the cutting faces to dig into the formation being drilled so that faster drilling may be obtained while simultaneously less downward thrust or weight need be applied to the bit.
A further object of the invention is to provide an improved rotary drill bit which is virtually equally effective in soft, medium, or hard formations so that there is no need to change the drill bit as strata of varying types of formation are encountered.
Yet another object of the invention is to provide an improved rotary drill bit which eliminates all cutting faces from the central axis of the bit, it having been found that there is no need to drill the very center of the formation face since this small core is broken off during bit rotation due to inherent wobbling or less than perfectly circular rotation of the drill bit.
A construction designed to carry out the invention will be hereinafter described, together with other features of the invention.
The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings, wherein examples of the invention are shown, and wherein:
FIG. 1 is a side elevational view of a four-bladed rotary drill bit constructed in accordance with this invention,
FIG. 2 is a bottom plan view of the drill bit of FIG. 1,
FIG. 3 is a diagrammatic view illustrating the cutting or drilling effect observed from the use of the drill bit of FIG. 1,
FIG. 4 is a diagrammatic view illustrating the means by which increased wearing surfaces are obtained,
FIG. 5 is a side elevational view, the top thereof being in section, of a three-bladed drill bit constructed in accordance with this invention,
FIG. 6 is a bottom plan view of the drill bit of FIG. 5,
FIG. 7 is a view similar to FIG. 3 illustrating the cutting action of the drill bit of FIG. 5,
FIG. 8 is a vertical, sectional view taken on the line 8-8 of FIG. 2,
FIG. 9 is a vertical, sectional view taken on the line 99 of FIG. 6, and
FIG. 10 is a schematic view illustrating the negative rake and angular offsetting of the cutting blades.
In the drawings, in FIG. 1 the numeral 16 designates a circular drill bit body having a plurality of spaced, depending drilling or cutting blades and an upstanding, tapered, screwthreaded pin 11 for connection to the lower end of the conventional drill collar or drill pipe. As shown in FIGS. 2 and 8, the pin 11 is formed with an axial water course 12, having a plurality of water passages 13 opening outwardly from its lower end into the spaces between the cutting blades, and having an axial reduced water course 14 opening diametrically downwardly into the space located centrally of the cutting blades.
The cutting blades are formed integrally with the drill body It? and include at their upper ends downwardly and outwardly inclined shoulders 15 which merge into substantially vertical cutting or reaming edges 16 formed on the outer edges of the drill blades and displaced radially outwardly from the drill body It). The lateral, substantially vertical, reaming edges 16 of the cutting blades adjoin at their lower ends downwardly and inwardly inclined cutting edges 17 terminating in obtuse cutting points 18 on each of the cutting blades.
In the form of the invention illustrated in FIGS. 1 and 2, there are four of the cutting blades, a diametrically opposed pair of the blades, 19 and 2%, having inwardly :and upwardly inclined cutting edges 21 extending approximately radially inwardly from the cutting points is of said blades 19 and 2%). The combined widths of the cutting edges 17 of the blades 19 and 25 and of the cutting edges 21 thereof are such that the blades 19 and have an effective cutting width of approximately onequarter of the cutting diameter of the bit or of the hole being drilled by the bit. Thus, the cutter blades 19 and 2d and the cutting edges thereof drill only the outermost portion of the bottom of the drill hole, this being the portion shown as double. cross-hatched at 22 in FIG. 3 and which represents an area of the magnitude of 75- 80% of the total area of the hole being drilled. As will be seen, this area is also drilled by the other two cutting blades.
The third cutter blade 23 is disposed between and approximately at right angles to the blades 19 and 2i) although it will be seen hereinafter that this is not exactly true. The third cutter blade 23 is formed with an inwardly and upwardly extending cutting edge 24 projecting radially inwardly from the cutting point 18 of the blade 23 toward the axis of the drill bit to a point spaced about one-third of the distance between the axis of the bit and the track of the inner extremities of the cutting edges 21 of the cutting blades 19 and 25). In addition, therefore, to drilling the area 22 shown in FIG. 3, the blade 23 also cuts an additional inner area 25 indicated by cross-hatching in FIG. 3 and representing 16-15% of the total cross-sectional area of the hole being drilled.
The fourth cutter blade 26 is disposed more or less diametrically opposite the blade 23 and has an inwardly and upwardly inclined cutting edge 27 extending radially inwardly from the cutting point 18 of the blade 26 and to a point spaced approximately two-thirds of the distance between the inner margin of the cutting area 22 and the axis of the drill bit. The blade 26, in addition to cutting the areas 22 and 25, thus in addition, cuts the innermost area 28, indicated in FIG. 3 by hatching, and representing 5-1 of the total bottom hole area being drilled. The very center portion of the drill hole bottom, indicated at 29 in FIG. 3, is therefore not cut or drilled by any of the blades, it having been found that as the drill bit progresses downwardly through a formation, a small slender core will tend to form in the area 29, and that this core will repeatedly be snapped off through the inherent wobbling or eccentric rotation of the drill bit so that there is no reason to expend cutting energy and cutting area thereon.
The drilling area percentages recited hereinabove are approximate only and are subject to variations, the important point being that the outer and predominantly larger area is subjected to the cutting action of all four cutter blades, the next inner and next larger area being subjected to the cutting action of two of the blades, and the innermost and smallest area requiring the cutting action of only a single one of the blades. In this manner, the cutting areas of the several blades may be largely concentrated in the outer portions of the formation area and needless and excessive cutting blade area in the center portions of the hole eliminated. This means not only that the drill bit will out faster because the bit digs in due to the reduced blade area, but also, that less weight is needed on the drill bit for obtaining the predetermined drilling rate. This also means that the hard metal inserts, for instance, tungsten carbide inserts, which will be described more fully hereinafter, may be made of thicker configurations without increasing the total weight of hard metal present in the bit and thereby increasing the cost thereof. The presence of the thicker hard metal inserts means that the bit will drill faster, and will last longer, because of the greater and the longer wear of the thicker inserts.
The hard metal cutting inserts for the reaming edges 16 may desirably be of an elongate rectangular shape and suitably secured, as by brazing or otherwise, in a rectangular groove 31 cut in the lateral edges of the several cutting blades. The hard metal inserts 32 forming the cutting edges 17 desirably are of a trapezoidal shape and present a cutting edge disposed at approximately 25 to the horizontal. The same hard metal inserts may be employed for forming the cutting edges 21 and the outer portions of the cutting edges 24 and 27, as indicated in FIGS. 1 and 2, and additional hard metal inserts 33 generally of parallelogram shape may be employed for forming the additional and inner portions of the cutting edges 24 and 27, one of the inserts 33 being employed in the blade 23, as shown in FIGS. 1 and 2, and two of the inserts 33 being employed for the blade 26, as shown in FIG. 8. Such an arrangement is by no means essential, but is convenient for fabrication and for minimizing the number of sizes and shapes of hard metal inserts which must be employed. The inwardly and upwardly inclined portions of the several cutting edges may also be inclined at an angle of approximately 25 to the horizontal, the same as the outer cutting edges 17.
In the fabrication of bits of this type, the hard metal inserts are normally fitted into complementary recesses formed in the edges of the cutting blades of the bit and therein secured by brazing or otherwise, following which the bit and the cutting edges thereof are ground to the desired dimensions and shape. In carrying out the grinding operation, or at any other convenient point in the fabrication of the hits, the cutting points of the several cutting blades are desirably misalined rotationally, or offset with respect to one another a distance of A of an inch or so measuring radially of the bit. Thus, for instance, the cutting points of the blades 19 and 20 may be rotationally alined, while the cutting points of the blades 23 and 26 are offset of an inch or so inwardly or outwardly with respect to the track of the cutting points of the blades 19 and 20, or one offset inwardly and the other offset outwardly. This avoids the tendency of the cutting points to track one another and otherwise aids in the more effective and smooth operation of the bit.
Another important feature of the invention is that in forming the working faces of the cutting blades, as by milling or otherwise, the blades are not evenly and equally spaced. Thus, assuming the blades 19 and 20 to be spaced 180 from one another, either or both of the blades 23 and 26 may be offset rotationally through an angle of 5-10 in either direction from strict 90 positioning with respect to the blades 19 and 20. A very effective angle of displacement has been found to be about 6. This shifting or misalining of the blades causes the drill bit to run more smoothly and eliminates the chattering or vibration which seemingly is a characteristic of drill bits having equally spaced cutting blades. Thus, instead of positioning the blade 23 at a 90 angle with respect to the blade 20, it is desirably positioned at an angle of -100 with respect to the blanc 19 and most desirably at an angle of 84-96". Similarly, the blade 26 may be oifset with respect to the blade 20 an angle other than or both the blades 23 and 26 may be so offset in either direction.
As shown in FIGS. 1 and 2 the forward longitudinal faces of the cutting blades have a negative rate or are sloped or inclined slightly rearwardly from top to bottom from the direction of cutting or drilling rotation. In a lateral or radially outward direction, the cutting blades also have a negative rake and are sloped rearwardly and outwardly from the direction of rotation. In both instances, the angle of rake may desirably be about 6, but may range from 5-10". This negative angle of rake in both horizontal and vertical planes has several beneficial effects, the first being that it causes the cutting edges of the bit to more or less drag over the formation being cut or drilled to provide a smoother and more effective cutting action with a minimum of vibration and chattering of the drill bit. Contrary to erroneous suppositions, drill bits of this type do not cut an earth formation in the manner in which a knife cuts an object, but instead, they wear, grind and scrape away the formation through an attrition process, and accordingly, the enhanced dragging action effected through the negative raking of the cutting blades has been found quite conducive to improved drilling operation.
As a second beneficial result, the negative raking of the blades reduces the tendency for the hard metal inserts to be ripped or torn from the drilling blades as the drill revolves. It is characteristic of drilling bits having hard metal inserts that the inserts are sometimes dislodged from the bit and lose their efiicacy as drilling or cutting surfaces besides adding to the possible accumulation of debris in the Well bore. The negative raking of the blades results in less stress being placed upon the bond between the hard metal inserts and the drill body, and accordingly, there is less tendency for the inserts to be forced from their bonded or brazed positions.
The third benefit of raking the cutting blades is illustrated on an enlarged scale in FIG. 4 of the drawings in which one of the hard metal inserts is shown in crosssection. The inserts wear, of course, at right angles to the axis of the bit, and if the inserts are vertically positioned so as to be parallel to the bit axis, the inserts will wear along the transverse line A shown at the top of FIG. 4. If, however, the inserts are inclined with respect to the bit axis, the inserts will still wear in a plane perpendicular to said axis which will be along line B shown in the middle portion of FIG. 4. Obviously, line B is longer than line A, and the inclined inserts will necessarily present a greater wearing area, because of the greater cross section at the wearing plane, to the bottom of the drill hole. It is noted that this will also be true of the hard metal inserts disposed along the lateral cutting or reaming edges 16.
A modified form of the invention is shown in FIGS. 5, 6 and 9, this form of the drill bit having three cutting lades rather than four. In all other respects, the modified form of the bit is essentially the same as that first described, and both bits include the same features and function in very much the same manner. In essence, the cutting blade 19 is deleted from the bit body and the blades 23 and 26 are shifted so that the three blades 20, 23 and 26 are disposed approximately 120 apart. Of course, as pointed out in connection with the first form of the invention, one or two of the blades should be offset from 5l0 from an exact 120 positioning in order to provide a smoother running bit and to eliminate the tendency of the bit to chatter. The offsetting of the cutting points, the negative rake of the cutting blades both vertically and laterally, and the concentration of the cutting surfaces in the outer portion of the area being drilled are all features common to both forms of the bit, and the several attendant advantages will not be repeated. As shown in FIG. 7 the outermost portion 34 of the bottom of the hole and which is shown in FIG. 7 as hatched and cross-hatched, represents approximately 75-80% of the total area of the hole being drilled, this area being drilled or cut by all three of the cuting blades of this second form of the invention. The next innermost area 35, shown as cross-hatched in FIG. 7 and representing 10- of the total cross-sectional area of the hole being drilled, is engaged by the inner portions of both the blades 23 and 26, while the innermost area 36, shown as hatched in FIG. 7 and representing 5-l0% of the crosssectional area, is drilled only by the innermost portion of the cutting blade 26. The primary difference in action, thus, is that the second form of the invention includes only a single cutting blade for functioning solely in the outermost area 34, and that the latter area is subjected to the drilling action of three blades rather than four. As to the areas 35 and 36, there is no difference of function, the inner core 3 7 not being subjected to drilling action but being readily snapped off at frequent intervals as the drill bit inherently wobbles or rotates eccentrically in its operation.
The longitudinal negative rake of the cutting blades in both forms of the invention is clearly shown in FIGS. 1
and 5, but the negative rake in a lateral or radial direction is not quite so apparent in the bottom plan views.
This arrangement is shown schematically in FIG. 10, the hetero-angular disposition of the blades being illustrated as the 5 offsetting or shifting of the left-most blade 38. The upper blade 39 and right-most blade 40 are spaced apart, but the blade 38 has been shifted 5 toward the blade 39 so as to lie l'l5 therefrom, and from blade 40. Of course, two of the cutting blades may be shifted so that none of the blades lie exactly 120 from the remaining blades. In the case of the four blade drill bit, the shifting would be from a 90 angular relationship.
The negative lateral rake of the cutting edges of the blades is also more readily apparent from an examination of FIG. 10, it being noted that each of the blades slants rearwardly and outwardly from the direction of rotation of the bit, the particular rake shown being 5. In the case of the blade 38, it is noted that this negative rake of 5 is in addition to the 5 by which the entire cutting blade is shifted with respect to blades 39 and 40'.
In both forms of the invention, the drilling action is concentrated in the outer area of the formation face being drilled, permitting the utilization of more or greater masses of hard metal inserts in this area with the resultant faster drilling and longer operating life. The bits also drill faster because the blade area is reduced allowing the bit to dig in more effectively while reducing the weight which need be applied to the bit along with the resultant wear thereon.
Both drill bits function quite effectively in soft, medium or hard formations so that there is no need to change bits as the formation in the well bo-re may change from time to time although one of the bits may be preferable to the other when certain types of formation are encountered consistently. In both instances one or two of the cutting blades are shifted 5l0 from exact equi-distant or equiangular spacing from the remaining blades, and all of the cutting blades are formed with a negative angle or rake both vertically and horizontally. In both instances, the cutting points are olfset rotationally with respect to one another so as to eliminate tracking of the cutting points, and in both instances, the carrying out of drilling at the exact center of the drill bore is eliminated as being unessential, permitting additional concentration of cutting surfaces.
The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention.
What I claim and desire to secure by Letters Patent is:
1. A rotary drill bit including, a drill body, drilling blades depending from the body, cutting edges on the lower ends of the drilling blades extending from the periphery of the bit approximately radially inwardly thereof, the cutting edge of one of said blades extending farther inwardly than the cutting edge of another of said blades, the peripheral edges of the cutting edges being spaced apart circumferentially of the drill body unequally, the cutting edges being V-shaped in configuration along vertical planes extending radially of the drill body so as to have depending vertices, and the vertices being spaced radially outwardly from the center of the drill body different distances and misalined rotationally.
2. A rotary drill bit including, a drill body, drill-ing blades depending from the body, cutting edges on the lower ends of the drilling blades extending from the periphery of the bit approximately radially inwardly thereof, the cutting edge of one of said blades extending farther inwardly than the cutting edge of another of said blades, the peripheral edges of the cutting edges being spaced apart circumferentially of the drill body unequally, the cutting edges being V-shaped in configura- 7 lion along vertical planes extending radially of the drill body so as to have depending vertices, and the vertices being spaced radially outwardly from the center of the drill body different distances and misalined rotationally by a. distance of the order of magnitude of one-sixteenth of an inch.
References Cited in the file of this patent UNITED STATES PATENTS 1,218,671 Lane Mar. 13, 1917 10 8 Zub1in Mar. 23, 1937 Hughes Jan. 9, 1940 Phipps May 9, 1950 Rassieur Aug. 25, 1953 Stokes June 4, 1957 SteflFes Jan. 24, 1961 FOREIGN PATENTS Great Britain Dec. 5, 1940 Great Britain Feb. 11, 1941