Abstract:
A cutting blade ( 10, 110, 210, 310, 410 ) is at least partially coated with an abrasive material ( 30, 32, 150, 250, 350, 450 ) applied by spraying metal particles onto one or both face surfaces of a cutting blade. The blade ( 10, 110, 210, 310, 410 ) is durable, with the abrasive layer ( 30, 32, 150, 250, 350, 450 ) typically not requiring replacement at anytime during the file of the table.

Description:
BACKGROUND AND SUMMARY  
         [0001]    The present invention relates to saws for cutting wood and other materials.  
           [0002]    It has been a problem with saw blades that, when cutting certain materials, a blade leaves a rough edge or burr, and in some instances splits the material being cut.  
           [0003]    The most common way to address these problems has been to increase the number teeth on a blade and reduce the spacing between the cutting tips. This is beneficial, but can substantially add to expense and is not always completely effective. Another approach, in the case of specialized rotary blades, has been to provide a sanding disk alongside the blade so that the sanding disk smoothes the workpiece being cut. Sanding disks may be useful, but are subject to rapid wear and must be replaced frequently.  
           [0004]    It has now been discovered that otherwise-conventional blades can be partially coated with an abrasive material applied by spraying metal particles onto one or both face surfaces of a cutting blade. The resulting blade can be used in the manner of a conventional blade, with no adjustments in operation being required. Such blades are extremely durable, with the abrasive layer typically not requiring replacement at anytime during the life of the blade. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0005]    In the drawings:  
         [0006]    [0006]FIG. 1 is a front elevational view of a circular blade having a surface with an abrasive metallized region;  
         [0007]    [0007]FIG. 2 is an enlarged, partial sectional view taken along line  2 -- 2  of FIG. 1;  
         [0008]    [0008]FIG. 3 a front elevational view of a another circular blade having a surface with an abrasive metallized region;  
         [0009]    [0009]FIG. 4 is front elevational view of a circular blade having a surface with plural abrasive metallized regions;  
         [0010]    [0010]FIG. 5 is a front elevational view of a another circular blade having a surface with plural abrasive metallized regions; and  
         [0011]    [0011]FIG. 6 is a partial front elevational view of a linear blade having a surface with an abrasive metallized region. 
     
    
     DETAILED DESCRIPTION  
       [0012]    Blades of the present invention are based on the designs of standard circular or linear cutting blades, most notably blades intended for cutting wood products, particularly plywood and veneer, or plastics or soft metals such as aluminum. An example is a circular blade  10  shown in FIGS. 1 and 2. Such blades are typically made of steel and have two face surfaces  14 ,  16 . The surfaces typically have large areas that are generally planar and that extend generally parallel to one another and that are spaced apart a distance W 2  from each other. Most styles of blades have two faces that are entirely generally planar, except for the teeth.  
         [0013]    Blades also have cutting tips arranged along a sidewall or edge that extends between the two face surfaces. The tips typically are formed by bending tip portions of the blade material so that the tip portions extend outwardly of the planes that contain the flat surfaces portions of the blades or by attaching separately fabricated blade tips to the sidewall. In the blade of FIGS. 1 and 2, separately fabricated carbide blade tips  20  are attached to a sidewall  18  that extends between the two surfaces  14 ,  16  at the perimeter of a blade body  12 .  
         [0014]    The attached blade tips  20  have a width W 1  that is wider than the width W 2  of the flat portions of the surfaces  14 ,  16  of the blade body  12  so that a portion of each tip extends axially outwardly of the planes that coincide with the flat portions of the surfaces  14 ,  16 . The extra width of the tips reduces the likelihood of binding during a cutting operation because the kerf created by the tips is greater in width than the width W 2  of the body  12 . In a blade with tips formed by bending, each tip extends axially outwardly to only one side of the blade, typically with every other tip extending to the left or to the right of the blade body as viewed from the edge. In such bent-tooth blades, the distance W 1  is the distance between the outermost portions of the tips on each side of the blade body  12  as viewed from the edge, such that the entire blade would just fit between two planes that are slightly farther apart than the distance W 1 .  
         [0015]    Blades of the present invention advantageously have one or more regions of abrasive material applied to the surfaces  14 ,  16 . In the blade of FIG. 1, abrasive. metal particles  30 ,  32  are applied to both of the surfaces  14 ,  16 .  
         [0016]    The metal particles are applied to an otherwise ordinary steel blade by a procedure that includes cleaning and roughening a flat portion of one or both of the surfaces  14 ,  16 . This can be accomplished by sandblasting using aluminum oxide particles or another suitable particulate material. The sandblasting grit must be sufficiently fine, and the particle velocity sufficiently low, to avoid warping of the substrate blade.  
         [0017]    Abrasive particles are then permanently applied to the sandblasted regions. This can be accomplished using an arc metal spraying system. Molten feedstock metal is divided into small particles of molten material by an atomizing jet. The molten metal particles are propelled against the blade where they adhere and harden to produce an abrasive surface layer. The size of the applied metal particles may be varied by adjusting the velocity of the atomizing jet, with best results with at 36-60 grit. Such abrasive metal particles can be made of carbide, such as tungsten carbide, or some suitably hard and durable metal material, such as titanium, or metal alloy. Other abrasive materials may be included.  
         [0018]    The methods and apparatus described in U.S. Pat. No. 4,937,417 (Fox) and U.S. Patent Publication No. 20010040188 (Seitz) can be used to metallize blade surfaces as discussed herein. The resulting metallized surfaces are substantially permanent and that do not require replacement during the normal life of a cutting blade.  
         [0019]    Best results are achieved when abrasive metal particles are applied in a substantially uniform layer, with the thickness of the particle layer being not greater than the distance to which the side surfaces of cutting tips extend outwardly from the flat surfaces of the blade body. Thus if a blade is metallized on both sides as shown in FIG. 2, with an even coating thickness on each side, the distance W 3  between the outermost portions of the coating should not be greater than the distance W 1  which is the distance between the outer most portion of the tips as viewed from the blade edge. Or in other words, the kerf cut by the tips should be at least as wide as the distance W 3  between the exposed surfaces of the metallized coatings.  
         [0020]    Although FIG. 2 shows a blade that is coated on both sides, it would be possible to metallize a blade only on one side if so desired. For certain ripping saws where the finished edge of a workpiece will always be cut on the same side of a blade, it might not be advantageous to metallize both sides of a blade to provide an abrasive coating on both sides.  
         [0021]    An entire side of a blade need not be metallized with the abrasive material to be effective. Cutting tips should not be spray coated with the abrasive material. And an area  40  near the arbor hole  42  of a circular saw best will remain uncoated, so that the saw may be mounted without interference from a coating.  
         [0022]    The metallized region  50  shown in FIG. 1 is generally annular, with most of the each face of the blade being coated. FIG. 3 shows a similar arrangement, only with a larger uncoated area  140 , the band  150  of metal abrasive particles being about 1-1.5 inches wide around the circumference of the blade. Other patterns of coating can be used, for example as shown in FIGS. 4 and 5 wherein plural regions  250 ,  350  of flat portions of blade surfaces are metallized.  
         [0023]    As shown in FIG. 6, a linear blade  410 , such as a band saw blade or a reciprocating saw blade, also can benefit from a metallized coating of abrasive metal particles. Special purpose blades, such as cylindrical hole saw blades (not shown), also beneficially can be coated with spray-applied abrasive metal particles.  
         [0024]    Any of the illustrated blades is effective to reduce the need for sanding and for using such accessory tools as joiners, electric sanders, sanding tables, block planes and like devices that are commonly used to remove burrs and saw marks produced by a sawing operation. With blades of the present invention, the edge of a workpiece is sanded as it is cut. Overheating and binding problems are reduced by the use of such blades. And the abrasive surfaces of such blades helps clear saw dust out of the area being cut. An anti-friction coating may be placed on the metallized regions, if desired, to reduce friction.  
         [0025]    Because the metallized surface coating extends substantially parallel to the planes which contain the flat portions of the blade surfaces  14 ,  16 , it is not necessary to mount blades according to the present invention at abnormal angles or to make any other adjustments to normal sawing procedures.  
         [0026]    Having illustrated and described the principles of the invention in multiple embodiments, it should be apparent to those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles.