US1365134A - Rotary boring-drill - Google Patents

Description

If'. L, 0. WADSWRIH.

ROTARY BORING DRILL.

APPLICATION FILED OCT. E, I9I9- 1,365,134. Patented Jan. 11, 1921.

2 SHEETS-SHEET I.

F. L. 0. WADSWORTH.l

ROTARY BORING DRILL.

APPLICATION FILED OCT. 8. l9l9. 1,365,134.

2 SHEETS-SHEEI 2.

.|1 l l lin? Patented Jan. 11, 1921.

:Inventor 32513, Hr: dmomaex/gcau F.L.O. Wmxsw omiH FRANK L. t). WADSWORTH, OF PITTSBURGH, PENNSYLVANIA.

ROTARY BORING-DRILL.

mesma.

Application filed ctober 8,1919.

To all whom, t 'may concern.'

Be it known that I, FRANK L. O. VADS- WORTH, a citizen ot the United States, residing at Pittsburgh, Pennsylvania, have invented a certain new and useful Improvement in Rotary Boring-Drills, of which the following is a full, clear, and exact description, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to rotary boring drills for use in boring wells in earth, rock or other hard material, and more especially to the type of rotary drills known as disk drills or bits, which are equipped with a disk-shaped cutter or cutters that act to cut away the hole and disintegrate the material thus loosened.

The object ot' my invention is the production ofa rotary disk drill consisting of a minimum number of parts and presenting a maximum degree oi" simplicity and ruggedness of construction. Another object of the invention is the provision of disk cutter elements which will have a very effective cutting action; which will resist any rapid wear under severe conditions oi' operation, and which can, when necessary, be replaced or renewed very quickly and at comparatively small expense. A further object of my invention is to obtain a definite and positive centering ot.' the drill in thel hole which is being bored, and prevent any wabbling or lateral displacement of the cutting members, and thereby minimizethe danger ot' producing a crooked hole when drilling through irregular and non-homogeneous strata or material. Additional objects of the improvements herein set forth will be obvious to those skilled in the art from the more detailed explanation of various exemplary embodiments ot' my invention which are illustrated in the accompanying drawings in which:

Figure 1 is a vertical elevation of one species of my improved rotary drill construction; Fig. 2 is a plan sectional view on the plane 2 2 of Fig. 1; Fig. 3 is a sectional elevation (on a vertical plane at right angles..

to the plane 1-1), of another species of the said construction; Fig. l is a sectional elevation on the broken plane 4-4-4 of Fig. 3: Fig. 5 is a cross section and plan view on and below the plane .5w-5 of Fig. 3; Figs. G and 7 are side elevations of different portions of the cutter disk elements Specification of Letters Patent.

Patented Jan. 11, 1921.

Serial No. 329.409.

of my improved construction; Figs. 8 and 9 are additional views showing other forms of disk members suitable tor use in conjunction with the aforesaid embodiments of my invention; Fig. 10 is a vertical elevation of a third species of my improved drill structure; Fig. 11 is a cross sectionallview on, the line, 11-11, ot' Fig. 10; Fig. 12 is another section on the line, 12-12, of Fig. 10; Fig. 13 is a diagram; Fig. 14 is a vertical section through the center of a drill illustrating still another embodiment of my invention; Fig. 15 is a side elevation on the plane, 15-15, of Fig. 14 showing certain elements of that construction; and Fig. 16 is a partial vertical section-similar to that of Fig. lll-illustrating a modilied form of disk members suitable for use in place of those shown in Figs. ll and 15. v

Generally described, my improved dril comprises a head which is threaded at its upper or rear end for attachment to an ordinary hollow drill sternwhich serves both to impart rotary movement to the head and convey a current of flushing water theretoand which is slotted at its lower or opposite end to receive a single centrally mounted revoluble disk member, whose diameter is the same as that of the hole to be produced,

l and whose peripheral face is provided with herringbone-shaped teeth that perform the conjoint functions of shearing or shaving the material from the sides and bottom of the drill hole; of disintegrating and grinding down the larger particles of detritus thus cut away (so as to permit ot' its removal in suspension in the flushing stream of water supplied through the hollon7 drill stem); and ot effecting, by the cutting action itself, acontinuous revolution of the disk member on its own axial mounting thereby equalizing the wear on all parts of its toothed peripheral surface. This axis of the cutting-crushing disk member may be either perpendicular to the axis of rotation of the drill head or inclined at an angle thereto; but in all cases this member is so positioned that the resistances to the cutting action of its opposite faces are symmetrically distributed about the axis of rotation of the drill so as to avoid any tendency to wabbling or whipping of the rotating partsfduring the drilling operation.

In the following description of the various illustrative embodiments of my invention the same reference characters will be usedas far as possible--to designate corresponding elements of the different constructions.

In the species shown in Figs. 1 and 2, 6 indicates the drill head which, in this case, consists of a single casting which has a threaded recess at its upper end to receive the ordinary hollow drill stem, T, and which is slotted at its opposite end to receive the disk member, 8, that is mounted to revolve freely on a cross shaft, 9. The disk member, 8, may be made in one solid piece-in which case the whole drill structure consists of only three separate parts ((3. 8, and 9)-but for convenience in cutting the oppositely inclined portions of the herringbone teeth on the periphery of the disc (and for other reasons), it is preferably formed in three parts, as shown in Fig. 2, viz: a central disk, 10, having a double coned surface, and two ring members, 11 and 12, clamped together on the central disk by a circumferential series of screw or rivet elements, 13. The disk, 10, is provided with a removable sleeve, 14:, and washers, 15, 15, which can be readily replaced when worn; and is formed with a large central cavity, IG--that communicates with the bearing surface between the shaft, 9, and the sleeve, 14, through suitable oil holes in the latter-which serves to contain a sufiicient supply of lubricant for continued periods of operation. lVater is conducted from the hollow drill stem, 7, to the slot in which the disk member, 8, is housed, and partially shrouded, through a hole, 17, drilled in the head, 6.

The herringbone teeth on the outer periphery of thoe disk member, 8, are so shaped that the sides of the herringbone which constitute the cutting elements on the right hand ring, 11, are sloped upwardly and backwardly with respect to the direction bf rotation (see Fig. 2) while the sides which constitute the opposite cutting elements on the left hand ring are sloped downwardly and backwardly with respect to this direction (see Fig. l). The reaction between the inclined sides of the teeth and the material removed thereby from the end of the bore holei. e., the thrust of the cut-therefore tends to revolve the disk member in a clockwise directionas viewed from the right hand end of the shaft support, 9-when the drill head is rotated in the clockwise direction (as shown by the arrow -in Fig. 2). This rotative driving tendency can be accentuated, if desired, by forming the teeth with substantially radial sides on their following edges as shown in detail in Figs. 6 and 7 in which the first illustration represents the edges of the teeth on the surface, 12-as they appear when viewed from the left of Figs. 1 and 2-and the second illustration represents the edges of the teeth on the surface, 11, when viewed from the right. It will be readily observed that both sets of teeth act to produce a rotation of the disk member in one and the saine direction; and the rotative driving effect thus secured is amply sufficient to overcome the frictional resistance to the revolution of the said disk under all ordinary conditions of operation, and to produce a regular and continuous rotative movement of the cutting elements on the shaft support, 9.

The revolution of the disk member, 8, on its own shaft-as the drill head rotates on its axis, l-l-brings all parts of the peripheral toothed surfaces successively into cutting engagement with the cup-shaped end of the hole in which the drill is operating; and it also results in the rapid and effective grinding and crushing of the larger particles of loose materialwhich are sheared off by the rotating and revolving teethbetween the broad bottom surface of the disk member and the cup-shaped end of the bore hole in which it is supported. The finely pulver-ized particles are carried away in suspension in the current of water 'which is discharged into the cavity surrounding the drill head through the passage way, 17, and which then flows upwardly around the drill stem to the surface of the ground. The discharge of this stream of water directly on top of the disk member also serves to keep the cutting teeth washed clean and prevent their balling up when operating in relatively soft material; and it is also possible, by inclining the lower end of the passageway. 1T, forward as shown in Fig. 4, to utilize the force of the discharge in assisting in the desired rotary movement of the said member.

The principal resistance to the revolution of the cutting-crushing disk, 8, is due to the contact between the extreme lower portion of its periphery and the adjacent central part of the,bore hole end. In drilling very soft formations the drag at this point may at times become excessive, owing'to faulty judgment on the part of the driller in his regulation of the pressure on the drill head. To overcome this difiiculty, I may, in such cases, usel a construction like that illustrated in Figs. 3-9. In this constructionI use, in conjunction with the main central disk member, 8, two smaller disk members, 19, 19, placed one on each side of the main disk, 8, and arranged to project slightly below it, so as to cut a central depression just under the extreme lower portion of its peripheral face. These disk members, 19, are provided with convexed hub portions on their inner faces, and are held in position on the coned stub shafts, 20 (which are referably made integral with the forks of the head, (in) by the engagement of the ends of these hubs with the adjacent faces of the intermediate main disk member, 8a. In order to provide `for assembling the disk members in position the head is split longitudinally on its central axis; and the parts are rigidly secured together by the joint action of the upper drill stem collar, 21, the beveled collar, 22, encircling the central part of the drill head` and the bolt, 23, which passes through the shaft supportv` 9LL of the main disk member' 8, 1n order to provide for the continuous lubrication of all of the disk shaft bearings the central portion of the divided head is cored outto receive a large lubricator cup, 2st, that is closed at the top with a suitable cap and is in communication at the bottom with the bearing surfaces through oil ducts. 25. 25. that lead to cross grooves on the shaft supports, 9*1 and 20. Passage vays, 17a. 1T` formed in the meeting faces of the two parts of the split head, serve -to conduct two streams of flushing water from the hollow drill stem, 7, to the upper part of the slot in which the main disk member, 8, is housed and partially shrouded; and as shown in Fig. Je, these passage ways are curved forwardly at their lower ends so as to discharge the streams of water against the peripheral teeth of this member in the direction in which it is intended to revolve.

'l`he disk member, S, is provided on its periphery with two rows of oppositely inclined. or herringbone` teeth, which, in this case, are cut on a single ring, 2G, that is secured 'to the central hub, 10a, by t ie series of screws or rivets, 13, 13, etc. in order to provide for the cutting of the two rows of oppositely inclined teeth. this ring member is preferably formed with a central groove. 2T v(see Fig. The hub, v10i, is provided with a central bearing sleeve, and with side bearing washers, 15a, which are cut away on the lower side of the shaft, 9, to form shrouds for the upper inner edges of the auxiliary cutting crushing members` 1S). These latter elements are slightly offset forwardly with respect to the axis of rotation of the drill head, so that only the front advancing edges of these disks come into cutting engagement with the sides of the cavity formed by them (see Fig. el). As the drill head rotates, these auxiliary disks are revolved counter-clockwise, on the shaft supports. 20, by the rolling engagement of their peripheral surfaces with the material on which they rest. movement more l positive, the peripheral faces are preferably provided with 'spirally cut teeth which slope upwardly and back? wardly from the front advancing edges.

Figs. 8 and 9 illustrate a modified combination of main and auxiliary disk members. U and 19, which differs from that shown in Figs. 3 and it in the detail construction of the main disk-which, in this case is formed of a grooved toothed ring, 26, clamped between the main hub member, 10', and the hub washer, 10"--and also in the form and ln order to make this mounting of the auxiliary disks, 19` 19a. These disks, 19, 19, are provided with cylindrical peripheralv surfaces having outer beveled portions, and are recessed on their outwardly turned faces to form cutting edges, 30, 30, on their rear 'ard following sides-the axial supports of these disks being offset rearwardly with respect to the axis of rotation so that the front advancing edges are in this case entirely out of contact with the side of the cavity in which the disks operate (see Fig. 9). Both the cylindrical faces and the beveled edges of these disks, 192 are preferably provided with teeth; the teeth on the cylindrical surface ruiming straight across. and the teeth on the beveled portion being inclined backwardly and downwardly like those on the left hand side of the main disk members, 8 and S".

ln the constructions shown in Figs. 10 and 11 and in Figs. 1-1, 15, and 16, the effect of the frictional drag on the lower side of the main disk members, 8b, is eliminated by tilting this member at a small an- ,gle to the axis of rotation, 1"-1b, of the drill head; so that this side rolls in a circular path of small radius, instead of twisting and sliding over the material at the center of the bore hole end. In this form of drill construction it. is important to locate the single central disk member in such position in the head that the resistances encountered by the opposite cutting edges# on the two sides of the cavity-are symmetrically balanced. so as to avoid any tendency to deflect the drill head from its longitudinal axis of rotation and thereby produce a crooked or irregular shaped bore hole. The manner in which this is done is indicated diag ammati lally in Fig. 13; where the line, lbwlb, represents the axis of rotation of the drill head; the lines, e-f and c f', represent, respectively, the cen tral plane and the axis of rotation of the disk member; the lines, gt and c-i-Z, represent the planes of the two cutting edges of that member; and the curve, s-/z-f- -f, represents the approximately semicircular section of the end of a bore hole cut by the disk edges, e-f and lit-. It is evident that the cutting duty of any unit ele ment on either of these edges-as for example the element, m-varies with the vertical distance m--n of this element above the horizontal plane bounding the lower edge of the disk member (because of thel increasing radii of the horizontal circles of cut described by these elements as the hei"It m-n increases); and because of tklS 2L' given displacement of the lower elei'llellt O one cutting edge (for example the lg ,7c-Z) to one side of the axis ot rotation, 1-1b, will have considerably less effect 1n producing a side thrust on thedrill head, than will result from an equal displacement of the central portion of the opposite edge, g-L, to the other side of the said axis, 1-1". In order to Vsecure a symmetrically, or axially balanced action, the mean displacement of the plane of the edge, g-L, from the drill axis must be less than the mean displacement of the plane of the edge, 7c-Z, from that same axis; or, to put it more simply, the central plane, e-f, of the disk member (i. e., the plane midway the planes, g-L, and c-Z, of the two opposite cutting edges) must intersect the axis of rotation, 1"-1*"- at a point, 71, which is above the center of the vertical radius of the semi-circle s-af-f-Z-t. I have found that, under most conditions, the distance of the point, r, below the horizontal diameter, s, t-or below the axis, e f', of the disk member-should be between 0.3 and 0.4 of the radius of the circle, s--z/-zg z'. e., the radius of the bore hole produced by the drill-this distance varying somewhat with the character of the material to be drilled and also with the axial separation, k-Z, of the two opposite cutting edges of the inclined disk member.

In this inclined disk species of my improved type of single disk drill structures, the two opposite cutting edges of the central disk member are of slightly different diameter, and in the construction of Figs. 10-11 the opposed cutting edges are formed on separate rings, 11b and 12b which are secured to the central hub, 10", by the row of screws or rivets, 13, in the manner clearly shown in cross section in Fig. 11. The peripheral faces of the members, 11", and 12b, may be either curved to fit the surface of the bore hole-as in the previo sly described constructions (see Figs. 1, Zig, 5 and 8)--or may be made straight, as shown in Figs. 10 and 11; the diameters of the two opposite cutting edges being made complementary, so as to obtain a full coperation between them in the removal and pulverization of the material. The peripheral faces are, as before, provided with oppositely inclined herringbone teeth arranged in the same manner and shaped to the same form as those illustrated in Figs. 1, 4, 5, 6 and 7. The head, 6", is also cored out to receive a central lubricator cup, 24h-which communicates with the bearing surface of the shaft support, 9b, through an oil duct, 25hand to provide a water passage, 17, leading from the interior of the hollow drill stem, 7", to the slot in which the disk member, 8", is housed and partially shrouded.

In the construction shown in Figs. 14, 15 and 16, the main inclined disk member (8c or 8d) is, as before, symmetrically positioned in the head, so as to obtain acomplemental balanced cutting action by the two opposite disk edges; and in these constructions the crushing and disintegrating action of the broad faced main disk is supplemented by a smaller broad faced auxiliary disk, 31 (or 31a) which is placed at one side of the main disk and supported on a coned stud shaft. 32, that is rigidly secured in the member, 33. bolted to one side of the drill head, 6c (or 6d). The main disk member, 8 (or 8d), is carried on the stud shaft support, 9c (or 9d) which is made integral with, or is rigidly secured in, the lower end of the drill head: and it is held in position on the said support by the face of the plate. 33 (or 33a), which also engages the reduced end portion of the support. 9 (or 9d). The main and auxiliary disk members are each provided with central sleeve bushings havingrheads, 34 and 35 (34, 35u), that may, if desired, be provided with engaging spur teeth (as shown in the detail view of Fig. 15), so as to aid each other in securing a continuous and uniform rotative movement. In this case the pitch diameters of the engaging gears are of 'substantially the same ratio as the mean diameters of the peripheral faces of the two disks. If gears are used they are ypreferably inclosed and protected from the water and loose material in the bore hole by means of a plate. 36- shown in sectionv in Fig. 15-which is screwed to the face of the plate. 33, after the disk member, 31, is mounted thereon, and before the member.- 33. is bolted to the drill head, 6C. y

In the two constructions last described the main disk member is made in one integral piece with herringbone teeth cut on its external periphery. the cutting of these teeth being facilitated by the provision of a central groove. 27, in the peripheral face.(see also Figs. 3, 5, and 8). The auxiliary disk member, 31 (or 31") may be mounted so that its lower face is slightly below the lower face of the member, 8c (or 8d)as in the previously described forms shown in Figs. 3, 4, and 8-but is preferably so positioned that the said faces are both substantially tangent to the same surface of revolution (as shown in the cross sectional views of Figs. 14 and 16). lVith the arrangement last described the edge. or edges, of the auxiliary disk do not need to have any cutting action; and the peripheral face of the said disk may, if desired, be left smooth. But this face is preferably provided with teethas shown best in Fig. 15-which may be longitudinally or spirally arranged; and it may also be provided, in certain cases, with spiral grooves as shown in Fig. 16. In this last construction the double series of longitudinal and spiral grooves forms a toothed surface similar to that illustrated and described in the Hughes cone-bit patents `(for example Nos. 979,496, and 1,143,272) and the auxiliary disk member, 31, (or 31u) then becomes an effective cone-bit rotary perform the exceptionally severe duty that' is imposed upon them in drilling deep holes in hard formations. The rotatable .cuttingcrushing members must also be so constructed and mounted as to revolve continuously, and substantially uniformly, when the drill is in operation so as to avoid unequal wear on different portions of the cutting and crushing faces of the members; and the latter must also be so designed and arranged as to preserve as long as possible their initial Shape and diameters-so as to avoid any substantial change in the gage of the hole being drilled-and to avoid, as far as possible, any tendency to lateral displacement of the drillhead from its axis of rotation. The type of construction hereinbefore disclosedwhich may be designated generally as the single central disk or S. C. l). type-is admirably adapted to secure all of the above designated advantages, because it presents (l) a minimum of operative parts (in the simplest forms only three main parts); (2) a single symmetrically disposed disk member of the full size of the hole to be drilled, and having broad cutting-crushing faces that are shaped to make contact, with the material to be drilled, over substantially their entire width, and are further so shaped as to secure, by the cutting action itself, a continuous semi-positive revolution of the disk member; and (3) a symmetrically balanced bearing and cutting engagement between the cutting-crushing member and the cup shaped end of the bore hole, which will tend to prevent any wabbling or whipping of the rotating and revolving parts and thereby prevent the production of crooked or irregular' shaped holes.

Rotary drill structures of the class herein considered must also be so constructed as to permit of the ready removal and renewal of the cutting elements, because, even under the most favorable condition, the life of those elements is limited. In all of the forms which are presented as varying embodiments of my present invention this important feature of structure is provided for by so mounting the disk member as to permit of its ready removal as a whole from the head g and so constructing it as to permitY the active cutting parts to be renewed, if desired, without necessarily replacing the e11- tire disk member. Adequate provision must also be made to prevent any of the securing means-which hold the assembled parts in position-from becoming detached when the drill is in operation; and in the constructions hereinbefore described this object is attained by providing Babbitt-metal sealssuch as those indicated by 40 (Fig. 2), 40, (Fig. 3), 40h (Figs. lO-ll), 40C (Fig. lll), and 40d (Fig. 16)-which are cast into polygonal or irregular shaped recesses surrounding squared or slotted ends (or hexagon nuts) on the bolts or screws used to hold the separable parts of the drill strueture together. This means of locking the holding parts in position may also be applied to the screws, 13, 13, etc., used to clamp the toothed cutting rings, ll, l2 (or ll, 12h 26, 26, etc.) on the central hub of the main disk member. When it is desired to separate the assembled elements, the Babbitt-metal or hard solder seals may be cut away wlth a sharp chisel-or melted away by the local application of an ordinary field torchsuiiiciently to release the locked parts (without any injury thereto) and permit the holding screws or bolts, of other holdmg means, to be removed.

lilith the general statements of the characteristic features of the invention as a basis, and with the various specific embodiments herein disclosed as a further guide; those skilled in the art will be able to recognize and appreciate the many advantages of my improved S. C. D. type of rotary drill bits, even though some of them may not have been expressly pointed out; and will be further able to devise numerous mechanical modifications which will embody my present invention.

What I claim is:

l. A rotary disk drill comprising a head, and a cutting means comprising a single centrally located disk member rotatably mounted in a slot and supported on a cross shaft at one end of the head', the periphery of said member having a broad grinding surface and the sides being recessed adjacent the periphery to secure a sharp cutting e ge.

2. A rotary disk drill comprising a head, and cutting means including a single centrally located disk member mounted on a cross shaft at one end of the head and having a diameter substantially equal to that of the hole to be drilled, the periphery of 'the said disk being provided with teeth inclined outwardly and forwardly from the center line of said periphery in the direction of rotation of said disk in such manner as to assist in its rotation.

3. d. rotary disk drill comprising a head, and a cutting means including a single centrally mounted disk member carried by; the said disk memberhaving two oppov site cutting edges so disposed with respect to the drill axis as to obtain a symmetrically balanced cutting effect, substantially as described.

4. A rotary disk drill comprising a head, and a cutting means including a single centrally mounted disk member carried thereby, the said disk member having two opposite cutting edgesI so disposed with respect to the drill axis as to obtain a symmetrically balanced cutting effect and having teeth on its periphery inclined outwardly from the median line and forwardly in the direction of rotation of the cutting edges thereof so as to assist in the rotation of the said member substantially as described.

5. A rotary disk drill, comprising a head, and a single centrally mounted disk member carried thereby; the said disk member having a broad crushing periphery and two opposite cutting edges having the plane midway of said edges so `positioned with respect to the drill axis and the axis ofthe cutter as to obtain a symmetrically balanced cutting effect substantially as described.

6. In a rotary disk drill, the combination of a head, and a single centrally supported cutting-crushing disk member rotatably mounted thereon and having oppositely disposed edges so positioned with respect to the head as to obtain a symmetrically balanced cutting action on opposite sides of the drill hole and also having a broad crushmg face .shaped to make contact with the sides of the hole over substantially the entire width of the disks periphery.

7. In a rotary disk drill, the combination of a head, and a centrally supported cuttingcrushing disk member rotatably mounted thereon and having oppositely disposed edges so positioned with respect to the head as to obtain a symmetrically balanced cutting action on opposite sides of the drill hole, with teeth on the periphery of the said disk which are inclined forwardly from the median line toward the cutting edges; the toothed periphery being shaped to make contact with the sides of the hole over substantially its entire width.

8. In a rotary disk drill, the combination of a head, and a centrally mounted disk member provided with herringbone teeth on its periphery. i

9. In a rotary disk drill, the combination of a head and a centrally mounted disk member provided with herringbone teeth on its periphery, the sides of said disk being recessed adjacent to the periphery to form sharp cutting edges thereon.

10. In a rotary disk drill, the combination of a head, and a single disk member, housed and partially shrouded in a central slot at one end of the head, the opposite sides of said disk member being recessed adjacent the edgel to provide cutting edges thereon.

11. In a rotary disk drill, the combina tion of a head and a single central disk member mounted in a slot at one end of the head and provided on its periphery with two sets of oppositely inclined teeth which wnstitute symmetrically balanced cuttingcrushing elements.

l2. In a rotary disk drill, the combination of a head, and a single central disk rotatably mounted thereon and recessed on its sides to form oppositely turned cutting edges that are symmetrically disposed with respect to the axis of the drill head.

13. In a rotary disk drill, the combination of a head, a disk member rotatably mounted thereon and provided on its periphery with teeth having radial faces, and a water passage arranged to project the flushing water against the radial faces of said teeth in the direction of rotation of said-disk.

14. In a rotary disk drill, the combination of a head, a rotatable single disk member of the full diameter of the hole centrally mounted at one end thereof, anda smallerL auxiliary disk member mounted at one side of the main central disk member.

15. In a rotary disk drill, the combination of a head, a rotatable disk member centrally mounted at one end thereof, and an auxiliary disk member mounted at one side of the central disk member Withits lower edge extei'iding below the adjacent edge of the said central disk for the purpose specified.

1G. In a rotary disk drill, the combination of a head, a rotatable disk member centrally mounted at one end thereof, and an auxiliary toothed disk member mounted at one side of the main central disk member, With its lower edge extending in advance of the said central disk, to dig a pilot hole to center said head.

17. In a rotary disk drill, the combination of a head, a rotatable disk member centrally-mounted at one end thereof, and two auxiliary disk members one on each side of the central disk and extending slightly in advance thereof.

18. In a rotary disk drill, thecombination of a head, a rotatable disk member of a diameter substantially equal to the hole to be drilled mounted at one end of the head, and a smaller disk member mounted at one side of the larger disk and arranged to coperate with the latter in supporting the Weight of the rotating parts and also in disintegrating and pulverizing the material sheared from the end of the bore cavity.

19. In a rotary disk drill, the combination v of a head, a rotatable disk member of a'diameter substantially equal tothe hole to be drilled mounted at one end of the head, and a smaller disk member mounted at one side of the larger disk near the axial line of the head and arranged to coperate with the latter in supporting the weight of the rotating parts in the manner specified.

20. In a` rotary disk drill, the combination of a head, a single large vertical toothed disk mounted thereon, and two smaller pilot disks mounted beside ot and slightly in advance of said large disk for the purpose specified.

2l. ln a rotary disk drill, the combination ot' a head, a single large vertical disk mount'- ed thereon, and two smaller pilot disks mounted one on each side of said large disk and slightly in advance thereof; the said smaller disks being retained in position by contact with said larger disk.

22. In a rotary disk drill, the combination ol' a head, a single large vertical toothed disk mounted thereon, and two smaller pilot disks mounted on said head one on each side of said large disk and slightly in advance thereof, the smaller disks being offset slightly with respect to each other.

'223. 1n a rotary disk drill. the combination ot' a head, a single large disk mounted on the lower end of said head, and two smaller pilot disks mounted on said head slightly in advance of said large disk, the said smaller disks heilig each mounted on an axis that is ollsetslightly from the longitudinal axis of the head.

24. In a rotary disk drill, the combination ot1 a longitudinally divided head, a single large disk adapted to eut the full diameter of the hole revolubly mounted in the lower end of said head, and a smaller disk mounted atone side of the larger disk on an inwardly projecting pin and held in position by Contact with the fiat side of said larger disk.

25. In a rotary disk drill, the combination of a head, and cutting means including a single disk member mounted thereon, the said member comprising a central hub and an annular cutting portion comprising an inwardly projecting attaching flange and a broad peripheral cutting and grinding suriace removably secured to the said hub, substantially as described.

In testimony whereof, I hereunto afiix my signature this the 7th day of October, A. D. 1919.

FRANK L. O. VADSVORTH.

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