MXPA95000684A - Cutting tool that has movib teeth - Google Patents

Abstract

A cutting blade having a cutting face is provided. A plurality of separate slots is formed in the cutting face, each slot having front and rear side walls. A tooth is received removably in each of the slots, each tooth having a top surface extending above the cutting face and having front and rear side walls. The upper step surface of reduced rear height. Retention bar is provided for each tooth, each retention bar having a leading end that is received in the step section. A pin extending through an opening in each retaining bar is threadably connected to the cutting face. By tightening the threaded pin the retaining bar retains each tooth during a cutting operation in such a way that the side walls of the tooth frictionally engage the side walls of the groove and by unscrewing the pin the retaining bar can be rotated to allow the removal and replacement of each of the dient

Description

CUTTING TOOL THAT HAS HQVIBLE TEETH CROSS REFERENCE TO RELATED REQUESTS This application claims the benefit of a prior filing date under 35 USC 119 based on British Patent Application No. 9401715.9 filed on January 29, 1994. 10 CROSS REFERENCE TO THE APPENDIX OF MICRQFICHAS This salicitud is not related to any appendix of icrof ichas. IB BACKGROUND OF THE INVENTION This invention relates to a cutting tool having removable teeth. The use of removable teeth or cutters is known in the prior art as represented by the following US Patents. ? Having replaceable teeth for a cutting tool has many obvious advantages, the primary one being economic. The useful life of a cutting tool is usually determined by the cutting capacity of the teeth. When the teeth wear out and lose their ability to cut, they can, in some cases, be sharpened in place. However, after repeated sharpening, sufficient material can be removed from the teeth in such a way that they can no longer perform a cutting function or the teeth can splinter or break. A cutting tool that has fixed teeth that have been too sharp or broken must be discarded which means discarding the cutting blade that supports the teeth even when the cutting blade itself can otherwise be usable. An additional advantage of removable teeth is that it is usually easier to sharpen or refinish the teeth when they are not part of a cutting blade. A major advantage, however, of replaceable teeth, is that when the teeth are no longer useful, either because of wear or because they break or splinter, it is much less expensive to replace one or more teeth in a cutting tool than to discard the teeth. complete cutting tool. One problem that exists with replaceable tooth cutters is that of retaining the removable teeth in their position on the cutting blade. Cutting tools are often used in applications that exert extreme forces on the teeth. For example, when using a cutting tool to cut a hole in a steel pipe by means of a circular cutting head the forces on the teeth can be enormous. In addition, substantial vibration can occur between the cutting tool and the workpiece. Another example of adverse cutting conditions is the use of a cutting tool to cut non-metallic workpieces, such as granite, concrete or the like. Obviously, if a tooth is lost in the cutting tool the cutting tool can be destroyed or the work piece can be damaged. Because of the problem of retaining removable teeth in cutting tools, the use of cutting tools that have removable teeth has not been universally employed regardless of the advantages that otherwise exist for removable tooth cutting tools.

BRIEF DESCRIPTION OF THE INVENTION This invention relates to cutting heads of a type that are provided to be mounted on drilling machines and to provide means for cutting into pipes by the addition of, for example, branch pipes or pressure relief valves or other forms of control apparatus. . The cutting heads are of the type that allows drilling to be carried out already when the pipe is dead, for example, when there is no material running through it, or when the pipe is alive, such as those that transport oil and gas. A particular area of application, but not exclusive, is the use of cutter heads to drill pipes that transport oil from oil wells to refineries and through several processing areas of said refineries. Reference will be made here to the use of the cutting head in relation to oil pipelines, but it should be taken into account that the invention described is equally important for any form of pipe. In any pipe, it is often required to add branched connections, control valves or pressure relief valves to the pipe after the pipe has been installed. There are machines available for drilling pipes and for drilling such pipes when oil continues to flow through the pipeline. This is a preferred method of drilling pipes because turning off a petroleum pipe for up to thirty minutes is extremely costly due to the period of shutdown of the oil flow and the oil refining apparatus. In order to drill the pipe using a conventional apparatus, the first step is to place a flange in position around the area of the proposed drill in the pipe and weld or mechanically fix it in a position on the pipe where the pipeline is to occur. addition of, for example, a valve. The valve is then mounted on the flange, but the pipe at this stage is still solid. A drilling machine of the normal type is then mounted on top of the valve and this drilling machine is provided with a downward arrow on which a cutting head is mounted. A pilot drill may also be provided in addition to the cutting head and the pilot drill is intended to enter the pipe first to provide means for securing the part of the pipe that is subsequently cut. The cutting head is then applied to the pipe to cut through it and when completed it leaves a marked line that has been completely cut from the pipe and that is removed from the pipe by retracting the pilot drill and the wires of retention provided on the pilot drill. In this way, the flange, and therefore the valve, is now connected to the oil pipe and is an integral part of it. At the same time, all the cut material is removed externally from the pipe and therefore the oil flow is not contaminated. This system has been used for a considerable number of years and is considered a conventional drilling system for pipes. The cutting head used in this system is typically a cylindrical head having at one end a number of cutting teeth welded thereon and these teeth, when the cutting head is rotated, serve to cut the pipe. Typically, a conventional cutter can be used to cut two holes in the pipes before checking for ions, such as sharpening the teeth. If the teeth are still relatively sharp, a third hole may be cut, but the teeth are then required to re-grind and sharpen to allow the cutting head to be used again. The cutting head is typically formed of steel while the teeth which are welded on the cutting head may be formed of any of tungsten hard metal, high speed steel, coated or uncoated with surface reversals or any normal cutting means . Typically, the teeth are welded on the cutting head and the cutting head will be used for specific pipes formed from specific materials. The uses of the pipes increase for various chemical substances in the same way that they increase the different forms of material from which the pipes are required to be made. For example, in the chemical industry, the use of stainless steel pipes is required and, in addition, when pipes are used to transport high temperature or high pressure materials, the pipes may experience work hardening and heat that alters the structure of the pipes during use. As a result of this, the materials for the cutter teeth for the cutter head are required to vary with respect to the pipe material to be cut. It is now common to provide two or three cutter heads to the site of any work to ensure that a correct cutting head is used after studying the material and condition of the pipe. Although this requirement is convenient when used in plants where the pipes are easily accessible and are relatively close to the supply point of the cutting heads, this causes major problems when the pipeline is in remote and inaccessible areas. This is particularly important with respect to oil pipelines that often run along areas that are remote, can not be accessed easily, and where climatic conditions can be adverse. Under these conditions, it is conventionally necessary to transport a considerable amount of cutting heads to overcome the wear problems of the cutting heads after two or three cuts in the pipe and also to ensure that the necessary heads with teeth formed of various materials are ready for take into account the material and condition of the pipe. This causes a serious inconvenience both in the quantities of materials that are required to be transported and also the inconvenience in the cost and expense of times if the cutting heads are equivalent. The object of the present invention is to provide a cutting head that can be adapted to have cutting teeth to suit the particular purpose for which they are to be used in terms of the material of the pipe in which the cutting will be made and to allow easy replacement. of the cutting teeth used. Providing a cutter of this type will eliminate the need to transport and carry numerous cutting heads and will be substantial in terms of cost and time. The present invention provides a cutting head for use in association with drilling and boring machines for drilling and cutting a marked line of a pipe, said cutting head comprising a cylindrical body provided with cutter teeth at one end thereof where at least some The cutter teeth are removable from the cutting head and are replaceable with teeth that are sharper and / or formed of a different material or different cutting characteristics. Preferably each cutting tooth is held in a notch locating on the edge of the cutting head, a plurality of said notches being provided around the periphery of the edge. In one embodiment, the cutting teeth will be formed in relation to the notches in such a way that they will be self-tracking in said notches and are only releasable by exerting force on them. In a second embodiment, the cutting teeth will be held in the notch by the provision of jaw teeth which, when a tooth is in position, act to keep the tooth therein. Preferably, the jaw means will be movable from a first position to allow the tooth to be adjusted and / or removed and a second position by which the jaw keeps the tooth in the location notch. The cutting head of the invention will be of any conventional size, but typically it can be in the range of 5 cm to 100 cm in diameter. The number of teeth provided in any cutting head will depend on the particular application of the cutting head. Preferably, the teeth will be manufactured from a scale of materials similar to those used for conventional teeth. Typically a set of teeth, if manufactured from, for example, high speed steel, can be used to cut a hole in a first pipe, but for a subsequent pipe made of a different material a set of teeth may be required. a second material and therefore the set of teeth fitted to the cutting head will be removed and the new set of teeth of the second material will be inserted in its place to allow the cutting of the second pipe. Similarly, if the set of teeth fitted to the cutting head has been used in two or three cuts and have been worn, they can simply be removed and replaced with new sharp teeth. The invention provides a cutting head that includes at one end thereof a face cutting machine comprising a plurality of teeth and the teeth are removable if required to allow inserting a new set of teeth of the same material or a different material to suit a particular use. The invention makes it possible to transport one or two cutting heads to a site together with a plurality of sets of cutting teeth, thereby minimizing the amount and size of materials that are to be transported to the site where the pipeline is to be drilled. In areas where transportation of materials is difficult and the area is remote, the ease of transport ensures that a wide range of cutting teeth can be carried out thus ensuring that the cutting head can be adapted to provide the best possible cut in the pipe and minimize time. An improved embodiment of the invention includes the arrangement wherein the separate notches of the cutting blade that hold the removable teeth have front and rear side walls that taper with respect to each other. The tapered side walls receive a tooth having opposite side walls that taper in the same manner. By means of this arrangement the tooth can be guided into a tapered groove in such a way that the tapered side walls of the tooth are securely frictionally engaged with the side walls of the notch in the cutting face of the cutting blade in such a way that the The tooth is held securely in its position on the cutter face.

This invention provides a cutting blade having a face in which a series of separate notches that receive the removable teeth is formed in an improved and very effective manner. The cutting blade can be tubular (i.e., with a toroidal cutting face), or the cutting blade can be flat with a circular cutting face (as commonly used in manual electric saws, radial arm saws and the like) or The cutting blade can be flat with a straight cutting face. A better understanding of the invention will be obtained from the following description and claims, taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS Figure 1 shows a perspective view of an arrangement of a cutting head and a typical punching machine. Figures 2A to 2D show the various stages that comprise drilling a pipe. Figure 3 shows a typical tooth of a conventional cutting head. Figure 4 shows a typical tooth arrangement of the cutting head of the invention.

Figures 5A to 5E show several views of a cutter tooth of the invention. Figure 6 is an elevation view of a tubular cutting blade, sometimes designated as a "shell cutter", as used to cut a marked line of a workpiece and showing improved means for retaining teeth in notches separated on the cutting face of the tool. Figure 7 is an end view of the tubular cutting cover, taken along line 7-7 of Figure 6, showing the disposition of the replaceable teeth. Figure 6 is an enlarged fragmentary view of a portion of the tubular cutter shell of Figure 6 showing two replaceable teeth as they are supported on the shell cutter face. Figure 9 is a fragmentary cross-sectional view of a portion of a tooth and the cutting shell showing in the relationship between the front side wall of the tooth and the front side wall of the cutter shell. Fig. 10 is a fragmentary cross-sectional view showing the relationship between the posterior side wall of the tooth and the rear side wall of the groove by which the tooth is removably retained in the cutting blade.

Figures HA to 11B show a configuration of a tooth as used in Figure 7. Figure 11A is a view in elevation? Figure 11B is a top plan view; Figure 11C is a rear elevation view and Figure 11D is a front elevation view. Figures 12A to 12D show an alternative embodiment of the replaceable tooth design in which the tooth is configured to cut along a right boundary. Figure 12A is an elevation view of the tooth; Figure 12B is a top plan view; Figure 12C is a rear elevation view; and Figure 12B is a front elevational view. Figures 13A to 13D show a third embodiment of the tooth designed to perform a central cutting action. Figure 13A is a side view in elevation of the tooth; Figure 13B is a top plan view; Figure 13C is a rear elevation view; and Figure 13D is a front elevation view.

DESCRIPTION OF THE PREFERRED MODALITIES Referring first to Figure 1 there is shown an arrangement for making perforations in a pipe 2. The apparatus consists of a drilling machine 4 which is mounted to a pilot drill 6 and a cutting head 6. The pilot drill 6 and the cutting head 6 they are arranged to rotate by the drilling machine 4 in such a way that the introduction of the pilot drill 6 to the pipe 2 causes an initial hole to be drilled followed by the application of the cutting head 6 and to the pipe 2 to cause the cut of the marked line shown in dashed lines on the pipe 2. The marked line 10 is removed from the pipe by means of the retention means of the pilot bit (not shown) that lifts the marked line away from the pipe and avoids that enters the flow of the pipe. While this operation occurs the pipeline may continue to transport the substance, such as the flow of oil through the pipe, without the interruption of the flow. The illustrations in figure 2 show the basic steps involved in drilling the pipe. Figure 2A shows a pipe 2 which, in this case, will be used to transport oil or chemical products and can be manufactured for example from stainless steel. In this case, a valve will be fitted to the pipe 2 and figure 2B shows said valve 12. In order to achieve the adjustment, the flange 14 is first mounted on the pipe in the desired position and is fixed or mechanically fixed to the pipe. the pipe along the line 16. When the flange is in position, but the pipe has not been perforated, the valve 12 is mounted on the flange 14 in a position for use. Figure 12 shows the valve in its position on the flange 14 and the pipe 2 and to the top of the valve 12 a flange 16 of the drilling machine is connected. With the drilling machine held in place on the flange, the pilot drill 6 and cutting head 6 move down through the valve housing 12 and through the housing of the flange 14 to enter pipe 2. The rotation of the pilot drill 6 and the cutting head 6 serves to cut through the pipe 2, and the marked line 10 formed is then removed by retracting the cutting head and the pilot drill through the flange and the housing of the valve. When this is complete, the drilling machine is removed and the valve housing is sealed to form a pipe as shown in Figure 2b with the valve in place and connected to the pipe. Similar operations can be carried out to install a branch line or to construct a diversion pipe to allow pipe maintenance. In all cases the perforating arrangement as shown and described can be carried out while the material flowing through the pipeline continues to flow without interruption. Referring now to Figure 3, a section of the edge of the conventional cutting head is shown wherein a series of teeth 20 is formed thereon which, when applied to a pipe and rotated, cause the cutting of the line marked 10 on the pipe. In a conventional cutting head as shown, the teeth 20 are welded on the cutting head 6 and, once welded thereon, can not be removed. The only action that can be performed on the teeth after having welded them on the cutting head is the possibility of re-grinding the teeth to sharpen them, however, it is impossible to remove the teeth and replace them with teeth of alternative materials or by new sharper teeth of the same material to be adjusted without substantial engineering work. Figure 4 illustrates various teeth of the cutting head of the invention. The teeth 22 of the invention are shown fitted in the location notches 24 that are provided in the cutting head 6. The teeth 22 are typically configured to self-adjust in the notches 24 but, if necessary, the gripping arrangements 26 are provided. . The grip arrangement comprises a pivotally movable bar 2ß on the pin 30 which is secured in the cutting head 6 and which can be tightened to secure the teeth 22 in place and has a locking wedge 27 provided therein to prevent it from turning during the use of the cutting head to allow the tooth to be released. Each of the jaws is movable from a first position where it protrudes from the edges of the cutting head to allow adjustment or removal of the tooth 22 ep the notch 24 from location to a second position as shown where the portion of the The jaw is on a notch provided in the tooth 22 which serves to locate the tooth 22 in this notch 24 of Location. When the cutting head is in this position it is now possible to use it and rotate it in the direction of the arrow 32. Figures 5A to 5E show several views of a tooth that can be used in the invention. The tooth consists of a cutting edge 34 which is located on the external head to look in the direction of rotation and the tooth is also provided with a series of sharp edges 36 and 36 which are configured to coincide with the location notch formed on the tooth. the cutting head to provide a self-adjustment of the tooth in the notch. Similarly, the base 40 is configured to allow sliding adjustment to be achieved and locking to be accomplished. The upper part 41 can also be configured to allow improved removal of the materials and is also provided with a step section 42 for the location of the jaw therein. The invention provides a cutter head as illustrated in FIG. 4 having teeth 22 and location notches 24. The cutter head can then be used to drill a pipe and can be used again to drill second and third holes as appropriate. If the teeth wear out later, these can be removed in place and new teeth can be introduced relatively quickly by a simple operation of releasing the provided jaw means. Therefore, successive drilling of pipes can be carried out with a minimum of time lost. Additionally, if the drilling of more than one type of pipe is required in a particular job and the pipes are made of different materials, it will be necessary to change the adjusted teeth to suit a set of teeth with the particular cutting requirements for the particular pipes. Again, the cutting head of the invention provides means by which sets of teeth made of different materials can be removed and replaced as appropriate in place. In addition, the teeth that have been removed can be returned to the factory at the operator's convenience to be reactivated and reused later. The present invention provides a cutting head that can be adapted to specific requirements for specific pipes and also allows the easy replacement of worn teeth in place. With the ability to change the accessories of the cutting head in place, considerable time and cost savings are obtained especially when the operations of cutting and drilling of the pipes are carried out in remote and adverse areas. No conventional cutting head can achieve this. Referring to Figures 6 to 6, an improved embodiment of the cutting head is shown. Figures 6 and 7 show a tubular cutting head generally indicated by the number 6. The cutting head 6 includes a body portion 44 which is adapted to be connected to a rotating device, such as bolt means extending through the openings 46. A portion 46 of integral tubular cutting blade provides a toroidal cutting face 50. The cutting face 50 is provided with a plurality of spaced slots 52. Each of the slots 52 includes a front side wall 54 and an opposite rear side wall 56. Formed on the cutting face 50 in the front of each slot 52 are a arcuate recess 56. The functions of recess 56 are primarily to provide clearances for the cutting edges of the teeth and an area to receive the cut portion of the workpiece (not shown) that is cut by the teeth. Figure 6 is an enlarged fragmentary view showing more details of the arrangement of the slots 52. The dotted lines 60A and 60B show an angle extension formed by the front and rear side walls 54 and 56, the angle being indicated by the arc 62. The angle indicated by the preferable arc 62 is approximately 12 ° which is exemplary in that the angular relationship between the side walls 54 and 56 of the rear and front grooves may vary. Slot 52 is further defined by stress relieving areas 64 and 66 for purposes that will be described subsequently. Positioned in each slot 52 is a tooth 66 of the type generally described with reference to FIGS. 4 and 5A through 5E, but having the important difference that the tooth 66 has a forward side wall 70 and a rear side wall 72 that extend in the planes forming an angle substantially equal to the angle indicated by the arc 62. That is, the angular relationship between the front and rear side walls 70 and 72 of the tooth 66 preferably conforms to the angular relationship between the side walls 54 and 56 front and back. The tooth 66 is guided to the position in the slot 52. Because the angular relationship, when a tooth 66 is properly seated in the slot 52, frictional engagement is formed between the side walls of the tooth and the side walls of the tooth. slot. As shown in Figures 9 and 10, the side walls of the groove and the side walls of the tooth are preferably configured to provide a contour relationship, that is, by which a tooth, once firmly placed in a slot is locked against lateral movement. This is achieved in the illustrated embodiment wherein, as shown in Figure 9, the front side wall 70 of the tooth 66 is of concave configuration and the front side wall 54 of the notch portion formed in the tubular cutting blade 46 is of a convex configuration. Figure 10 shows the same relationship between the rear side wall 72 of the tooth and the rear side wall of the groove-notch 56. It can be seen that the relationship by sliding and interlocking between the side walls of each tooth and the side walls of the teeth. Slots can be of different configurations while still providing a locking relationship. For example, instead of being formed of angular configurations the side walls can be arcuately concave and convex and achieve the same results. Because the teeth 66 of the embodiment of Figs. 6 to 10 are configured to be guided in place or at least positioned in such a way that frictional engagement is achieved between the sidewalls of the teeth and the grooves, the apply a force due to the angular relationship, tending to separate the side walls 54 and 56 of the slot. To absorb the force of this spacer action, the groove is provided with semicircular stress relieving areas 64 and 66 in such a way that stress is not concentrated on the tubular cutting blade portion. As discussed above with reference to FIGS. 5A-5D, each tooth is provided with a step portion 42 that is of a reduced height compared to the top portion of the tooth 41. This step portion receives the bar 26 as It was previously discussed. The bar 26 is held in place by a bolt or threaded thread 30 that extends into a threaded opening 74 formed in the cutting face 50. As previously discussed, it is desirable to provide a grip arrangement, generally indicated by the number 26, to maintain the bar 26 in orientation with the cutting face 50. In the embodiment illustrated in Figures 6 to 6, and best seen in Figure 7, this can be achieved by providing a semicircular recess 76 in the cutting face 50 in which the semicircular contoured rear end 76 of the bar 26 is received. The forward end 60 of each bar 26 is received in a step section 42 of the tooth 46. When the pin 30, which as previously indicated is preferably a bolt or thread, is screwed firmly into position, the front end 60 of each bar 26 engages the tooth 66 to hold it securely in position. Each tooth 66 has a cutting edge 34 as previously described. As shown in Figure 7, tooth 66 can be provided with a variety of cutting edge configurations. This technique is commonly used in the cutting action. As shown in FIG. 7, two of the teeth 66 have a cutting edge 34A that cuts off first on the internal perimeter of the cutting face 50. The teeth 34B are configured to cut primarily on the outer perimeter, and the 34C are configured to cut in the middle part, that is, between the internal and external perimeters. In this way, it is not required that one of the teeth cut the full notch formed in the work weight. However, if desired, each tooth may be identical, in which case the cutting edge of each tooth must therefore be of a width greater than the width of the cutting face 50 because the cut of the notch must exceed the width of the portion 46 of tubular cutting blade to allow the cutting blade to advance as the notch is formed in a workpiece by the cutting action. Figures HA to 11D show details of the configuration of tooth 66 having the tooth configuration 34A, i.e., when the tooth has a cutting edge 34A that is concentrated on the inside of the tooth. Figures 12A to 12D show the configuration of a tooth 66 where the cutting edge 34A concentrates the cutting action on the external perimeter of the cutting face, while figures 13A to 13D show the teeth having the cutter face 34C which concentrates the cutting action in the center. The principles of this invention have been illustrated applied to a circular closure sometimes called a cutting shell where the cutting blade is tubular and has a toroidal cutting face. The principles of the invention, that is, the concept of an improved method for mounting removable teeth on the cutting face of a cutting blade can be applied to saws of another configuration, such as a circular saw, ie, where the cutting blade is in a plane having a circular cutting face, or a straight saw where the cutting blade is in a plane having a straight cutting face. As previously indicated, the principles of the invention are applicable to a saw for cutting metal or other non-metallic materials, such as stone, concrete, plastic or the like. The claims and the specification describe the presented invention and the terms that are used in the claims delineate their meaning from the use of said terms in the specification. The same terms used in the prior art may be broader in meaning than those specifically employed herein. In any case where there is doubt between the broadest definition of such terms used in the prior art and the more specific use of the terms herein, it will refer to the more specific meaning. Although the invention has been described to a certain degree of particularity, it remains to be seen that many changes can be made in the details of construction and arrangement of the components without departing from the spirit and scope of this description. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is limited only by the scope of the claim to appended claims, including the broad equivalence regime to which each element thereof. It's destined.

Claims (7)

NOVELTY OF THE INVENTION CLAIMS

1. A cutting tool comprising: a cutting blade having a cutting face, the cutting face having a plurality of spaced apart grooves therein, each slot having opposite front and rear side walls; and a removable tooth received in each of said grooves, each die having a top surface and opposed side walls, the side walls of the tooth being diessioned to slidably engage said front and rear side walls of the cutter head as the tooth the top surface of the tooth having a cutting edge is placed in said notch. A cutting tool according to claim 1, further characterized in that the side walls of each tooth frictionally engage the side walls of a groove of said cutting blade as the tooth is placed in said groove. 3. A cutting tool according to claim 2, further characterized in that each tooth is adjusted by pressure in a groove. A cutting tool according to claim 1, further characterized in that the side walls of each groove taper toward each other in the direction away from the cutting face and where the side walls of each tooth taper toward each other in the direction away from the upper surface. A cutting tool according to claim 4, further characterized in that the grooves and the teeth are tapered at an angle of approximately twelve degrees. 6. A cutting tool according to claim 1, further characterized in that it comprises means formed of at least one additional component for retaining a tooth in a groove. A cutting tool according to claim 6, further characterized in that the means for retaining said tooth in a slot comprise: a retention bar; and means for releasably retaining the retention bar on the cutting face of the cutting blade whereby a portion of the retention bar engages the upper surface of the tooth. A cutting tool according to claim 7, further characterized in that the retention bar is of a width no greater than the cutting face and has a leading end and a trailing end, the leading end engaging the upper surface of a tooth . 9. A cutting tool according to claim 7, further characterized in that the means for releasably retaining the retraction rod includes a threaded bolt received in an opening in the retention bar, the opening being intermediate the opposite ends of the rod. , the bolt being threaded being received in a threaded hole in the cutting face of the cutting blade, whereby the holding bar can be rotated in a position around the bolt to allow the tooth to be removed and rotated in another position to engage a tooth to retain the tooth in its position in a groove. A cutting tool according to claim 6, further characterized in that the cutting face of the cutting blade has a recess therein spaced apart from each rear side wall of the slot and wherein said rear end of said holding bar is received. said slot when the leading end is in engagement with a tooth. A cutting tool according to claim 1, further characterized in that the cutting blade is tubular for use in cutting a circular hole. 1

2. A cutting tool comprising: a cutting blade having a cutting face, the cutting face having a plurality of spaced slots therein, a tooth received removably in each slot, each tooth having a top surface extending above the cutting face, the upper surface having a front cutting edge and a lower step height section; a retaining bar for each tooth having a leading and a trailing end, the leading end being received in a step section; and means for securing each retention bar to the cutting face. A cutting tool according to claim 12, further characterized in that the means for securing each retention bar to the cutting face is a pin received in an opening formed in the intermediate retention bar at the front and rear ends, the pin being secured to the cutting face of the cutting blade. A cutting tool according to claim 13, further characterized in that the pin is in the form of a threaded bolt having a head portion that engages the retaining bar, the threaded bolt being received in a threaded opening formed on the cutting face. A cutting tool according to claim 14, further characterized in that it includes means for holding the holding bar in engagement with a tooth when the pin is tightened. A cutting tool according to claim 15, further characterized in that the means for holding the retention bar in engagement with a tooth when the pin is tightened include a notch formed in the cutting face in which the rear end of the bar Retention is received. CUTTING TOOL THAT HAS REMOVABLE TEETH SUMMARY OF THE DESCRIPTION A cutting blade having a cutting face is provided. A plurality of separate slots is formed in the cutting face, each slot having front and rear side walls. A tooth is received removably in each of the slots, each tooth having an upper surface extending above the cutting face and having front and rear side walls. The upper surface of each tooth has a front cutting edge and a reduced rear height step section. Retention bar is provided for each tooth, each retention bar having a leading end that is received in the step section. A pin extending through an opening in each retaining bar is threadably connected to the cutting face. By tightening the threaded pin the retaining bar retains each tooth during a cutting operation in such a way that the side walls of the tooth frictionally engage the side walls of the groove and by unscrewing the pin the retaining bar can be rotated to allow the Removal and replacement of each of the teeth. r.K / cgt * crm * mep