Patent Abstract:
Operating a power saw between a pair of parallel guide rails, which engage opposing sides of saw base plate to constrain the motion of the saw to a straight path, allows for precise cuts. A set of two or more fences allows for multiple cutting options. In some embodiments, non-parallel fences coupled to the guide rails allow for precise cuts at more than just a single angle. In some embodiments, two fences may engage opposing sides of the object to be cut simultaneously, holding the object more securely with respect to the guide rails than would a single fence. A possible clamping force holding the two fences against the object allows the miter guide to remain fixed relative to the object so that the user&#39;s hand may be freed for another task, such as holding the saw with both hands.

Full Description:
RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 11/607,763, filed Dec. 1, 2006, now U.S. Pat. No. 7,757,592 issued Jul. 20, 2010 and claims priority thereto. 
    
    
     TECHNICAL FIELD 
     The invention relates generally to woodworking and industrial power tools, and more particularly, to providing a cutting guide for a hand-held power saw. 
     BACKGROUND 
     Miter boxes are cutting guides that allow precision cuts using hand-held saws, because they both constrain the saw to move in a straight line and also align the cutting path with respect to the object being cut. Typical miter boxes are designed for hand-operated saws, and include cutting guides for 90-degree cross cuts, as well as 45-degree miter cuts. The cutting guides in a typical miter box are usually pairs of notches on opposing sides of the box, barely wider than the saw blade, and which are oriented at a precise angle with respect to the box&#39;s inner surfaces. These surfaces are a cutting surface, which the blade will score as it cuts through the object, and at least one other alignment surface, which may be identified as a fence. A miter box typically forms a 3-sided trough with a cutting surface at the bottom, and two fences protruding above the cutting surface. The notches are in the fences. 
     An object to be cut is placed on the cutting surface and held firmly against a fence. The saw blade is then placed in a set of notches, and the user may cut the object by sliding the saw blade back and forth within the notches. The notches work well for guiding hand-operated saws, because the blade spans the width of the miter box and is held in place by both notches. Further, the cutting edge of the blade only engages the object to be cut and the cutting surface. That is, the cutting edge of the blade does not contact the fences. 
     A typical miter box will not work with a common hand-held power saw, because the blade will not be held in place by both notches simultaneously when the cutting starts. Further, because the blade is circular, it will strike the distant fence and likely cut a new notch in it. For example, if an object to be cut is placed in a typical miter box, the power saw blade is set in one the notch of the first fence, and the saw is turned on, the single notch is unlikely to properly constrain the blade. As a result, as the user passes the saw through the object toward the second fence, the blade will likely engage the fence somewhere other than the pre-cut notch in the second fence. The cutting edge of the blade will then just cut a new notch in the second fence. The miter box will become damaged, and will not have achieved its purpose. 
     A common power tool for making precision cuts is a power miter saw. A power miter saw arrangement provides a cutting surface, typically a single fence, and a power saw attached to a precisely-oriented moving arm. The arm is allowed to move in an arc about a pivot point, and the angle of the arm motion is usually adjustable. A power miter saw allows precise cuts by guiding the blade via a calibrated arm attached to the motor and coupled to the fence. 
     Unfortunately, power miter saws may be expensive and heavy, and are often unsuited for some of the tasks for which a power saw is commonly used. Thus, a user may have two saws: a power saw for general cutting tasks and power miter saw for precision cuts. This duplication of power saws can be expensive and burdensome to transport to a job site. 
     BRIEF SUMMARY 
     Operating a power saw between a pair of parallel guide rails, which engage opposing sides of saw base plate to constrain the motion of the saw to a straight path, allows for precise cuts. A set of two or more fences allows for multiple cutting options. In some embodiments, two fences may engage opposing sides of the object to be cut simultaneously, holding the object more securely with respect to the guide rails than would a single fence. A possible clamping force holding the two fences against the object allows the miter guide to remain fixed relative to the object so that the user&#39;s hand may be freed for another task, such as holding the saw with both hands. The clamping force may result from one fence being adjustable, or the fences may be spaced apart to fit snugly over common sizes of pre-cut lumber. 
     In some embodiments, non-parallel fences coupled to the guide rails allow for precise cuts at more than just a single angle. One fence may be oriented at an angle between 59 degrees and 91 degrees with respect to the guide rails, and another fence may be oriented at an angle between 29 degrees and 61 degrees with respect to the guide rails. Because the fences are not parallel, they have a closest point on one side of the guide rails. The ends of the fences may be angled so that the end of each fence is parallel to the other fence at the closest point. Some embodiments do not require a cutting surface. That is, unlike a traditional miter box, in which the object to be cut is placed inside the box, embodiments of the invention may be placed on top of the object, with open space below the object. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  shows a prior art cutting guide; 
         FIG. 2  shows another prior art cutting guide; 
         FIG. 3A  shows an embodiment of a power saw miter guide; 
         FIG. 3B  shows another view of the power saw miter guide of  FIG. 3A ; 
         FIG. 4A  shows another embodiment of a power saw miter guide; 
         FIG. 4B  shows another view of the power saw miter guide of  FIG. 4A ; 
         FIG. 5  shows another embodiment of a power saw miter guide; and 
         FIG. 6  shows a method for using an embodiment of a power saw miter guide. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows prior art cutting guide  10  for making 90-degree cross cuts with power saw  101 . Prior art cutting guide comprises guide rail  103  and  104 , saw support surface  105 , parallel fences  107  and  108 , and cutting surface  109 . Saw support surface  105  comprises notch  106  through which saw blade  102  passes when cutting an object. Because notch  106  completely separates saw support surface  105  into two pieces, each of guide rails  103  and  104  must be firmly attached to both fences  107  and  108  for structural rigidity. As a result, in the prior art device  10 , fences  107  and  108  are not adjustable. 
     In operation, a user places an object to be cut on cutting surface  109 , between fences  107  and  105 , completely to the side of one of guide rails  104  and  103 . The object is then slid along cutting surface  109  until the part of the object to be cut is beneath notch  106 . Since the object must be able to slide along cutting surface  109 , and fences  107  and  108  are not adjustable, fences  107  and  108  cannot hold the object firmly. As a result, the user must use one hand to hold the object firmly against one of fences  107  or  108  while the object is being cut. This either requires the use of an assistant, or else leaves the user only a single hand for operating the saw. 
       FIG. 2  shows prior art cutting guide  20  for making cuts at an arbitrary angle. Cutting guide  20  comprises a single guide rail  201  attached to a single fence  202 , whereby guide rail  201  pivots about hinge  203 . Adjustable arc slot  204  works with hinge  203  to allow guide rail  201  to be oriented at a range of angles with respect to fence  202 . As with prior art cutting guide  10  from  FIG. 1 , prior art cutting guide  20  only engages the object to be cut with a single fence, requiring that object be held against prior art cutting guide  20 . Further, since prior art cutting guide only has single guide rail  201  a saw may wander away from guide rail  201 , resulting in an imprecise cut. 
       FIG. 3A  shows an embodiment of power saw miter guide  30 . Power saw miter guide  30  comprises first guide rail  303 , second guide rail  304 , first fence  307  and second fence  308 . Second guide rail  304  is oriented parallel to first guide rail  303 . First fence  307  is coupled to first guide rail  303  and second guide rail  304  and is oriented at an angle between 59 degrees and 91 degrees with respect to guide rails  304  and  304 . As shown in  FIG. 3A , first fence  307  is oriented at an angle of approximately 90 degrees with respect to guide rails  304  and  304 . Second fence  308  is also coupled to first guide rail  303  and second guide rail  304  and is oriented at an angle between 29 degrees and 61 degrees with respect to guide rails  304  and  304 . As shown in the figure second fence  308  is oriented at an angle of approximately 45 degrees with respect to guide rails  304  and  304 . 
     Guide rails  303  and  304  constrain motion of saw  101  to a straight path by engaging opposing sides of the base plate of saw  101  as saw  101  rides on saw support surface  305 . Saw blade  102  passes through notch  306  to cut an object that may be set on cutting surface  309 , and aligned against either fence  307  or fence  308 . Window  302  in saw support surface  305  between guide rails  303  and  304  allows a user to see that the object being cut is aligned properly within miter guide  30  between fences  307  and  308 . Window  302  does not span the entire distance between guide rails  303  and  304 , so that a portion of saw support surface  305  is still available to support saw  101 . 
     The arrangement of guide rails  303  and  304 , fences  307  and  308  with respect to saw support surface  305  and cutting surface  309  can be seen in  FIG. 3A . Saw support surface  305  and cutting surface  309  are parallel. Fences  307  and  308  are on top of cutting surface  309 , and saw support surface  305  is on top of fences  307  and  308 . Guide rails  303  and  304  are the above saw support surface  305 . Fences  307  and  308  are thus coupled to guide rails  303  and  304  through saw support surface  305 . Optional carrying handle  301  in cutting surface  309  makes miter guide  30  conveniently transportable. Alternatively, optional carrying handle  301  could be placed at any convenient location on miter guide  30 . 
     Since fences  307  and  308  are not parallel, there is a point at which they would intersect, if they were not truncated. This arrangement could limit the length of the object to be cut, or at least limit the length that could be cut from it. As a result, unlike fences  107  and  108  of prior art cutting guide  10  from  FIG. 1 , fences  307  and  308  of miter guide  30  must be truncated shortly outside of guide rails  303  and  304 . Fences  307  and  308  reach a closest point just outside guide rail  303 . In this area, end  310  of fence  307  is parallel to fence  308 , while end  311  of fence  308  is parallel to fence  307 . With proper spacing, ends  310  and  311  of fences  307  and  308 , respectively, could provide an extra alignment point for common sized pre-cut lumber. 
     For example, if the distance between ends  310  and  311  may be set so that if one side of a 2×4 piece of lumber is pressed against fence  307 , the opposing side of the 2×4 could contacts end  311 . Alternatively, a 2×4 pressed against  308  may also contact end  310 . This arrangement will provide added stability for the object to be cut. Typical dimensions for miter guide  30  to accommodate commonly available power saws would be: the distance between guide rails  303  and  304  set between 5 inches and 7 inches, the distance between saw support surface  305  and cutting surface  309  set between 1 inch and 5 inches, and notch  306  set between 1 and 3 inches in depth. 
     Other dimensions may be used without departing from the spirit and scope of the invention. Further, if cutting surface  309  was eliminated, miter guide  30  would be placed on top of the object to be cut, rather than the object to be cut being placed inside miter guide  30 . That is, the underside of saw support surface  305  or guide rails  303  and  304  would rest on top of the object to be cut. Fences  307  and  308  must then be taller than the depth of notch  306  at the point where notch  306  passes through fences  307  and  308 . 
       FIG. 3B  shows another view of power saw miter guide  30 , but without saw  101 . The extent of window  302  between guides  303  and  304  and fences  307  and  308  is more easily seen in  FIG. 3B , as well as the location where notch  306  intersects fence  308 . Note that miter guide  30  allows precision cuts at two different angles, which is not possible with prior art cutting guide  10 , and holds both sides of saw  101 , whereas prior art cutting guide  20  cannot. 
       FIG. 4A  shows another embodiment of the invention as reflected in power saw miter guide  40 . Miter guide  40  comprises guide rails  403  and  404 , along with fences  407  and  408 . Saw support surface  405  is the top surfaces of fences  407  and  408 . Since there is no cutting surface, fences  407  and  408  are taller than the depth of notch  406 , and notch  406  is separated into two parts. End  410  of fence  407  is parallel to fence  408 , while end  411  of fence  408  is parallel to fence  407 . Miter guide  40  is used by setting miter guide  40  atop the object to be cut, rather than setting the object to be cut on a cutting surface. As can be seen from  FIGS. 4A and 4B , top surfaces  405  of fences  407  and  408  are parallel and lie in a common plane with the undersides of guide rails  403  and  404 . 
     Miter guide  40  also has two additional fences  412  and  413 , both of which are visible in  FIG. 4B . Fence  412  is parallel to fence  407 , while fence  413  is parallel to fence  408 . With proper spacing between pairs of fences  407  and  412  or  408  and  413 , commonly-sized pre-cut lumber may be held firmly with respect to miter guide  40 . That is, fences  407  and  412  may be set apart such that miter guide  40  fits snugly over a 2×4. Additionally, the spacing of fences  408  and  413  may be set to accommodate a common size of lumber. Typical dimensions for miter guide  40  may be a distance between fences  407  and  412  or  408  and  413  of between 1 inch and 5 inches. 
       FIG. 5  shows yet another embodiment of the invention as reflected in power saw miter guide  50 . Miter guide  50  comprises guide rails  503  and  504 , along with fences  507  and  508 . Saw support surface  505  is the top surfaces of fences  407  and  408 , along with some extensions added to improve the rigidity of miter guide  50  at the intersections of guide rail  503  with fences  507  and  508 . Fences  507  and  508  are taller than the depth of notch  506 . Ends  510  and  511  of fences  507  and  508 , respectively, are parallel with the opposing fence,  508  and  507 , respectively. 
     Fences  512  and  513  are two sides of adjustable fence assembly  514 , where fence  512  is parallel to fence  507  and fence  513  is parallel to fence  508 . Adjustable fence assembly  514  has two slots  515  and  516 . Adjustment bolts  517  and  518  in guide rail  504  pass through slots  515  and  516 , so that adjustable fence assembly  514  rides along an angled path with respect to both fences  507  and  508 . For example, if fences  507  and  508  form a 45-degree angle, then fences  512  and  513  also form a 45 degree angle. Slots  515  and  516  then could be at a 22.5-degree angle with respect to both fences  507  and  507 . This way, as adjustable fence assembly  514  moves inward, toward the closest point between fences  507  and  508 , the distance between fences  507  and  512  closes. The distance between fences  513  and  508  will also close as adjustable fence assembly  514  moves inward. Conversely, as adjustable fence assembly  514  moves outward, away from the closest point between fences  507  and  508 , the distances between fences  507  and  512  or  508  and  513  will increase. 
     In operation, miter guide  50  may be set on top of an object to be cut, and aligned using either fence  507  or  508 . Adjustable fence assembly  514  is then moved so that the object is held between either fences  507  and  512  or fences  508  and  513 . Adjustment bolts  517  and  518  may then be tightened so that miter guide  50  is held firmly relative to the object. Spring loaded or other flexible tension methods may alternatively be used, rather than bolts, in order to provide holding force for adjustable fence assembly  514 . 
       FIG. 6  shows method  600  for using an embodiment of a power saw miter guide. In process  601 , an object to be cut is aligned against a first fence. In process  602 , a second fence, parallel to the first fence, is brought against the opposing side of the object. If the distance between the parallel fences is not adjustable, but is rather set to be snug against opposing sides of commonly-sized pre-cut lumber, process  602  may be nearly simultaneous with process  601 . In process  603 , a saw base plate is set between parallel guide rails. In process  604 , the saw is operated between two parallel guide rails. The guide rails engage opposite sides of the base plate to constrain motion of the saw to a straight path. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Technology Classification (CPC): 1