Abstract:
A bit includes a body, a cutting edge, and a shim. The body has a shank end and a cutting end, and the shank end is arranged to be held by a drill or router. The cutting edge is positioned at the cutting end of the body. The shim is between the cutting end of the body and the cutting edge, and the shim is arranged to absorb forces so as to protect the cutting edge.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to bits such as those used with drills or routers to process abrasive materials. In the case of a routers, the bit disclosed herein can be used, for example, with portable or stationary routers to form edges, cutouts, or holes in abrasive materials. 
       BACKGROUND 
       [0002]    Bits are commonly employed for forming holes in wood and other similar cutting resistant materials. Such bits frequently include an elongated steel shank or shaft with one end formed for removable attachment to a drill or router. The opposite end is formed with a cutting edge typically having a centering tip and a pair of spur tips on opposite sides of the centering tip. During operation, the centering tip centers the bit, and the spur tips cut the material as the hole is being formed. 
         [0003]    Router bits are commonly employed for forming smooth edges, or cutouts in wood and other similar cutting resistant materials. Such bits frequently include an elongated steel shank or shaft with one end formed for attachment to a router. The opposite end is formed with a cutting edge, or edges, that are primarily used for side cutting or edge forming but also for center cutting by plunging through material. During operation, the bit can be plunged through the material to begin an edge cutting operation, or can enter from the outside of the material and begin an edge cutting operation. 
         [0004]    While such a bit adequately trims or cuts woods and other relatively soft materials, problems occur when these bits are used to cut harder and more abrasive materials such as particle board, MDF, plywood, double sided melamine, and other laminate materials. The abrasiveness of these materials easily dulls the cutting edges of known bits. Moreover, the heat generated by the friction between the material being cut and the bit reduces the cutting capability of the bit cutting edges. 
         [0005]    Solid carbide or carbide tipped bits are often employed to cut into these hard composites and more abrasive materials. However, there is limit to the hardness of the carbide used in these bits because harder carbide is more fragile and can be damaged or break due to the friction and vibration generated during operation and due to the force required to cut through hard composites and more abrasive materials. 
         [0006]    The composite bit disclosed herein overcomes one or more of these or other problems. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0007]    Features and advantages of the composite bit disclosed herein will become more apparent from the following detailed description when taken in conjunction with the drawing in which: 
           [0008]      FIG. 1  is an isometric view of the composite bit disclosed herein; 
           [0009]      FIG. 2  is a side view of a bit body used for the composite bit of  FIG. 1 ; 
           [0010]      FIG. 3  is a side view of the composite bit of  FIG. 1 ; and, 
           [0011]      FIG. 4  is an end view of the cutting tip of the composite bit of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    A composite bit  10  is illustrated in  FIGS. 1-4 . The composite bit  10  includes a bit body  12 . The bit body  12  can be of any suitable length and, for example, is a first metal such as Hot Work Tool Steel (H). There are a variety of suitable Hot Work Tool Steels, such as the Chromium and Tungsten varieties. One such steel is H13 although other varieties of steel could be used. The bit body  12  has a shank end  14  that is received by a drill or router and a bit end  16  that performs cutting when the composite bit  10  is rotated by the drill or router. 
         [0013]    As can be seen in  FIGS. 1 and 4 , the bit end  16  of the bit body  12  has a tip  18  that is generally Z shaped forming first and second inwardly directed faces  20  and  22  and first and second outwardly directed faces  24  and  26 . The planes of the first and second inwardly directed faces  20  and  22  are generally parallel to one another, and the planes of the first and second outwardly directed faces  24  and  26  are generally parallel to one another. The first inwardly directed face  20  and the first outwardly directed face  24  form an acute angle such as 75°, and the second inwardly directed face  22  and the second outwardly directed face  26  similarly form an acute angle such as 75°. The first and second inwardly directed faces  20  and  22  extend a suitable distance along a longitudinal axis X from the tip  18  and into the bit end  16  away from the tip  18  as shown in  FIG. 1 . The tip  18  could be a centering tip, as desired. 
         [0014]    Although the first and second inwardly directed faces  20  and  22  are shown as planar faces, the first and second inwardly directed faces  20  and  22  could be curved faces or other geometrically shaped faces. Similarly, although the first and second outwardly directed faces  24  and  26  are shown as planar faces, the first and second outwardly directed faces  24  and  26  could be curved faces or other geometrically shaped faces. 
         [0015]    A first cushion core  28  is suitably affixed such as by brazing to the first inwardly directed face  20  as shown in  FIGS. 1 and 4 , and a second cushion core  30  is suitably affixed such as by brazing to the second inwardly directed face  22  as also shown in  FIGS. 1 and 4 . As shown in  FIG. 4 , the first cushion core  28  extends radially beyond the first inwardly directed face  20  by a desired amount, and the second cushion core  30  extends radially beyond the second inwardly directed face  22  by a desired amount. 
         [0016]    As shown in  FIG. 1 , the first cushion core  28  comprises a first shim  32  and a first cutting edge  34 , and the second cushion core  30  comprises a second shim  36  and a second cutting edge  38 . 
         [0017]    The first cutting edge  34  may be formed from a second metal such as hard carbide that is typically harder than normal carbide which has been used in bits. For example, normal carbide used in bits has a hardness of 1500 (based on HV30 values), whereas the carbide chosen for the first cutting edge  34  may have a hardness of greater than 1800 (based on HV30 values). As a further example, the carbide chosen for the first cutting edge  34  may have a hardness of around 2000 (based on HV30 values). Such carbide, for example, may be HB20UF grade carbide and may be supplied by LMT Boehlerit. 
         [0018]    Other carbide manufacturers who make a grade of carbide with similar hardness, cobalt content and grain size could be selected. 
         [0019]    Therefore, the first cutting edge  34  employs a harder grade carbide than is normally used, the first cutting edge  34  has a longer life than normal carbide cutting edges, the first cutting edge  34  exhibits more abrasion resistance than normal carbide cutting edges, and the first cutting edge  34  resists edge wear better than normal carbide cutting edges. 
         [0020]    However, the use of a harder material for the first cutting edge  34  means that the first cutting edge  34  can be more fragile that the normal material used in bits. Indeed, if the first cutting edge  34  were brazed directly to the bit body  12  similar to the manner in which all other cutting edges are brazed to bit bodies, the impact forces on the first cutting edge  34  during normal use would cause micro-cracks in the first cutting edge  34  resulting in its premature failure. 
         [0021]    Therefore, the first shim  32  is used to affix the first cutting edge  34  to the bit body  12  so as to cushion the first cutting edge  34 . The material of the first shim  32  is chosen so that the first shim  32  absorbs thermal expansion and/or impact shocks to eliminate or materially reduce fracturing of the first cutting edge  34 . The material of the first shim  32  might also be a conveniently selected alloy that can be used to braze the first cutting edge  34  to the bit body  12 . For example, the material of the first shim  32  can be a third metal such as Plymetal #5031. 
         [0022]    Plymetal #5031 may be supplied by Bellman Melcor, Inc. of Tinley Park, Ill. 60477. Plymetal #5031 comprises copper sandwiched between brazing alloys such as 50% silver with other alloying agents including nickel, copper, and/or zinc. Copper is sufficiently soft, such as F40 Rockwell hardness, and has a high enough melting point, such as 1900° F., that it will not fail in the intended application. Other materials could be used provided that they are sufficiently soft and durable to act as the shims  36  and  20 . 
         [0023]    The material of the second shim  36  can be similar to or the same as the material of the first shim  32 . Also, the material of the second cutting edge  38  can be similar to or the same as the material of the first cutting edge  34 . 
         [0024]    Accordingly, the first and second shims  32  and  36  permit the use of the harder materials for the first and second cutting edges  34  and  38  than is otherwise the case. The harder material for the first and second cutting edges  34  and  38  allows the first and second cutting edges  34  and  38  to cut through more abrasive materials than existing cutting edges. 
         [0025]    The description herein is to be construed as illustrative only. The details may be varied substantially without departing from the spirit of the invention as defined by the claims below, and the exclusive use of all modifications which are within the scope of these claims is reserved.