TOOL AND METHOD FOR VERY HIGH FEED MACHINING This application is based upon and claims priority to and the benefit of U.S. provisional application Serial No.62/914,883 filed October 14, 2019, the disclosures of which are hereby incorporated in their entirety by reference herein. BACKGROUND OF THE INVENTION The invention addresses cutting tools and methods used to remove material such as from a workpiece by way of a machining process. The process of machining acts on a workpiece to remove an existing, often but not always un-machined, surface, in order to create a new surface and, in doing so, producing chips of removed material. The process involves providing, by a machine tool on which the process takes place, a relative cutting motion between a cutting tool, comprising a body and one or more cutting inserts, and a workpiece, in order for material to be removed from the workpiece by the cutting tool. The rate associated with the cutting motion is referred to as the cutting speed or the surface speed and is generally measured in feet per minute or meters per minute. We limit our consideration here to machine tools that provide the cutting motion by way of a spindle rotating either the cutting tool or the workpiece at a spindle speed measured in, for instance, revolutions per minute. To accomplish material removal, at least one cutting insert must physically (mechanically) engage with the workpiece to remove a thin layer of material in order to create a new surface. The new surface is created by the furthest protruding points (in the depth of cut direction) on the furthest protruding cutting insert(s), each furthest protruding point on each cutting insert being referred to here as its tooth tip. The noted engagement between the cutting tool and the workpiece is accomplished by setting the position of the cutting insert(s) relative to the workpiece, specifically setting the tooth tip on the cutting edge of each cutting insert to its depth- of-cut position. This is achieved by way of setting the position of the cutting tool relative to the workpiece, to define a depth of cut (a _p ) that is measured normal to the new surface to be created. Further, the machine provides a feeding motion of the cutting tool relative to the workpiece that is characterized by a feed speed. Often times the total depth of material to be removed (a _p,total ) in producing the new surface is greater than can be removed with a single pass of the cutting tool in which case multiple passes of the cutting tool are made, each pass i at a depth of cut ap,i, such that the summation of ap,i, i = 1 to P, removes ap,total in P passes. The depth of cut for each pass (ap,i) may or may not be equal to that of any other pass a _p,j . It is common, though not a requirement, for a _p,total to be divided equally, resulting in P passes of equal depth of cut (a _p,i = a _p,total /P, i = 1 to P). However, it is also common to desire a final or finishing pass to occur at different conditions, whether a different depth of cut and/or feed or/or speed. In this case, there is a final/finishing pass at depth of cut a _p,P and P–1 passes of other depths of cut, again, often but not necessarily of equal depth of cut (ap,i = (ap,total – ap,P)/(P–1), i = 1 to P–1). The cutting tool feeding motion for each pass generally traces a path that corresponds to the new surface with an offset from the tooth tip of each cutting insert measured normal to the new surface, the difference in that offset between successive passes being the aforementioned depth of cut for the respective pass i (ap,i). With the exception of the P ^th pass where the offset equals zero at all points on the path, in spite of the general approach noted above, in practice the offset of any one pass may vary along the path, whether a result of the varying offset along the path, or for other reasons. The feeding motion is characterized by a feed per revolution, which is the change in position of the cutting tool relative to the workpiece along the path, that change in position occurring over the time elapsing between subsequent traversings of any particular cutting insert through any angular position of cutting rotation, specifically 360 degrees for the feed per revolution. When there is more than one cutting insert spaced circumferentially around the cutting tool and set at substantially the same depth of cut, the feeding motion is further characterized by a feed per tooth. The feed per tooth, or feed per insert as the case may be, is the change in position of the cutting tool relative to the workpiece along the path, that change in position occurring over the time elapsing between subsequent cutting inserts at the similar depth of cut traversing any angular position of cutting rotation, specifically the spacing between the noted subsequent cutting inserts. The types of machining processes where the present invention and aforementioned speed, feeding motion, and depth-of-cut/offsets/surfaces/paths etc. applies include those that employ a non-rotating tool. This includes lathe processes where the outer diameter of the workpiece is machined, often referred to as OD turning, or the inner diameter of the workpiece is machined, often referred to as ID turning or lathe-boring, or the end is machined, often referred to as facing. In contrast, there are other machining processes where the tool rotates and the workpiece does not rotate. This includes processes like face milling, peripheral milling, and cylinder boring. The present invention can apply in those as well in both method and device. A machining operation commences when a cutting tool engages a surface on a workpiece and concludes when that same cutting tool disengages the workpiece, generally being preceded by and followed by rapid traverses. In an abstract sense, each pass noted above may be considered a machining operation, while at the same time the accumulation of passes is often considered to comprise what is referred to as a machining operation. A final or finishing pass, the P ^th pass noted earlier, is often referred to as a finishing operation. For some cutting tools, such as a step face mill (often just called a “step mill”) some cutting inserts on the cutting tool are cutting at a greater offset from the new surface than others. Those inserts for which the offset of their tooth tips from the new surface are zero are finishing inserts, whereas the others are roughing inserts. Typically, a step mill may not even be considered using the term “finishing” for any of its cutting inserts since step mills are often used in roughing applications/operations. However, here the term “finishing” insert is used to identify those inserts on such a cutting tool that create the final/new surface during a pass of the tool while the “roughing” inserts are those that remove additional material but do not directly participate in producing the final/new surface during that pass of the cutting tool. These types of tools, using a step face mill as an example, generally have a set of cutting inserts, call it an insert set, that are arranged with the “finishing” insert positioned at the smallest diameter and protruding furthest from the spindle in the axial direction. Defining “directions” (or coordinates/axes) is helpful. The “feed direction” F is a translational coordinate defined as positive radially outward from the face mill’s axis of rotation, the “depth direction” D is a translational coordinate defined as positive axially from the spindle (or the spindle-mounting end of the cutting tool) toward the cutting inserts, and the cutting direction C is an angular coordinate defined as positive in the direction the cutting tool rotates in order to perform its cutting function. In terms of directions, a step face mill has its roughing inserts located angularly ahead of the respective finishing insert, meaning in the positive cutting (C) direction, and in the negative depth (D) direction relative to the finishing insert. Each successive roughing insert is spaced from its adjacent predecessor by the same or differing amounts as the first roughing insert is spaced from the respective finishing insert in the insert set. At times there is also a shift in the feed (F) direction and when using round inserts as is the case in the present invention, a sizeable feed- direction shift is quite important. Thus, starting from the finishing insert of an insert set, each successive roughing insert k is located relative to its predecessor cutting insert j in the positive cutting direction by an amount ΔC _jk (a positive value), in the negative depth direction by an amount ΔDjk (a positive value), and in the positive feed direction by ΔFjk (a positive value). There may be one insert set resulting in one “effective tooth,” sometimes referred to as a “flute,” or there may be more than one inert set in which case the finishing inserts of each insert set are substantially/nominally aligned with one another in the depth direction. As noted, for a face mill, the depth direction is axial (positive away from the spindle-mounting end of the cutting tool toward the cutting inserts) and the feed direction is positive outward radially from the face mill’s axis of rotation. This idea of a step mill can be extended to other tools, such as a cylinder boring tool. In this case, the feed direction is axial (positive away from the spindle-mounting end of the cutting tool toward the cutting inserts) and the depth direction is positive outward radially from the boring tool’s axis of rotation. In the case of a stepped cylinder boring tool all the above applies in regard to relative tooth locations in terms of ΔC _jk , ΔD _jk , and ΔF _jk where each “finishing” insert is positioned closest to the spindle in the axial (feed, F) direction and protrudes greatest in the radial (depth, D) direction. Likewise, for face mills in particular but the same can apply for cylinder boring tools, some finishing tools have what is referred to as one or more “wiper” inserts. Abstractly they bear similarity to what is referred to here as a “finishing” insert, but generally there are fewer wiper inserts than non-wiper inserts or even groupings (sets) of non-wiper inserts as described above. Because there is, by definition of a step tool, one “finishing” insert for each insert set, a finishing tool implementing what is known in the field as “wiper” inserts is fundamentally different in that there is not one wiper per “set” of non-wiper inserts; typically the non-wiper inserts are all aligned with one another, not stepped in the depth direction as is the case in a “step” tool. Further, a “wiper” inert is intended by design to only remove a very small depth of material, on the order of 0.002 inch (50 µm) or less whereas the finishing insert on a step tool is more likely to remove 5 to 10 times that depth; that is, the ΔDjk from the finishing insert to the first/adjacent roughing insert is typically, but without restriction, 0.005 to 0.020 inch (125 to 500 µm) or more. In other words, whereas the purpose of a wiper insert is to skim the surface produced by the other (primary) cutting inserts to wipe way the feed groove roughness to make the surface smoother, the finishing insert on a step mill, at least in the present invention, is doing real “work” in removing a substantive amount of material in the overall removal performed by the step tool. The step tools of the present invention do not include any cutting inserts that equate to a wiper insert as is normally defined in the field. As noted, a finishing insert in this presentation is any cutting insert that is responsible for (ultimately contributes to) creating the dimension, that is, the position of the new surface relative to another reference surface, and the roughness of the new surface. There may be one or more than one finishing inserts, as noted. Furthermore, all cutting inserts on a cutting tool may be (intended/purposed as) finishing inserts, and some cutting inserts may be (intended/purposed as) cutting inserts that do not contribute to the actual final/new surface, as noted in the case of a step tool. Finishing inserts, in fact any cutting insert, be it finishing or not, may be of various shapes such as but not limited to triangular, square, rectangular, rhombic, pentagonal, hexagonal, octagonal, and round. Finishing inserts, for the purpose of creating a good/low surface roughness, may have a higher radius of curvature on the cutting edge, as measured at the tooth tip, than other inserts might. Regarding insert shape, the present invention more specifically addresses such cutting tools and methods/processes that employ a round cutting insert. Round cutting inserts are a natural way of accomplishing a large cutting-edge radius of curvature at the tooth tip. A round cutting insert may be fixed to the tool as are cutting inserts of the many other shapes noted. But, unlike non-round cutting inserts, round cutting inserts may alternatively be allowed to rotate under the force of the material removal process as a result of the cutting insert being affixed to a support device that permits rotation about the axis of the round cutting insert. Like other non-round cutting inserts, round cutting inserts can be of a type mounted in a conventional “radial mount” or in a “tangential mount.” The difference between these mountings relates to the orientation of the insert axis relative to the tool body and the direction of cutting motion. In other words, the mounting type relates to which surface on the cutting insert is the flank surface that provides clearance relative to the new surface created, and which surface on the cutting insert is the rake surface on which the chip of removed material is formed. Regardless of insert shape, these two surfaces, the rake surface and flank surface, exist and form the cutting edge at their intersection. A round cutting insert, by definition, exhibits a substantially round or circular cutting edge.

[0012] A conventional radial-mount configuration is shown in Figure 1 (a face milling tool as an example). The tool comprises a body 1 and, in this example, has three round cutting inserts 2 each having an insert axis 3. In a radial mount, the flank surface 6 is the peripheral surface 4 and the rake surface 7 is one of the end surfaces 5. This type of configuration is the subject of numerous patents, such as U.S. 2,885,766A and 3,329,065. A tangential-mount configuration is shown in Figure 2 (a face milling tool as an example) where the rake surface 7 is the peripheral surface 4 and the flank surface 6 is one of the end surfaces 5. This type of configuration is the subject of numerous patents, such as U.S. 2,127,523 and 2,233,724 for single-point lathe processes used to create surfaces of revolution and more recently U.S. application 16/266,883 for a variety of multi-tooth processes. In both examples the circular intersection of the flank surface 6 and the rake surface 7 defines the round or circular cutting edge 8, located on which is the tooth tip 9; as noted earlier, the tooth tip 9 is the point on the cutting edge 8 that protrudes furthest in the positive depth direction (axial away from the spindle-mounting end of the face mill toward the cutting inserts).

[0013] While radial or tangential mounting of a round cutting insert may be stationary, these four aforementioned patents cover examples of tools that allow the round cutting insert to rotate under the forces of chip formation. When machining, heat energy is generated by friction and deformation of the workpiece material (i.e., the cutting process) that is then imparted from the cutting process into the cutting insert. Increased temperature is a primary cause of increased tool wear rate. Allowing the cutting insert to rotate helps to moderate the effect of heat energy generated by the cutting process, extending tool life for a given cutting/surface speed. Rotation of the cutting insert without human intervention also allows the entire circumference of the round cutting insert, the round/circular cutting edge, to be fully consumed with no need for human intervention to rotate to fresh regions of the circumference (referred to as indexing), which is required for non-rotating cutting inserts.

[8014] For a round cutting insert, whether fixed or rotating, there is the possibility to gain more tool life without compromising, and often enhancing, productivity by simply taking advantage of the present invention rather than the conventional approach of reducing cutting/surface speed to increase tool life, which reduces productivity all else held constant.

BRIEF SUMMARY OF THE INVENTION

[0015] The present invention provides a means for increasing tool life for cutting tools using round cutting inserts by using unconventional proportions of feed and depth of cut, depth being much smaller than conventional levels and feed being relatively much larger than conventional levels. One embodiment is a method of use in which there may be one or more intermediate tool paths, generally more paths than would be applied under conventional proportions of feed and depth of cut. Productivity is preserved while tool life can be doubled or more by having the feed at least 0.75 times the depth of cut in at least some portions of some paths, or even higher to greater benefit. This embodiment can be applied for many machining processes whether the tool or the workpiece is rotating to achieve the cutting motion. For machines that do not have sufficient feed speed to take full advantage of the method embodiment, the same benefit is achievable using a step tool having low depth on each cutting insert and proportionally higher feed realized on each cutting insert. One embodiment is a face mill. Another embodiment is a cylinder boring tool. All embodiments incorporate one or more round cutting inserts, and furthermore one or more of the round cutting inserts may be fixed/non-rotating, or allowed to freely rotate under the force of chip formation. Another embodiment includes a combination of rotating and non-rotating round cutting inserts. Another embodiment uses radially-mounted round cutting inserts while another embodiment employs tangentially-mounted round cutting inserts, while yet another embodiment employs a combination of radially- and tangential-mounted round cutting inserts, some, all, or none being allowed to freely rotate under the force of chip formation. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a face mill as an example illustration, with the flank surface and rake surface called out, in a conventional radial mounting of a round cutting insert. Figure 2 is a face mill as an example illustration, with the flank surface and rake surface called out, in a tangential mounting of a round cutting insert. Figure 3 is the chip formation and cutting process geometry for a round cutting insert. Figure 4 is a graph showing how the number of equivalent cutting edges on a round cutting insert changes as depth of cut changes as a percent of the cutting insert radius. Figure 5 is a graph showing how the number of equivalent edges changes as feed (chip load) is increased while depth of cut is proportionally decreased, and number of passes proportionally increased, maintain productivity and net tile of cutting insert contact per part while realizing significantly more equivalent edges (tool life). Figure 6 is the chip formation and cutting process geometry for a step tool having round cutting inserts. Figure 7a is a top (axial) view of a non-stepped face mill with radially-mounted round cutting inserts. Figure 7b is a front view of a non-stepped face mill with radially-mounted round cutting inserts. Figure 8a is a top (axial) view of a non-stepped face mill with tangentially-mounted round cutting inserts. Figure 8b is a front view of a non-stepped face mill with tangentially-mounted round cutting inserts. Figure 9a is a top (axial) view of a stepped face mill of the present invention with radially-mounted round cutting inserts. Figure 9b is a front view of a stepped face mill of the present invention with radially-mounted round cutting inserts. Figure 10a is a top (axial) view of a stepped face mill of the present invention with tangentially-mounted round cutting inserts. Figure 10b is a front view of a stepped face mill of the present invention with tangentially-mounted round cutting inserts. As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. DETAILED DESCRIPTION OF THE INVENTION The cutting process using a round cutting insert 2 is shown in Figure 3 where the positive cutting direction (C) is out of the page (not shown); shown also are the depth direction 14 (D) and the feed direction 15 (F). A previous pass by this point on the workpiece 13, of this or another cutting insert, produced a remaining cusp surface 12 (the dashed arc) shown. In the time elapsed since the remaining cusp surface 12 was created there has been a translation of the tool body 1 (not shown), to which cutting insert 2 is attached, relative to the workpiece 13, in the feed direction 15 by the feed 16 (typically “feed per tooth” as defined in the background). In this image, the cutting insert 2 is currently removing the chip area 11 that constitutes the cross-sectional area of material bounded by the cutting edge 8, the remaining cusp surface 12, and the existing surface 58. The cutting insert is removing an existing surface 58 and producing a new surface 59. The amount of the round/circular cutting edge 8 that is instantaneously engaged with the workpiece 13 is referred to here as the edge angle of engagement 18. The major edge angle of engagement 19 lies on the leading or approach side of the tooth tip 9 (in the positive feed direction 15, relative to the insert axis 3). The major edge angle of engagement 19 equals cos ⁻¹ (1 − a _p /r _ε ) where a _p is the depth of cut 17 and r _ε is the radius of the cutting insert 2. Thus, as the depth of cut 17 decreases, for a given radius of the cutting insert 2, the major edge angle of engagement 19 decreases. There is then a small additional minor edge angle of engagement 20 on the trailing side of the tooth tip 9 (in the negative feed direction 15, from the insert axis 3) where the feed- groove cusp is formed. The minor edge angle of engagement 20 equals sin ⁻¹ (f/(2rε)) where f is the feed 16. Thus, as the feed 16 increases, for a given radius of the cutting insert 2, the minor edge angle of engagement 20 increases. The total edge angle of engagement 18, E _ae , is the summation of the major edge angle of engagement 19 and the minor edge angle of engagement 20. Tool life then relates to the number of equivalent edges, Eeq, where Eeq = 360/Eae. The benefit of the invention comes from exchanging conventional levels/proportions of depth of cut 17 and feed 16 for unconventional levels of the same. The present invention allows longer tool life (higher Eeq) to be achieved under the same cutting/surface speed by significantly reducing E _ae (making E _eq larger). This occurs by simply reducing depth of cut 17 and proportionally increasing feed 16, taking advantage of the stronger nonlinear relationship between the depth of cut 17 and the radius of the cutting insert 2, as compared to the nonlinear relationship between feed 16 and the radius of the cutting insert 2. This applies whether the round cutting insert 2 is fixed or rotating. Conventionally, the depth of cut 17 is larger or much larger than feed 16; generally/conventionally the depth of cut 17 is more than two times the feed 16. In contrast, the illustration of Figure 3 is to-scale at unconventional proportions according to the present invention (specifically, feed 16 is 1.2 times the depth of cut 17 as illustrated, or, rather, depth of cut 17 is only 0.82 times feed 16). That is, Figure 3 is representative of the present invention, as opposed to conventional proportions. Figure 4 shows how the number of equivalent edges (E _eq ) changes exponentially with depth of cut 17 from the conventional end of the spectrum, where depth of cut 17 is large (and feed 16 is small), down to the unconventional end of the spectrum (the present invention), where depth of cut 17 is small (and feed 16 is large). In the figure, when the depth of cut 17 equals one-half the radius of the cutting insert 2, the major edge angle of engagement 19 is 60° resulting in the (total) edge angle of engagement 18 being slightly more than 60° (due to the small addition of the minor edge angle of engagement 20). As depth of cut 17 decreases from 50% of the radius of cutting insert 2; E _eq increases from about 6 (5.97 more exactly) to twice that (about 12) at a depth of cut 17 that is about 13% of the radius of the cutting insert 2, which is the proportions illustrated in Figure 3. In other words, the situation illustrated in Figure 3 would provide twice the tool life as would a case where the depth of cut 17 is 3.8 times that shown in Figure 3 and the feed is reduced to 1/3.8 (= 0.31) times that shown in Figure 3 (to maintain chip area 11, and hence productivity, constant). This ratio of feed 16 to depth of cut 17 being 0.3 – 0.5 is, as noted, conventional, compared to the present invention where the feed 16 is pushed to be unconventionally large relative to the depth of cut 17 (i.e., the ratio of feed 16 to depth of cut 17 is greater than or equal to 0.75) by means of reducing the depth of cut 17 from a conventional level to an unconventionally small level and proportionally increasing the feed 16 to an unconventionally high level. As seen, reducing the depth of cut 17 by a factor X > 1, and increasing the feed by that same factor X, has the net effect of reducing E _ae and increasing E _eq . Setting X = 2 for ease of illustration, splitting the total depth removed (a _p,total ) in half and removing it in P = 2 passes maintains the same productivity (neglecting small contributions of rapid traverses, etc.), but consumes less of the cutting edge. That is, at any instant of time there is less of the circular cutting edge engaged in the cutting action, otherwise stated as the total edge angle of engagement being smaller (Eae has reduced). Taking 2 passes may initially seem to offset the benefit. However, since each pass has one-half as many revolutions of the cutter, since it is moving at two times the feed rate, the two passes together expose the insert to wear for the same number of cutter revolutions as in the original full depth in a single pass at the original lesser feed. In other words, there is no appreciable change in the time of contact/wearing of the cutting insert with the workpiece even though two passes are used. Thus, the net effect is that less of the cutting edge is consumed per part machined and the round cutting insert can exhibit more life or usefulness. This is illustrated in Figure 5 in terms of edge equivalents (Eeq). The graph is for a constant chip area (products of feed (or often called “chip load”) and depth of cut) of 1 mm ² . As feed (chip load) increases, depth of cut is proportionally decreasing (as shown on the scale at the top of the plot). Thus, under the present invention, running a round cutting insert at a much higher feed 16 in proportionally more passes at proportionally lower depth of cut 17 can produce significant increases in tool life, nearly 2.7 times in the specific case illustrated. For a fixed insert, this may be advantageous if one can coordinate the depth of cut 17 in such a way as to achieve a near-integer value of Eeq; for instance (referring to Figure 4), running depths of cut 17 (as a percent of cutting insert radius) at about 50%, 37%, 28%, 23.5%, 18.8%, and so on will result in E _eq = 6, 7, 8, 9, 10, and so on. Thus, the present invention does apply to cutting tools and processes employing fixed/non-rotating round cutting inserts. But the present invention more seamlessly applies for cutting tools and processes that employ rotating round cutting inserts since the rotation allows the round cutting insert to evenly expose its full circumference (round/circular cutting edge), continually and evenly distributing wear at all times, not requiring the depth of cut 17 to be set such that there is an integer number of equivalent edges (that is, E _eq need not be an integer). As such, the greater benefit of the present invention comes with rotating round cutting inserts. Returning to Figure 5 we revisit this in quantitative terms, clearly showing there is an advantage to applying a round cutting insert by taking may passes at proportionally higher feed. A non-round cutting insert, or even a conventional implementation of a fixed/non-rotating round cutting insert, might perform a heavy roughing cut at a depth of cut 17 of 5 mm (or 0.2 inches) and a feed per tooth/insert 16 of 0.2 mm (0.008 inch). Using a 25.4-mm (1-inch) diameter round cutting insert instead at, say, 10 passes, each pass at depth of cut 17 of 0.5 mm (0.02 inch) and at a feed per tooth/insert 16 of 2 mm (0.08 inch), will result in 17.4 equivalent edges rather than 6.76 equivalent edges, or 2.6 times tool life with equal productivity, simply by applying the method of this invention. Cutting at feed per tooth/insert 16 only slightly less than or greater than the depth of cut 17 is not conventional, surpassing the typical feed-depth proportion used with even modern “high-feed” face mills that employ non-round cutting inserts at a low approach angle. One way to gain the benefits described above using the present invention is the method by which a cutting tool with one or more round cutting inserts, as described thus far, is used to remove an existing, physical first surface from a workpiece, creating a physical new/third surface on the workpiece while employing an unconventionally high feed 16 at one or more passes at unconventionally low depth of cut 17. The method comprises the following steps. 1. Defining a virtual second surface, which is substantially equivalent to the desired final new/third surface in size, shape, and position. 2. Defining one or more (N _s ≥ 1) virtual intermediate surfaces that are offset, from the virtual second surface defined in step 1, toward the existing physical first surface, by a successively increasing distance as measured normal to the virtual second surface. 3. Defining a path of the cutting tool as a series of points, as is typical in defining a tool path via CAM or via G-code programming, from a start point to an end point, all points being on the virtual second surface (desired final/new surface to be created) defined in step 1. Of course, as is typical, there may be a cutter radius offset imposed in this relation between the path of the tool and the desired final new surface to be created. 4. Defining in the same way as in step 3 one path corresponding to each of the Ns virtual intermediate surface defined in step 2. 5. Defining the rate of feeding motion between adjacent points on the second path defined in step 3 based on the desired feed per tooth on the cutting tool. 6. Defining the rate of feeding motion between adjacent points on each intermediate path defined in step 4. For at least one pair of adjacent points, the feed per tooth should be greater than three-quarters of the depth of cut (feed-multiplier greater than or equal to 0.75) experienced anywhere between the adjacent points, the depth of cut measured to the nearest other intermediate surface that is successively closer to the first surface. This high feed per tooth, being so large relative to the depth of cut, is again where the present invention departs from conventional machining methods. 7. Providing a cutting motion to the cutting tool or workpiece, whichever is rotating by way of the spindle, by turning on the spindle. 8. Initiating the tool feeding motion, which will follow the tool paths, starting with intermediate path N _s through to and including intermediate path 1 and finishing with the path defined in step 3, in a substantially tangential fashion, point to point according to how CNC controllers work. The depths of cut for any path may be constant or not constant along the path. This method may use a cutting tool with at least one fixed/non-rotating round cutting insert or at least one rotating round cutting insert, or a combination of the two. The feed multipliers noted may be higher than 0.75, but for the purpose of the invention, as noted should be greater than or equal to 0.75 at least somewhere on one of the paths. In applying the method for face milling, successive paths may traverse the workpiece 13 in essentially the same direction or in the opposite direction or any direction. In applying the method in lathe operations like OD turning, ID boring, and facing, successive paths may follow essentially the same direction or, with a tool that is generally neutral in the angles of the cutting insert 2 relative to the tool body 1, in the opposite direction, which can eliminate much of the rapid traverse times. Some machine tools may reach their maximum feed speed (e.g, inches per minute) before achieving the (in this illustration) 2 mm per tooth feed 16 at the chosen spindle speed (feed per tooth, times number of teeth spaced circumferentially on the tool body 1, times revolutions per minute, yields feed speed in distance per minute) using the method just described. In such a case, the same advantages can be realized by implementing a round-insert step tool that takes advantage of the aforementioned exchange of proportion between feed and depth of cut in a different way. In this case, each stepped insert removes a portion of the total depth of cut ap,total and, unlike conventional step tools, does so at a proportionally higher feed when measured relative to the cutting insert at its same depth location on the preceding insert set. For instance, (using the notation introduced in the background) a non-step 10-insert tool running the conditions above (5 mm depth of cut at 0.2 mm per tooth/insert) could be replaced with a 10-insert tool running a single insert set with ΔD _jk = 0.5 mm and get similar tool-life benefit without having to run the tool at a higher feed speed. Or, it could be replaced with a 10-insert tool running two insert sets, each with 5 inserts, with ΔDjk = 0.5 mm, run in two passes at twice the original (non-round insert) feed speed to get the full 5 mm total depth of cut (ap, total) and get similar tool-life benefit. Or, it could be replaced with a 10-insert tool running two insert sets, each with 5 inserts, with ΔD _jk = 1.0 mm, run in one pass and get the some, but lesser, tool-life benefit. The cutting process for this case is illustrated in Figure 6 where the positive cutting direction (C) is out of the page; shown also are the depth direction 14 (D) and the feed direction 15 (F). This figure shows the profile of the cutting edge 8 of three cutting inserts 2 making up an insert set, each cutting insert 2 having insert axis 3 and tooth tip 9. An insert set may have only two cutting inserts 2, three (as illustrated), or more than three. A previous pass by this point on the workpiece 13, of this or another insert set, produced a remaining cusp surface 12 (the dashed arcs) corresponding to each cutting insert 2. In the time elapsed since each remaining cusp surface 12 was created there has been a translation of the tool body 1 (not shown), to which all cutting inserts 2 are attached, relative to the workpiece 13, in the feed direction 15 by the feed 16. The feed 16 is the same for each cutting insert 2 if there is a single insert set, otherwise feed 16 may be different for each cutting insert 2 (achieved by non-constant angular spacing of the cutting inserts from one insert set to another). The insert set shown is removing the total depth of cut 36 measured between the existing surface 58 and the new surface 59 produced by the finishing insert 31. Finishing insert 31 follows (in the passing/cutting order) the first roughing insert 32, which follows the second roughing insert 33. Finishing insert 31 is currently removing its respective chip area 44 that constitutes the cross-sectional area of material bounded by its respective cutting edge 50, its respective remaining cusp surface 47, and the respective free surface 53 that was created by the first roughing insert 32. The first roughing insert 32 is currently removing its respective chip area 45 that constitutes the cross-sectional area of material bounded by its respective cutting edge 51, its respective remaining cusp surface 48, and the respective free surface 54 that was created by the second roughing insert 33. The second roughing insert 33 is currently removing its respective chip area 46 that constitutes the cross-sectional area of material bounded by its respective cutting edge 52, its respective remaining cusp surface 49, and the respective free surface which, being the last roughing insert, is the existing surface 58. So that each insert j does not experience a greater depth of cut than approximately ΔD _jk , the feed-direction shift (radial on a face mill) ΔF _jk must be such that the profile of cutting insert j intersects its respective free surface at, or to the negative feed-direction side of, the tooth tip 9 of cutting insert k. Referring to Figure 6 to illustrate, finishing insert 31 intersects with its respective free surface 53 at intersection point 56. The illustration has set the feed-direction shift 37 of the first roughing insert 32 at its minimum value, meaning such that tooth tip 42 of the first roughing insert 32 is coincident with intersection point 56. Likewise, the second roughing insert 33 intersects with its respective free surface 54 at intersection point 57. The illustration has set the feed-direction shift 38 of the second roughing insert 33 at its minimum value, meaning such that tooth tip 43 of the second roughing insert 33 is coincident with intersection point 57. Note that the minimum value of feed-direction shift of cutting inert k relative to cutting insert j is influenced by how far the tool body 1 has translated during the time elapsed between the passing of cutting insert k and cutting insert j, as follows: where R _j is the radius of curvature at the tooth tip 9 of cutting insert j, and f _max is the maximum feed per revolution for which the cutter is designed. The depth-direction shift 34 for the first roughing insert 32 and the depth-direction shift 35 for the second roughing insert 33 need not be the same, as is illustrated, causing the respective feed-direction shifts to be unequal. If the cutting insert radius of curvature Rj changes from one cutting insert to another, and/or the angular spacing ΔCjk between successive inserts varies, this can also cause the values of feed- direction shift to vary. Figures 7a and 7b show, for comparative reference, a non-stepped face mill with four round cutting inserts 2 that are radially mounted to tool body 1. Figures 8a and 8b show, again for comparative reference, a non-stepped face mill with four round cutting inserts 2 that are tangentially mounted to tool body 1. In all cases it is visible that each cutting insert has its respective feed direction 15, for a face mill pointed radially outward from cutter/rotation axis 62, and each insert has its tooth tip 9 located on and following the cut diameter 63 as the tool rotates in the positive cutting (C) direction 61. Stepped versions of these two four-insert face mills are shown in Figures 9a and 9b for radial mount, and Figures 10a and 10b for tangential mount. To illustrate multiple insert sets, each (radial or tangential version) has a first finishing insert 71 and a paired roughing insert 72 that comprise a first insert set, and a second finishing insert 73 and a paired roughing insert 74 that comprise a second insert set. The angular spacing 65 is illustrated to be the same for both insert sets, though this is not necessary and may be advantageous as is variable helix or variable tooth- pitch designs for reducing the propensity to chatter. The feed-direction shift 37 and depth-direction shift 35 are shown to define the location of the roughing inserts (72 and 74) relative to their respective finishing inserts (71 and 73). Since the tangential mounting produces a much larger radius of curvature R _j at the tooth tip 9, it is advantageous for producing a better surface finish for a given feed per insert set. As such, radial-mount and tangential-mount inserts may be mixed on a single cutter, typically though not necessarily with tangential-mount inserts as finishing insert and radial-mount inserts as roughing inserts. Where possible (sufficient feed speed on the machine tool), however, running a non-stepped tool at low depth and very high feed, instead of a stepped tool at the X times the depth and 1/X times the feed, is that the non-stepped tool has demonstrated less propensity to chatter. For all of the above in regard to step tools, while illustrated with face mills, all applies for cylinder boring tools where each cutting insert has its respective depth direction 14 pointed radially outward from cutter/rotation axis 62. While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.