Abstract:
This invention relates generally to power tools, and more particularly to a portable, multifunction saw and uses thereof (e.g., for household, commercial (e.g., for use in window removal and replacement) and medical (e.g. for bone cutting) applications).

Description:
[0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 11/300,854, filed Dec. 15, 2005, which claims the benefit of U.S. Provisional Application No. 60/636,301 filed Dec. 15, 2004, the disclosure of each of which is incorporated herein by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to power tools, and more particularly to a portable, multifunction saw assembly comprising a protective guard-guide subassembly (e.g., for household, commercial (e.g., for use in general carpentry and finish carpentry) and medical (e.g. for bone cutting) applications). 
       BACKGROUND OF THE INVENTION 
       [0003]    Saws are used for a variety of purposes. For example, saws are used in a variety of carpentry-type applications. For example, when a window begins to fail (e.g., warp, rot or leak) the costs in terms of energy costs add up. Window replacement serves as a means to overcome the expenses associated with failing old windows. New window technology has resulted in dramatic savings and increased comfort for home-owners through the use of reformulated frame materials and glazing products that require significantly less maintenance. However, current methods and devices used for the removal of old windows are time consuming, damaging and often dangerous. For example, current methods (e.g., use of a chisel and hammer or a reciprocating saw) lead to disruption of the inside trim and destruction of wood that otherwise need not be replaced. 
         [0004]    Saws also find use in medicine (e.g., orthopedic medicine). For example, knee replacement surgery typically involves removal of all or a portion of the existing knee joint, and the insertion of artificial prostheses (or components). The orthopedic surgeon utilizes a series of sequential instruments and guides to cut and shape the patient&#39;s host bone on which implants are fixed, resulting in replacement of the worn surfaces of all three compartments of the knee with smooth articulating artificial surfaces. 
         [0005]    Currently available saws are not ideal for many tasks (e.g., window removal or use in the operating room) because of safety concerns. Specifically, some saws lack protective guards that cover the entire blade of the saw while others may have a partially enclosing protective cover that requires manual adjustment by the user. Both of these types of guards prohibit a user from getting close enough to a cut site to permit the blade to make a flush cut. Still other saws do not permit the user to make a straight cut. Therefore, a need exists for a safer and easier to use saw (e.g., that allows for safer, more efficient and less expensive removal and replacement of old windows, or, that permits a straight cut to be made in a safe manner (e.g., for use in commercial or medical settings). 
       SUMMARY OF THE INVENTION 
       [0006]    This invention addresses the problems outlined above by providing a portable, multifunction saw assembly comprising a protective guard-guide subassembly (e.g., for household, commercial (e.g., for use in general carpentry and finish carpentry) and medical (e.g. for bone cutting) applications). 
         [0007]    Accordingly, in some embodiments, the present invention provides a saw assembly, comprising: an electric motor subassembly, the electric motor subassembly having an electric motor adapted to produce rotational movement about a first axis of rotation and a spindle rotatably powered by the electric motor for rotation about a second axis of rotation that is perpendicular to the first axis of rotation; a blade mounted on the spindle, and a retractable, fully enclosing blade guard-guide subassembly, the blade guard-guide subassembly comprising a top main guard-guide slidably mounted on the electric motor subassembly and a bottom guard-guide plate fixed to the top main guard-guide assembly. In some embodiments, the blade is mounted on a flush-mount comprising a countersunk dimple with a hardened screw. In some embodiments, the blade is mounted on a blade spacer/adapter removably attached to the saw. In some embodiments, the blade is mounted onto the spacer/adapter using three or more counter sunk screws. The present invention is not limited by the type of material used to make the spacer. Indeed, a variety of materials are contemplated to be useful for making a spacer of the present invention including, but not limited to, TEFLON, aluminum, DELRIN, copper, rubber or plastic. In some embodiments, the blade has teeth that extend to an outer circumference of the blade. In some embodiments, the blade guard-guide subassembly is spring-loaded. In some embodiments, the blade guard-guide subassembly fully encloses the blade until the blade guard-guide subassembly operably contacts a surface. In some embodiments, the operable contact comprises physical contact between a surface and the guard-guide subassembly such that the blade guard-guide moves into a retracted position, wherein the amount of retraction directly correlates with the amount of pressure asserted against the guard-guide subassembly by the surface. In some preferred embodiments, a saw of the present invention is used to make a flush-cut. For example, in some embodiments, the blade comprises oblong cutouts for attachment (e.g., with screws) to a flanged hub. In some embodiments, the flanged hub attaches to and drives the blade. The present invention is not limited by the configuration of the flanged hub. Indeed, a variety of configurations are possible including, but not limited to, a flanged hub with an oval section that protrudes from the hub a dimension equal to the thickness of the blade (e.g., so as to be flush with the blade when the two are joined by screws (e.g., machine screws). In some embodiments, the blade is attached to a spacer/adapter. The spacer/adapter may be made of any suitable material. The present invention is not limited by the type of material used to make the spacer. Indeed a variety of materials are contemplated to be useful including, but not limited to, TEFLON, copper, DELRIN, aluminum, rubber or plastic. Furthermore, the spacer/adapter may comprise one or more (e.g., three or more) holes for receiving screws for attachment of the blade. In some embodiments, the blade alternatively provides other means for attaching to the saw (e.g., at three or more locations to provide a stable attachment). In some embodiments, the blade and/or guard-guide subassembly comprises a spacer so as to minimize run out or galloping of the blade on a surface to be cut (e.g., thereby preventing uneven blade exposure to a surface during cutting). 
         [0008]    The present invention is not limited by the type of surface contacted. Indeed, many types of surfaces are contemplated to be contacted by the saw including wood, plastic, metal, glass, ceramic, tile and bone. In some embodiments, the maximal amount of retraction of the guard-guide subassembly exposes 10% of the blade (in some embodiments, the maximal amount of retraction exposes 10-25% of the blade, in some embodiments, the maximal amount of retraction exposes 25-50% of the blade, in some embodiments, the maximal amount of retraction exposes 50-75% of the blade, and in still other embodiments, the maximal amount of retraction exposes greater than 75% of the blade). In some embodiments, the cutting blade is adjustably positioned with an adjustable stop for depth in vertical alignment with the cutting surface. In some embodiments, the blade guard-guide subassembly comprises an aluminum alloy or plastic. In some embodiments, the bottom guard-guide plate is fixed to the top main guard-guide (e.g., via screws). In some embodiments, the bottom guard-guide plate is fixed to the top main guard-guide (e.g., via screws). In further embodiments, the guard-guide subassembly comprises a retractable (e.g., spring loaded) bottom guard-guide that is retracted (e.g., fully to completely expose the bottom portion of the blade (e.g., for flush-cutting)) separate from retraction of the top, main guard-guide (e.g., the top, main guard guide will remain in place while a user retracts the bottom guard (e.g., to make a flush-cut). In some embodiments, the fully enclosed (fixed bottom guard) guard-guide assembly incorporates a “U” shaped notch so as to allow a pipe or other object whose diameter or width is less than the notch, to become engulfed in the notch as the cut proceeds. 
         [0009]    In some embodiments, the guard-guide subassembly comprises angled housing. In some embodiments, the saw assembly further comprises an electric motor with a momentary contact switch (e.g., a dead man&#39;s switch). In some embodiments, the contact switch comprises a variable speed throttling switch. In some embodiments, the throttling switch permits the blade speed to ramp up or down. In some embodiments, the saw assembly further comprises a handle. In some embodiments, the electric motor is adapted to operate at rotational speeds between 3000-5000 revolutions per minute (rpm) (in some embodiments, the motor operates at speeds between 5000-7000 rpm, in other embodiments, the motor operates at speeds between 7000-10,000 rpm, and in still other embodiments, the motor is adapted to operate at rotational speeds greater than 10,000 rpm). In some embodiments, the blade comprises a carbide tip. In some embodiments, the outer diameter of the blade is between 2-4 inches (in some embodiments, the diameter is between 4-5 inches, in still other embodiments, the blade diameter is between 5-7 inches, and in some embodiments, the diameter of the blade is greater than 7 inches. In some embodiments, the saw assembly further comprises a vacuum attachment. 
         [0010]    The present invention also provides a method of cutting a surface using the saw of the present invention. The present invention is not limited by the nature of the surface being cut. Indeed, a variety of surfaces are contemplated, including, but not limited to, wood, plastic, metal, glass, ceramic, cement, tile and bone. In some embodiments, the guard-guide of the saw permits a user to make a straight cut in a surface (e.g., house siding (e.g., wood cement, composite or the like). In some embodiments, cutting a surface comprises making a flush, plunge cut in the surface. In some embodiments, cutting a surface comprises undercutting a door jamb. In some embodiments, cutting a surface comprises undercutting a base molding. 
         [0011]    The present invention also provides a method of removing windows comprising using saws of the present invention and related devices. 
         [0012]    The present invention further provides a method of removing a window, comprising removing an existing sash of the window, the removing comprising cutting stops present in the window, the cutting comprising using a saw configured so as not to have a blade exposed to the user during any portion of its use, wherein the method does not disrupt the inside window trim. In some embodiments, the window is replaced with a new window after the old window is replaced. In some embodiments, there is no need for new pieces of wood to assist in the replacement of the old window (e.g., in some embodiments, only caulk is needed). 
         [0013]    A sash is the framework into which glass is set. Double-hung windows have two sashes: an upper and a lower sash. The window sashes slide within a window frame. The top horizontal member of the frame is called the head. The side frames are called jambs. Concealed behind the side jambs on old double-hung windows may be heavy metal sash weights connected to the sash with rope-and-pulley systems. The weights provide a counterbalance that makes the sash easier to open. Newer windows use a revolving drum in the head or tubed tension springs in the side jambs instead of sash weights. The lower horizontal part of the window frame is called the sill. A series of stops attached to the jambs provides channels in which the sashes can slide. Blind stops are permanently attached to the outside edges of the jambs, but both a parting stop (separating the two sashes) and an inside stop can be pried loose (or cut) to remove a sash. Interior casings at the sides and top and an apron across the bottom cover any gaps between the window frame and the walls. The lower sash comes to rest behind a flat stool or interior sill; its outside counterpart, the exterior sill, is sloped so that water will run off. 
         [0014]    In some embodiments, the present invention provides a saw assembly comprising a motor; a linkage for converting rotating power of the motor into linear reciprocating (e.g., vibrating) movement; a slider shaft mounted at an end of the linkage having an angle of approximately 90 degrees with respect to the linkage; a slider, for attaching a saw blade, which moves reciprocatingly along the slider shaft, and a fully enclosing blade guard-guide subassembly, the blade guard-guide subassembly comprising a top main guard-guide slidably mounted on the electric motor subassembly and a bottom guard-guide plate fixed to the top main guard-guide assembly. In some embodiments, the blade used with reciprocating, vibrating or oscillating saw is non-circular (e.g., is a file saw blade). 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  depicts a side view of a saw assembly constructed according to the invention. 
           [0016]      FIG. 2  depicts a frontal view of a saw assembly constructed according to the invention. 
           [0017]      FIG. 3  depicts an exploded frontal view of a saw assembly constructed according to the invention. 
           [0018]      FIG. 4  depicts a top view of a saw assembly constructed according to the invention. 
           [0019]      FIGS. 5A and 5B  depict a window blind stop (A) before and (B) after cutting with a saw assembly constructed according to the invention. 
           [0020]      FIG. 6  depicts a top view of a saw assembly constructed according to the invention with the blade partially deployed into a surface. 
           [0021]      FIG. 7  shows a top view of one embodiment of a blade and blade spacer of the present invention. 
           [0022]      FIG. 8  shows a side view of one embodiment of a blade and blade spacer of the present invention. 
           [0023]      FIG. 9  shows one embodiment of a guard-guide subassembly with screws used to attach a blade spacer to a blade. 
           [0024]      FIG. 10  shows one embodiment of a blade partially deployed beyond an angled guard-guide subassembly housing. 
           [0025]      FIG. 11  depicts one embodiment of a blade ground or turned to produce a chamfered shoulder (e.g., for use with an integral spacer and bearing surface). 
           [0026]      FIG. 12  shows a side view of one embodiment of a spacer for use with a blade of the present invention. 
           [0027]      FIG. 13  depicts a side view of one embodiment of a saw assembly comprising a guard-guide subassembly comprising a retractable bottom guard-guide that is retracted separate from retraction of the top, main guard-guide. 
           [0028]      FIG. 14  depicts a cutaway side view of one embodiment of a saw assembly comprising a guard-guide subassembly comprising a retractable bottom guard-guide that is retracted separate from retraction of the top, main guard-guide. 
           [0029]      FIG. 15  depicts an oblique top view of one embodiment of a saw assembly comprising a guard-guide subassembly comprising a retractable bottom guard-guide that is retracted separate from retraction of the top, main guard-guide. 
           [0030]      FIG. 16  depicts an oblique bottom view of one embodiment of a saw assembly comprising a guard-guide subassembly comprising a retractable bottom guard-guide that is retracted separate from retraction of the top, main guard-guide. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0031]    Described below are certain preferred embodiments. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described compositions and methods of the invention that are obvious to those skilled in the field are intended to be within the scope of the claimed invention. 
         [0032]      FIGS. 1-4  of the drawings show various details of one embodiment of a saw assembly  19  ( FIG. 1 ) constructed according to the invention. Generally, the saw assembly  19  includes an electric motor subassembly  17  ( FIG. 1 ) and a spindle  1  ( FIGS. 1-4 , and  6 ) rotatably powered by the electric motor  17 . These components can take any of various forms. For example, in some embodiments, the electric motor subassembly  17  is of the 4-inch, right angle drive grinder model  8313  that is commercially available under the trademark TALON from Jenn Feng U.S.A. of Lincolnshire, Ill. That electric motor assembly weighs about five pounds and measures roughly 2½ inches in outside diameter and about ten inches long so that it can be conveniently grasped with one hand. In some embodiments, the electric motor subassembly is a 4½ inch to 6 inch, right angle drive grinder (e.g., model numbers WSS6.5-115, WSS 12-125, WSG 12-125, WSG 12-70 E. WSG 12-150) available under the trademark FEIN Angle Grinders from C. &amp; E. FEIN, Stuttgart, Germany. 
         [0033]    In the illustrated embodiment, the electric motor subassembly  17  is a high speed motor operating on 120-volt, 60 Hz, 650-1200-watts of power at between 3000-5000 revolutions per minute (rpm) (in some embodiments, the motor operates at speeds between 5000-7000 rpm, in other embodiments, the motor operates at speeds between 7000-10,000 rpm, and in still other embodiments, the motor is adapted to operate at rotational speeds greater than 10,000—e.g., a no load speed of 12,000). The electric motor subassembly  17  is adapted to produce a rotational movement about a first axis of rotation  20  ( FIG. 1 ) and the spindle  1  is rotatably powered by the electric motor subassembly  17  for rotation about a second axis of rotation  21  ( FIG. 1 ) that is perpendicular to the first axis of rotation  20 . For that purpose, the electric motor subassembly  17  includes a right angle drive  22  that couples rotational movement by suitable known means from the electric motor subassembly  17  to the spindle  1 . 
         [0034]    In some embodiments, a circular blade  5  ( FIGS. 1-4 , and  6 ) is removably mounted on the spindle  1  with a countersunk blade attachment screw  9  ( FIGS. 2 and 3 ) that screws into a countersunk spindle hole  12  ( FIG. 3 ) on the spindle  1 . Having the blade mounted on a flush-mount (e.g., comprising a countersunk dimple with a hardened screw) allows the blade to make a flush cut. In some embodiments, the blade  5  comprises oblong cutouts for attachment (e.g., with screws  9 ) to a flanged hub  27  (See  FIGS. 7 ,  8 ,  11 , and  12 ). In some embodiments, the flanged hub  27  attaches to and drives the blade  5 . The present invention is not limited by the configuration of the flanged hub  27 . Indeed, a variety of configurations are possible including, but not limited to, a flanged hub  27  with an oval section that protrudes from the hub a dimension equal to the thickness of the blade  5  (e.g., so as to be flush with the blade when the two are joined by screws  28  (e.g., machine screws). In some embodiments, the blade  5  is attached to a spacer/adapter  30  (See  FIG. 12 ). The spacer/adapter  30  may be made of any suitable material. The present invention is not limited by the type of material used to make the spacer. Indeed a variety of materials are contemplated to be useful including, but not limited to, TEFLON, copper, DELRIN, aluminum, rubber or plastic. Furthermore, the spacer/adapter  30  may comprise one or more (e.g., in preferred embodiments, the spacer comprises three) holes for receiving screws  28  for attachment of the blade  5 . Thus, in preferred embodiments, the blade  5  and/or guard-guide subassembly comprises a spacer  30  so as to minimize run out or galloping of the blade on a surface  26  to be cut (e.g., leading to uneven blade exposure to a surface during cutting). 
         [0035]    In a preferred embodiment, the blade  5  is not only removable, but also reusable, disposable and/or easily replaced with a blade  5  possessing a desired characteristic(s) (e.g., a carbide tipped blade, a grinder wheel, or a file). The present invention is not limited by the nature of the blade  5 . The blade  5  may comprise one or more materials. The material may be selected from, but not limited to, carbide tipped blades, diamond tip blades, a grinder wheel or a sanding wheel. In some embodiments, the blade  5  is a sterile blade  5  (e.g., for use in medical procedures). In some embodiments, the blade  5  comprises one or more materials useful for medical procedures (e.g., including, but not limited to, a medically useful coating). In some embodiments, the blade  5  has teeth that extend to an outer circumference of the circular blade  5 . In some embodiments, the blade has a chamfered shoulder  29  (See, e.g.,  FIG. 11 ). A saw assembly  19  that utilizes a blade  5  comprised of one or more of these materials can be used for cutting many types of surfaces  26  ( FIG. 6 ), including, but not limited to, wood, plastic, metal, glass, cement, ceramic, cement, tile or bone. The invention is not limited by a particular size blade  5 . In some embodiments, the blade  5  is a 4-inch diameter blade. In some embodiments, the blade  5  chosen has a diameter from 2 inches to 4 (in some embodiments, the diameter is between 4-5 inches, in still other embodiments, the blade diameter is between 5-7 inches, and in some embodiments, the diameter of the circular blade is greater than 7 inches or less than 2 inches (e.g., is 0.5-2 inches in diameter). 
         [0036]    In some embodiments, a blade guard-guide subassembly  23  ( FIG. 2 ) is mounted to guide rods  13  ( FIGS. 4 and 6 ) attached to a sliding bearing block  10  ( FIGS. 1 ,  4 ,  6  and  9 ) comprising return springs  14  ( FIGS. 4 ,  6  and  10 ) or other material that spring biases the guard-guide subassembly  23  toward the closed position depicted in  FIGS. 1-4 . In some embodiments, the guard-guide subassembly is adjustably controlled with an adjustable stop (e.g., for adjustably positioning the depth of the cutting blade (e.g., the length of the blade exposed beyond the guard-guide subassembly (e.g., determining the cutting depth))). 
         [0037]    In some embodiments, a sliding bearing block  10  is mounted on the electric motor subassembly  17  via an attachment bracket  2  ( FIGS. 1 and 6 ). In an alternative embodiment, a sliding lug  25  ( FIG. 1 ) is attached to a bearing block  10  mounted on the electric motor subassembly  17 . In some embodiments, a slide channel  24  ( FIG. 1 ), connected to the lug  25 , holds the guard-guide subassembly  23  in place over the blade. In one preferred embodiment, the guard-guide subassembly  23  covers the entire blade  5  when not in operable contact with a surface. 
         [0038]    The guard-guide subassembly  23  comprises a top, main guard-guide  4  ( FIGS. 1-4 ,  6 ,  9  and  10 ) and a bottom guard-guide  7  ( FIGS. 1-3 , and  9 ). The present invention is not limited by the nature of the material that comprises the guard-guide subassembly  23 . Indeed, a variety of materials are contemplated including, but not limited to, aluminum, aluminum alloys, plastic, plastic compounds, metal, or metal alloys. The guard-guide subassembly  23  is configured such that there is clearance between itself and the blade  5 . In some embodiments, the guard guide subassembly  23  further comprises ports  15  ( FIGS. 1 ,  4 ,  6 ,  10  and  17 ) for attachment of additional components (e.g., a sawdust collecting bag (e.g., attached to a vacuum source). In some embodiments, the guard-guide subassembly  23  (e.g., comprising the top, main guard guide  4 ) is angled (See, e.g.,  FIG. 10 ). It is contemplated that use of an angled guard guide subassembly may permit cuts (e.g., flush cut of a door jamb, baseboard, or base molding) that are not possible with a non-angled guard-guide. 
         [0039]    According to one aspect of the invention, the blade guard-guide subassembly  23  retracts when in operable contact with a surface  26 . In some embodiments, operable contact comprises a physical contact between a surface  26  and the guard-guide subassembly  23 , with the amount of retraction directly corresponding to the amount of pressure asserted against the guard-guide subassembly  23  by the surface  26 . In a preferred embodiment, the blade  5  is not exposed above the surface  26  of which it is cutting (i.e., the guard-guide subassembly  23  continues to enclose that part of the blade  5  that does not penetrate the surface  26 ; See, e.g.,  FIGS. 6 and 10 , wherein the blade  5  remaining protected by the guard-guide subassembly  23  is depicted by hashed lines and that portion of the blade  5  below the surface  26  to be cut is depicted by a solid line). In some embodiments, the electric motor subassembly  17  cannot run without contact between the guard-guide subassembly  23  and a surface  26  to be cut. In still further embodiments, the guard-guide subassembly  23  comprises a retractable (e.g., spring loaded) bottom guard-guide  7  that can be retracted fully (e.g., to completely expose the bottom portion of the blade (e.g., for flush-cutting)) separate from retraction of the top, main guard-guide  4  (e.g., the top, main guard guide will remain in place while a user retracts the bottom guard  7  (e.g., to make a flush-cut) and will not retract until in operable contact with a surface  26 ). The invention is not limited by the means by which the bottom guard-guide is made retractable. Indeed, any means known in the art that permits the bottom guard-guide to be retracted separately from the top, main guard-guide can be used. For example, in some embodiments, the bottom guard-guide exists as a discrete component separate from the top main guard-guide (e.g., can be independently removed and reinstalled by an operator. In some embodiments, the bottom guard-guide is retractable (e.g., partially or fully (e.g., via a spring loaded mechanism)) from the top main guard guide that itself is not spring loaded (e.g., it is fixed to the saw). In some embodiments, the bottom guard-guide is retracted (e.g., partially or fully) separate from retraction of the top main guard-guide using a eccentric cam (e.g., in order to reduce retraction tension (e.g., at full retraction of the bottom guard-guide)). In some embodiments, the bottom guard-guide is retracted (e.g., partially or fully) separate from retraction of the top main guard-guide using a spiral torsion spring. In some embodiments, the bottom guard-guide is retracted (e.g., partially or fully) separate from retraction of the top main guard-guide utilizing differential spring tensions (e.g., bottom guard-guide spring requires less force to extend or load than top guard-guide spring, thereby allowing bottom guard-guide to retract while the top guard-guide remains in place (e.g., until such time that the guard-guide subassembly makes physical contact with a surface and the amount of retraction directly corresponds to the amount of pressure asserted against the guard-guide subassembly by the surface to be cut)). 
         [0040]    In one embodiment, the bottom guard-guide is retracted separately from the top, main guard-guide via making the bottom guard-guide spring loaded with an eccentric cam (e.g., thereby reducing retraction tension at full retraction of the bottom-guard-guide). In some embodiments, the saw is configured such that an operator must have two hands upon the saw in order for the saw to run (e.g., when the bottom guard-guide  7  is completely retracted prior to use of saw). 
         [0041]    The invention is not limited by the type of material cut by a saw of the invention. Indeed, any type of material may be cut including, but not limited to, wood, stone, brick, bone, plastic, composite, metal, or other material. In some embodiments, a saw incorporates a motor subassembly and a guard-guide subassembly that allows the operator to produce a flush cut. For example, a saw of the invention allows an operator of the saw to remove or move away (e.g., slide or retract) the bottom guard portion of the guard-guide subassembly (e.g., thereby permitting the bottom of the blade/abrasive cutter to contact a surface parallel to the bottom surface of the blade/abrasive cutter. In one embodiment, a blade or abrasive cutter of the saw assembly is deployed forward parallel to the surface (e.g. in order to cut or abrade a material proud of that surface). 
         [0042]    In some embodiments, the saw assembly comprises one or more safety features that protect an operator and/or bystander from the blade/abrasive cutter. In some embodiments, the saw assembly comprises one or more safety features that protect an operator and/or bystander from dust and/or debris. Safety feature include, but are not limited to, a guard-guide that fully, or partially, depending on the configuration, covers the blade/abrasive cutter. In some embodiments, a saw assembly comprises a spring-loaded guard-guide (e.g., that retract during operation) that extends to cover the blade/abrasive cutter when the operator releases pressure, or the saw slips from the operator&#39;s hand or hands. In some embodiments, a saw assembly comprises a momentary contact switch (also known as a “dead man&#39;s” switch) that removes power from the motor if deliberately released by the operator, or released inadvertently, such as if the saw were to slip from the operator&#39;s hand or hands. In some embodiments, a saw assembly comprises a throttling momentary contact switch that provides “dead man” protection as well as variable speed capability to allow the operator to vary the speed of the blade/abrasive cutter in direct proportion to pressure applied to the switch by the operator. In some embodiments, a saw assembly comprises a mechanical lock (e.g., a spring-loaded pin, a hook loaded by a tension spring or other mechanical device) that acts as a “safety” and prevents the momentary contact “dead man” switch from being depressed (e.g., completing an electrical circuit without deliberate and independent action by the operator to disengage it prior to depressing the switch). In some embodiments, a saw assembly comprises a guard-guide that ports away dust and/or debris generated during operation. For example, in some embodiments, a saw assembly comprises a guard-guide that vents dust and debris generated during operation into a port diverting it away from the operator (e.g., into a vacuum or other retention device). In some embodiments, a saw assembly comprises an electric sensing circuit (e.g., via electromechanical switches, or electronic sensors) that prevents the motor from operating (e.g., from starting to run or continuing to run) without both the operator&#39;s hands placed on a specific portion of the saw assembly (e.g., specific handles). For example, in one embodiment, if an operator removes one or both hands from the saw (e.g., where electromechanical sensors are located (e.g., within handles)), power is removed from the motor of the saw assembly and the saw will not operate. 
         [0043]    An exemplary embodiment of a saw assembly comprising a guard-guide subassembly comprising a retractable bottom guard-guide that is retracted separate from retraction of the top, main guard-guide is shown in  FIGS. 13-17 . For example, in one embodiment, the blade guard-guide subassembly  42  ( FIG. 13 ) is utilized to produce a flush cut. As shown in  FIG. 13 , the saw may comprise a retractable (e.g., spring loaded) bottom guard-guide  26  with attached rollers  28 , that ride on guide rails  27  and that can be retracted fully (e.g., to completely expose the bottom portion of the blade (e.g., for flush cutting)) separate from retraction of the top, main guard-guide  4 . The top, main guard guide  4  will remain temporarily locked together with the electric motor subassembly, by top guard-guide lock  32  ( FIG. 14  cutaway) comprised of horizontal trigger bar, springs  33 , spring retainers  34  and vertical lock pins  35  that engage holes in top guard-guide  4  while a user&#39;s ring and little finger engage spindle  30 , connected to bottom guard  26 , and the user&#39;s hand slides rearward along the longitudinal axis of the handle of the electric motor subassembly  17  and paddle switch  16  so as to retract the bottom guard  26 . Once the bottom guard  26  has moved (e.g., far enough aft) to allow its leading edge to engage the chamfer  31  ( FIG. 13 ) on bottom guard-guide  4  and rollers  28  ( FIG. 13 ) to engage guide rail cutouts  38 , the bottom guard  26  tilts vertically so as to allow it to clear the bottom of the top guard-guide  4  (e.g., thereby permitting flush cutting). Once the bottom guard is fully retracted and the rollers  28  are fully engaged in cutouts  38 , a portion of the tension of spring  29  is held by rollers  28  engaged in cutouts  38 , another portion of the tension of spring  29  is relieved by the partial over-center effect of the tilt of bottom guard  26  as well as frictional forces of the leading edge of bottom guard  26  impinging on chamfer  31 . Once the bottom guard  26  is fully retracted, the fingers of the user&#39;s other hand holding handle  18  may engage the horizontal bar of guard-guide lock  32 , and lift it vertically so as to unlock the top guard-guide  4  from the electric motor subassembly  17  and allow the blade  5  to slide forward when the top guard-guide is pressed against work piece to be cut. 
         [0044]    In some embodiments, a differential spring tension between bottom guard spring  29  ( FIG. 13 ) and top guard-guide spring  14  is employed to allow the bottom guard  26  to retract and permit its rollers  28  ( FIG. 13 ) to engage the guide rail cutouts  38  before blade  5  deploys. In some embodiments, an elliptically shaped cam subassembly is placed between spring  29  and bottom guard  26  (e.g., to further change leverage and/or add mechanical advantage so as to relieve tension of spring  29  (e.g., when bottom guard  26  is in the fully retracted position)). 
         [0045]    In some embodiments, a crankset subassembly is placed between spring  29  and bottom guard  26  (e.g., in order to change leverage and/or add mechanical advantage so as to relieve tension of spring  29  (e.g., when bottom guard  26  is in the fully retracted position)). 
         [0046]    In some embodiments, an operator must grip handle  18  with one hand, and motor subassembly handle  41  ( FIG. 13 ) with the other, to complete a sensing electrical circuit (e.g., through grip switches (e.g., wired in series and/or amplified)) to operate a relay or bias a transistor, before the motor in the electric motor subassembly  17  will operate or for the motor to continue operating. 
         [0047]    In some embodiments, the handle  18  and motor subassembly handle  41  ( FIG. 13 ) are each charged with a small voltage the differential of which causes a milliampere current to travel through the operator&#39;s body when the operator grips handle  18  with one hand, and motor subassembly handle  41  ( FIG. 13 ) with the other (e.g., the current can be detected by a sensor and amplified to operate a relay, or bias a transistor before the motor in the electric motor subassembly  17  will operate or for the motor to continue operating. In some embodiments, a small spring loaded mechanical safety lock (e.g., such as a springloaded pin, or a hook loaded by a tension spring, or other mechanical device) is installed on/in paddle switch  16  that must be physically depressed by the operator so as to allow paddle switch  16  to operate and complete a circuit to allow the motor in the electric motor subassembly  17  to operate or for the motor to continue operating. In some embodiments, the lock  32  is not installed, only differential spring tensions of springs  29  and  14  are utilized. 
         [0048]    In some embodiments, a vacuum dust collector  40  is attached to a guard/guide exhaust port  15  by a flexible hose  39  (See  FIG. 10 ). While any vacuum system of the art may be used, in some embodiments, the vacuum system comprises a high-efficiency particulate arrestance (HEPA) filter and/or system. 
         [0049]    In some embodiments, the electric motor subassembly  17  possesses a trigger  16  ( FIG. 1 ) with a momentary contact switch (e.g., a “dead man” switch), that when engaged/depressed, allows the motor to run, and when disengaged, results in no power to the motor. In some embodiments, the contact switch comprises a variable speed throttling switch. In some embodiments, the throttling switch permits the blade speed to ramp up or down (e.g., to gradually increase or decrease blade speed). In some embodiments, the maximum amount of retraction of the guard-guide subassembly  23  exposes 10% of the blade  5  (in some embodiments, the maximal amount of retraction exposes 10-25%, in some embodiments, the maximal amount of retraction exposes 25-50%, in some embodiments, the maximal amount of retraction exposes 50-75%, and in still other embodiments, the maximal amount of retraction exposes greater than 75%) of the blade  5 . In some embodiments, the amount of retraction is dependent upon the position or setting of an adjustable stop (e.g., for adjustably controlling the depth at which the cutting blade (e.g., in vertical alignment with the cutting surface) can cut). In some embodiments, the saw assembly  19  comprises a handle  18  ( FIG. 1 ). The handle  18  has many uses. For example, the handle  18  can be used to move the saw from place to place, to hold the saw steady when the saw is in use, or it can be used to push the saw assembly  19  against a surface  26 , with the resulting pressure exerted by the surface  26  causing the guard-guide subassembly  23  to retract. 
         [0050]    According to another aspect of the present invention, the blade  5  diameter (e.g., less than 5 inches) facilitates the cutting of material that a larger blade  5  (e.g., larger than 5 inches) may not cut well. For example, the saw assembly  19  of the present invention can be used to cut any type of surface, including, but not limited to, wood, plastic, metal, glass, cement, bone, ceramic or tile (e.g., the saw can be used to cut a window sash made of the aforementioned materials). In some embodiments, the saw assembly  19  can be used to undercut (e.g., a floor installer may use the saw assembly  19  of the present invention to undercut a baseboard, a door jamb, a base molding, or the like). In other embodiments, the saw assembly  19  can be used to cut window blind stops (e.g., during the removal and replacement of windows). In some embodiments, the saw assembly  19  of the present invention is used to cut a surface  26  under conditions in which it is not desired to have a blade exposed above the cutting surface  26  (e.g., for reasons such as safety, efficiency, cleanliness, etc.; See, e.g.,  FIG. 6 ). In some embodiments, the sliding bearing block  10  comprising return springs  14 , and/or sliding lug  25 , further comprises a regulator (acting as a depth gauge), that does not allow the guard-guide subassembly  23  to retract past a designated position. The use of a regulator is contemplated to allow a user to configure the saw assembly  19  to cut to a desired depth. Accordingly, in some embodiments, the regulator is demarcated with graduated length indicators (e.g., a ruler). 
         [0051]    In some embodiments, the present invention provides a method of removing a window, comprising cutting stops present in the window, the cutting comprising using a saw configured so as not to have a blade exposed to the user during any portion of its use, wherein the method does not disrupt the inside window trim. In preferred embodiments, the user removes an existing sash of the window by cutting one or more stops (e.g., blind stops; See, e.g.,  FIGS. 5A-B ) with a saw configured so as not to have a blade exposed to the user during any portion of its use (e.g., the saw assembly  19  of the present invention). Furthermore, the guard-guide sub-assembly  23  functions to guide the saw, allowing the saw to ride on the brick mould and enabling the saw to make a straight cut (See, e.g.,  FIGS. 5A-B ). Thus, in preferred embodiments, the guard-guide permits a user to make a straight cut (e.g., either alone, or, using an existing, adjacent surface as a “rip fence” (e.g., for guiding the saw along a straight line)). In some embodiments, a companion piece may be used for guiding the saw (e.g., in medical uses, the companion piece may be a cutting guide (e.g., a speed block, all-in-one block, or four-in-one block)). In some embodiments, the window is replaced with a new window after the old window is replaced. In some embodiments, there is no need for new pieces of wood to assist in the replacement of the old window (e.g., in some embodiments, only caulk is needed). Using such a method dramatically decreases the amount of time needed to replace windows (e.g., double-hung windows) and decreases expenses (e.g., there is no need for new pieces of wood nor is any damage caused to the inside window trim) for work crews that are tasked with replacement of many windows (e.g., in an apartment complex, school, etc.). The time and cost savings are substantial. 
         [0052]    Thus, the invention provides a saw assembly  19  that includes a guard-guide subassembly  23  configured to prevent exposure of the saw blade  5  to the user whether or not the saw is in use. A preferred embodiment utilizes a high speed 4-inch blade  5  mounted on a small, less than 10,000 rpm, right angle drive electric motor subassembly  17  of a commercially available 4-inch portable grinder. The resulting saw assembly  19  provides a device that is safe for cutting a variety of surfaces. The right angle drive makes it easy to manipulate, like a portable disk grinder. The smaller blade  5  does not damage surfaces that may be damaged when cut with a larger blade  5 . 
         [0053]    In a preferred embodiment, the saw assembly  19  of the present invention is configured to be fitted with blades  5  that are removable, reusable and/or disposable. Such blades  5  can be supplied by one or more suppliers. Suppliers of replaceable blades  5  may configure the blades for a particular purpose (e.g., for cutting blind stops during window replacement or for undercutting). In some embodiments, the replaceable blades  5  may be sold in kits designed for a particular purpose (e.g., a window replacement kit). 
         [0054]    In some embodiments, the saw assembly  19  of the present invention may be generated by modifying an existing saw that lacks one or more elements of the present invention (e.g., a method of modifying an existing saw into the saw of the present invention by introducing to the existing saw a retractable, fully enclosing blade guard-guide subassembly). 
         [0055]    The guard-guide subassembly of the present invention finds use with other types of saws. For example, the guard-guide subassembly can be modified to be compatible with a vibrating saw, a reciprocating saw or an oscillating saw. In some embodiments, the present invention provides a saw assembly comprising a motor; a linkage for converting rotating power of the motor into linear reciprocating movement; a slider shaft mounted at an end of the linkage having an angle of approximately 90 degrees with respect to the linkage; a slider, for attaching a saw blade, which moves reciprocatingly along the slider shaft, and a fully enclosing blade guard-guide subassembly, the blade guard-guide subassembly comprising a top main guard-guide slidably mounted on the electric motor subassembly and a bottom guard-guide plate fixed to the top main guard-guide assembly. In some embodiments, the blade used with a vibrating, oscillating or reciprocating saw is non-circular (e.g., is file shaped, See, e.g., blades described in U.S. Pat. No. 6,896,679, herein incorporated by reference in its entirety). In some embodiments, the blade guard-guide subassembly used with a vibrating, oscillating or reciprocating saw is spring-loaded. In some embodiments, the blade guard-guide subassembly fully encloses the non-circular blade (e.g., a file blade) until the blade guard-guide subassembly operably contacts a surface (e.g, a bone). In some embodiments, the operable contact comprises physical contact between a surface and the guard-guide subassembly such that the blade guard-guide moves into a retracted position, wherein the amount of retraction directly correlates with the amount of pressure asserted against the guard-guide subassembly by the surface. The present invention is not limited by the type of surface contacted. 
         [0056]    Various modifications and variations of the described compositions and methods of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention that are obvious to those skilled in the relevant fields are intended to be within the scope of the present invention.