Patent Publication Number: US-8534329-B2

Title: Joint making jig

Description:
FIELD OF THE INVENTION 
     This invention relates to methods and apparatus for guiding a woodworking power tool used to cut joint members in wood workpieces. In particular, the device of the present invention is a template intended for making dovetail and similar joints. 
     BACKGROUND 
     Wooden boxes, drawers and storage chests, and a variety of other wooden furniture and objects, often use dovetail joints as a means of securely assembling components. A dovetail is a joint, usually right angled, formed of one or more projecting parts, i.e., tenons or pins, that fit tightly within corresponding recesses, i.e., mortises or gaps between tails, to form a joint. The pin is typically broader at its end than at its base. Dovetail joints are considered by most cabinet makers to be the strongest and most permanent joint typically made in cabinet making. A dovetail joint is generally employed in articles made of thinner materials such as drawers, boxes, chests, and the like. 
     Dovetails are used for both their decorative appearance and their high strength. Such joints can be made without industrial machinery in one of two principal ways, either using hand tools such as saws and chisels, or using power tools such as a router. In both cases, making such a joint requires a high degree of skill and precision. Furthermore, making such a joint using hand tools is time consuming. The desire to save time motivates most woodworkers to use power tools, and the need for precision, often in the relative absence of skill, makes jigs or machines that control the power tools desirable. 
     The use of a power tool such as a router allows two different approaches. The router can be held stationary and the workpiece moved relative to the position of the router, or the workpiece can be held stationary and the router moved relative to the workpiece. Additionally, in a variation of both basic approaches, both the router and the workpiece may move. 
     The modern electric router has made this process much easier with the help of router cutters, holding fixtures and templates. With fixtures, the workpiece is clamped into the fixtures and machined after the template location is set. 
     Most dovetail and other joint-making jigs utilize an array of “fingers” to guide a router cutter during engagement of the workpiece or workpieces to remove waste material and leave “pins” on one work piece and “tails” on the other work piece. The array of fingers are typically provided in one of two ways. In the first alternative template structure, a machined plastic or metal template has multiple fingers, each of which has a fixed position relative to other fingers on the template. In the second alternative, fingers are attached to and can be moved relative to each other on a finger-carrying plate, which facilitates manufacture of joints with variably spaced pins and tails rather than ones that are spaced only the predetermined amounts required by the machined template. 
     Prior art fixtures and templates are costly. Smaller versions may be less expensive, but they limit the width of workpieces. This suggests a need for a jig that is less costly than current jigs, can adapt to different sized workpieces, and that includes a template that can be used quickly and efficiently to cut joint members of various shapes and dimensions. 
     SUMMARY 
     Embodiments of this invention are jigs that facilitate cutting dovetail and other wood joints such as box joints or rounded shaped joints. 
     This jig uses a template that supports and guides an electric router to cut joint members in the workpieces. A locating structure facilitates moving the template with respect to the workpiece a pre-determined distance between a first position to cut joint members on the work pieces, and a second position to cut additional joint members on the workpieces. The jig also has a side stop and a plurality of pin plates that accurately position the template with respect to the workpiece. 
     The template is provided with multiple sets of guide fingers that guide the electric router. Each set of guide fingers is shaped and dimensioned to permit cutting of a particular size of joint member. In one embodiment, the template comprises more than one set of guide fingers. 
     Alternative arrangements of the template guide fingers are possible. For example, other embodiments of templates are disclosed in U.S. Pat. Nos. 5,711,356 and 5,114,265, where the templates are slidably attached to a bar, which patents are incorporated herein by reference. A pin positions the prior art template on the bar in two locations in the X axis to provide the correct offset for two mating boards. Additional holes in the template allow for other X axis positions used to make box joints that are half or a quarter the size of the array of fingers. The Y axis positioning for these templates and finger assemblies relative to the jigs&#39; clamp face is provided by the sliding scales on the jig support brackets. In an embodiment on conventional bench mounted type jigs, a box joint template can have the X axis positioning holes at one end of the active front array of fingers and a matching low tolerance slot at the other end. 
     The present invention can be incorporated into various types of jig arrangements. The present invention uses fixed pins spaced apart on a beam, on jig brackets, or on the jig frame, either on conventional bench mounted type jigs, on purpose-made router table jigs or, in the case of the beam model, either ‘upside-down’ on a router table or ‘right side up’ using a hand held router. 
     On beam type jigs, the relatively short and lower cost template is “stepped over” with absolute precision from No&#39;s 1 &amp; 2 pins to No&#39;s 2 &amp; 3 pins, and so on. This concept lends itself to a ‘kit’ version because precise X and Y axis positioning of steel plates and index pins on a beam is achieved by use of integral set-up holes in the template, permitting the user to check and precisely adjust the pin plate positions through screwdriver access holes as necessary to correct for any beam expansion or contraction that may occur between uses. This jig may be used right side up for hand routing or upside down on a router table. 
     On each conventional bench mounted and beam type jig, the fixed jig pins and additional template holes provide precise X axis template offsetting for mating box joints as well as half and quarter size joints. 
     Among other attachment alternatives, templates can be attached to the steel pin plates by powerful rare earth magnets set flush with, or just below the template surface, by mechanical means such as sliding clips on the router table jig, or by turnbuckle clips. The indexing pins restrain movement of the templates horizontally, creating a very secure set-up that is quick and easy to use. 
     The indexing pins also provide precise Y axis template positioning (relative to the jig front face) for routing through dovetail pins. The through dovetail pin mode has Y axis control holes that step the assemblies in or out relative to the clamp face to allow for routing different sized through dovetail pin guides to match the dovetail bit socket. 
     Moving the template with respect to fixed workpiece positioning members requires no adjustment of the positioning members or workpieces. This allows for more accurate and faster cutting of the joints. For workpieces wider than the template, the present invention allows the user to simply move the template over or move the beam and workpiece over. 
     This invention therefore provides a versatile joint making machine for use with a router to make woodworking joints. The machine of this invention is accurate, easy to use, and easy to set up for making a wide range and variety of different joints. Other advantages and benefits of this invention will be apparent from the drawings and the following description of the invention and claims. This invention provides a dovetailing jig assembly that includes a dovetailing jig removably attachable to a workpiece, a scab board that abuts the workpiece, and a backup board, supporting the scab board removably attached to the jig. The jig may include a side stop, a template, and a plurality of removable pin plates that variably position the template with respect to the workpiece. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of the tail face, top, and one end of a first embodiment of the woodcutting jig of this invention shown mounted on a positioning beam and scab board. 
         FIG. 2  is a top plan view of the woodcutting jig shown in  FIG. 1  with the template removed. 
         FIG. 3  is a top plan view of the woodcutting jig shown in  FIG. 1 . 
         FIG. 4  is the same view of the components of the woodcutting jig kit of this invention shown in  FIG. 1 , but without the positioning beam, scab board, or backup board. 
         FIG. 5  is an enlarged isometric view of the template shown in  FIGS. 1 and 4 . 
         FIG. 6  is an enlarged isometric view of one of the pin plates depicted in  FIG. 4 . 
         FIG. 7  is an enlarged isometric view of the side stop depicted in  FIG. 1 . 
         FIG. 8  is an isometric view of a portion of the underside, pin side, and an end of a locking mechanism of the embodiment depicted in  FIG. 1 . 
         FIG. 9  is an isometric view of the tail face, top, and one end of the embodiment of the mounted woodcutting jig depicted in  FIG. 1  with the template stepped over from the side stop. 
         FIGS. 10A and 10B  are views of different embodiments of the template. 
         FIG. 11  is a top plan view of the woodcutting jig shown in  FIG. 1  with the template positioned to set the location of the positioning members. 
         FIG. 12  is a view of the woodcutting jig shown in  FIG. 1  with two clamps securing the workpiece for cutting box joints. 
         FIG. 13  is a view of another embodiment of the woodcutting shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The woodcutting jig  1  of this invention, shown in  FIG. 1 , is used for securing workpieces and providing a path for an electric router to cut joint members in wood workpieces. A workpiece is temporarily secured by clamping the workpiece to a backup board and scab board. A cutter positioned in an electric router is then guided by the template  2  to cut pins and tails in the workpiece. Jig  1  has six components: template  2 , positioning members  4 , side stop  6 , beam  8 , scab board  10 , and backup board  12 . Alternatively, the woodcutting jig  1  may be used as a bench mounted jig as shown in  FIG. 13 . 
     A workpiece is positioned against backup board  12  and scab board  10 , as is depicted in  FIG. 12 , with a finger joint patterned template. The work piece is generally a rectangular board and clamps  38  secure the workpiece against backup board  12 . In the embodiments in  FIGS. 1 and 12 , backup board  12  and beam  8  have a row of evenly spaced clamp holes  22  that can be used to attach clamps  38 . Jaws  40  and  41  of clamp  38  bear against the front face of backup board  12 , and the clamp bars  42  and  43  to which the jaws  40  and  41  attach pass from the rear through the holes  22  in beam  8  and backup board  12 . Clamps  38  hold the workpiece against the scab board and backup board. After the workpiece is secured in place, a router (not shown) is used to cut pins and tails in the workpieces using a straight cutter for the pins and a dovetail shaped cutter for dovetail shaped tails. 
     The path of the router is restricted by template  2 . The template  2 , depicted in  FIG. 5 , is relatively short and costs less than longer prior art templates. Template  2  has a planar surface  28  for supporting a cutting tool reference surface, such as a conventional electric router base, to cut joint members in workpieces positioned below template  2 . Template  2  is formed with at least one set of protruding uniform fingers  30  defined by one or more surfaces orthogonal to the planar surface  28 . A bushing mounted in an electric router base, or a bearing on the shank of a router cutter, (typically above the cutter blades) bears against the finger-defining surface to guide the cutting tool. Fingers  30  are spaced apart from adjacent fingers at a distance  32  equal to the pitch of the joint members to be cut, nominally twice the diameter of the router cutter. The design of the template allows other sets of guide fingers  30  to be formed on planar surface  28 . Every set of guide fingers  30  is spaced and dimensioned to form joint members of a pre-determined pitch and size. Other embodiments of template  2  are shown in  FIGS. 10A and 10B . Other embodiments of template  2  allow the cutting tool to vary the style and design of pin cuts and tail cuts, creating other dovetail joints. 
     As the pin and tail cuts are made, scab board  10 , positioned under template  2  and abutting the workpiece, will be breached by the cutting tool. Scab board  10  is a replaceable board that can be removed without upsetting the positions of the other components by sliding scab board  10  longitudinally into or out of the jig assembly  1  between positioning beam  8  and side stop  6 . 
     Scab board  10  and/or backup board  12  may be made of medium-density fiberboard, an engineered wood product formed by breaking down softwood into wood fibers, combining it with wax and a resin binder, and forming panels by applying high temperature and pressure. 
     Where the workpiece is wider than template  2 , template  2  can be “stepped over” to accurately cut the pins and tails 
     In  FIG. 2 , beam  8  and scab board  10  are shown with four pin plates,  16 ,  17 ,  18 ,  19 . Fewer or more pin plates can be used depending on the width of the workpiece. As shown in  FIG. 2 , pin plates  16 ,  17 ,  18 ,  19  are spaced equal distances apart on positioning beam  8 . Anchoring screws  20 ,  21  secure each pin plate  16 ,  17 ,  18 ,  19  into positioning beam  8 , but any other appropriate fastener can be used. 
     Pin plates  16 ,  17 ,  18 ,  19  have anchoring screws  20 ,  21  and indexing pin  34  as depicted in  FIG. 6 . In some embodiments, pin plates  16 ,  17 ,  18 ,  19  are made of steel. In these embodiments, template  2  can be attached to one embodiment of pin plates  16 ,  17 ,  18 ,  19  made of steel either by powerful rare earth magnets set flush with, or just below planar surface  28 , by mechanical means sliding clips, or by turn buckle clips. Indexing pin  34  retains template  2  horizontally, creating a very secure set-up that is quick and easy in use. Indexing pin  34  also provides precise Y-axis template positioning (relative to the front face of woodcutting jig  1 ) for routing dovetail pins. Lock  26  shown in  FIG. 8  is one mechanical means of securing template  2  to the pin plates  16 ,  17 ,  18 ,  19 . 
     Template  2  may be used to establish the appropriate distance between the pin plates  16 ,  17 ,  18 ,  19  as depicted in  FIG. 11 . Pin plate  16  (not shown in  FIG. 11 ) is positioned on positioning beam  8 , and template  2  is positioned as shown in  FIG. 11 , with the proper location of pin plate  17  shown through template holes  36  on template  2 . After pin plate  17  has been secured to beam  8 , the template  2  can be stepped over, as shown in  FIG. 9 , to locate pin plate  18  at the appropriate distance from pin plate  17 . When connected to pin plates  16  and  17 , template  2  is aligned with side stop  6 . 
     Side stop  6  has side stop screws  14  which penetrate through side stop  6  and backup board  12  into positioning beam  8  to attach side stop  6  to positioning beam  8  as depicted in  FIG. 1 . Further, side stop  6  orients the workpiece with respect to template  2 , backup board  12 , scab board  10 , and positioning beam  8 . 
     When measuring the distances between pin plates  16 ,  17 ,  18 ,  19 , the user utilizes template holes  36  in template  2  to determine a location to insert anchoring screws  20 ,  21  in this embodiment. The user then “steps over” template  2 , and determines the next location of the anchoring screws  20 ,  21 . 
     The “step over” functionality allows template  2  to be used to cut joints into workpieces wider than template  2  because the positioning of pin plates  16 ,  17 ,  18 ,  19  and anchoring screws  20 ,  21  is provided by positioning holes  44  in template  2 . The user can precisely adjust the positions of pin plates  16 ,  17 ,  18 ,  19 . Furthermore, measuring the distance between pin plates  16 ,  17 ,  18 ,  19  using template  2  maintains accuracy in the pin and tail interaction despite any positioning beam expansion or contraction that may occur between uses. 
     Components for a woodcutting jig  1  may be provided as a kit  24 , depicted in  FIG. 4 , reducing its size and cost. Such a kit  24  may include the following components: pin plates  16 ,  17 ,  18 ,  19 , template  2 , side stop  6 , at least one lock  26 , and other fastening devices. Side stop screws  14  and anchoring screws  20 ,  21  are conventional wood screws that optionally might not necessarily be supplied with kit  24  components. Thus, the screws are not necessarily provided in the kit. 
     The above-described embodiments are merely illustrative of this invention. Other embodiments may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope of the following claims.