Patent Publication Number: US-2005115376-A1

Title: Jig for cut-off saw

Description:
BACKGROUND OF THE INVENTION  
      This invention relates to jigs adapted to be used with power cut-off saws of the type shown in U.S. Pat. No. 5,483,858 to Chen (1996), which have clamping mechanisms for holding a piece of work on a support table of a saw.  
      A typical prior art power saw has an adjustable backup plate, which can be set at different angles with respect to the cutting plane of the saw to permit pieces of work to be sawed off at various angles to the longitudinal axis of the work. Normally the backup plate is set so that the work is cut at 90° to the longitudinal axis of the work, and must be adjusted when work is to be cut at some other angle.  
      The jig of this invention quickly and easily fits on the support table of a conventional saw so that work may be held and cut off at any desired angle without having to adjust the position of the backup plate on the saw. This reduces typical cutting time from about three or four minutes to less than 30 seconds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of an embodiment of a jig in accordance with the present invention;  
       FIG. 2  is a plan view of the jig shown in  FIG. 1 ;  
       FIG. 3  is a view taken on line  3 - 3  of  FIG. 2 ;  
       FIG. 4  is a plan view of an alternate embodiment of a jig in accordance with the present invention;  
       FIG. 5  is a view taken on line  5 - 5  of  FIG. 4 ;  
       FIG. 6  is a view taken on line  6 - 6  of  FIG. 4 ;  
       FIG. 7  is a perspective view of another embodiment of a jig of this invention, with a workpiece mounted in the jig;  
       FIG. 8  is a fragmentary perspective view of the jig showing the use of a gauge plate to position the workpiece in the jig;  
       FIG. 9  is a fragmentary perspective view of the jig shown in  FIG. 8  showing how the workpiece is rotated 180° to position it for a second cutting;  
       FIG. 10  is a perspective view of a workpiece after it has been cut twice to form a saddle to fit over a second workpiece;  
       FIG. 11  is a fragmentary perspective view of another embodiment of the jig of this invention mounted on a cutoff saw table and with a workpiece clamp in position for cutting;  
       FIG. 12  is a perspective view of yet another embodiment of the jig of this invention;  
       FIG. 13  is a plan view of an embodiment of the jig of this invention using an adjustable stop for setting the angle at which a workpiece is presented to the cutoff saw;  
       FIG. 14  shows separate elements of another jig of this invention using an adjustable plate for setting the angle at which a workpiece is presented to the cutoff saw; and  
       FIG. 15  is a plan view of the jig of  FIG. 14  assembled to hold a workpiece at a 45° cutoff angle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION  
      Referring to  FIG. 1 , a conventional circular saw  10  includes a cutting blade  12  which rotates in a cutting plane that contains the major plane of the saw blade, and is perpendicular to the axis of rotation of a horizontal shaft  14 , which supports the blade.  
      The saw also includes a horizontal support table  16  with an upwardly opening elongated guide groove  18  extending substantially parallel to the cutting plane of the saw, and extending vertically through the saw support table.  
      A vertical backup plate  20  is mounted on the support table to pivot about a vertical shaft  22  extending through an adjusting mechanism  24 , which can be locked in various positions for work to be cut by the saw.  
      A vertical table clamping plate  30  is secured by a bracket  32  to pivot about a vertical shaft  34  which extends down through a sleeve  36  secured at its upper and lower ends to the bracket. The forward end of a horizontal and longitudinally extending clamping screw  38  is threaded through a pillow block  40  secured by bolts  41  to the support table. A handle  42  on the rear end of the clamping screw permits the table clamping plate  30  to be moved toward and away from the backup plate  20 .  
      A jig  50  of this invention includes a horizontal and rectangular base plate  52  and an upright work engaging front wall  53  having a lower edge secured to the forward edge of the base plate at  54 . An upright rear wall  56  is secured at its lower edge to the rear edge of the base  52 . The front wall includes a substantially vertical work surface  58  lying in a major plane substantially parallel to the longitudinal axis of an elongated piece of work (not shown in  FIG. 1 ) on the base plate of the jig as shown in  FIG. 7 .  
      The jig base plate  52  rests on the support table  16 , and a vertical guide pin  60  welded to the bottom of the base plate extends down into the guide groove  18  to make a close sliding fit within the groove.  
      An angle-setting projection  62  (in the form of a horizontal plate with four non-parallel sides) welded to the forward face of the front wall extends toward the backup plate  20 . An aligning surface  64  on the forward end of projection  62  faces the backup plate, and lies in a vertical plane at an angle to the major plane of the work surface  58  of the front wall.  
      A work clamp  70  is secured to the forward end of a horizontal screw  72 , the rear end of which carries a handle  74 . The screw  72  is threaded through the left (as Viewed in  FIG. 1 ) end of the rear wall  56  so a piece of work (not shown in  FIG. 1 ) can be clamped within the jig between the front and rear walls.  
      The jig shown in  FIGS. 1-3  is used by placing the jig in the position shown in  FIG. 1 , and thereafter placing an elongated pipe (not shown) or other piece of work having a central longitudinal axis (not shown) in the jig and clamping the work in the jig with work clamp  70 . The table clamping plate  30  is then adjusted to drive it forward against the rear wall  56  of the jig, causing the guide pin  60  to slide forward (to the right as viewed in  FIG. 1 ) until the aligning surface  64  along the forward edge of the angle-setting projection  62  contacts the backup plate, which is set in the 0° position so that the backup plate  20  is perpendicular to the cutting plane of the saw. The angle of the aligning surface  64  with respect to the work surface  58  of the forward wall of the jig and causes the jig and clamping plate  30  to rotate in a counterclockwise (as viewed from above) direction around the guide pin  60  and vertical shaft  34  until the clamp  30 , jig, work, and angle-setting projection are all firmly locked in the position shown in  FIG. 1 . The angle between the aligning surface  64  and the major plane of work surface  58  can be any desired amount. However, 30° is a good angle for forming a saddle  74  on the end of a pipe  75  or cylindrical tube so the end of the pipe with a saddle makes a snug fit perpendicular to a similar piece of tubing  76  as shown in the phonograph of  FIG. 10 , The saddle is formed by first cutting the pipe or tubing at an angle of 30° thereafter rotating the pipe in the jig 180° about the longitudinal axis of the pipe, and making a second cut at 30°.  
      Typical dimensions of the jig are as shown on  FIGS. 2 and 3 , which also show that the jig base plate  52 , rear wall  56 , and forward wall  58  are conveniently formed by bending a single piece of rectangular plate into a U-shape.  
      An alternate embodiment of the invention is shown in  FIGS. 4-9 . Referring to  FIGS. 4-7 , a jig  80  includes a U-shaped body  82  having a horizontal base  84 , and vertical front and rear parallel walls  86  and  88 , respectively, each formed integrally along its respective lower edge with forward and rear edges of &lt;the base. A portion of the right and rear part of the base is cut away along lines intersecting  87  and  89  to leave a notch  93  which opens to the rear and right (as viewed in  FIG. 4 ) of the base. The portion of the base forward of line  89  extends to the right to be coterminous with the right edge of the front wall  86 . The right (as viewed in  FIG. 4 ) half of the rear wall  82  is also cut away along a vertical plane which includes line  87 .  
      The rear face  90  of the front wall forms a work-engaging surface  91  against which a piece of elongated work bears as described below.  
      A forwardly extending angle-setting projection  92  in the shape of a horizontal plate is welded to the forward face of front wall  86 . As shown best in  FIG. 4 , projection  92  includes an aligning surface  94  which extends rearwardly and to the right (as viewed in  FIG. 4 ) with respect to the major plane of front wall  90  at an angle of 30°, as shown by phantom line  96 . The projection  92  includes a right edge  98 , which is perpendicular to the major plane of front wall  90  and extends forward from the front wall for a distance of about equal to about one-half the distance between the front and rear walls of the jig. The rear end of aligning surface  94  begins at the forward end of edge  98 . The forward end of aligning surface  94  makes a right angle with a trailing edge  100 , which extends from the forward end of aligning surface  94  to the forward surface of front wall  86 . The angle-setting projection is welded to the front face of the forward wall.  
      A vertical gauge plate  104  ( FIGS. 4 and 6 ) is between and parallel to the front and rear walls of the jig. The gauge plate is substantially square, and is welded to the forward end of a horizontal rod  106 , which makes a close sliding fit through a bore  108  in the left (as viewed in  FIG. 4 ) end of the rear wall  82 . As shown best in  FIG. 4 , the vertical left edge  110  of the gauge plate is coplanar with the vertical left edge  112  of the base  84  and the vertical left edge  113  of front plate  86 . The left (as viewed in  FIG. 4 ) edges of the gauge plate  104  and front wall  86  each carry index marks  116  and  118 , respectively, to indicate the center line of various size pipes or tubing placed to rest on the base  84  of the jig.  
      As shown in  FIGS. 4 and 7 , and described above, the right half of the rear wall  88  and the base  84  are cut away so the table clamping plate  30  can engage the workpiece (pipe or tubing)  119  directly, and clamp it against the rear face  90  of the front wall in the cutting position shown in  FIG. 7 . The guage plate and rod  106  are not shown in  FIG. 7 . The pipe or tubing is marked with a soap stone marker (not shown), or other suitable device, to provide a horizontal line  120  ( FIG. 7 ) which lies in a horizontal plane passing through the longitudinal central axis of the pipe. The pipe is also marked with a substantially vertical line  122 , which lies in a plane that contains the left edge  124  of the front wall  86 . The right end of the pipe (i.e., the end of the pipe adjacent the table clamping plate  30 ) is sawed off at the angle (say, 30°) set by the aligning surface  94  on projection  92  secured to the forward face of front wall  86  of the jig  50 . The pipe or tubing is then released from the table clamp, and rotated 180° around its longitudinal axis so that the longitudinal mark  120  lines up with the appropriate mark on the left edge of gauge plate  104 , and so that mark  122  lies in the same plane as the left edge of rear plate  88 . The table clamp is reset to hold to the pipe firmly in the jig and so that jig is clamped against the backup plate  20 . Thereafter, the pipe is cut a second time. If the pipe has been cut at an angle of 30° each time, it forms a perfect saddle to fit on a pipe of similar diameter so it can be welded in position as shown in the photograph of  FIG. 10 .  
      As shown best in  FIGS. 4 and 5 , a guide pin  130  extends downwardly from the right front edge of base  84 . Conveniently, the guide pin is a carriage bolt  132  having a head  134  and an upwardly extending shank  135  disposed in a bore  136  extending through the base  84 . The upper end of the bolt shank is welded in the bore  136  to be substantially flush with the top surface of the base. The upper end of the bolt shank and the surrounding base  84  are ground to a flat finish. The carriage bolt can be of any convenient size. A {fraction (5/16)}″ carriage bolt has a shank which fits in the guide groove  18  ( FIG. 1 ) of most power saws. The right (as viewed in  FIG. 4 ) side  137  of the bolt head is cut off to be flush with the right edge of the shank and lying in a vertical plane as shown in  FIGS. 4 and 5 . This permits the guide pin  130  to be fitted into most guide slots or cut-off saws by simply rotating and tilting the jig. The guide pin is easily removed when desired by reversing those steps. Other retaining means can be used on the lower end of the guide pin. For example, the bolt head can be of any shape which has a horizontal dimension greater than and transverse to width of the guide groove  18  when the jig holds the workpiece in cutting position, and which has a horizontal dimension less than and transverse to the guide groove when the jig is rotated so the front plate is perpendicular to the guide groove.  
      In another embodiment of the jig of this invention, the entire base and rear wall can be omitted, and the guide pin  130  can be secured to the lower edge of the front plate. With this arrangement the work piece rests and slides on the support table  16  as the work piece is moved into position for cutting.  
      As shown in  FIGS. 8 and 9 , if desired, the gauge plate  104  and rod  106  of the embodiment shown in  FIGS. 4, 5  and  6  can be omitted and replaced by a gauge card or plate  140 , say, a thin square plate about 3×3 inches. As indicated above, the entire rear wall of the jig may also be omitted. The edges of the gauge card are provided with indexing marks  142  for pipes of various diameters. For example,  FIG. 8  shows a 2″ pipe with marks  120  and  122  previously applied and rotated 180° so that the longitudinal mark  120  lines up with the 2″ index mark on the gauge card, and so that the vertical mark  122  lines up with the left edge of the card gauge, which lies in the plane defined by the left edges of the base and front wall of the jig.  
       FIG. 11  shows in perspective an alternate embodiment of a jig  150 , which is similar to the jig shown in  FIG. 7 , except that an angle-setting projection  162  is formed integrally with a front wall  153 , which is cut vertically at  155  from the upper edge of the front wall  153  down to about the mid point of the height of the front wall. The angle-setting projection  162  is bent forward to present a horizontal aligning surface  164 , which is cut to position the jig at the desired angle for cutting the workpiece  199 , which is clamped firmly against the work engaging front wall  153  by the clamping plate  30 .  
      A flexible clip  169  is welded at its lower edge (shown only in  FIG. 12 ) to the lower edge of the rear wall. The clip  169  permits the gauge plate  140  to be stored in a convenient location when not in use.  
      A gauge label  171  is mounted on the forward face of the front wall to provide a series of vertically spaced horizontal marks indicating the center line of various tubular workpieces having a diameter from one half inch to three inches. This facilitates marking the tubing as previously described to facilitate rotating at 1000 to the proper position for making a second cut to form a saddle at the cut end of the tubing.  
      Elements shown in  FIGS. 11-13  corresponding with those shown in  FIGS. 1-9  are given corresponding reference numerals, and those elements are not described again with respect to  FIGS. 11-13  for simplicity.  
      The jig  250  shown in  FIG. 12  is almost identical to that shown in  FIG. 11 , except that a vertical gauge plate  271  perpendicular to the front wall is welded to the left end of the forward wall  153 , and includes vertically spaced horizontal indexing marks to show the center line of the tubular workpieces placed in the jig and having a diameter between one half inch and three inches. This facilitates marking the center line of the workpiece as described above. The jig of  FIG. 12  also includes a clip  169  welded to the forward face of the rear wall  188  for holding the gauge plate  140 . Alternatively, the gauge plate may be secured to the forward face of the front wall  153  by a wing nut  251  threaded onto a horizontal screw  252  welded to the forward face of the front wall. A hole  253  through the gage plate permits the plate to be slipped on and off the screw  252 . Alternatively, the gauge plate  140  can be secured to the rear face of the rear wall  188  by similar wing nut and screw combination (not shown).  
      The jig  350  shown in  FIG. 13  is similar to that shown in  FIG. 4 , except that the plate forming the angle-setting projection  92  is omitted, and replaced by an internally threaded horizontal sleeve  351  secured at its rear end by external threads  352  in an internally threaded socket  353  in the front wall  90 . The sleeve is perpendicular to, and extends forward from the front wall. A screw  354  is threaded into the sleeve to provide an adjustable angle-setting projection, which can be locked in any desired position by a locking nut  356 , which can be tightened to bear against the forward end of sleeve  351 . With the screw  354  in its most extended position, as shown in  FIG. 13 , it and the right end of the front wall form an angle-setting projection which holds the longitudinal axis of the workpiece at an angle of 45° with respect to the cutting blade of the cutoff saw. With the screw  334  threaded fully into sleeve  351 , the forward end of the screw and the right end of the front wall form an angle-setting projection at an angle of 30° between the longitudinal axis of the workpiece and the major plane of the saw blade. The screw is provided with suitable marks or color coding (not shown) to facilitate setting it in the correct position for any desired angle between 30° and 45°. For smaller angles, the sleeve shown in  FIG. 13  is replaced by a shorter sleeve and screw (not shown) of similar construction. The remaining elements of the jig shown in  FIG. 13  are given reference numerals corresponding to those of corresponding elements in  FIG. 4 , and the detailed description of those elements is not repeated here for simplicity.  
       FIG. 14  shows the various elements of another jig  400  of this invention, which includes a jig body  402  having a vertical front wall  404  and a horizontal base  406 , which has the same shape as the base  84  for the jig shown in  FIG. 4 . A downwardly extending guide pen  408  is welded to the lower surface of the base  406 , and includes a downwardly extending shank  410  which terminates at its lower end in a head  412  in the shape of an elongated rectangle with the longer dimension of the rectangle perpendicular to the front wall. The width of the rectangle is slightly less than the guide groove on the support table of the saw so the guide pin  408  will fit down into the guide groove  18  when the front wall is perpendicular to the elongated axis of the guide groove. As the jig is rotated counterclockwise (as viewed in  FIG. 15 ) to position a workpiece for cutting at a proper angle, the elongated head  412  of the guide pin  408  is rotated so that it makes a close fit against the under surface of the support table adjacent the guide slot, and thus locks the jig to the support table as the workpiece is cut.  
      A horizontal shelf  414  is welded to the forward face  416  of the front wall  404 , and includes an internally threaded vertical bore  418  adapted to receive an externally threaded screw  420  with an outwardly extending circular stop  422  at the upper end of the screw. An elongated horizontal handle  424  is secured at one end of the upper end of the screw to facilitate tightening the screw in the internally threaded bore  418 .  
      A flat angle-setting projection plate  430  is adapted to rest on the top surface of the shelf  414  as shown in  FIG. 15 . The projection plate is in the shape of a pentagon having first, second, third, fourth and fifth sides  432 ,  433 ,  434 ,  435 , and  436 , respectively. As shown in  FIG. 15 , the angle-setting projection plate  430  is secured to the top surface of a shelf  414  with the second side  433  bearing against the forward surface  416  of the front plate  404 . A pair of inwardly extending first and second slots  438  and  439  are formed in the plate  430  at opposite ends of the first side  432 . The inner end of each slot is semi circular to make a close fit around the externally threaded screw  420 . A load washer  442  rests on the plate  430  over the second slot  349 , and a lock washer  444  rests on the load washer. The screw  420  extends down through the tube washers and is threaded in the bore  418  as shown in  FIG. 415 . Handle  424  is used to tighten the screw  420  so the plate  430  is clamped firmly in place on the shelf so that the forward most portion of the plate  430  is the apex formed by adjacent portions of the third and fourth sides  434  and  435 , respectively. The interior angle between the second side  433  and the fourth side  435  is 45° so that when the jig and workpiece (not shown) are advanced to the cutting position, the jig rotates as described above in a counterclockwise direction until the fourth side  435  of the plate  430  fits against the backup plate on the support table of the saw. A workpiece is then in position for being cut at a 45° angle. If a 30° cut is required, the screw  422  is loosened, the plate  430  is pulled out, rotated counterclockwise (as viewed in  FIG. 15 ) until the first slot  438  is aligned over internally threaded bore  418  and fits around the screw  420 , which is then tightened to clamp the projection plate  430  with the first side  432  fitting firmly against the forward face  416  of the front plate  404 . With the projection plate in this position, the most forward point of the plate is the apex between the third and fourth sides  434  and  435 , respectively. The third side  434  makes an interior angle of 30° with the first side  432  so that with the plate  430  mounted as just described, a workpiece can be cut at an angle of 30°. A cut at an angle of 22.5° is made by positioning the fifth side  436  against the forward face of the front plate, and aligning a third slot  450  formed in the plate  430  between adjacent fourth and fifth sides  435  and  436 , respectively, around the screw. With the plate clamped in that position, the forward most part of the projection plate  430  is the apex formed by the second and third sides  433  and  434 , respectively. The interior angle between the second side  433  and the fifth side  436  is 22.5°. For convenience, the plate is labeled adjacent the second, third and fourth sides to indicate the angle of the cut made when those sides are parallel to the backup plate on the support table of the saw.  
      From the foregoing description of the various jigs, it will be clear that the present invention provides a quick and economical way of supporting elongated workpieces in a cutoff saw for cutting workpieces at various angles.