Patent Publication Number: US-7594526-B2

Title: Table saw jig for cutting box joints

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a divisional application of U.S. patent application Ser. No. 11/039,031, filed Jan. 19, 2005, now U.S. Pat. No. 7,347,233; the disclosure of which is incorporated herein by reference. 
   The present invention claims priority from U.S. patent application Ser. No. 10/662,192, filed Sep. 15, 2003, now abandoned, entitled JIG FOR FORMING A BOX JOINT. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to jigs for cuffing wood and related products and more specifically to jigs used to form box joints with a table saw. 
   Jigs have long been used to make repetitive cutting simpler. In a typical jig, boards or other material to be cut are uniformly laid on a jig and marked or cut at a specific location. For instance studs to be cut to a certain length may all be abutted along a straight edge. A marker of some form may be positioned at the distance away from the straight edge at which the cut is to be made. Without measuring any of the boards, the woodworker knows where to make the cut across all the boards, e.g., at the point of the marker. Jigs in essence remove the need for repeated measuring. 
   Various complex joints have been proposed and used for joining adjacent corners of furniture. The dove tail, box joint and many other varieties of joints have been developed in this regard. Each type of joint has certain benefits and detriments associated with the joint. Typically, these joints all suffer from complexity of cutting. 
   Some jigs have been proposed for cutting the box joint. These jigs generally allow only two of the four boards to be cut at the same time. Thus, the woodworker needs to adjust the jig for the first pair of boards, turn the boards over and continue cutting. Then the jig is readjusted and the process of cutting turning and cutting is repeated. If the jig is not set up correctly between the pairs of boards, wood is wasted and the process is continued until the cuts are at the right location. Moreover, these jigs typically have a maximum size of board that can be used with the jig further adding to their limitations. 
   What is needed is a jig that allows all four boards to be cut simultaneously. The jig should be simple to arrange, preferably mechanical, have manner of aligning the boards which does not require adjustment and be suitable to use with boards of any conceivable length. 
   SUMMARY OF THE INVENTION 
   The present invention is a jig that allows all four boards to be cut simultaneously. The jig is simple to arrange, mechanical, has manner of aligning the boards which does not require adjustment and is suitable to use with boards of any conceivable length. 
   The present jig for cutting box joints on a table saw may be provided with guide bar clamps adapted to be joined to guide bars of a table saw. A spacer may be joined to the guide bar clamps. A spacer strip may be joined to the spacer. The spacer strip defines spacer apertures, having a gap therebetween. The gaps preferably are equidistant in length. A board clamp can join to an engagement pin with the engagement pin engaging one of the spacer apertures of the spacer strip. Desirably, mechanism is provided for offsetting pairs of boards such that grooves and projections on a pair of boards is cuttable offset from a corresponding pair. 
   The present jig is also provided with a method of cutting boards for a box joint, including joining a jig to a table saw; clamping at least two pairs of boards to the jig; positioning the clamped boards relative to the table saw; cutting a groove through all boards; repositioning the clamped boards relative to the table saw; cutting another groove spaced apart from the first groove; repeating the steps of repositioning and cutting another groove until grooves have been cut from one edge to an opposing edge with projections disposed between the grooves; and interlacing the projections and grooves of the pairs of boards to form a box joint. 
   Advantageously, the present invention allows cutting of all four boards on a table saw to form box joints between the boards. 
   Also advantageously, the present invention provides for alignment of the boards such that the saw blades of a table saw may be moved in a straight line from one board to the next and cut all four boards at the correct location. 
   As yet a further advantage, the present invention provides a mechanism for properly aligning the boards for cutting with the boards being of unlimited length. 
   As still another advantage, the present invention is usable with any table saw, avoiding the need for additional power tools. 
   These and other advantages will be made clear from the detailed description below. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the upper surface of a table saw, showing the blade and guide bars; 
       FIG. 2  is a perspective view of the guide bar clamps joined to the guide bars; 
       FIG. 3  is a perspective view of the table saw with the spacer joined to the guide bar clamps; 
       FIG. 4  is a perspective view showing the blade guard joined to the spacer; 
       FIG. 5  is a perspective view showing the spacer strip joined to the spacer; 
       FIG. 6  is a perspective view of the back surface of the spacer, showing the sink; 
       FIG. 7  is a perspective view of the zero tolerance insert joined to the spacer; 
       FIG. 8  is a perspective view, showing a portion of the board clamp and engagement pin; 
       FIG. 9  is a perspective view showing the board clamp fastened to the boards; 
       FIG. 10  is a front perspective view of the jig joined to a table saw and boards; 
       FIG. 11  is a top view of the jig joined to a table saw and boards; 
       FIG. 12  is a back perspective view, showing the jig joined to a table saw and boards; 
       FIG. 13  is a left side view, showing the jig joined to a table saw and boards; 
       FIG. 14  is a right side view, showing the jig joined to a table saw and boards; 
       FIG. 15  is a perspective view, showing the boards with the grooves and projections cut in one end thereof; 
       FIG. 16  is a perspective view partially exploded showing an alternate embodiment of the present invention; 
       FIG. 17  is an end view showing of the alternate embodiment; and 
       FIG. 18  is a side view showing the jig with boards secured thereto. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The jig  10  for cutting box joints on a table saw  12  may include a table saw  12 , guide bar clamps  30 , a spacer  50 , a blade guard  80 , a spacer strip  90 , a zero tolerance insert  100 , a board clamp  110 , and boards  140 . These components interact, as described below to cut box joints on a table saw, while cutting all four boards at the same time. Each component will be discussed in serial fashion below. 
   Referring to  FIG. 1 , the table saw  12  desirably has cutting blades  14 , a pair of guide grooves  16  defined in the upper surface  18  of the table saw  12 . The cutting blade  14  may determine the width of grooves  144  in the boards  140 . The guide grooves  16  are disposed on either side of the cutting blades  14 , cooperatively engaging a pair of guide bars  20 . Each guide bar  20  slidably moves within one of the guide grooves  16 , carrying material toward and away from the cutting blades  14  in a direction parallel to the cutting blades  14 . The jig  10  is joined to the table saw  12 . 
   Guide bar clamps  30 ,  FIG. 2 , may be of any design, shape or configuration that is suitable for joining the spacer  50  to the guide bars  20 . Herein, the preferred design for guide bar clamps  30  is shown as a piece of angled iron. Fasteners  34  may join the guide bar clamps  30  to the guide bars  20  and fasteners  38  may join the guide bar clamp  30  to the spacer  50 . Alternatively, guide bar clamps  30  each with a guide bar segment  32  may be contiguously formed with a spacer segment  36 . 
   The spacer  50  ( FIG. 3 ), which may be contiguously joined to the guide bar clamps  30 , has a front surface  52  connected to both of the guide bar clamps  30 . The front surface  52  may define a notch  54 , sized and adapted to allow the cutting blades  14  to pass therethrough. A top surface  56  of the spacer  50  may define a groove  58  sized and adapted to receive the spacer strip  90  therein. The back surface  60  may define a sink  62  disposed about the notch  54 , such notch  54  extending from the front surface  52  through the spacer  50  to the back surface  60 . The sink  62  is sized and adapted to receive a zero tolerance insert  100  therein. The spacer  50  may further have a bottom surface  64 , a right end  66  and a left end  68 . 
   The blade guard  80 ,  FIG. 4 , may be any suitable guard to protect the user&#39;s hands from the cutting blades  14 . The blade guard  80  may have ears  82  and define a channel  86 . The channel  86  extends coaxially with the notch  54 , shielding the cutting blades  14  after the cutting blades  14  pass through the notch  54 . The ears  82  provide a surface for fasteners  84  to secure the blade guard  80  to the spacer  50 . 
   The spacer strip  90 , which may be contiguously joined to the spacer  50  or replaceable with a variety of other spacer strips  90 , may define fastener apertures  92  and spacer apertures  94 . The fastener apertures  92  allow for selective attachment of the spacer strip  90  to the spacer  50  within the groove  58 . In this manner a variety of spacer strips  90  may be used with the present jig  10 . The spacer apertures  94  cooperate with the board clamp  110  to perpendicularly position the board clamp  110  relative to the cutting blades  14 . 
   The distance between the spacer apertures  94 , herein referred to as the gap  96 , determines the amount of distance the board clamp  110  is perpendicularly repositionable relative to the cutting blades  14 . The gaps  96  of a particular spacer strip  90  are equidistant in length. Thus, the spacer strip  90  is selected such that the gap  96  is of a dimension corresponding to the width of the cut formed by the cutting blades  14 . The gap  96  and cutting blade  14  determine the width of a projection  146  of the boards  140 , while the cutting blades  14  determine the width of the grooves  144 . The spacer strip  90  is selected such that the grooves  144  and projections  146  are of the same width. A plurality of interchangeable spacer strips  90  may have different gap  96  lengths to vary the width of the projections  146  and grooves  144  at the behest of the user. 
   Alternatively, the spacer apertures  94  may defined in a plurality of rows through the top surface  56  of the spacer  50  as shown in  FIG. 16 . With reference to  FIG. 16 , part numbers use a leading “ 2 -” to assist in coordinating other parts of the discussion to that shown in  FIG. 16 . For instance spacer apertures  94  are denoted  2 - 94  in  FIG. 16 . The engagement pin  2 - 116  may have a plurality of ports  2 - 117  that each correspond to a row of spacer apertures  2 - 94 . That is, placing the engagement pin  2 - 116  into a particular port selects the row of spacer apertures  2 - 94  that the engagement pin  2 - 116  may interact. In the preferred mode, the engagement pin  2 - 116  the port  2 - 117 , and the spacer apertures  2 - 94  have engageable threading, as a nut and bolt, and the front portion  2 - 112  of the board clamp  2 - 110  has a lip  2 - 51  that hooks around the spacer  2 - 50  and preferably has a pair of handles  2 - 149  on board clamp  110 . Handles  2 - 149  assist in moving jig  10  along table saw  12  towards and away from saw blades  14  by manually exerting a force on handles  2 - 149 . Such an arrangement selectively secures the front portion  2 - 112  to the spacer  2 - 50  as shown in  FIG. 17 . In use the engagement pin  2 - 116  engages the first spacer aperture  2 - 94  and the first groove  144  is cut. Then the board clamp  110  is moved so that the engagement pin  2 - 116  indexes to the next spacer aperture  2 - 94  where the next groove  144  and so forth. Further operation is described shortly below with regard to the board clamp  110 . 
   The zero tolerance insert  100  ( FIG. 7 ) may have fasteners  102  and a blade slot  104 . The zero tolerance insert  100  places pressure on the boards  140  adjacent the cutting blades  14  to prevent splintering of the boards  140  during cutting. The zero tolerance insert  100  preferably is received within the sink  62  and fasteners  102  join the insert  100  to the spacer  50  such that the exposed surfaces of the spacer  50  and insert  100  are co-extensive. The blade slot  104  is sized and adapted to closely receive the blades  14  therethrough. 
   The board clamp  110  ( FIGS. 8-10 ) may come in a variety of sizes, shapes and designs, but generally should interact with the spacer strip  90 , such that it may be moved a predetermined distance perpendicularly to the cutting blades  14 . A suitable board clamp  110  has a front portion  112 , a back portion  122  and clamps fasteners  128 . The preferred front portion  112  has a spacer segment  114  contiguously connected to a board segment  118  with the spacer segment contiguously joined to at least one engagement pin  116 . The engagement pin  116  is positioned and adapted to engage the spacer apertures  94  of the spacer strip  90 . The board clamp  110  may then be manually moved to engage the engagement pin  116  with consecutive spacer apertures  94  as the grooves  144  are cut. The board segment  118  of the front portion  112  may define apertures  120 . The back portion  122  may have a board segment  124  defining apertures  126 . Clamp fasteners  128  extend through the apertures  120 ,  126  of the board segments  118 ,  124  of the front and back portions  112 ,  122  respectively. The fasteners  128  may be tightened to firmly grip the boards  140  and loosened to release the boards  140 . 
   At least one pair of boards  140 , preferably two or more pairs, may be disposed within the board clamp  110 . The board  140  is positioned to cut grooves  144  and projections  146  in at least one end thereof. The grooves  144  are sized to snugly receive the projections  146  of another board  140  therein. A pair of boards  140 , as used herein, is intended to be the boards  140  that will form opposing sides of a box. Two pairs of boards  140  may be cut at the same time such that one pair of boards  140  form sides adjacent to the sides formed by the other pair of boards  140 . Thus, all four sides of a box may be cut at the same time. 
   The pairs of boards  140  need to be offset a distance  142  such that a groove  144  on one board  140  lines up with a projection  146  on another board. ( FIGS. 9-15  and  16 ). The offset  142  is equivalent to the width of a groove  144  or projection  146  (which are the same width). That is, the offset lines up all grooves  144  and all projections  146  on both pairs of boards  140 . Accordingly, the jig  10  is provided with an offset mechanism  148  as shown in  FIG. 16  for offsetting a pair or pairs of boards  140  such that the grooves  144  and projections  146  on one or a pair of boards is cuttable offset from a corresponding one or pair of boards  140 . The mechanism  148  includes an alignment bar  151  which may be adjustably joined to the front portion  112  of the board clamp  110  and which includes an adjustable plate  150  having a pair of offset faces  153  and  155  offset from each other the thickness of the offset  142  as shown particularly in  FIG. 16 . Interchangeable adjustment plates  150  may be used to accommodate different sized offsets  142 . 
   Alternatively, the cutting blade  14  may be the mechanism for offsetting as demonstrated in  FIG. 10 . There, a surface of the cutting blade  14  is made coplanar with the edges of one pair of boards  140 , while indenting or offsetting a second pair of boards  140 . Alternatively, a shim of suitable dimension may be inserted between the clamp fastener  128  and the edges of a pair of boards  140 , with the shim being of the width of a projection  146  or groove  144 . As yet another alternative, a pair of boards  140  may be offset a distance measured with a tape measure or other device; again the offset being equivalent to the width of a projection  146  or groove  144 . 
   The boards  140  desirably have grooves  144  and projections  146  cut into both ends of the boards. The projections of one pair of boards  140  is sized to be snugly received within the grooves  144  of the second pair of boards  140  in an interlaced manner. Four boards  140  are put together in an interlacing manner to form a box. 
   The method of cutting boards  140  for a box joint may include the following steps including joining a jig  10  to a table saw  12 ; clamping at least two pairs of boards  140  to the jig  10 ; positioning the clamped boards  140  relative to the table saw  12 ; cutting a groove  144  through all boards  140 ; repositioning the clamped boards  140  relative to the table saw  12 ; cutting another groove  144  spaced apart from the first groove  144 ; repeating the steps of repositioning and cutting another groove  144  until grooves  144  have been cut from one edge to an opposing edge with projections  146  disposed between the grooves  144 ; and interlacing the projections  146  and grooves  144  of the pairs of boards  140  to form a box joint. Desirably, the step of clamping includes clamping more than two pairs of boards  140  simultaneously. When clamping multiple pairs of boards  140 , it is preferable that the pairs of boards  140  are offset the width of a groove  144  before clamping the boards  140 . 
   Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize changes may be made in form and detail without departing from the spirit and scope of the invention.