US 2940522 A
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Description (OCR text may contain errors)
June 14, 1960 J. w. TAYLOR ETAL 2,940,522
CUTTING TOOL 2 Sheets-Sheet 1 Filed March 5, 1957 W//// 0/77 K /70//er0/7 INVENTORS ATIOR/VL'VJ June 14, 1960 J. w. TAYLOR ETAL 2,940,522
CUTTING TOOL Filed March 5, 1957 2 Sheets-Sheet 2 dose a6 W Tay/or W////a/77 K //0//e/'0/7 INVENTORS ATTORNEYS CUTTING TOOL Joseph W. Taylor and William K. Holleron, Houston, Tex, assignors to US. Industries, Inc., New York, N.Y., a corporation of Delaware Filed Mar. 5, 1957, Ser. No. 644,035
Claims. (Cl. 166-55) This invention relates to tools for cutting down in the bore of a Well and more particularly to tools for cutting out a section of well casing or cutting out obstructions in the well such as a stuck packer.
In the drilling and production of petroleum wells, it is frequently necessary to cut out a section of easing. This may be done to expose a Well formation during production of the Well. It also may be done during drilling of the well to permit sidetracking operations, that is, drilling around some undesirable condition such as a cavernous formation which has been encountered. It is also sometimes necessary to drill out an obstruction in a well bore.
In the past, it has been necessary to use steel cutters for both the end mills and casing mills. No practical way has been devised for tipping the cutters with very hard cutting material such as the cemented carbides. As the hard cutter tips are also characterized by being very brittle, they tend to break off in use. In previous attempts to use hard cutters, it has been found that in breaking the fracture line sometimes runs in a direction to render a cutter substantially useless. This condition cannot be tolerated due to the expense of pulling the tool from the well to replace the cutter. The necessity of using hardened steel cutters has made window cutting and end milling in wells a slow tedious process which frequently requires two or more sets of cutters to mill out a window of the desired size for sidetracking.
By this invention there are provided both an end mill and a casing cutter which successfully employ hard brittle cutting tips of cemented carbide or the like.
By this invention we provide a tipped cutter in which fracturing of one tip does not destroy the entire effectiveness of the cutter. This is of particular advantage when the tipped cutter is used in conjunction with a casing mill utilizing the principles taught in the Earl I. Robishaw Patent No. 2,690,217, issued September 28, 1954. This patent provides for the eccentric rotation of the casing mill so that the knives move radially while cutting casing. By this invention we provide a knife in which crumbling away of a cutter tip will only impair the cutting efficiency of a small radial distance of the cutter and the cutter will continue to function.
We have found that cutters for end mills and casing cutters may be provided with knives employing rows of separate small slabs of hard cutting material such as the cemented carbides and that knives so tipped will standup under the heavy loads imposed in modern day milling. When one of the tips fractures or breaks away to provide a new cutting edge, the fracture line will not extend to adjacent tips and, therefore, a bad fracture line will effect only a small portion of the cutting edge of the cutter.
Use of mills constructed in accordance with this invention have raised new problems. For most efficient cutting the load on the cutters should be very high. This results in chips of large size which are hard to pump to the surface. Many of the chips will be spirals of several nited States Patent inches in length. A number of these chips could gather in one area in the well and cause difliculty.
By this invention we provide a chip breaker which turns the chips back on themselves as they are cut and forcesthem to'break off of the workpiece in small pieces.
It is an object of this invention to provide anend mill or casing cutter for use in wells which will cut much more rapidly than those heretofore in use.
Another object of'this invention is to provide a milling tool for use in wells such as an end mill or a casing cutter which successfully employs very hard brittle cutting tips.
Another object of" this invention is to provide an end mill or casing cutter for Wells employing cemented carbide cutting tips;
Another object is to provide an end mill or casing cutter for wells employing self-sharpening cemented carbide cutters.
Another object is to provide an end mill or casing cutter for wells employing cemented carbide cutters which progressively break off to provide new sharp cutting edges in which it is impossible for the fracture line to extend completely across the cutting face of the cutter.
Another object is to provide a cutting tool having cemented carbide cutters which are supported to permit their use under very high force conditions and in which the support and carbide are gradually Worn and broken away to successively provide new cutting edges.
Another object is to provide a casing cutter which rotates about an axis eccentric to the casing being cut in which the cutters or knives are provided with tips of very hard brittle material which crumble and break off in use and yet in which each crumbling of each tip is localized and effects only a short section of the cutting face of the cutter.
Another object is to provide an end mill or casing cutter for use in wells with a chip breaker which limits the size of the chips cut.
Other. objects, features and advantages of this invention will be apparent from the drawings, the claims and the specification.
In the drawings wherein there is shown by way of illustration several embodiments of this invention and wherein like reference characters are used throughout to designate likeparts:
Fig. 1 is a vertical sectional view through a casing being cut by a casing mill therein with the casing mill shown partly in elevation and partly in vertical cross section;
Fig. 2 is a perspective view of one of the cutters of the casing mill;
Fig. 3 is a perspective view of a fragment of the cutter of Fig. 2 on an enlarged scale and in an inverted position;
Fig. 4 is a view along the lines 44 of Fig. 1;
Fig. 5 is a perspective view of a fragment of a modified form of cutter;
Fig. 6 is a perspective view of a fragment of a still further modified form of cutter;
Fig. 7 is an elevational view of an end mill constructed in accordance with this invention;
gig. 8 is a bottom plan view of the end mill of Fig. 7; an
Fig. 9 is a perspective view of one of the cutter inserts of the end mill of Fig. 7.
Referring first to Fig. 1, the casing mill illustrated is substantially identical with the casing mill shown in Patent No. 2,690,217, issued to E. l. Robishaw on September 28, 1954, with the exception of the construction of the individual cutters or blades. Reference is'made to the Robishaw patent for a full description of the several components of the mill and the functions thereof.
In general, the mill includes a body 10 having an Patented June 14, 1960 eccentric guide assembly indicated generally at 11 on its lower end. As shown in this figure and in Fig. 4, the guide assembly causes'the mill to rotate aboutan eccentric axis relative tothecasing 12; Whichfis, being cutby'tlre ;tool This eccentric vrotationcauses the knivesto rnjoweradially in cutting and pro vides'a much greaterarea: of each cutter for effective cutting of a window in acasing as well as minimizing the tendency ofrthe cuttersto groove and increase their hearing area in engagement ;wit h the. casing being cut., 7 1 a The eccentric assemblyfis providedq with a bearing:
proper position within the well, fluid is pumped down through the drill string andacts'against the piston to move it downwardly. As it moves downward, the cam portion 19 of. each cutter is engaged by the' slottedpiston and the cuttersare urged'radially outward of the mill. While the cutters are urged radially outward by fluid pressure, '-the mill is rotated and the cutting surface 21 of each cutter 16 bears against the inner wall of the casing 12 and cuts an annular window'therethrough. As this windowis' cut, the pressure on the piston 14 moves it down'to'the position illustrated in the drawings and the knives 16 are extended radially untiltheir undersurface 23 extends substantially perpendicular to the casing 12. Further rotation of the tool will cause a section of the pipe 12 to be cut out. It will be noted that the body. 141 bears against the cutters 16 at a point intermediate the pivot 17 and the casing 12 being-cut and, therefore, considerable force maybe exerted on the string 'to force the cutters against the workpiece Before the/knives penetrate through the casing, fluid circulation is provided through the piston passageway shown in dashed lines at 24. Fluid passes from the piston out through the slots 18 and down through the dotted passageway 25 to the bore 26 in the lower-end of the tool and thence out the bottom of thetool. This fluid washes cuttings to the surface. After thepiston 14 moves down into the position shown, a pluralityv ofhlateral ports 27 areuncovered which permits an increase in the volume .of'fiuid passing through the .tool and indicates to the operator that the initial window has been cut and he may apply pressure to the string to begin cutting a section out of the casing. r I
Referring now to Figs. 2 and 3, there is shown the,
preferred form-of cutter 16. -'Ihe cutter 16 is formed in more or less the usual general configuration of: cutters employed 'in' this service.- For cutting the initial window in the pipe, the cutting surface 21 is provided by an inlay of high gradecuttingsteel.
The undersurface 23 of the cutter 16 provides the cutting face for cutting the section out of a pipe and when making this cut, faces endwise of the tool as shown in Fig. 1. The actual cutting done by the cutting face 23 is done by a plurality of hard cutters 28. These cutters are provided from the group of cutting tips which are so veryhard that they are brittle' and, therefore, give trouble when subjected to high shock loads such as normally encountered with a casing mill. It will' be appreciated that the load on the cutters 16 is so high that they are actually bent. This is particularly truewhen the knives or cutters first break through the casing wall as the cutters may then hang in the window until the lower edge of the window is smoothed by the action of the cutting surface 23; i
. e .This high shock load and bending raemr no'rmu encountered has prevented the use of cutting tips of the very hardlbrittle material in the past.
The'hard brittle'material referred to above maybe 2,940,522 a j? V any of the well known cutter tips used in tipping tools generally such as the cemented carbides. Tungsten carbide tips are preferred for this service.
The brittleness of the cutting tips is both an advantage and a disadvantage. In use they tend to fracture and crumble away at the cutting edge and this presents new.
sharp cutting edges whichis desirable. However, the
fracture line may be such as to. remove. a large chunk I of thetip and impair or destroy the effectiveness of the weld has been completed are such that a large carbide tip will be popped oif of the cutter when subjected to heavy shock load.
The above problems have stymied the past attempts to use hard brittle tips in casing cutters. 7 These problems are solved by' the cutters illustrated in the-drawings by using a plurality ofslabs of hard brittle cutting material 28 l 7 The slabs of cutting material are arranged in a row with edges of the several slabs contiguous with each other and with each slab having one edge terminating at the cutting face 23 of the cutter. As there are a number of slabs providing the cutting face of the cutter, any free ture line in one of the slabs which causes loss of the cutting surfaceprovided by. the particular slab will not extend to the adjacent slabs Therefore, an. unfortunate fracture'will effect only a small portion of the cutting edge of the cutter; Of course, as the cutter wears down, the residue of the slab which hadalargechunk broken off will again come into play and be effective; P 7 Running of a casing cutter in a deep holerequire's .a number o'fhours' due to the time necessary to make up the drill string for a distance 'of many'thousand' feet; Therefore, it is highly de'sirablejthat the individual cutters of thecasing mill becapable ofvcu'tting out the com plete section of the casing desired before they are worn through. With thisfactor in mind, it is desired that-the. individual, slabs of hard materialextend away from the cutting face 23 of the cutter as far as possible. However,
as pointed out above, the maximum dimension of the slabs 28 is limited bysetting up of undesirable stress loadsduring the welding process Therefore, they should not be long enough to give rise to these undesirable stress In thickness, the slabs 28 should be such that they are difiicult to break but will break after the slabs be come dull.-
By way of example a typical insert for 'a 9% inch casingmill'may have the following dimensions: fizinch thick, of an inch high, and ofan inch in Width.
In the preferred form of this invention, a groove is provided in the cutting face 23 of the cutter as by notching theleading faceof the cutter at29. hisnotch 29 is dimensioned. to receive the several slabs 23 with their exterior faces flush. with the periphery of'thecutter.
It vhas been found that' the base metal portion 23a of the cuttingj face 23 will 'wear away to approximately a two degree bevel commencing'at'the slabs of hard material. The-hard material will also project slightly .beyond the base metal at the juncture between the slabs and base metal. Therefore, it is preferred to form the knife with the base' mctal'portion of the' cutting face at a two degree bevel so that the knife may 'begin cuttin g immediately-withjfull efliciency and not have to 'wait for wearing away of the base, metal to gain'full efficiency. In use it has been found that the :best performance will be obtained when the knife is loaded with sufiicient force to cause the slab tips to bear against the casing being cut with a force exceeding the yield strength of the casing. Use in this manner probably accounts for the wearing away of the base metal to the two degree bevel as pointed out above. In actual use, cutters constructed in accordance with this invention have successfully milled casing having a yield strength in excess of 100,000 lbs. per square inch.
Referring to Fig. 5, there is shown a modified form of cutter for use with the mill of Fig. 1. As pointed out above, the maximum dimension of the carbide is limited as it is desired to avoid excessive stresses resulting from the welding of the carbide to the cutter. To increase the life of the cutter, it is in some cases desirable to have tips which extend away from the cutting face 23a a greater distance than possible with one row of tips. In these circumstances, a second row of tips indicated generally at 31 may be provided on the side of the first row of tips indicated generally at 32 remote from the cutting face 23a. In this cutter, the groove 29a is formed of a sufficient size to receive the two rows of tips.
Fig. 5 also illustrates the general manner of wear of the cutters when used in the casing mill of Fig. 1. At 33 there is illustrated the manner in which a tip may break otf and render a section of the cutter inoperative due to the fracture line of the break removing a large slab of the tip. However, this does not render ineffective the entire knife and as the knife wears this broken slab will again become efiective.
Referring now to Fig. 6, there is shown a further modified form of this invention in which the size of the cuttings resulting from use of the casing mill is controlled. It'has been found that the cuttings produced by the mill when employing the Fig. 2 form of cutter will frequently be spirals of as much as from four to six inches. It is preferred to maintain the cuttings of as small a size as possible to avoid any possibility of their fouling the casing cutter or drill string and for this purpose a chip breaker is provided. The chip breaker may be provided by any means which will precede the cutting tips 28 and engage the chips as they are cut to force them to break off in small pieces. In the preferred form illustrated in Fig. 6, the chip breaker is provided by a metallic bar 34 secured over the leading face of the several tips 28 and having a surface 35 positioned to engage a chip as it is curled up by action of the tips 28. It is preferred that the surface 35 be beveled as shown and the metal from which the chip breaker is formed should be such that it will gradually wear away at substantially the same rate at which the tips 28 wear. In this way it will retain substantially the same relationship to the cutting face of the cutters at all times. The groove 29!) may be recessed sufl'lcient to receive both the tips 28 and the chip breaker 34 if desired.
Referring now to Figs. 7 through 9, there is shown an end mill equipped with this invention. The end mill body 41 is formed in more or less conventional style. Notches 42 are provided in the bottom face of the mill to receive replaceable knives 43. As in conventional end mills, these knives extend from approximately the center of the tool radially outward to its outer edge so that they are capable of milling away anything inside of the bore hole which is blocking the hole. The cutting face 44 of each of the knives 43 is provided at its leading edge with a recess 45. A plurality of slabs 46 of hard brittle material such as tungsten carbide are positioned in a row in the groove 45. These slabs are arranged in the same manner as in the casing-mill with adjacent edges contiguous to each other and with one edge terminating at the cutting face 44 of the knife. Again the several slabs extend away from the cutting face 44 a sufiicient distance to provide for wear of the knives and yet are not sufi'icient in size to set up undesirable stresses when the slabs are welded to the knives.
It is frequently necessary to spud the mill to break up fish in a well which are free to rotate and, therefore, cannot be cut by rotation of the tool. While the spudding operation tends to cause breakage of the slabs 46, it has been found that this breakage is not overly severe and the tipped tool is vastly superior to the conventional untipped tool.
From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects herein above set forth, together with other advantages which are obvious and which are inherent to the apparatus.
It will be understood that certain features and subcombinations are of utility and may be employed withcomprising, a tool body having a lower end, a cutter body mounted on the tool body to extend laterally of the tool body and having a leading face and also having a cutting face facing the lower end of the tool body, a plurality of slabs of cemented metal carbide secured in a row to the leading face of the cutter body and positioned so that each slab has one end adjacent said cutting face. said slabs also being positioned in close side-by-side rela tionship with respect to each other with substantially no space existing between adjacent sides of adjacent slabs so that said slab ends together form a substantially continuous cutting edge for cutting contact with the tubular goods to be cut.
2. The tool of claim 1 wherein said slabs are in abutment along adjacent sides of adjacent slabs.
3. The tool of claim 1 wherein there is a second row of slabs secured to the leading face of the cutter body. said second row extending parallel to the first-mentioned row and positioned on the side of the first-mentioned row remote from said cutting face.
4. The tool of claim 1 wherein chip breaker means are attached to the cutter for engaging a chip cut by the slabs to turn the chip back toward the surface being cut.
5. The tool of claim 4 wherein said chip breaker means is a member carried by the cutter body in front of the slabs and having an upwardly and outwardly inclined surface spaced from the cutting face and positioned to engage a chip cut by the slabs and turn the chip back toward the surface being cut.
References Cited in the file of this patent UNITED STATES PATENTS 1,923,487 Howard et a1. Aug. 22, 1933 2,299,528 Conner Oct. 20, 1942 2,353,284 Barrett July 11, 1944 2,690,217 Robishaw Sept. 28, 1954 2,690,897 Clark Oct. 5, 1954 2,693,938 Roberts Nov. 9, 1954 2,725,936 Hester Dec. 6, 1955 FOREIGN PATENTS 1,115,540 France Ian. 3, 1956