Abstract:
A knife for cutting a profile including a curved surface in a workpiece may comprise a cutting face including a cutting edge in the shape of the profile to be cut, a bore for mounting the knife on a rotary cutterhead, the bore oriented parallel to the substantially planar cutting face, and a back surface adjacent the cutting face and including the cutting edge, the back surface contoured in the shape of the profile and partially radially encompassing the bore. The knife may be sharpened by grinding the cutting face to expose a new cutting face. The back surface is in the shape of the profile, therefore each new cutting face includes a cutting edge with a substantially similar profile. Knives having tips of, for example, carbide may be radially interspersed on the rotary cutterhead between the profile knives.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application Ser. No. 60/708,229 filed Aug. 15, 2005, the disclosure of which is incorporated in its entirety herein. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to rotating cutting devices and, more particularly, to a rotating head and a profile knife that can be sharpened without changing the original cutting profile.  
         [0004]     2. State of the Art  
         [0005]     A rotating head having removable cutting blades may be used to cut a profile in a workpiece. For example, a piece of wood may be cut with a profile to form a door molding. The head may have an arbor collar to hold the head about a rotating spindle. The arbor collar may comprise a high pressure grease fitting. The hydraulic pressure of the grease secures the head to the rotating spindle. Two or three cutting blades, known as knives or inserts, may be positioned about the perimeter of the head. Each knife conventionally comprises a polygonal blade having the desired cutting profile on the cutting edge. The cutting edge of the knife may extend beyond the head peripheral surface and remove a shaving from the workpiece as the head rotates. The thickness of the shaving depends on the advance rate of the workpiece and the rotational speed of the head.  
         [0006]     The knives may become damaged or wear down during use, requiring replacement. Operating costs may depend on how long a knife remains sharp and free of damage. Holders for the knives may be inserted or removed from the head of the cutting device. However, conventional knife holders enable only a single position for the blade relative to the holder, and a re-sharpened blade may be a different size. Blade material may be removed during sharpening; therefore the blade may cut to a different depth if remaining in the same position. Thus, adjustment of the entire head may be required to continue the identical cutting profile. Profile cutting knives conventionally have only one cutting edge with a unique cutting shape, and therefore, cannot be turned to a different cutting edge when the first is dulled, as in the case of a stock polygonal knife having multiple cutting edges.  
         [0007]     Accordingly, what is needed in the art is a profile knife which may be sharpened and re-used. An arbor collar which reliably transmits rotational force from the spindle to the head may additionally be useful. Knives for cutting a workpiece comprising layers of different materials are desirable.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The present invention relates to a knife having a profiled cutting edge, which may be re-sharpened. The knife may comprise a unitary wedge-shape, and include a substantially planar cutting face having a cutting edge in the shape of a profile to be cut into a workpiece. A bore through the knife enables the knife to be mounted on a rotary cutterhead, the bore being oriented parallel to, and offset from, the substantially planar cutting face. A back surface of the knife is adjacent the cutting face and includes the cutting edge, the back surface being contoured in the shape of the profile and partially radially encompassing the bore.  
         [0009]     The back surface of the knife may include a concave or convex surface, and may include a depressed portion distal from the substantially planar cutting face. The depressed portion may be configured to provide an indicator of undue sharpening of the knife, to discourage use of the knife beyond the intended life. Optionally, the back surface may include a coating, for example of zirconium nitride thereon.  
         [0010]     A cutterhead for cutting a profile in a workpiece may include an arbor collar and two annular end plates mounted to radially extend from a portion of each longitudinal end of the arbor collar. The annular end plates may have a plurality of spaced apertures therethrough, and an attachment element may be mounted through one of a plurality of apertures of the first plate and an aligned aperture of a plurality of apertures of the second plate. A knife as described above may be mounted on the attachment element between the plates, the attachment element extending within a bore through the knife. The attachment element may include an automotive taper for joining with the aperture of the plate. Thus, a surface of an end of the attachment element may be flush with an outer surface of the plate.  
         [0011]     In one embodiment of the present invention, the arbor collar may include a star-shaped perimeter which interlocks with at least one plate of the two for rotationally driving the cutterhead. Additionally, the arbor collar may include a grease fitting on a circumferential surface thereof. High pressure grease may be inserted through the fitting, and the hydraulic pressure of the grease may secure the cutterhead to a rotating spindle. The surface of the arbor collar may expand radially inward with the pressure of the grease to grip the rotating spindle. Alternatively, a bore through the arbor collar may be tapered, and configured to mate with a tapered spindle, The tapered bore may secure the cutterhead to a rotating, tapered spindle.  
         [0012]     A method of sharpening a profile knife may include providing a cutterhead having profile knives annularly attached thereto, grinding a cutting surface of each profile knife to provide a cutting edge in the shape of the curved profile to be cut in a workpiece, and aligning the plurality of profile knives with the cutting edge of each profile knife extending radially a substantially similar distance from the cutterhead.  
         [0013]     Another embodiment of a knife for cutting a profile comprises a cutting face including a cutting edge having at least one protrusion and at least one valley, a bore through the knife for mounting the knife, the bore having an off-center position in the knife, and a back surface adjacent the cutting face and including the cutting edge, the back surface following the shape of the at least one protrusion and the at least one valley in cylindrical relief. The back surface of the knife may be concentric, sharing a common axis which is centrally located through the bore.  
         [0014]     The back surface of the knife may include a depressed portion distal from the substantially planar cutting face. Additionally, the back surface may include a coating, for example zirconium nitride, thereon.  
         [0015]     The cutting edge may comprise a plurality of erratic hills and valleys, and may be configured to form a woodgrain-like texture on a workpiece. Alternative cutting edges may comprise one or a plurality of concave or convex edges, right-angle corners, or substantially straight edges. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0016]     The foregoing and other advantages of the present invention will become apparent upon review of the following detailed description and drawings in which:  
         [0017]      FIG. 1  shows a cutterhead and knives of the present invention;  
         [0018]      FIG. 2A  shows a first embodiment of a knife of the present invention;  
         [0019]      FIG. 2B  shows a top view of the knife of  FIG. 2A ;  
         [0020]      FIG. 2C  shows a side view of the knife of  FIG. 2A ;  
         [0021]      FIG. 2D  shows a top view of a second embodiment of a knife of the present invention;  
         [0022]      FIG. 3A  shows a third embodiment of a knife of the present invention;  
         [0023]      FIG. 3B  shows a side view of the knife of  FIG. 3A ;  
         [0024]      FIG. 3C  shows a workpiece formed using the knife of  FIG. 3A ;  
         [0025]      FIG. 4A  depicts a fourth embodiment of a knife of the present invention;  
         [0026]      FIG. 4B  illustrates a top view of the knife of  FIG. 4A   
         [0027]      FIG. 5A  shows a sharpening method for a knife of the present invention;  
         [0028]      FIG. 5B  depicts a fifth embodiment of a knife of the present invention;  
         [0029]      FIG. 6A  illustrate a cutterhead of the present invention;  
         [0030]      FIG. 6B  shows another view of the cutterhead of  FIG. 6A ;  
         [0031]      FIG. 6C  illustrates an attachment element of the cutterhead of  FIG. 6A ;  
         [0032]      FIG. 7  shows a method of filling a grease fitting of the cutterhead of  FIG. 6A ;  
         [0033]      FIG. 8A  depicts an alignment tool and cutterhead of the present invention;  
         [0034]      FIG. 8B  depicts a side view of the alignment tool and cutterhead of  FIG. 8A ;  
         [0035]      FIG. 9  illustrates another cutterhead of the present invention;  
         [0036]      FIG. 10A  depicts a sixth embodiment of a knife of the present invention;  
         [0037]      FIG. 10B  depicts a side view of the knife of  FIG. 10A ;  
         [0038]      FIG. 11  illustrates a seventh embodiment of a knife of the present invention; and  
         [0039]      FIG. 12  shows a stack of knives of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0040]      FIG. 1  shows a cutterhead  100  having a first, annular end plate  110  and a second, annular end plate  120  connected by an arbor collar  130 . The arbor collar  130  may include an aperture  135  therethrough, enabling the cutterhead  100  to be mounted on a spindle (not shown) for rotation thereabout. The arbor collar  130  may comprise a high pressure grease fitting, to secure the arbor collar  130  about the spindle. Alternatively, the aperture  135  of the arbor collar  130  may include a taper, and the spindle may also include a taper, configured to matingly engage with the aperture  135  of the arbor collar  130 . The spindle may be threaded, and a safety nut may secure the arbor collar  130  on the spindle.  
         [0041]     The first end plate  110  and the second end plate  120  may each include a plurality of spaced apertures  115  about the perimeter thereof. The end plates may be circumferential, square, or any other suitable shape. The spaced apertures  115  of the annular end plates  110 ,  120  may be aligned, enabling attachment elements  140  to be placed therethrough, coupling the first end plate  110  and the second end plate  120 . The attachment elements  140  may be, for example bolts or screws, and be secured by nuts  150 . The attachment elements  140  may be, by way of example, ⅝-inch in diameter, a non-conventional size. Attachment elements  140  of any size diameter are within the scope of the invention. Attachment elements  140  having a non-circular transverse cross-sectional shape are additionally within the scope of the present invention. For example, the cross-sectional shape of the attachment elements  140  may be elliptical, triangular, square, or hexagonal.  
         [0042]     A knife  160  may be mounted on an attachment element  140  and positioned between the first end plate  110  and the second end plate  120 . The knife  160 , shown in detail in  FIGS. 2A through 2C , may include a bore  165  therethrough, for mounting the knife  160  on the attachment element  140 . The knife  160  may have the approximate shape of a wedge from a cylinder, and the bore  165  may extend longitudinally through a corner  161  of the knife  160 , the corner  161  being the portion of the wedge-shape proximate the central axis of the cylinder from which the wedge-shape is derived. Thus, the bore  165  extends through the knife  160  in an off-center location. The corner  161  may be chamfered. Optionally, the knife  160  may have the approximate shape of a half cylinder, cut longitudinally, or a cylinder with a quarter-wedge missing.  FIG. 2D  depicts a side view of a knife  160 ′ with the approximate shape of a cylinder with a quarter-wedge missing.  
         [0043]     Returning to  FIGS. 2A through 2C , a cutting face  163  of the knife  160  may have a cutting edge  162  in the shape of the desired profile to be cut on the workpiece. The cutting face  163  may approximately follow a radial surface of the wedge-shape.  
         [0044]     Illustrated in  FIG. 2B  is a profile view of the knife  160 , looking through the bore  165 . This profile may be a claw-shape. The cutting edge  162  need not precisely follow a radius line from the center of the bore  165  to a back surface  164 , the back surface  164  being the circumferential surface of the wedge-shape; rather the cutting edge  162  may be hooked to attack the surface of the workpiece. The hook angle of the cutting edge may vary, for example, according to the density or hardness of the workpiece material.  
         [0045]     The bore  165  through the knife  160  is in an off-center location with respect to the rotational center of mass of the knife  160 . However, the back surface  164  of the knife is concentric, sharing a common center axis at which is a central axis of the bore  165 . ( FIG. 2C ) Thus, following sharpening, as described hereinbelow, the cutting edge  162  will always be equidistant from the bore  165 . The knife  160  may be envisioned as a wedge from a cylinder, with the bore  165  as a central axis through the cylinder. The bore is therefore in an off-center location through the knife  160 .  
         [0046]     Illustrated in  FIG. 2C  is another profile view of the knife  160 , a longitudinal profile of the bore  165 . The desired profile shape of the cutting edge  162  is shown, the desired profile shape including curved edges. The back surface  164  of the knife  160  is defined on one edge by the cutting edge  162 . The desired profile shape may further define the contour of the back surface  164 . The profile shape of this embodiment of a knife  160  according to the present invention and as depicted in  FIGS. 2A-2C , includes a plurality of protrusions  196  and valleys  197 . The plurality of protrusions and valleys are defined by a first concave portion  162   a,  a second concave portion  162   b,  and a right-angled portion  162   c  positioned between the first concave portion  162   a  and the second concave portion  162   b.  It will be understood by one of ordinary skill in the art that any profile shape is within the scope of the present invention, including curved edges, as well as straight-line edges. The resulting profile shape of the workpiece may include, for example, a concave or a convex surface, as well as a flat surface, meeting at right, acute, or obtuse angles. The profile shape may be planar, or may be textured. The profile shape may be, for example, the desired shape of a molding. The profile shape may be, for example, a finger joint profile.  
         [0047]     The knife  160  may comprise a high speed steel, such as a blend of tool steel that uses the alloying elements Molybdenum, Chromium, Vanadium, Tungsten, and Cobalt, for example, A.I.S.I. (American Iron and Steel Institute) M-2. Another suitable material may be A.I.S.I. M-42, a grade of high speed steel with a high content of cobalt in the alloy.  
         [0048]     The knife  160  may comprise a unitary body, and may have a height h of between about half of the width w and about twice the width w. The knife  160  may thus have a height h which encompasses a cutting edge  162  including at least one protrusion  196  and/or at least one valley  197 .  
         [0049]     Optionally, a knife  360  may include a coating  190 , as shown in  FIGS. 10A and 10B . The coating  190  may be a ceramic coating comprising, for example, zirconium nitride, which may be deposited by physical vapor deposition. Other examples of suitable coatings include chromium, titanium nitride, titanium carbo nitride, titanium aluminum nitride, chromium nitride, and a diamond coating. A nanoparticle coating, for example one sold under the trade name NanoTek® by Nanophase Technologies of Romeoville, Ill. may be suitable. The entire knife  360  may be coated, and the cutting face  363  of the knife  360  may be ground to take the coating off. The material of the coating  190  may be “cooked” into the material of the body of the knife  360 , impregnating the knife material at a temperature of about 900° Fahrenheit. Impregnated coatings  190  do not add significant quantities of material to the knife  360 , and do not alter the tolerance of the knife  360 .  
         [0050]     The material of coating  190  may be harder than the material of the body of the knife  360 . As the knife  360  is used to cut material, for example wood or a synthetic wood product, the material of the body of the knife  360  may wear away faster than the material of the coating  190 . The coating  190  may form a sharp cutting edge  195  which protrudes from the cutting face  363  of the knife, and which may be characterized as a “lip.” The knife  360  having a coating  190  thereon may thus be self-sharpening. In conventional finger joint knives and in conventional profile cutting knives, the material at the cutting edge is very thin, and the knife becomes very hot with use due to contact with the workpiece. Coatings of convention knives may thus degrade. For example, a diamond coating will begin to break down at a temperature of about 750° Fahrenheit.  
         [0051]     The knife  360  has a cylindrical relief, that is, the profile of the knife continues, in a cylindrical form, about the bore  365  in the knife  360 . In comparison with conventional knives, there is a substantially greater mass of material behind the cutting edge  363  of a knife  360  of the present invention, having cylindrical relief. Thus, as heat is generated during use, the body of the knife  360  acts as a heat sink, and the cutting edge  363  does not overheat. The knife  360  may cut for 1,100 hours without sharpening and without overheating and degrading the coating  190 . The knife  360  may efficiently cut through a harder wood, or through a glue line of a laminate workpiece, without the need for a separate tip, such as a carbide tip as described hereinbelow. The thickness of the coating  190  has been exaggerated in  FIGS. 10A and 10B  for clarity.  FIG. 10B  depicts another cutting profile design, a V-shaped profile, for a knife of the present invention.  
         [0052]      FIG. 3A  depicts a perspective view of another embodiment of a knife  160   a  of the present invention. The knife  160   a  includes a different profile shape, the back surface  164   a  of the knife  160   a  having two convex portions. A profile view of the knife  160   a  is shown in  FIG. 3B .  FIG. 3C  depicts a profile view of a workpiece  180  formed using the knife  160   a.    
         [0053]     Yet another embodiment of a knife  260  of the present invention is shown in  FIGS. 4A and 4B . The cutting face  263  of knife  260  has two teeth,  263   a,  each with a separable tip  269  of a harder material, for example, carbide. The separable tip  269  may more efficiently cut through a harder wood, or a glue line of a laminate workpiece. The separable tip  269  may be attached to the knife  260  using an attachment member (not shown), for example a bolt or a screw, or using an adhesive. The knife  260  having a separable tip  269  may be circumferentially interspersed on a cutterhead  200 , as shown in  FIG. 8A , between knives  160 . Thus, the cutting face of the knives  160 ,  260  together may be used to cut a desired profile in a workpiece. Optionally, a knife may include a cutting edge  162  having a profile wherein portions of the cutting face  163  have separable tips  269  thereon, similar to the knife  260  of  FIGS. 4A and 4B , and portions of the cutting face  163  are formed of the unitary body of the knife, similar to the knives  160 ,  160   a  of  FIGS. 2A through 2C  and  FIGS. 3A and 3B .  
         [0054]     The knife  160  may be sharpened as shown in  FIG. 5A . A grinding wheel  170  may be pressed against the cutting face  163  to sharpen the knife  160 . By grinding the cutting face  163 , the entire profile of the cutting edge  162  is uniformly sharpened. The knife  160  may be sharpened a number of times, each time removing a portion of a cutting face  163  of the knife  160  including the cutting edge  162 , until a final cutting face  163 ′ and final cutting edge  162 ′ are exposed. Each time the knife  160  is sharpened, the knife  160  on the cutterhead  100  may be turned incrementally about the bore, placing the newly exposed cutting edge  162  in the exact position with respect to the cutterhead  100  as the previous cutting edge  162 . Each sharpening may shave approximately 0.001 inch from the cutting face  163 . The knives  160  may be sharpened in situ, on the cutterhead. In contrast, conventional knives must be removed from a cutterhead for sharpening.  
         [0055]     Sharpening is described with respect to the knife  160 ; however, any embodiment of a knife of the present invention, including knife  160 ,  160 ′,  160   a,    160   b,    360 ,  460 ,  560 ,  660 ,  760  may be sharpened as described hereinabove.  
         [0056]     Optionally, a heel  168  of the knife  160  may be shaped as shown in  FIG. 5B  such that further sharpening beyond the final cutting edge  162 ′ will not leave a long enough cutting edge  162 , and the knife  160  must be replaced. The may prevent the knife  160  from being used when too little of the heel  168  of the knife  160  remains, risking fracture of the knife  160 . The heel  168  may be the portion of the knife  160  circumferentially distal from the cutting edge  162 . Returning to  FIG. 5A , the radial distance from the bore  165  to the back surface  164  is substantially equal across the arc of the knife. That is, the radial distance from the bore  168  to the back surface  164  at the cutting edge  162  is substantially similar to the radial distance from the bore  165  to the back surface  164  at the heel  168 , unless the heel is reduced in volume as shown in  FIG. 5B . This enables the knife  160  to be sharpened, rolled forward about the bore  165 , and to provide a cutting edge  162 ′ in substantially the same position as the pre-sharpened cutting edge  162 . If the radial distance from the bore  165  to the back surface  164  substantially differs in portions of the knife  160 , the sharpened cutting edge  162 ′ will not match the position of the pre-sharpened cutting edge  162 .  
         [0057]     The knife  160   b  depicted in  FIG. 5B  includes a reduced-volume heel  168   b,  such that the back surface  164  is chamfered or depressed at the reduced-volume heel  168   b.  A chamfered portion  167  of the back surface  164  does not extend as far from the bore  165  as the back surface  164 . The outline of a full volume heel is depicted with dashed line  166 . Thus, sharpening the knife  160   b  beyond the final cutting surface  163 ′ causes the cutting edge  162  to include the chamfered portion  167  of the back surface  164 , and the profile no longer matches the profile of the original cutting edge  162 . This may discourage use of the knife  160   b  beyond the intended life.  
         [0058]     Another embodiment of the present invention, depicted in  FIG. 6A , is a cutter head  200 , including a first annular end plate  210  having a plurality of counterbores  212  for attachment elements  240 . The counterbores  212  enable attachment elements  240  having a flange (not shown) at one end to be fitted therewithin, and the end of the attachment elements  240  may be flush with a surface  217  of the first end plate. Alternatively, the attachment elements  240  and counterbores  212  may have a taper, for example an automotive taper for mating the attachment elements  240  within the counterbores  212 .  FIG. 6C  depicts an attachment element  240  having a tapered end  242 . The longitudinal end of the attachment element  240  has the greatest circumference, preventing an attachment element  240  from passing through a counterbore  212 . The opposite longitudinal end  244  may be threaded, for attachment to a nut  150 , for example, or screwed into a threaded bore  115  of the annular end plate  220 . A safety arbor collar  230  has a star-shaped perimeter  214 , preventing the first end plate  210  from slipping on the safety arbor collar  230 , even if the hydraulic pressure of the grease fitting is not maintained. The star-shaped perimeter provides a drive mechanism, transferring the rotation of the spindle from the arbor collar to the first end plate  210 . Another perspective view of the cutter head  200  is shown in  FIG. 6B .  
         [0059]     The arbor collar  230  may further include a grease fitting  232  on the circumferential perimeter thereof, as shown in  FIG. 6B .  FIG. 7  depicts the arbor collar  230  mounted on a spindle  270 . A grease gun  280  may be used to fill an annular chamber  234  surrounding the bore  235  of the arbor collar  230  with high pressure grease through the grease fitting  232 , causing the wall  233  defining the bore  235  of the arbor collar to expand radially inward and seize the spindle  270 . The grease fitting  232  mounted on the circumferential perimeter of the arbor collar enable the tube  237  for transporting the grease to the annular chamber  234  surrounding the bore  235  to be shorter in length compared to a conventional tube, attached to grease fittings on the longitudinal end surface  236  of the arbor collar, proximate an annular end plate of the cutterhead. Conventional cutter heads may have grease fittings on a circumferential edge of the annular end plate, and a fluid pathway for grease may extend through the annular end plate to a fluid pathway within the conventional arbor collar.  
         [0060]     Alternatively, the bore  235  of the arbor collar  230  may include a taper, and the spindle may also include a taper, configured to matingly engage with the bore  235  of the arbor collar  230 . The star-shaped perimeter  214  of the safety arbor collar  230  may prevent the first end plate  210  from slipping on the safety arbor collar  230 .  
         [0061]     An alignment tool  300  is illustrated with the cutter head  200  in  FIGS. 8A and 8B . The alignment tool  300  may include a support plate  310  and a plurality of alignment posts  320  spaced at radial intervals. The cutter head  200  may be placed on the alignment tool  300 , and the knives  160  may be individually adjusted such that the cutting face  163  of each knife  160  is in contact with an alignment post  310 . The knives may be simultaneously individually adjusted by loosening the nuts  150  securing the attachment elements  150 , placing the cutterhead  200  on the alignment tool  300 , and rolling the knives up in unison to the alignment posts  320 . The alignment tool  300  may be particularly useful for initial positioning of the knives on the cutterhead, or following sharpening. The nuts  150  on the attachment elements  140  may be tightened, securing each knife  160  in the desired position. The alignment tool  300  may be used to ensure that the cutting edge  162  of each knife  160  extends to the same radial position from the cutter head  200 . Thus, each knife  160  performs an equal amount of work, removing an equal amount of material during each cut.  
         [0062]     Another embodiment of the present invention is depicted in  FIG. 9 . Mounted about the arbor collar  130  of the cutterhead  500  is a multi-knife pinwheel  400 . The pinwheel  400  may include protrusions  410  having separable tips  269  mounted thereon. Interspersed between the protrusions  410  may be knives  160 , mounted upon attachment elements  140 , as described hereinabove. The protrusions  410  having the separable tips  269  may be configured to mimic a portion of the profile of the knives  160 , for example if portions of the workpiece are expected to include harder materials. Alternatively, the protrusions  410  may be configured to remove additional material from the workpiece, adding to the profile shape of the knives  160 .  
         [0063]      FIG. 9  additionally illustrates the positioning of the knives  160  on the cutterhead  500 . The cutting edge  162  of the knife  160  is not positioned on the radial line  510  extending from a central location of the cutterhead  500  through a central location of the knife bore  165 . The knife  160  is positioned to enable cutting clearance behind the cutting edge  162 . There is relief behind the cutting edge  162 , as the back surface  164  drops away from the outside edge of the cutterhead  500 . The relief enables the knife  160  mounted on the cutterhead  500  to have cutting properties.  
         [0064]     Another embodiment of a knife  460  of the present invention is depicted in  FIG. 11 . The knife  460  has a substantially planar cutting edge  362 ; however, the cutting edge  462  has a textured relief. The knife  360  may be useful for forming a relief in a synthetic wood product. Synthetic wood may be formed from a blend of high density polyethylene plastic and sawdust. The synthetic wood may be extruded in the desired shape such as a board. It may be desirable to have a synthetic wood product with the texture and relief of wood grain. Conventionally, warm synthetic wood may be brushed with a wire wheel to form the desired texture. However, brushing the warm, synthetic wood may produce a dimensionally unstable and erratic texture. The knife  460  of the present invention may be used to cut a reliably reproducible texture into a synthetic wood material.  
         [0065]     Yet another embodiment of the present invention is depicted in  FIG. 12 . A plurality of knives  560   a,    560   b,    560   c,    560   d,    560   e  may be stacked on an attachment element  140 , and may be used to cut a thicker material. The profile of the stacked knives of  FIG. 12  include at least one central knife  560   b,    560   c,    560   d  and a knife  560   a,    560   e  having a concave profile at either end. The stack of knives  560   a,    560   b,    560   c,    560   d,    560   e  may be used to cut eased edges on a board. Each knife  560   a,    560   b,    560   c,    560   d,    560   e  may have a substantially similar thickness. For example, each knife may have a cutting edge about three (3) inches (7.6 centimeters) long. The embodiment depicted in  FIG. 12  includes five (5) knives, and may be useful to chamfer the edges of a board about 15 inches (38.1 centimeters) thick. Stacked knives may be configured to chamfer the edges of conventionally sized lumber, for example 2×4 and 2×6 boards, both wood and synthetic. Stacked knives, with each knife having a different profile are also within the scope of the present invention. For example a stack of knives may alternate, with a knife having a straight profile stacked between knives having serrated profiles.  
         [0066]     The knives  160  of the present invention may shorten the time required to cut a profile in a plurality of workpieces, and eliminate the costs associated with conventional, planar, disposable insert knives because the knives  160  have a longer run time without sharpening, and may be resharpened and aligned with tight tolerances on the cutterhead. Less down time of the machinery may be required for sharpening the knives as compared to replacing and aligning conventional knives. For example, the same total length of workpieces may be cut to a desired profile in 24 to 48 hours using a cutterhead and knife of the present invention as would be cut in two (2) to four (4) days using a conventional cutterhead and knife. Additionally, the knives  160  of the present invention may be useful for cutting a piece of wood at the end grain, or with the grain. That is, the end grain surface of the wood may be cut into the desired profile, or the flat grain surface of the wood may be cut into the desired profile.  
         [0067]     The tolerances of a cutterhead  200  and knife  160 ,  160 ′,  160   a,    160   b,    260   360 ,  460 ,  560 ,  660 ,  760  of the present invention are very tight. The knives  160 ,  160 ′,  160   a,    160   b,    260 ,  360 ,  460 ,  560 ,  660 ,  760  may hold a ±0.001 inch runout on a workpiece. That is, the cutting depth will only vary ±0.001 inch from the desired profile depth on the workpiece. The attachment elements  140 ,  240 ,  640  may be precisely aligned within the center of the apertures  115  of the annular end plates  110 ,  120 ,  210 ,  220  to within ±0.001 inch. The knives  160 ,  160 ′,  160   a,    160   b,    260 ,  360 ,  460 ,  560 ,  660 ,  760  fit over the attachment elements  140 ,  240 ,  640  with a tolerance of only a few thousandths of an inch.  
         [0068]     Any number of knives  160 ,  160 ′,  160   a,    160   b,    260 ,  360 ,  460 ,  560 ,  660 ,  760  may be circumferentially spaced about a cutterhead  100 ,  200 ,  500 ,  600 ,  700 . For example, two (2), four (4) six (6), eight (8), or as many as twenty (20) knives  160  may be included on a single cutterhead  100 ,  200 ,  500 ,  600 ,  700 .  FIG. 13  depicts a cutterhead  600  having four (4) attachment elements  640 , each attachment element  640  having three (3) knives  660   a,    660   b,    660   c  stacked thereon. The stacked knives  660   a,    660   b,    660   c  are configured for cutting a substantially linear profile and forming a substantially planar surface on a workpiece.  FIG. 14  depicts a wing-shaped cutterhead  700  having two (2) attachment elements  740 , each attachment element  740  having a single knife  760   a,    760   b  disposed thereon. The knives  760   a,    760   b  are each mounted at opposing ends of the wing-shaped cutterhead  700 .  
         [0069]     The knives  160 ,  160 ′,  160   a,    160   b,    360 ,  460 ,  560 ,  660 ,  760  of the present invention are safer than conventional profile knives. Conventional profile knives may include knife inserts which may be clamped or screwed in place. These clamps and screws may loosen or detach during cutting operations, which may cause injury to operators and equipment. In contrast, the knives  160 ,  160 ′,  160   a,    160   b,    360 ,  460 ,  560 ,  660 ,  760  of the present invention are attached to the cutterhead  100  with attachment elements  140  secured through apertures  115  of the cutterhead  100  and a bore  165  through each knife  160 .  
         [0070]     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.