Abstract:
An adjustable router or shaper cutter assembly that facilitates the formation of an edge contour such as a rounded over contour on work-pieces of differing thicknesses.

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/199,448 filed Nov. 17, 2008, the contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to woodworking cutters generally, to router bits and, in particular, to edge-forming router bits. 
     BACKGROUND OF THE INVENTION 
     In woodworking, wood work-pieces not yet brought to final shape and size are often pieces of wood about three-fourths to one inch thick with front and back faces (or top and bottom faces) and with “edges” as broad as the thickness of the work-piece. The edges usually intersect the front and back faces at right angles, forming an “arris” where the plane or face of an edge and each of the front and back faces intersect. 
     It is often desirable to shape the edge of a wood work-piece. This is often most easily accomplished by shaping only a portion, such as one “corner” proximate one arris, of the work-piece edge at a time, requiring multiple operations to shape an entire work-piece edge. However, it is sometimes desirable simultaneously to shape the entire edge of a work-piece, that is, to shape the entire edge in one operation. Existing cutters are available for doing so, including rounding over cutters, bull nose cutters, and a variety of stacking and re-configurable cutters. Some such cutters are adjustable, but the capacity of such cutters to be adjusted is typically severely limited, usually within an adjustment range of only a few thousandths of an inch. 
     One of the complexities associated with edge-shaping or forming is the desirability of being able to form edge shapes on work-pieces having differing thicknesses. For instance, a huge fraction of all work-pieces used in cabinet making range in thickness between 0.75 inch and 1.0 inch, but many different thicknesses are used within that range. 
     As an example of an application requiring edge-shaping, it is often necessary to create a handle (or tote) for an item being made or repaired, such as a bench plane or a table saw jig to be slid on the saw table by manipulating a handle attached to the jig. The need to make a handle is particularly frequent when restoring or customizing an antique tool. Wooden handles on such tools are prone to damage and often need to be replaced. Furthermore, a user may want to replace a handle with one that better fits the user&#39;s grip. 
     These handles are often fairly complex, curved shapes, and getting a smooth shape can be very difficult. The typical approach is to cut the shape out using a scroll or band saw and then shape the final curves with rasps, files and sandpaper. 
     This exemplary need for a means for shaping edges with different thicknesses illustrates the desirability of a router cutter with such capability. 
     SUMMARY OF THE INVENTION 
     The cutter of this invention is an adjustable router bit or cutter assembly (or other rotating cutter such as a shaper cutter) that facilitates the formation of a particular edge contour on work-pieces of differing thicknesses. While other ways of guiding the cutter assembly are possible, in one embodiment, the cutter assembly uses a bearing to follow a template to establish the basic shape of the work-piece. Templates can be made of thinner, easier to shape materials that can be more accurately cut with smoother curves than a thick, typically solid wood, work-piece. This results in a final part that is closer to the desired shape than might otherwise be the case. Moreover, use of a template rather than guiding the cutter assembly by reference to a portion of the work-piece itself enables the cutter to remove all of the original work-piece edge surface, which is not possible with a cutter assembly guided by reference to (i.e., by contact with) a portion of that surface. 
     The profile of the embodiment of the cutter or bit of this invention illustrated in the Figures is such that it creates a full (continuous) “round-over” on the edge of the part, such that once the bit has been run around the part blank following the template (or the work-piece has been moved relative to and in contact with the bit or cutter), the finished part is both the correct over-all shape and has a desired cross-sectional shape, such as a shape usable as a handle. Further shaping may be desired by the user to refine the cross-section, however such further shaping typically only requires the removal of relatively small amounts of material from the work-piece. 
     The bit or cutter assembly of the embodiment depicted in the Figures is configured such that it is adjustable for work-piece thickness or width within the range of typical handle thicknesses (most are between approximately ¾ and one inch thick). The bit has two independent cutters, one preferably (but not necessarily) permanently fixed to the shaft, while the second cutter is positionable on the shaft at different locations relative to the other (typically fixed) cutter. The cutters “interlock,” which is to say that they overlap and lock so that: (a) one cannot rotate relative to the other, (b) cutting “heights” of the two cutters can over-lap without the cutters (or their blades) contacting each other, and (c) the entire edge of the work-piece is contacted and shaped by the cutter assembly. The two cutters can be positioned at selected different positions to each other, by use or removal of shims or washers between the two cutters, or by any other appropriate spacing structure or means. 
     In one embodiment, each of the two cutters cuts approximately one quarter-round, and the two cutters together create a substantially half round shape (the shape need not actually be a constant radius, but can be a modified curve to give the best results within the range of adjustment). Other profiles could also be used. 
     Alternate designs for this bit may use three or more cutters to create a “stack” that makes up the desired profile, and less than all of such cutters may be usable to shape a thinner profile than is possible with all of the cutters in the stack. 
     The cutters may be of a two-flute design, but can also be made with one flute, or with more than two flutes as desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an end view of the cutter assembly of one embodiment of this invention. 
         FIG. 2  is a side view of the cutter assembly shown in  FIG. 1  with washers between the cutters so that they are somewhat separated. 
         FIG. 3  is a side view of the cutter assembly shown in  FIG. 1 , rotated 90 degrees from the view of  FIG. 2  and with the cutters, bearing, washers and nut shown in section. 
         FIG. 4  is an exploded perspective view of the cutter assembly shown in  FIG. 1 . 
         FIG. 5  is substantially the same as  FIG. 2  but located on the page so that it can be directly compared to  FIG. 6 , which is a view like  FIGS. 2 and 5 , except that, in  FIG. 6 , washers shown positioned between the cutters in  FIGS. 2 and 5  have been re-positioned (for “storage”) between the bearing  24  and nut  30 , so that the two cutters  12  and  14  are closer together in  FIG. 6  than in  FIGS. 2 and 5 . 
     
    
    
     DETAILED DESCRIPTION 
     In an embodiment of the cutter assembly  10  of this invention illustrated in the Figures, two cutters  12  and  14  on a shaft  13  may be are adjusted for cutter assembly width (or height), which is to say that their relative positions on shaft  13  may be changed, using a number of shim washers  16  between reference surfaces on the two cutters  12  and  14 . For instance, shims of 0.050″, 0.020″ and 0.010″ thicknesses may be combined in different configurations to create desired spacing. This could also be achieved with shims of uniform thickness, or with a range of specific shims for specific spacing. 
     In the alternative, spacing could be set using a spring (not shown) on shaft  13  between the cutters  12  and  14 , and with appropriate means for locking the cutters relative to each other. For instance, one of the cutters can be locked or permanently attached to the shaft and the other can be repositionably secured with a locking nut. 
     The illustrated embodiment  10  of the cutter assembly depicts use of carbide inserts or attachments to the bodies  11  and  13  of cutters  12  and  14  to provide pairs of cutter blades  18  and  20 . Other appropriate materials could be used as alternatives to carbide inserts. Moreover, cutters  12  and  14  could utilize solid carbide or solid steel bodies  11  and  15 , appropriately shaped and sharpened to provide integral cutter blades  18  and  20 . 
     As mentioned above, and as can be appreciated by reference to the Figures, the cutter blades  18  and  20  on the two different cutters  12  and  14  must overlap in order to cut a full profile without a gap. Modest overlapping of carbide blade inserts in, for instance, dado blade sets is not uncommon, but the amount of such overlap is typically no more than the amount of carbide insert projection beyond the tool body to which the carbide is attached, and only limited carbide projection is feasible without risk of breakage. 
     In order to achieve the significant overlap between the blades  18  and  20  of cutter assembly  10  necessary to accommodate changes in cutter width on the order of as much as one quarter inch or more, there must be overlap not only of the blades  18  and  20  but also of portions of the cutter bodies  11  and  15 . 
     This is achieved by providing each of the cutter  12  and  14  body  11  and  15  structures with recesses  22  (one of which may be best seen in  FIG. 4 ) defined by (or between) protrusions  23 . Recesses  22  in one cutter  12  or  14  receive protrusions  23  from the other cutter  14  or  12 . This enables significant overlapping of the blades  20  on cutter  12  with blades  18  on cutter  14  and interlocks the two cutters  12  and  14  to prevent rotation of one cutter relative to the other. 
     Such locking of cutters relative to each other can be desirable even if two or more cutters are used to form a profile that doesn&#39;t require blade overlap of the sort present in the cutter assembly  10  depicted in the Figures. Where there is blade overlapping, the interlocking or inter-fitting described above and shown in the Figures insures that brittle and somewhat fragile blades  18  and  20  cannot contact and risk damage to each other. Such interlocking also assures that blades in one cutter do not align with blades in another cutter and engage the work-piece at the same time but rather engage the work-piece sequentially, thereby making cutting easier. 
     The geometry of the cutter bodies in the illustrated embodiment provide both inter-fitting (or overlapping) and locking of the cutters  12  and  14  to prevent rotation of one relative to the other during us. However, other structures such as a dowel pin received in holes in the cutters, or with a pin on one cutter received in a hole in the other cutter could also prevent rotation of one cutter without equal rotation of the other. Locking could also be achieved using one or more splines on the shaft interfacing with the floating cutter. Other similar devices may also be used, including, possibly keyways and a key. 
     Careful inspection and comparison of the Figures will reveal that protrusions  23  do not contact shaft  25  along the second half or so of their extensions. Instead, the protrusions  23  and recesses  22  define and are occupied by a sleeve or collar  26  or  33  (see  FIGS. 3 and 4 ), each having a face  28  (see  FIG. 3 ). The collar  26  associated with cutter  12  may be externally threaded and may be attached to or a part of shaft  13  so that an internally threaded cutter  12  may be threaded onto the shaft  13 , as can be seen in  FIG. 3 . (Cutter  12  could be attached to shaft  13  in other ways, or need not necessarily be fixed to prevent rotation on shaft  13  except when the cutter assembly  10  is configured and assembled for use with all of its components (except the rotating portion of bearing  24 ) fixed in position on shaft  13 ). Collar or sleeve  33  associated with cutter  14  may be formed as part of cutter  14  and may have a smooth cylindrical surface as is depicted in  FIG. 3 . The two faces  28  of collars  26  and  23  oppose each other and contact each other when the cutter assembly  10  is configured for the thinnest work-pieces it can shape (with full contact with the work-piece edge). Interposition of one or more shim washers  16  on the shaft  25  between the faces  28  of collars  26  and  33  configures cutter assembly  10  for thicker work-pieces. 
     As will be appreciated by reference to  FIGS. 5 and 6 , this cutter component geometry permits adjustment through a significant range of thicknesses that differ by up to the full “x” distance marked between  FIGS. 5 and 6 .  FIGS. 5 and 6  are approximately full scale drawings of one embodiment of the cutter assembly  10  of this invention that can shape the edges of work-pieces varying between about 0.75 inch and 1.0 inch, in which case the range of adjustment “x” is about 0.25 inch. Appropriate adjustments to the size (and geometry, if desired) of cutters  12  and  14  could result in other adjustment ranges such as larger ranges of approximately ⅜ inch or ½ inch or smaller adjustment ranges of approximately 3/32 or ⅛ inch (or the metric equivalents of all of these measurements). 
     A ball bearing guide or pilot  24  can be used to guide the bit  10  around the template. Such a bearing  21  is located in the assembly  10  depicted in the Figures on the side of “floating” or adjustable cutter  14  opposite the fixed cutter  12  and is sized to match the minor diameter of the cutters  12  and  14  (if it is desired that widest portion of the finished part match the template). This location places the template on top of the work-piece if the bit  10  is used in a router table. The bearing  24  could also be located adjacent to the fixed cutter  12  or could be the major diameter of the bit  10  (or have some other relationship to the cutting portions of bit  10 ) if the particular use so required. In order to assure free rotation, bearing  24  is separated from the face  29  of cutter  14  by a boss  32  (best seen in  FIGS. 4 and 6 ). 
     Indeed, a bearing may not be required if other guide mechanisms are employed (such as, among others, guide mechanisms associated with a pin router or a CNC router). Neither does the bearing  24  need to be a roller element bearing, it could simple be a non-cutting section of one of the cutters  12  and  14  or of the shaft  26  that bears or runs against the template. 
     Numerous other modifications and variations of the subject matter described above are possible without departing from the scope and spirit of this invention or the following claims. For instance, the round-over profile created by the cutters describe above and depicted below could instead be a wide variety of other profiles. As an example the cutters  12  and  14  could have radiuses of ¼ inch and essentially straight overlapping portions so that they would impart a ¼ inch radius on the corners of a work-piece with a flat intermediate edge portion. 
     As an example of another possible modification, while the shaft  25  depicted in the Figures is externally threaded with threads  31  and receives an internally threaded nut  30 , the assembly could also be secured together using a cap screw or another screw positioned in an internally threaded hole in the threaded end of shaft  25 . 
     Other cutters providing a variable profile will benefit from interlocking multiple cutters. As noted above, cutter assemblies can have more than two independent cutters; there could be three or more cutters in a cutter assembly of this invention, and each cutter  12  and  14  could have one blade  18  or  20 , two (as depicted in the Figures), three or some other number of blades.