Patent Publication Number: US-11021953-B1

Title: Material-removal systems, cutting tools therefor, and related methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 14/811,699 filed on 28 Jul. 2015, which claims priority to U.S. Provisional Application No. 62/030,525 filed on 29 Jul. 2014, the disclosure of each of which is incorporated herein, in its entirety, by this reference. 
    
    
     BACKGROUND 
     Material-removal systems, such as mining machines, commonly use cutting tools or picks that engage and cut into target material. For example, cutting tools may be mounted on a rotatable mining head of the mining machine. While the mining head rotates, the mining machine and/or the mining head thereof may be advanced toward and into the target material. Hence, the cutting tools may engage, cut, or otherwise fail the target material as the mining head advances into the target material. Subsequently, the failed target material may be recovered or removed from its location, such as from a mine. 
     Particular target material may vary from one mining application to another. For example, mining machines may be used to fail and recover Trona or similar minerals and materials. In any event, operation of the mining machines typically results in wear of the cutting tools, which may lead to reduced useful life and reduced productivity as well as failure thereof, among other things. 
     Therefore, manufacturers and users continue to seek improved cutting tools and material-removal systems to extend the useful life thereof. 
     SUMMARY 
     Embodiments described herein relate to material-removal systems and cutting tools that may be used in the material-removal systems. More specifically, for example, the material-removal systems, and particularly the cutting tools thereof, may engage and fail target material. In some instances, the material-removal systems may be used in mining operations. Hence, the material-removal systems may mine the target material. In other words, For example, the material-removal systems may fail and remove or recover the failed target material (e.g., Trona). 
     At least one embodiment includes a material-removal system, which has a movable cutting head. The material-removal system includes a plurality of cutting tools mounted on the cutting head. Each of the plurality of cutting tools includes a tool body and a cutting element attached to the tool body. Each of the cutting elements has a substrate bonded to superhard table that includes a substantially planar working surface that is oriented at a back rake angle and a side rake angle. At least two of the plurality of cutting tools are positioned at different locations on the cutting head. 
     Embodiments also include a method of removing material. The method includes moving a plurality of cutting tools about a rotation axis. At least two of the plurality of cutting tools are positioned at different positions. Each of the plurality of cutting tools includes a substrate bonded to a superhard table that forms a working surface. Also, the superhard material forms at least a portion of a cutting end of the cutting tool. The method further includes advancing the plurality of cutting tools toward a target material. The method also include engaging the cutting ends and the working surfaces of the cutting tools with the target material, and thereby failing at least some of the target material while having the working surfaces oriented at back rake angle and at a side rake angle. 
     Features from any of the disclosed embodiments may be used in combination with one another, without limitation. In addition, other features and advantages of the present disclosure will become apparent to those of ordinary skill in the art through consideration of the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate several embodiments, wherein identical reference numerals refer to identical or similar elements or features in different views or embodiments shown in the drawings. 
         FIG. 1A  is an isometric view of a cutting tool for a material-removal system according to an embodiment; 
         FIG. 1B  is a cross-sectional view of the cutting tool of  FIG. 1A ; 
         FIG. 2  is a cross-sectional view of a cutting tool for a material-removal system according to another embodiment; 
         FIG. 3  is a cross-sectional view of a cutting tool for a material-removal system according to yet another embodiment; 
         FIG. 4  is a top view of a cutting tool for a material-removal system according to one or more embodiments; 
         FIG. 5  is a top view of a cutting tool for a material-removal system according to one or more additional or alternative embodiments; 
         FIG. 6  is an isometric view of a cutting element for a cutting tool according to an embodiment; 
         FIG. 7  is a cross-sectional view of a cutting element for a cutting tool according to another embodiment; 
         FIG. 8  is an cross-sectional view of a cutting element for a cutting tool according to yet another embodiment; 
         FIG. 9A  is an isometric view of a cutting element for a cutting tool according to one other embodiment; 
         FIG. 9B  is a cross-sectional view of the cutting element of  FIG. 9A ; 
         FIG. 10  is a schematic isometric view of a material-removal system according to an embodiment; 
         FIG. 11  is an isometric view of a cutting tool attached to a tool holder according to an embodiment; 
         FIG. 12  is an isometric view of a long-wall material-removal system according to at least one embodiment; and 
         FIG. 13  is an isometric view of a material-removal system that include a cutter head that may rotate about rotation axis and/or move linearly along a vertical axis according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments described herein relate to material-removal systems and cutting tools that may be used in the material-removal systems. For example, the material-removal systems and, particularly, the cutting tools thereof may engage and fail target material. In some instances, the material-removal systems may be used in mining operations, such as to cut and mine Trona. In other words, For example, the material-removal system may fail and remove or recover the failed target material (e.g., Trona or other material). 
     Generally, the material-removal systems may include a rotatable cutting head and a plurality of cutting tools attached to the cutting head. Moreover, in an embodiment, at least some of the cutting tools may include superhard material. For example, the superhard material may form or define at least a portion of a working surface and/or at least a portion of a cutting end of the cutting tool. In particular, the working surface and/or the cutting end of the cutting tool may engage the target material (e.g., by plunging and/or cutting, and/or otherwise entering into and/or contacting the target material) and may fail the target material as the cutting head of the material-removal system rotates and/or advances into the target material. 
       FIGS. 1A-1B  illustrate a cutting tool  100  according to an embodiment. For example, the cutting tool  100  may include a tool body  110  (partially shown) and cutting element  120  attached to the tool body  110 . Generally, the cutting element  120  may be attached to the tool body  110  in any number of suitable ways and with any number of suitable mechanisms. More specifically, examples of attaching the cutting element  120  to the tool body  110  include brazing, press-fitting, fastening, combinations thereof, or the like. 
     In some embodiments, the cutting element  120  may include a substrate  121  and a superhard table  122  bonded to the substrate  121 . For example, the substrate  121  may include cemented carbide, and the superhard table  122  may include polycrystalline diamond, as described below in more detail. Also, in one or more embodiments, the superhard table  122  may be bonded directly to the tool body  110 , which in some instances may include cemented carbide. In any event, the superhard table  122  may include at least a portion of a working surface  130 . 
     As described below in more detail, particular cutting element size, shape, configuration, or combinations thereof may vary from one embodiment to the next. In an embodiment, the cutting element  120  may have a 13 mm diameter and may be 13 mm thick. Alternatively, the cutting element  120  may be thicker or thinner than 13 mm. Likewise, in some instances, the cutting element  120  may have a diameter greater or less than 13 mm. In any event, the cutting element  120  may have a sufficient diameter and/or thickness to withstand operating conditions of the cutting tool  100 . For example, a ratio of a width or diameter of the cutting element  120  to a thickness or height of the cutting element  120  may be at least one 1, greater than 1, about 1.2 to about 1.4, or about 1.0 to about 1.5. 
     In an embodiment, the superhard table  122  may include polycrystalline diamond and the substrate may comprise cobalt-cemented tungsten carbide. Furthermore, in any of the embodiments disclosed herein, the polycrystalline diamond table may be leached to at least partially remove or substantially completely remove a metal-solvent catalyst (e.g., cobalt, iron, nickel, or alloys thereof) that was used to initially sinter precursor diamond particles to form the polycrystalline diamond. In another embodiment, an infiltrant used to re-infiltrate a preformed leached polycrystalline diamond table may be leached or otherwise have a metallic infiltrant removed to a selected depth from a working surface. Moreover, in any of the embodiments disclosed herein, the polycrystalline diamond may be un-leached and include a metal-solvent catalyst (e.g., cobalt, iron, nickel, or alloys thereof) that was used to initially sinter the precursor diamond particles that form the polycrystalline diamond and/or an infiltrant used to re-infiltrate a preformed leached polycrystalline diamond table. Examples of methods for fabricating the superhard tables and superhard materials and/or structures from which the superhard tables and elements may be made are disclosed in U.S. Pat. Nos. 7,866,418; 7,998,573; 8,034,136; and 8,236,074; the disclosure of each of the foregoing patents is incorporated herein, in its entirety, by this reference. 
     The diamond particles that may be used to fabricate the superhard table in a high-pressure/high-temperature process (“HPHT)” may exhibit a larger size and at least one relatively smaller size. As used herein, the phrases “relatively larger” and “relatively smaller” refer to particle sizes (by any suitable method) that differ by at least a factor of two (e.g., 30 μm and 15 μm). According to various embodiments, the diamond particles may include a portion exhibiting a relatively larger size (e.g., 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm, 15 μm, 12 μm, 10 μm, 8 μm) and another portion exhibiting at least one relatively smaller size (e.g., 15 μm, 12 μm, 10 μm, 8 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.5 μm, less than 0.5 μm, 0.1 μm, less than 0.1 μm). In an embodiment, the diamond particles may include a portion exhibiting a relatively larger size between about 10 μm and about 40 μm and another portion exhibiting a relatively smaller size between about 1 μm and 4 μm. In another embodiment, the diamond particles may include a portion exhibiting the relatively larger size between about 15 μm and about 50 μm and another portion exhibiting the relatively smaller size between about 5 μm and about 15 μm. In another embodiment, the relatively larger size diamond particles may have a ratio to the relatively smaller size diamond particles of at least 1.5. In some embodiments, the diamond particles may comprise three or more different sizes (e.g., one relatively larger size and two or more relatively smaller sizes), without limitation. The resulting polycrystalline diamond formed from HPHT sintering the aforementioned diamond particles may also exhibit the same or similar diamond grain size distributions and/or sizes as the aforementioned diamond particle distributions and particle sizes. Additionally, in any of the embodiments disclosed herein, the superhard cutting elements may be free-standing (e.g., substrateless) and/or formed from a polycrystalline diamond body that is at least partially or fully leached to remove a metal-solvent catalyst initially used to sinter the polycrystalline diamond body. 
     As noted above, the superhard table  122  may be bonded to the substrate  121 . For example, the superhard table  122  comprising polycrystalline diamond may be at least partially leached and bonded to the substrate  121  with an infiltrant exhibiting a selected viscosity, as described in U.S. patent application Ser. No. 13/275,372, entitled “Polycrystalline Diamond Compacts, Related Products, And Methods Of Manufacture,” the entire disclosure of which is incorporated herein by this reference. In an embodiment, an at least partially leached polycrystalline diamond table may be fabricated by subjecting a plurality of diamond particles (e.g., diamond particles having an average particle size between 0.5 μm to about 150 μm) to an HPHT sintering process in the presence of a catalyst, such as cobalt, nickel, iron, or an alloy of any of the preceding metals to facilitate intergrowth between the diamond particles and form a polycrystalline diamond table comprising bonded diamond grains defining interstitial regions having the catalyst disposed within at least a portion of the interstitial regions. The as-sintered polycrystalline diamond table may be leached by immersion in an acid or subjected to another suitable process to remove at least a portion of the catalyst from the interstitial regions of the polycrystalline diamond table, as described above. The at least partially leached polycrystalline diamond table includes a plurality of interstitial regions that were previously occupied by a catalyst and form a network of at least partially interconnected pores. In an embodiment, the sintered diamond grains of the at least partially leached polycrystalline diamond table may exhibit an average grain size of about 20 μm or less. Subsequent to leaching the polycrystalline diamond table, the at least partially leached polycrystalline diamond table may be bonded to a substrate in an HPHT process via an infiltrant with a selected viscosity. For example, an infiltrant may be selected that exhibits a viscosity that is less than a viscosity typically exhibited by a cobalt cementing constituent of typical cobalt-cemented tungsten carbide substrates (e.g., 8% cobalt-cemented tungsten carbide to 13% cobalt-cemented tungsten carbide). 
     Additionally or alternatively, the superhard table  122  may be a polycrystalline diamond table that has a thermally-stable region, having at least one low-carbon-solubility material disposed interstitially between bonded diamond grains thereof, as further described in U.S. patent application Ser. No. 13/027,954, entitled “Polycrystalline Diamond Compact Including A Polycrystalline Diamond Table With A Thermally-Stable Region Having At Least One Low-Carbon-Solubility Material And Applications Therefor,” the entire disclosure of which is incorporated herein by this reference. The low-carbon-solubility material may exhibit a melting temperature of about 1300° C. or less and a bulk modulus at 20° C. of less than about 150 GPa. The low-carbon-solubility, in combination with the high diamond-to-diamond bond density of the diamond grains, may enable the low-carbon-solubility material to be extruded between the diamond grains and out of the polycrystalline diamond table before causing the polycrystalline diamond table to fail during operations due to interstitial-stress-related fracture. 
     In some embodiments, the polycrystalline diamond, which may form the superhard table, may include bonded-together diamond grains having aluminum carbide disposed interstitially between the bonded-together diamond grains, as further described in U.S. patent application Ser. No. 13/100,388, entitled “Polycrystalline Diamond Compact Including A Polycrystalline Diamond Table Containing Aluminum Carbide Therein And Applications Therefor,” the entire disclosure of which is incorporated herein by this reference. 
     In some embodiments, the tool body  110  may include a recess  111  that may accept at least a portion of the cutting element  120  (e.g., at least a portion of the substrate  121  of the cutting element  120  may be positioned within the recess  111 ). Moreover, in some embodiments, the recess  111  may locate and/or orient the cutting element  120  relative to one or more features of the tool body  110  (e.g., relative to one or more surface of the tool body  110 , such as a side surface  112 , front surface  113 , front slanted surface  114 , etc.). As described below in more detail, For example, the recess  111  may orient the cutting element  120  in a manner that the working surface  130  forms one or more rake angles (e.g., a back rake angle and/or a side rake angle). 
     In some embodiments, the recess  111  in the tool body  110  may orient the cutting element  120  in a manner that forms the back and/or side rake of working surface  130 . For example, the working surface  130  may be formed by the superhard table  122  and/or may be generally parallel to a back surface  123  of the substrate  121 . Hence, to form the back rake and/or side rake angles, the recess  111  may orient the substrate  121  in a manner that orients the working surface  130  at a desired or suitable back and/or side rake angles. 
     Additionally or alternatively, in an embodiment, the working surface  130  may lie in a plane that is non-parallel relative to the back surface  123  of the substrate  121 . For example, the superhard table  122  may be cut (e.g., wire EDM cut) or ground at an angle relative to the back surface  123  of the substrate  121  to produce a side and/or back rake angles. However, the side and/or back rake angles produced by orienting the working surface  130  at a non-parallel angle relative to the back surface  123  of the substrate  121  may be smaller or greater than a desired or suitable back and/or side rake angle. Hence, in some embodiments, the recess  111  may provide further orientation and/or location of the working surface  130 , which is non-parallel to the back surface  123  of the substrate  121 , in a manner that the recess  111  orients the working surface  130  to a desired and/or suitable back and/or side rake angles. 
     In an embodiment, a portion of the substrate  121  may be exposed outside of the recess  111  and/or tool body  110 . For example, a top portion of the peripheral surface of the substrate  121  may be exposed and located outside of the tool body  110 . Moreover, in an embodiment, at least part of the top portion of the peripheral surface of the substrate  121  may be, generally, tangent to a back surface  115  of the tool body  110  and/or may form an extension thereof. In other words, the back surface  115  of the tool body  110  may smoothly transition to the exposed portion of the peripheral surface of the substrate  121 . 
     In some embodiments, the exposed portion of the substrate  121  may engage cuttings of the target material. Hence, for example, the exposed portion of the substrate  121  may erode or wear during operation of the cutting tool  100 . Also, in some embodiments, the exposed portion of the substrate  121  may protect or shield at least a portion and/or one or more surfaces of the tool body  110  from wear during operation of the cutting tool  100 . For example, the exposed portion of the substrate  121  may shield one or more portions of the tool body  110  from engagement with target material, which may increase useful life of the tool body  110  and the cutting tool  100 . 
     In an embodiment, the working surface  130  may be substantially planar and/or may have a substantially circular shape (i.e., may be defined by a circular perimeter or boundary). Alternatively, the working surface may be non-planar (e.g., conical, bullet-shaped, etc.). Likewise, the general shape of the cutter element may vary from one embodiment to the next and may be generally cylindrical or non-cylindrical. 
     Also, the cutting tool  100  may include a cutting end  150 . The cutting end  150  may define at least a portion of a perimeter or boundary of the working surface  130 . Generally, in some embodiments, the cutting end  150  may be formed or defined at an edge region, which may be formed by and between two or more surfaces of the cutting element  120 . For example, the cutting end  150  may be formed at an interface between the working surface  130  and a peripheral surface of the cutting element  120 . It should be appreciated, however, that the cutting end may be formed at or include a surface, such as a chamfer, which may extend between two or more surfaces of the cutting element  120 , as described below. 
     The working surface  130  and/or cutting end  150  may engage the target material. For example, the working surface  130  may penetrate into the target material, and movement of the working surface  130  and/or cutting end  150  within and/or against the target material may cut, grind, combinations thereof, or otherwise fail the target material. In some embodiments, the working surface  130  may be oriented at an angle relative to a longitudinal axis  10  ( FIG. 1B ), in a manner that forms a back rake angle θ with the longitudinal axis  10 . The longitudinal axis  10  may be substantially perpendicular to a tangent line  20 , where tangent line  20  is tangent (at an uppermost point of the cutting end  150 ) to a circular path along which the cutting tool  100  moves during rotation thereof. 
     For example, the back rake angle θ may be a negative back rake angle in one or more of the following ranges: about 1 degree to about 5 degrees; about 4 degrees to about 10 degrees; about 8 degrees to 20 degrees (e.g., greater than 17 degrees); and about 15 degrees to 30 degrees. In some embodiments, the back rake angle θ may be less than 1 degree or greater than 30 degrees. Moreover, as shown in  FIGS. 1A-1B , according to an embodiment, the working surface  130  may have a negative back rake angle. Alternatively, however, as described below in more detail, the working surface may have a positive back rake angle (e.g., a back rake angle formed by the working surface  130  rotated clockwise from the longitudinal axis  10  is negative, while the back rake angle formed by the working surface  130  rotated counterclockwise from the longitudinal axis  10  is positive). 
     As described above, in an embodiment, the tool body  110  may include the slanted surface  114 . For example, the slanted surface  114  may be approximately parallel to the working surface  130 . Moreover, the slanted surface  114  may be offset from the working surface  130 . In any event, the working surface  130  and/or the  114  may be oriented in a manner that facilitates movement or flow of the failed target material away from the cutting tool  100 . For example, the failed target material may move or slide along the working surface  130  and away from the cutting end  150 . 
     The tool body  110  may have any suitable shape and/or configuration, which may vary from one embodiment to the next. Generally, the tool body  110  may be configured to be attached to a cutting head of the material-removal system. In one or more embodiments, the tool body  110  may have an elongated portion  116 , which may extend from an attachment portion (not shown) that may secure the cutting tool  100  to the cutting head of the material-removal system. 
     In some embodiments, the elongated portion  116  may have a width  117  that may be similar to or the same as the width or diameter of the cutting element  120 . For example, the peripheral surface of the substrate  121  may not protrude past one or more of the side surfaces of the tool body  110  (e.g., side surface  112 ). Thus, according to an embodiment, matching the width of the cutting element  120  and tool body  110  may reduce drag experienced by the tool body  110  during movement in or through the target material. 
     While, as described above, the working surface  130  may form a negative back rake angle θ, in another embodiment, the working surface  130  may form a positive back rake angle. More specifically,  FIG. 2  illustrates a cutting tool  100   a  according to an embodiment, which includes working surface  130   a  that has a positive back rake angle (p. Except as otherwise described herein, the cutting tool  100   a  and its materials, elements, or components may be similar to or the same as the cutting tool  100  ( FIGS. 1A-1B ) and its corresponding materials, elements, and components. For example, the cutting tool  100   a  may include a cutting element  120   a  that may be attached to a tool body  110   a ; the cutting element  120   a  may be similar to or the same as the cutting element  120  ( FIGS. 1A-1B ). 
     Particularly, in some embodiments, the back rake angle φ may be formed between the working surface  130   a  and a longitudinal axis  10 . The magnitude of the back rake angle φ may be in one or more ranges described above in connection with back rake angle θ ( FIG. 1B ). In any event, the working surface  130   a  may be angled or oriented in a manner that facilitates flow or movement of failed target material away from the working surface  130   a  and/or from a cutting end  150   a.    
     In some instances, the failed target material may move along the working surface  130   a  and toward the tool body  110   a . Furthermore, in an embodiment, the tool body  110  may be configured to channel the failed target material away from the cutting tool  100  (e.g., away from the working surface  130   a  and/or cutting end  150   a ). For example, the tool body  110   a  may include one or more slanted surfaces, such as the slanted surface  114   a , which may guide or channel failed target material away from the cutting tool  100 . In other words, the failed target material may move across the working surface  130   a  and onto a portion of the tool body  110  (e.g., the slanted surface  114   a ), which may further guide or channel the failed target material away from the cutting tool  100   a.    
     In one or more embodiments, the slanted surface  114   a  may be oriented at a non-parallel angle relative to the longitudinal axis  10  (i.e., the slanted surface  114   a  may be oriented at an obtuse or an acute angle relative to the longitudinal axis  10 ). Additionally or alternatively, the slanted surface  114   a  may have a non-parallel orientation relative to the working surface  130   a . For example, the slanted surface  114   a  of the tool body  110   a  may be oriented at a non-parallel angle relative to the working surface  130   a.    
     As described above, in some embodiments, the cutting element  120   a  may include a superhard table  122   a  bonded to a substrate  121   a . Moreover, a portion of the substrate  121   a  may be exposed outside of the tool body  110   a . For example, an upper portion of the peripheral surface of the substrate  121   a  may be exposed outside of the tool body  110   a . In an embodiment, the exposed portion of the peripheral surface of the substrate  121   a  may extend from a back surface  115   a  of the tool body  110   a . Furthermore, in some instances, the back surface  115   a  of the tool body  110   a  may smoothly transition to the exposed portion of the peripheral of the substrate  121   a.    
     Alternatively, in an embodiment, the back surface  115   a  of the tool body  110   a  may have a non-smooth transition (e.g., angled, stepped, uneven, etc.) between a back surface of the tool body and the exposed portion of the peripheral surface of the substrate.  FIG. 3  illustrates a cutting tool  100   b , which includes such a transition between back surface  115   b  of the tool body  110   b  and upper portion  124   b  of the peripheral surface  121   b , according to an embodiment. Except as otherwise described herein, the cutting tool  100   b  and its materials, elements, or components may be similar to or the same as any of the cutting tools  100 ,  100   a  ( FIGS. 1A-2 ) and their corresponding materials, elements, and components. For example, the cutting tool  100   b  may include a tool body  110   b  that may be similar to or the same as the tool body  110  ( FIGS. 1A-1B ). 
     In an embodiment, the cutting tool  100   b  may include a cutting element  120   b  secured to the tool body  110   b . The cutting element  120   b  may include a superhard table  122   b  bonded to a substrate  121   b . Moreover, in some examples, the cutting element  120   b  may be attached in a recess  111   b  of the tool body  110   b  (e.g., the substrate  121   b  of the cutting element  120  may be at least partially positioned within the recess  111   b ). As described above, at least a portion of the substrate  121   b  may be exposed out of the tool body  110   b . In particular, for example, an upper portion  124   b  of the peripheral surface of the substrate  121   b  may be exposed outside of the tool body  110   b.    
     In an embodiment, the upper portion  124   b  of the peripheral surface of substrate  121   b  may be tapered in a manner that forms a non-parallel angle α (e.g., acute or obtuse angle) with a working surface  130   b  of the cutting tool  100   b  (e.g., with the working surface  130   b  formed by the superhard table  122   b ). In an embodiment, at least a portion of the peripheral surface of the substrate  121   b  may have a tapered shape (e.g., a partially or completely conical shape). Also, For example, working surface  130   b  may form the angle α with a reference line  15 , which may be substantially parallel to the cross-section of the peripheral surface of the substrate  121   b  at an uppermost location of the upper portion  124   b  thereof. 
     Tapering the upper portion  124   b  of the peripheral surface of the substrate  121   b  may facilitate clearance between the substrate  121   b  and the target material. Likewise, the taper of the upper portion  124   b  may provide clearance for failed material that may be between a new surface (formed after failing and/or removing target material) and the substrate  121   b . Thus, in some embodiments, tapered upper portion  124   b  of the substrate  121   b  may increase useful life of the cutting tool  100   b.    
     Generally, the angle α may vary from one embodiment to the next. In some embodiments, the angle α may be in one or more of the following ranges: about 15 degrees to 30 degrees; about 20 degrees to 45 degrees; about 40 degrees to 70 degrees; and about 50 degrees to 89 degrees. It should be appreciated that, in some embodiments, the angle α may be less than 15 degrees or greater than 89 degrees. 
     In some instances, the upper portion  124   b  of the substrate  121   b  may resemble and/or may define a chamfer. Moreover, the taper of the upper portion  124   b  of the substrate  121   b  may extend from a back surface  123   b  of the substrate  121   b  to an interface  125   b  between the substrate  121   b  and the superhard table  122   b . Alternatively, the taper of the upper portion  124   b  may extend only part of the distance between the back surface  123   b  and the interface  125   b.    
     For example, the taper may start and extend from the back surface  123   b  and terminate at a distance less than the distance between the back surface  123   b  and the interface  125   b  (e.g., the upper portion may include a step between the tapered portion and a non-tapered portion, which may extend from the tapered portion to the interface). Alternatively or additionally, a taper of the upper portion may extend from the interface and may terminate at a distance that is less than the distance between the interface  123   b  and the back surface  125   b.    
     Furthermore, as described above, the cutting tool  100   b  may include a step or other discontinuity between a back surface  115   b  of the tool body  110   b  and the peripheral surface of the substrate  121   b  (e.g., the upper portion  124   b  of the peripheral surface). More generally, the portion of the peripheral surface of the substrate  121   b  extending from the back surface  115   b  may be incongruous with the adjacent portion of the back surface  115   b . Accordingly, in some embodiments, the failed material that flows or moves along the upper portion  124   b  of the peripheral surface of the substrate  121   b  may change direction of movement as the material encounters the back surface  115   b  and may further move away from the substrate  121   b.    
     In one or more embodiments, at least a portion of the peripheral surface of the superhard table  122   b  also may include a taper. For example, the taper of the peripheral surface of the superhard table  122   b  may generally form a continuation or extension of the taper formed on the upper portion  124   b  of the peripheral surface of the substrate  121  (i.e., the taper may form an angle with the working surface  130   b ). Hence, in some instances, the taper angle of the peripheral surface of the superhard table  122   b  may be in one or more ranges described above in connection with angle α. Also, in an embodiment, the taper of the peripheral surface of the superhard table  122   b  may be different from the taper of the peripheral surface of the substrate  121   b.    
     In other embodiments, the substrate and/or superhard table may be tapered in a variety of other manners than those illustrated. For example, U.S. Pat. No. 5,881,830, which is incorporated herein in its entirety by this reference, discloses a variety of tapering geometries that may be employed in other embodiments. 
     As mentioned above, the working surface may be oriented in a manner that forms a side rake angle during operation of the cutting tool.  FIG. 4  illustrates a cutting tool  100   c  that includes a working surface  130   c , which forms a side rake angle λ, according to an embodiment. Except as otherwise described herein, the cutting tool  100   c  and its materials, elements, or components may be similar to or the same as any of the cutting tools  100 ,  100   a , or  100   b  ( FIGS. 1A-3 ) and their corresponding materials, elements, and components. For example, the cutting tool  100   c  may include a tool body  110   c  that may be similar to or the same as the tool body  110  ( FIGS. 1A-1B ). In some embodiments, the cutting tool  100   c  may include a cutting element  120   c , which may have a superhard table  122   c  bonded to a substrate  121   c . Moreover, the superhard table  122   c  includes at least a portion of the working surface  130   c . The cutting element  120   c  may be attached to the tool body  110   c.    
     In an embodiment, the side rake angle λ may be formed between the working surface  130   c  and a reference line  25 , which may be perpendicular to a path or direction of movement of the cutting tool  100   c  during operation thereof. For example, the reference line  25  may be an imaginary line extending between a rotation axis of the cutting head to which the cutting tool  100   c  is attached and a nearest point of working surface  130   c  wherein the imaginary line is substantially perpendicular to a rotation axis of the cutting head to which the cutting tool  100   c  is attached (e.g., as shown in  FIG. 10 , the reference line  25  may be perpendicular to a tangent line  30 , which may be tangent to a radial path of the cutting tool rotating together with the cutter head). Generally, the side rake angle λ may vary from one embodiment to the next. For example, the side rake angle λ may be in one or more ranges described above in connection with back rake angle θ ( FIG. 1A ). Moreover, it should be appreciated that in addition to the side rake angle λ, the working surface  130   c  may be oriented at a back rake angle. 
     As noted above, the working surface  130   c  may be oriented relative to the tool body  110   c  at a desired or suitable side rake angle λ and/or back rake angle by orienting the working surface  130   c  at such angle relative to a back surface  123   c  of the substrate  121   c  or by orienting the pocket in which the cutting element is disposed. In an embodiment, a portion of the superhard table  122   c  may be thinner than another portion of the superhard table  122   c . In particular, in some embodiments, the superhard table  122   c  may be a tapered (e.g., one side of the superhard table  122   c  may be thinner than another side of the superhard table  122   c ) in a manner that forms a suitable or desired angle between the working surface  130   c  and the back surface  123   c . Moreover, the angle formed between the working surface  130   c  and the back surface  123   c  may be the same as the side rake angle λ and/or the back rake angle θ (described above). Thus, in some embodiments, the working surface  130   c  and the back surface  123   c  may exhibit selected angles with respect to different cross-sectional views taken through cutting element  120   c.    
     Alternatively, the back rake angle and/or the side rake angle may be formed by orienting the cutting element relative to the tool body.  FIG. 5  illustrates a cutting tool  100   d  according to an embodiment, which includes such configuration. Except as otherwise described herein, the cutting tool  100   d  and its materials, elements, or components may be similar to or the same as any of the cutting tools  100 ,  100   a ,  100   b , or  100   c  ( FIGS. 1A-4 ) and their corresponding materials, elements, and components. For example, the cutting tool  100   d  may include a tool body  110   d  that may be similar to or the same as the tool body  110  ( FIGS. 1A-1B ). 
     In some embodiments, the cutting tool  100   d  may include a working surface  130   d  that is substantially parallel to a back surface  123   d  of a cutting element  120   d . For example, the cutting element  120   d  may be attached to the tool body  110   d  of the cutting tool  100   d  and may provide the working surface  130   d  at a desired or suitable side and/or back rake angle. Furthermore, the cutting element  120   d  may include a substrate  121   d  and a superhard table  122   d  bonded to the substrate  121   d , and the substrate  121   d  may include the back surface  123   d.    
     In an embodiment, the back surface  123   d  may abut or contact a surface  118   d  of the tool body  110   d . For example, the cutting element  120   d  may be secured in a recess (as described above), and the back surface  123   d  of the substrate  121   d  may be positioned and/or oriented by the surface  118   d  of the tool body  110   d , which define a portion of the recess of the tool body  110   d . Moreover, in some embodiments, the back surface  123   d  may be attached to the surface  118   d  of the tool body  110   d  (e.g., by brazing, etc.). In any event, in some embodiments, the surface  118   d  of the tool body  110   d  may position and/or orient the back surface  123   d . Thus, according to an embodiment, the surface  118   d  of the tool body  110   d  may orient the working surface  130   d  at a suitable side rake angle and/or at a back rake angle. More specifically, in some embodiments, the superhard table  122   d  may have an approximately uniform thickness and/or the working surface  130   d  may be substantially parallel to the back surface  123   d , and the surface  118   d  may orient the working surface  130   d  at a suitable side and/or back rake angle(s). 
     Generally, in some embodiments, the cutting element may include a cutting end that may be formed by and between the peripheral surface of the superhard table and the working surface. In other words, the cutting end of the cutting element may be a substantially sharp corner between the working surface and the peripheral surface of the superhard table, which may facilitate penetration of the cutting element into the target material. In additional or alternative embodiments, the cutting element may include one or more chamfers that may at least partially surround the working surface, which may improve impact resistance or durability of the superhard table or cutting edge.  FIG. 6  illustrates a cutting element  120   e  that includes a chamfer  126   e  that surrounds a working surface  130   e , according to an embodiment. 
     Except as otherwise described herein, the cutting element  120   e  and its materials, elements, or components may be similar to or the same as any of the cutting elements  120 ,  120   a ,  120   b ,  120   c , or  120   d  ( FIGS. 1A-5 ) and their corresponding materials, elements, and components. For example, cutting element  120   e  may include a substrate  121   e  and a superhard table  122   e  that may be bonded to the substrate  121   e ; the substrate  121   e  and/or the superhard table  122   e  may be similar to the substrate  121  and superhard table  122  of the cutting element  120  ( FIGS. 1A-1B ). The cutting element  120   e  may include a cutting end  150   e  that may be defined or formed by: the chamfer  126   e ; an edge between the working surface  130   e  and the chamfer  126   e ; an edge between the chamfer  126   e  and superhard table  122   e ; or at least a portion of one or more of the foregoing. Accordingly, in some instances, the cutting end  150   e  may include at least a portion of an edge or corner and/or may include at least a portion of a surface (e.g., the surface formed by the chamfer  126   e ). 
     Also, under some operating conditions, the chamfer  126   e  may improve impact resistance or durability of the superhard table  122   e  and/or of the cutting end  150   e  (as compared with the cutting end formed at a sharp corner between the peripheral surface of the superhard table and the working surface). Furthermore, it should be appreciated that the size and/or orientation of the chamfer  126   e  may vary from one embodiment to the next. In some embodiments, the sharp edge between the working surface  130   e  and the peripheral surface of the superhard table  122   e  may be broken to form a relatively small chamfer  126   e  or radius (e.g., chamfer or radius of 0.001 inch, 0.005 inch, etc.). The chamfer  126   e , however, may be larger if desired. For example, the chamfer  126   e  may be 0.05 inches, 0.10 inches, 0.15 inches, 0.020 inches, 0.030 inches, etc. Moreover, in some embodiments, the chamfer  126   e  may be larger than 0.05 inches. 
     In an embodiment, the working surface  130   e  may have an approximately circular shape. Consequently, the chamfer  126   e  also may have an approximately conical geometry (i.e., the chamfer  126   e  may encircle the working surface  130   e  and may define the shape and size of the working surface  130   e ). It should be appreciated, however, that a particular shape and/or size of the working surface  130   e  may vary from one embodiment to the next, as described below in further detail. 
     In some embodiments, working surface  130   e  may be substantially planar. Further, in some instances, the superhard table  122   e  may be bonded to the substrate  121   e  over a substantially planar interface  125   e . In an embodiment, however, the superhard table may be bonded to the substrate over a nonplanar interface.  FIG. 7  illustrates a cutting element  120   f  according to one or more alternative or additional embodiments. More specifically, in some examples, the cutting element  120   f  may include a superhard table  122   f  bonded to a substrate  121   f  over a nonplanar interface  125   f . Except as otherwise described herein, the cutting element  120   f  and its materials, elements, or components may be similar to or the same as any of the cutting elements  120 ,  120   a ,  120   b ,  120   c ,  120   d ,  120   e  ( FIGS. 1A-6 ) and their corresponding materials, elements, and components. 
     According to an embodiment, the interface  125   f  may include multiple corresponding and/or complementary grooves formed on the substrate  121   f  and superhard table  122   f . In alternative or additional embodiments, a nonplanar interface between the superhard table the substrate may include any number of features, which may be complementary with one another, such that a feature protruding from the substrate may enter a recess in the superhard table and vice versa. In any event, in an embodiment, a nonplanar interface between the substrate a superhard table may improve impact resistance or durability of the cutting element (as compared with a cutting element that has a planar interface between the superhard table and the substrate). 
     As described above, in some embodiments, a cutting element may include a working surface that is oriented at a nonparallel angle relative to a back surface of the cutting element.  FIG. 8  illustrates a cutting element  120   g  that includes a working surface  130   g  that is oriented at a nonparallel angle relative to the back surface  123   g , according to an embodiment. Except as otherwise described herein, the cutting element  120   g  and its materials, elements, or components may be similar to or the same as any of the cutting elements  120 ,  120   a ,  120   b ,  120   c ,  120   d ,  120   e ,  120   f  ( FIGS. 1A-7 ) and their corresponding materials, elements, and components. For example, the cutting element  120   g  may include a superhard table  122   g  bonded to a substrate  121   g , which may be similar to substrate  121  and superhard table  122  ( FIGS. 1A-1B ). 
     According to an embodiment, the cutting element  120   g  includes the working surface  130   g  that forms an angle β with the back surface  123   g . More specifically, the angle β may form, at least to some extent, the side rake and/or back rake angle, as described above. Accordingly, in some embodiment, the cutting element  120   g  may be formed in a manner that predefines the side and/or back rake angles, depending on the orientation of the cutting element  120   g  (e.g., in addition to or in lieu of such angles being defined by the tool body). 
     Also, in some embodiments, the cutting element may have non-circular working surface.  FIGS. 9A-9B  illustrate a cutting element  120   h  that includes a working surface  130   h , which may have an approximately or generally trapezoidal shape, according to an embodiment. Except as otherwise described herein, the cutting element  120   h  and its materials, elements, or components may be similar to or the same as any of the cutting elements  120 ,  120   a ,  120   b ,  120   c ,  120   d ,  120   e ,  120   g , or  120   h  ( FIGS. 1A-8 ) and their corresponding materials, elements, and components. For example, the cutting element  120   h  may include a superhard table  122   h  bonded to a substrate  121   h , which may be similar to the respective substrate  121  and superhard table  122  of the cutting element  100  ( FIGS. 1A-1B ). 
     In some embodiments, the working surface  130   h  may be bounded by one or more fillets or radii  126   h ,  127   h ,  128   h , which may extend from the working surface  130   h  to a periphery of the superhard table  122   h  (e.g., to a peripheral surface of the superhard table  122   h ). As such, the radii  126   h ,  127   h ,  128   h  may define an approximately trapezoidal shape of the working surface  130   h . For example, the radii  126   h  may define two opposing, sides of the trapezoidal shape of the working surface  130   h . Additionally, the radii  126   h  and  128  may define two opposing sides of the trapezoidal shape of the working surface  130   h.    
     Also, the cutting element  120   h  may include a cutting end  150   h  (e.g., the cutting end  150   h  may be formed by the radius  128   h ). It should be appreciated that the cutting element  120   h  may have a sharp corner or edge instead of the radius  128   h . Accordingly, embodiments may include the cutting end  150   h  that is formed by a sharp corner, a chamfer, a radius, or combinations thereof. Moreover, in lieu of any of the radii  126   h ,  127   h ,  128   h  the cutting element  120   h  may include a shape edge. 
     The cutting element  120   h  may include one or more slanted surfaces, such as slanted surfaces  129   h . For example, the slanted surfaces  129   h  may pass through an otherwise cylindrical shape of the cutting element  120   h . Moreover, the slanted surfaces  129   h  may be included on a portion of the substrate  121   h  and/or of the superhard table  122   h.    
     In the illustrated embodiment, one or more of the slanted surfaces  129   h  may include a protective coating  141   h  that may protect the slanted surfaces  129   h  from wear and/or damage during operation of the cutting tool. In other words, as the cutting element  120   h  engages the target material, the slanted surfaces  129   h  may contact the target material as well as the failed target material, which may wear or damage the slanted surfaces  129   h  in a manner that reduces the useful life of the cutting element  120   h . Accordingly, protecting the slanted surfaces  129   h  from wear and/or damage may increase the useful life of the cutting element  120   h . For example, the protective coating  141   h  may comprise titanium nitride (TiN), titanium aluminum nitride (TiAlN), chemical vapor deposited diamond, binderless tungsten carbide, similar coatings, or combinations thereof. In an embodiment, the binderless tungsten carbide layer may be formed by chemical vapor deposition (“CVD”) or variants thereof (e.g., plasma-enhanced CVD, etc., without limitation). An example of a commercially available CVD tungsten carbide layer (currently marketed under the trademark HARDIDE®) is currently available from Hardide Layers Inc. of Houston, Tex. In other embodiments, a tungsten carbide layer may be formed by physical vapor deposition (“PVD”), variants of PVD, high-velocity oxygen fuel (“HVOF”) thermal spray processes, or any other suitable process, without limitation. However, in other embodiments, the one or more protective coating  141   h  may be omitted and the substrate  121   h  may be exposed. 
     In an embodiment, the cutting element  120   h  may include a substantially planar interface  125   h  between the superhard table  122   h  and the substrate  121   h . For example, the interface  125   h  may extend between the opposing slanted surfaces  129   h  ( FIG. 9B ). Hence, the superhard table  122   h  may extend between the uppermost edges of the slanted surfaces  129   h.    
     It should be appreciated that any of the cutting tools described herein may include any of the cutting elements described herein. Moreover, any of the cutting elements may include one or more features or elements described herein in connection with any other cutting element. Also, as described above, any of the cutting tools described herein may be attached to a cutting head of a material-removal system. 
       FIG. 10  illustrates a material-removal system  200  according to an embodiment. More specifically, the material-removal system  200  may include a cutting head  210  that is rotatable about a rotation axis  35 . Furthermore, the cutting head  210  includes a plurality cutting tools secured thereto. Specific arrangement of the cutting tools on the cutting head  210  may vary from one embodiment to the next. For example, the cutting head  210  may include cutting tools  100   j - q  secured thereto. 
     For example, as shown in  FIG. 11 , the cutting tool  100   j  may be mounted on and/or attached to a holder  220 . Generally, except as otherwise described herein, the cutting tool  100   j  and its materials, elements, or components may be similar to or the same as any of the cutting tools  100 ,  100   a ,  100   b ,  100   c ,  100   d  ( FIGS. 1A-5 ) and their corresponding materials, elements, and components. In an embodiment, the cutting tool  110   j  may include a tool body  110   j  that has an elongated portion  116   j  projecting outward from a base portion  117   j . For example, the tool body  110   j  and/or the elongated portion  116   j  may be similar to or the same as the tool bodies and/or elongated portions or elongated regions described in U.S. patent application Ser. No. 14/266,437, entitled “Cutting Tool Assemblies Including Superhard Working Surfaces, Material-Removing Machines Including Cutting Tool Assemblies, And Methods Of Use,” filed on Apr. 30, 2014. In some embodiments, the tool body  110   j  may be similar to or the same as pick bodies described in U.S. patent application Ser. No. 14/275,574, entitled “Shear Cutter Pick Milling System,” filed on May 12, 2014. Furthermore, in at least one embodiment, the tool body  110   j  may be similar to or the same as pick bodies described in U.S. patent application Ser. No. 14/273,360, entitled “Road-Removal System Employing Polycrystalline Diamond Compacts,” filed on May 8, 2014. Each of the foregoing U.S. Patent Applications is incorporated herein in its entirety by this reference. 
     Referring back to  FIG. 10 , in some examples, the cutting head  210  may include multiple holders  220  that may secure the cutting tools  100   j - q . The holders  220  may be attached to or integrated with the cutting head  210 . In any event, in an embodiment, the cutting tools  100   j - q  may be attached to the cutting head  210  and may rotate together therewith about the rotation axis  35 . Additionally, as described above, as the cutting head  210  rotates and advances toward and/or into the target material, the cutting tools  100   j - q  may also advance toward and/or into the target material, thereby cutting into and/or failing the target material (as the cutting head  210  rotates). 
     In an embodiment, the cutting tools  100   j - q  may include corresponding working faces that may generally face in the direction of rotation of the cutting head  210  and cutting tools  100   j - q  (as indicated by the arrow). Hence, the working surfaces and/or cutting ends of the cutting tools  100   j - q  may engage and fail the target material as the cutting head  210  rotates about the rotation axis  35 . Moreover, as described above, the working surface may have back and/or side rake angles. 
     For example, the side rake angles of one, some, or all of the cutting tools  100   j - q  may open toward the rotation axis  35  or away therefrom. In other words, in some embodiments, at least some of the working faces may have a side rake angle that faces toward the rotation axis  35 , such that the portion of the working face that is farthest from an imaginary radius line is closer to the rotation axis  35  than the portion of the working surface that is closest to an imaginary radius line. Conversely, in an embodiment, at least some of the working faces may have a side rake angle that faces away from the rotation axis  35 , such that the portion of the working face that is closest to an imaginary radius line is closer to the rotation axis  35  than the portion of the working surface that is farthest from the imaginary radius line 
     In some embodiments, two or more of the cutting tools  100   j - k  may have different positions or locations one from another relative to the rotation axis  35 . In other words, two or more of the cutting tools  100   j - k  may have different radial spacing one from another. For example, the cutting tools  100   j  may be spaced farther away from the rotation axis  35  than cutting tools  100   k - q.    
     In an embodiment, the cutting tools  100   j - q  may be the same or substantially the same (e.g., the cutting tools  100   j - q  may include the same or similar cutting elements). Alternatively, one or more of the cutting tools  100   j - q  may be different from other cutting tools  100   j - q . In one or more embodiments, the cutting tools  100   j - k  may vary depending on their respective radial position relative to the rotation axis  35 . 
     For example, the cutting tools located closer to the rotation axis  35  may have a larger side and/or back rake angle than the cutting tools located farther from the rotation axis  35 . For example, the side and/or back rake angles of the working surfaces may increase as the distance from the rotation axis of the cutting tool decreases (i.e., as the radial path of the cutting tool in operation decreases). More specifically, in an embodiment, the cutting tools  100   q  may include working surface that have larger side rake angles than the working surfaces of the cutting tools  100   j , which may be located at a position that is farther away from the rotation axis  35  than the cutting tools  100   q.    
     In one or more embodiments, impact resistance of the cutting elements of the cutting tools  100   j - q  may vary with distance from the rotation axis  35 . More specifically, in an embodiment, the cutting tools located closer to the rotation axis  35  may have cutting elements that have greater impact resistance than the cutting tools that are located farther away from the rotation axis  35 . For example, the cutting tools  100   q  may include cutting elements that have a higher impact resistance that cutting elements of the cutting tools  100   j.    
     As described above, the cutting elements that include a chamfer that forms a cutting end, and which at least partially surrounds the working surface may have an increased impact resistance (as compared with cutting elements that have a sharp edge in lieu of a chamfer). Also, cutting elements that have a nonplanar interface between the substrate and superhard table may have increased impact resistance (as compared with cutting elements that have a planar interface). Accordingly, in some embodiments, some of the cutting tools located closer to the rotation axis  35  may include cutting elements that include a chamfer and/or a nonplanar interface (superhard table to substrate interface), while some of the cutting tools located farther from the rotation axis  35  may include cutting elements that do have a sharp edge (in lieu of a chamfer) and/or planar substrate to superhard table interface. 
     For example, one, some, or all of the cutting tools  100   q  may include cutting elements that have a chamfer and/or nonplanar interface. Additionally, for example, one, some, or all of the cutting tools  100   j  may include cutting elements that have a sharp edge (in lieu of a chamfer) and/or planar substrate to superhard table interface. Moreover, in some embodiments, sizes of chamfers may vary with distance of the cutting tools from the rotation axis  35 . In an example, the closer the cutting tool to the rotation axis  35 , the larger may be the chamfer included on the cutting element (e.g., the cutting tools  100   j  may have a chamfer of about 0.01 inch, while the cutting tools  100   q  may have a chamfer of about 0.10 inch). It should be also appreciated that impact resistance of the cutting elements may be varied by varying diamond grain size of the polycrystalline diamond superhard table (e.g., cutting tools closer to the rotation axis  35  may have diamond tables with smaller grain size, and cutting tools farther away from the rotation axis  35  may have diamond tables with larger grain size). 
     While in some embodiments the material-removal system may include a bore mining head or bore mining machine, which may bore into the target material, the present disclosure is not so limited. Specifically, for example, the material-removal system may be a long-wall material-removal system, such as a chain system, drum system, plow system, etc., that may move along a wall and may remove the target material therefrom during such movement.  FIG. 12  illustrates a long-wall material-removal system  200   a  according to at least one embodiment. Except as otherwise described herein, the material-removal system  200   a  and its materials, elements, or components may be similar to or the same as the material-removal system  200  ( FIG. 10 ) and its corresponding materials, elements, and components. Furthermore, the material-removal system  200   a  may include any cutting tool and/or combination of the cutting tools described herein. 
     In an embodiment, the material-removal system  200   a  may include multiple cutting tools  100   r  (not all labeled) mounted to a cutting head  210   a . For example, the cutting head  210   a  may be advanced linearly and the cutting tools  100   r  may engage, cut, scrape, or otherwise fails and/or remove target material during advancement of the cutter head  210   a . In at least one embodiment, the cutter head  210   a  may be slideably or movably mounted on an elongated support member  220   a  and may be advance generally linearly along the elongated support member  220   a  (e.g., in first and/or second directions, as indicated with arrows). In some embodiments, the material-removal machine  200   a  may include a chain  230   a  (or a similar movable attachment), which may be connected to the cutter head  210   a  and to an advancement mechanism, such as a motor. In an embodiment, the chain  230   a  may advance the cutter head  210   a  in the first and/or second directions, thereby engaging the target material with the cutting tools  100   r  and removing the target material. 
     In some embodiments, the cutting tools  100   r  may include corresponding working surfaces  130   r  (not all labeled), which may engage the target material. In an example, at least some of the working surfaces  130   r  may generally face in the direction of movement of the cutter head  200   a . As mentioned above, the cutter head  210   a  may move in the first and second directions. According to at least one embodiment, at least some of the working surfaces  130   k  may generally face in the first direction, and at least some of the working surfaces may general face in the second direction. 
     In some embodiments, the material-removal system may produce linear movement and/or rotation of the cutting tools.  FIG. 13  illustrates an embodiment of a material-removal system  200   b  that include a cutter head  210   b  that may rotate about rotation axis  35   b  and/or move at least partially vertically (e.g., generally radially in a direction  40   b  that is substantially perpendicular to the rotation axis  35   b  or vertically with no radial movement). Except as otherwise described herein, the material-removal system  200   b  and its materials, elements, or components may be similar to or the same as any of the material-removal systems  200 ,  200   a  ( FIGS. 10, 12 ) and its corresponding materials, elements, and components. Furthermore, the material-removal system  200   a  may include any cutting tool and/or combination of the cutting tools described herein. 
     In an embodiment, the cutting head  210   b  may include multiple cutting tools  100   m  secured thereto. For example, the cutting tools  100   m  may generally extend outward and away from the rotation axis  35   b . In some embodiments, working surfaces of the cutting tools  100   m  may face generally in the direction of rotation (e.g., as indicated with the arrows). 
     In some examples, the material-removal system  200   b  may include a material removal ramp  240   b . Failed target material may be swept or otherwise moved onto the ramp  240   b  and may be removed from site of operations by the material-removal system  200   b . It should be also appreciated that the cutting tools described herein may be mounted on any suitable cutting head or included in a material-removal system, and the specific examples of material-removal systems described herein are for illustrative purposes and are not intended to be limiting. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting. Additionally, the words “including,” “having,” and variants thereof (e.g., “includes” and “has”) as used herein, including the claims, shall be open ended and have the same meaning as the word “comprising” and variants thereof (e.g., “comprise” and “comprises”).