Patent Publication Number: US-11638987-B2

Title: Wear resistant tool bit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national phase filing under 35 U.S.C. 371 of International Application No. PCT/US2018/063677 filed Dec. 3, 2018, which claims priority to U.S. Provisional Patent Application No. 62/593,526, filed on Dec. 1, 2017, and to U.S. Provisional Patent Application No. 62/632,875, filed on Feb. 20, 2018, the entire contents of which are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention pertains to wear resistant tool bits and methods of making the same. More particularly, the present invention pertains to wear resistant tool bits made from tool steel manufactured by a powdered metal process. 
     Tool bits, such as driver bits, are typically made of steel materials that contain iron carbide (Fe 3 C), but not other alloy carbides (M x C). 
     SUMMARY OF THE INVENTION 
     In one embodiment, the invention provides a tool bit for driving a fastener. The tool bit includes a shank having a tool coupling portion configured to be coupled to a tool. The tool coupling portion has a hexagonal cross-sectional shape. The shank also has a head portion configured to engage the fastener. The head portion is composed of powdered metal (PM) steel having carbide particles distributed uniformly throughout the head portion. 
     In another embodiment, the invention provides a method of manufacturing a tool bit for driving a fastener. The method includes the steps of providing powdered metal (PM) steel, atomizing the PM steel into micro ingots, injecting the atomized PM steel micro ingots into a mold, and sintering the atomized PM steel micro ingots, while in the mold, into the tool bit such that carbide particles are uniformly distributed throughout the tool bit. The tool bit includes a tool coupling portion having a hexagonal cross-sectional shape configured to be coupled to a tool and a head portion configured to engage the fastener. 
     In yet another embodiment, the invention provides a method of manufacturing a tool bit for driving a fastener. The method includes the steps of providing a round stock of powdered metal (PM) steel having carbide particles uniformly distributed throughout the round stock, providing a hex stock of non-PM steel, joining the round stock of PM steel to the hex stock of non-PM steel, milling the hex stock of non-PM steel into a tool coupling portion of the tool bit having a hexagonal cross-sectional shape configured to be coupled to a tool, and milling the round stock of PM steel into a head portion of the tool bit configured to engage the fastener. 
     In yet still another embodiment, the invention provides a method of manufacturing a tool bit for driving a fastener. The method includes the steps of providing powdered metal (PM) steel, sintering the PM steel to form a hex-shaped block having carbide particles uniformly distributed throughout the hex-shaped block, and milling the hex-shaped block into the tool bit. The tool bit includes a tool coupling portion having a hexagonal cross-sectional shape configured to be coupled to a tool and a head portion configured to engage the fastener. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a scanning electronic microscope (SEM) image of a conventional driver bit material without carbide particles. 
         FIG.  2    is an SEM image of a high speed steel (HSS) powdered metal (PM) material, including about 10% to about 15% carbides by area. 
         FIG.  3    is an SEM image of a wrought tool steel, including larger, less uniform carbide particles than the HSS PM material shown in  FIG.  2   . 
         FIG.  4    is a side view of a tool bit composed of a PM material. 
         FIG.  5    is a side view of another tool bit composed of a PM material. 
         FIG.  6    is a side view of yet another tool bit composed of a PM material. 
         FIG.  7    is a top view of the tool bit of  FIG.  4   . 
     
    
    
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
     DETAILED DESCRIPTION 
     The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (for example, it includes at least the degree of error associated with the measurement of the particular quantity). The modifier “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression “from about 2 to about 4” also discloses the range “from 2 to 4”. The term “about” may refer to plus or minus 10% of the indicated number. For example, “about 10%” may indicate a range of 9% to 11%, and “about 1%” may mean from 0.9-1.1. Other meanings of “about” may be apparent from the context, such as rounding off, so, for example “about 1” may also mean from 0.5 to 1.4. 
     For the recitation of numeric ranges herein, each intervening number there between with the same degree of precision is explicitly contemplated. For example, for the range of 6-9, the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range 6.0-7.0, the number 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly contemplated. 
     The present disclosure is generally directed toward tool bits made from powdered metal (PM) having a significantly higher wear resistance than conventional tool bits. The present disclosure is also directed toward methods of making tool bits having high wear resistance. 
     Bit Material 
     Powdered metal (PM) is a material made from metal powder, as compared to more typical wrought materials, for example. Without wanting to be limited by theory, tool bits prepared from PM material may have a final microstructure characterized by a significantly more uniform, homogeneous distribution of carbide particles, which results in bits having high wear resistance, toughness, and/or hardness. 
     Suitable PM materials include metal alloys, such as high speed steel (HSS), preferably “M” grade high speed steel, most preferably M4 steel (herein PM-M4). Although a PM material is preferred, bits made from wrought materials are also contemplated herein. Alternately, the bits may comprise a combination of PM material and non-PM material (e.g., more common steel, such as tool steel). For example, in some embodiments, the tip of a bit may be made of PM material, while the remainder of the bit is made of non-PM material. In such embodiments, the bit is considered a bi-material bit, where the PM tip of the bit is welded to the remainder of the bit made of a more conventional material. 
       FIG.  1    illustrates a conventional steel material without carbide particles used for making tool bits.  FIG.  2    illustrates a HSS PM material according to the present disclosure. Carbide particles  10  in  FIG.  2    are seen by the small white regions embedded in an iron-based matrix, shown by the gray background of the SEM image. The illustrated carbide particles  10  are homogenous. In other words, the carbide particles  10  are generally uniform in shape, size, and distribution. A size of the carbide particles may be defined as an area of the respective carbide particle. For example, the illustrated carbide particles have a generally round shape such that the area of the respective carbide particle is based on determining an area of a circle. Furthermore, uniform distribution of the carbide particles is defined as each of the particles have about the same shape, size, and distribution throughout the material. 
     Carbide particles are present in the material in at least 6% by volume. In certain embodiments, carbide particles are present in the material in the range of about 10% to about 15% by volume. In certain other embodiments, the carbide particles are present in the range of about 5% to about 20%, about 6% to about 19%, about 7% to about 18%, about 8% to about 17%, about 9% to about 16%, about 10% to about 16%, about 10% to about 17%, about 10% to about 18%, about 10% to about 19%, about 10% to about 20%, about 9% to about 15%, about 8% to about 15%, about 7% to about 15%, about 6% to about 15%, or about 5% to about 15% by volume. 
     Alternately or additionally, carbide particles may be present in an amount greater than or equal to about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%, or about 15% by volume. Carbide particles may be present in an amount less than or equal to about 25%, about 24%, about 23%, about 22%, about 21%, about 20%, about 19%, about 18%, about 17%, about 16%, about 15%, about 14%, about 13%, about 12%, about 11%, or about 10% by volume. Carbide particles may be present in an amount of about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 10.5%, about 11%, about 11.5%, about 12%, about 12.5%, about 13%, about 13.5%, about 14%, about 14.5%, about 15%, about 16%, about 17%, about 18%, about 19%, about 20%, about 21%, about 22%, about 23%, about 24%, or about 25% by volume. 
       FIG.  3    illustrates a wrought tool steel including carbide particles  20 . The carbide particles  20  (white to light gray regions) have non-uniform size, shape, and distribution. In particular reference to the carbide particles of the HSS PM material embodying the invention shown in  FIG.  2   , these carbide particles have a relatively more uniform distribution in comparison to the carbide particles of the wrought tool steel of  FIG.  3   . 
     Bit Geometry 
     The HSS PM material shown in  FIG.  2    may be used to make tool bits in accordance with the present disclosure. In some embodiments, the wrought tool steel shown in  FIG.  3    may also be used to make tool bits in accordance with the present disclosure. The disclosed tool bits may have any suitable form known in the art. As described in more detail below, however, certain types of bits are particularly advantageous: for example, bits having tips that are prone to wearing out, such as PH2 or SQ2 tips. 
       FIG.  4    illustrates a Phillips head #2 (PH2) tool bit  100 . The tool bit  100  includes a shank  104  having a first end  108  configured to be connected to a tool (e.g., a drill, an impact driver, a screw driver handle, etc.), and a second or working end  112  configured to engage a workpiece or fastener (e.g., a screw, etc.). The shank  104  includes a tool coupling portion  130  having the first end  108 , and a head portion  134  having the working end  112 . 
     The tool coupling portion  130  has a hexagonal cross-sectional shape. The tool coupling portion  130  has an outer dimension. The illustrated outer dimension is defined as a width extending between two opposite flat sides of the hexagonal cross-sectional shape. 
     As shown in  FIG.  4   , the head portion  134  includes a plurality of flutes  116 , or recesses, circumferentially spaced around the head portion  134 . The flutes  116  extend longitudinally along the head portion  134  and converge into vanes  138 . The vanes  138  are formed with flat, tapered side walls  120  and outer walls  142 , such that the outer walls  142  are inclined and form the front ends of the vanes  138 . The vanes  138  are also equidistantly disposed around the head portion  134 . As shown in  FIG.  7   , the illustrated flutes  116  are defined by a single, curved surface having a radius of curvature R. Without wanting to be limited by theory, having the radius R in the flutes  116  allows for better impact strength and/or makes it feasible to use a high hardness material, such as M4 steel for example, without shattering the tip of the bit  100  during routine drill operation. In certain embodiments, the flute radius R is preferably between about 0.8 mm and about 1.0 mm to optimize fitment and strength. Alternately, the flute radius R may be smaller than 0.8 mm. 
     In certain other embodiments, the flute radius R is between about 0.5 and about 1.2, about 0.6 and about 1.1, about 0.7 and about 1.0, about 0.8 and about 0.9, about 0.7 and about 1.0, about 0.6 and about 1.0, about 0.5 and about 1.0, about 0.8 and about 1.1, or about 0.8 and about 1.2 mm. The flute radius R may be less than or equal to about 1.5, about 1.4, about 1.3, about 1.2, about 1.1, about 1.0, about 0.9, or about 0.8 mm. The flute radius R may be greater than or equal to about 0.1, about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, or about 1.0 mm. The flute radius R may be about 0.1, about 0.2, about 0.3, about 0.4, about 0.5, about 0.55, about 0.6, about 0.65, about 0.7, about 0.75, about 0.8, about 0.82, about 0.84, about 0.85, about 0.86, about 0.88, about 0.9, about 0.92, about 0.94, about 0.95, about 0.96, about 0.98, about 1.0, about 1.05, about 1.1, about 1.15, about 1.2, about 1.3, about 1.4, or about 1.5 mm. 
     The shank  104  further includes a first intermediate portion  124  extending between the first and second ends  108 ,  112 . The first intermediate portion  124  extends between the tool coupling portion  130  and the head portion  134 . The illustrated first intermediate portion  124  has a cylindrical shape. In certain embodiments, the shank  104  may include multiple intermediate portions. For example, the illustrated tool bit  100  further includes a second intermediate portion  146  extending between the first intermediate portion  124  and the tool coupling portion  130 . Each of the plurality of intermediate portions  124 ,  146  has a diameter. In particular, the diameter of each of the plurality of intermediate portions  124 ,  146  is less than the outer dimension of the tool coupling portion  130 . Furthermore, the diameter of each of the plurality of intermediate portions  124 ,  146  may be the same or different. Additionally or alternately, the tool bit  100  may include a specialized bit holder with a reduced diameter intermediate portion designed specifically for the bit  100 . 
     The diameter of the thinnest intermediate portion  124  of the plurality of intermediate portions  124 ,  146  is preferably chosen such that the thinnest intermediate portion  124  has a strength about 10% stronger than the shear strength of the head portion  134  of the tool bit  100 . For example, the first intermediate portion  124  may be about 3.6 mm in diameter. Each of the plurality of intermediate portions  124 , 146  has a length. The length of the first intermediate portion  124  (or effective length when there are multiple intermediate portions) is preferably between about 13 mm and about 23 mm, and more preferably about 18 mm. 
     In certain embodiments, the diameter of the first intermediate portion  124  is between about 2.0 and about 5.0, about 2.5 and about 5.0, about 3.0 and about 5.0, about 3.1 and about 5.0, about 3.2 and about 5.0, about 3.3 and about 5.0, about 3.4 and about 5.0, about 3.5 and about 5.0, about 2.0 and about 4.5, about 2.0 and about 4.0, about 3.0 and about 4.0, about 3.1 and about 4.0, about 3.2 and about 4.0, about 3.3 and about 4.0, about 3.5 and about 4.0 mm. The diameter may be at most about 5.0, about 4.5, about 4.0, about 3.9, about 3.8, about 3.7, and about 3.6 mm. 
     In certain embodiments, the effective length of the first intermediate portion  124  is between about 10 and about 26, about 11 and about 25, about 12 and about 24, about 13 and about 23, about 14 and about 22, about 15 and about 21, about 16 and about 20, about 17 and about 19, about 13 and about 18, about 13 and about 19, about 13 and about 20, about 13 and about 21, about 13 and about 22, about 18 and about 23, about 17 and about 23, about 16 and about 23, about 15 and about 23, or about 14 and about 23 mm. 
       FIG.  5    illustrates another PH2 tool bit  200 . Similar to the tool bit  100  shown in  FIG.  4   , the tool bit  200  includes a shank  204  having a first end  208  configured to be connected to a tool (e.g., a drill, an impact driver, a screw driver handle, etc.), and a second or working end  212  configured to engage a workpiece or fastener (e.g., a screw, etc.). The illustrated tool bit  200 , however, is relatively shorter than the tool bit  100 . Furthermore, the shank  204  includes a tool coupling portion  230  having the first end  208 , and a head portion  234  having the working end  212 . 
     The head portion  234  of the tool bit  200  defines a plurality of flutes  216 , or recesses, and a plurality of vanes  238 . The vanes  238  are formed by side walls  220  and outer walls  242 . The flutes  216  are defined by a single, curved surface having a radius of curvature (similar to tool bit  100  including the flues  116  having the radius of curvature R as shown in  FIG.  7   ). An intermediate portion  224  extends between the tool coupling portion  230  and the head portion  234 . The flute radius and the intermediate portion  224  may have similar dimensions as the flute radius R and the first intermediate portion  124  described above. 
     In certain embodiments, one end of the intermediate portion  224  may function as a c-ring notch for connecting the tool bit  200  to the tool. Alternatively, the tool bit  200  may have a separate c-ring notch, although this may reduce the total length of the intermediate portion  224 . 
       FIG.  6    illustrates another tool bit  400  having a square head #2 (SQ2) tool bit  408  received in a bit holder  300 . The illustrated bit holder  300  includes a shank  304  having a first end  308  configured to be connected to a tool (e.g., a drill, an impact driver, etc.) and a second end  312  configured to receive the tool bit  400 . The shank  304  of the bit holder  300  also defines an intermediate portion  316 , which may have similar dimensions as the first intermediate portion  124  described above. The shank  304  includes a tool coupling portion  330  having the first end  308 . 
     The tool bit  400  includes a shank  404  having a first end received in the bit holder  300  and a second or working end  412  configured to engage a workpiece or fastener (e.g., a screw, etc.). The shank  404  of the tool bit  400  also defines an intermediate portion  416 , which may be similar to the first intermediate portion  124  described above. The shank  404  includes a head portion  434  having the working end  412 . As such, the intermediate portion  316  of the bit holder  300 , and the intermediate portion  416  of the tool bit  400  extend between the tool coupling portion  330  and the head portion  434 . 
     Production 
     The disclosed tool bits  100 ,  200 ,  400  and bit holder  300  are preferably manufactured by lathe turning and milling, metal injection molding (MIM), or with a bi-material process, although other methods may also be used. For a turning and milling process, the material to form the tool bits  100 ,  200 ,  400  and bit holder  300  is preferably provided in hex shaped bar stock. 
     MIM is typically an expensive process compared to turning and milling. As MIM wastes essentially none of the source material, however, it may be a cost effective option when working with more expensive materials, such as HSS PM (e.g., PM-M4 and the like). In comparison, a typical turning and milling process may involve milling away about 45% of the source material. In some embodiments, the tool bits  100 ,  200 ,  400  and bit holder  300  may be formed using MIM to obtain the net shape geometry of the desired bits. The bits may then be subjected to a secondary process to obtain very high density (and, thus, very high performing) parts. In some embodiments, the secondary process can include a liquid phase sintering process. In other embodiments, the secondary process can include a hot isotatic pressing (HIP) process. 
     In the bi-material concept, two different materials are combined to form the tool bits  100 ,  200 ,  400 , for example. This allows a vast majority of the tool bits  100 ,  200 ,  400  to be made from a lower cost material, while the tips (i.e., the head portion  134 ,  234 ,  434 ) of the bits are made from HSS PM, for example, which may be welded to the lower cost shaft (i.e., tool coupling portion  130 ,  230 ,  330 ) of the bit. In other embodiments, the tips (or head portions  134 ,  234 ,  434 ) of the bits are made from carbide. The lower cost material may include a non-PM steel such as, for example, 6150 steel or D6A steel. With such materials, the majority (or body  130 ,  230 ,  330 ) of the tool bits  100 ,  200 ,  400  is still made from a quality material that is capable of handling high temperature heat treating and has sufficient ductility for use in, for example, an impact driver. 
     In other words, the tip of the bit can be made of a first material having a first hardness, and the shank of the bit can be made of a second material having a second, different hardness. The first and second materials may be chosen such that the first hardness is greater than the second hardness. Accordingly, the hardness of the tip is greater than the hardness of the shank to reduce wear imparted to the tip during use of the bit. The reduced hardness of the shank relative to the tip may also increase the impact-resistance of the bit. 
     In some embodiments, the two materials used to create the bi-material bits may also initially have different geometries. For example, a round (i.e., circular cross-sectional shape) stock of higher quality high speed steel, such as PM steel, may be welded or otherwise secured to a hex (i.e., hexagonal cross-sectional shape) stock of lower cost material. The round stock, which is more common than the hex stock, can then be machined into the desired shape of the bit tip. With reference to the tool bits  100 ,  200 ,  400 , the head portion  134 ,  234 ,  434  and the plurality of intermediate portions  124 ,  224 ,  416  may be formed from the round stock, and the tool coupling portion  130 ,  230 ,  330  may be formed from the hex stock. Furthermore, the bit holder  300  may also be formed from the hex stock and the round stock. The bit holder  300  may be also be formed from the same material or different materials. 
     An insert-molding process, such as a two-shot metal injection molding (MIM) process, may be used to manufacture a bit having a conjoined tip (i.e., the head portion  134 ,  234 ,  434  and plurality of intermediate portions  124 ,  224 ,  416 ) and shank (i.e., the tool coupling portion  130 ,  230 ,  330 ) made from two different metals. Particularly, the tip may be made of a metal having a greater hardness than that of the shank and a drive portion. Because the dissimilar metals of the tip and the shank are conjoined or integrally formed during the two-shot MIM process, a secondary manufacturing process for connecting the tip to the remainder of the bit is unnecessary. Alternately, rather than using an insert molding process, the tip may be attached to the shank using a welding process (e.g., a spin-welding process). 
     A sintering process such as a hot isostatic pressing (HIP) process may be used to manufacture the tool bit  100 ,  200 ,  400  and bit holder  300 . Specifically, the PM is atomized into micro ingots. In one embodiment, the PM is atomized with Argon gas. The atomized PM micro ingots are injected into a mold. Subsequently, the atomized PM micro ingots are sintered, while in the mold, into a block. Specifically, the high pressure of the HIP process molds or welds individual PM particles together into the block. In some embodiments, the atomized PM micro ingots may be injected into a mold that has a hexagonal cross-sectional shape such that the block has a hexagonal cross-sectional shape after the HIP process. In other embodiments, the atomized PM micro ingots may be injected into a mold that has a near net shape of the desired tool bit. The mold may be machined away such that only the block remains. A milling process may then be used to mill the block to predetermined dimensions of the tool bit  100 ,  200 ,  400 . In another embodiment, the atomized PM micro ingots are sintered, while in the mold, into the tool bit  100 ,  200 ,  400 . As such, minimal or no milling may be required to achieve the predetermined shape of the tool bit  100 ,  200 ,  400  after sintering the atomized PM micro ingots into the tool bit  100 ,  200 ,  400 . In the illustrated embodiment, the PM is formed of HSS material. 
     Rather than using different materials during the manufacturing process to create a tool bit, the tip (i.e., the head portion  134 ,  234 ,  434  and plurality of intermediate portions  124 ,  224 ,  416 ) of the tool bit may include a layer of cladding having a hardness greater than the hardness of the shank. Furthermore, the hardness of the cladding may be greater than the hardness of the underlying material from which the tip is initially formed. The cladding may be added to the tip using any number of different processes (e.g., forging, welding, etc.). The addition of the cladding to the tip may increase the wear resistance of the tip in a similar manner as described above. 
     Without wanting to be limited by theory, heat treatment contributes to the high wear resistance of the bits. Heat treatment is typically completed in a vacuum furnace, although it may also be performed in a salt bath or by another method commonly known in the art. 
     In certain embodiments, the heat treatment includes preheating, austenitizing, and/or tempering. In some embodiments, the heat treatment can be done with two preheats. The first preheat can be done at, for example, about 1525 degrees Fahrenheit. The second preheat can be done at, for example, about 1857 degrees Fahrenheit. In other embodiments, the heat treatment can be done with a single preheat. In further embodiments, the heat treatment may be done with three or more preheats. In still other embodiments, the heat treatment may be done without preheats or the temperatures of the preheats may be different. 
     In some embodiments, the tool bits  100 ,  200 ,  400  and bit holder  300  may be austenitized at a temperature between about 1975 and about 2025 degrees Fahrenheit. In other embodiments, the austenitizing temperature may be about 2000 degrees Fahrenheit. In such embodiments, the temperature may be held for about 3 minutes. In other embodiments, the temperature may be held for between about 2 and about 4 minutes. In further embodiments, the temperature may be held for at least about 3 minutes. 
     Tempering may be done in a vacuum two times. In some embodiments, the tool bits  100 ,  200 ,  400  and bit holder  300  may be tempered at a temperature between about 1000 and about 1050 degrees Fahrenheit each time. In other embodiments, the tempering temperature may be about 1025 degrees Fahrenheit. In such embodiments, the temperature may be held for about 2 hours each time. In other embodiments, the temperature may be held for between about 1 and about 3 hours each time. In further embodiments, the temperature may be held for at least 2 hours each time. In still other embodiments, the tempering may be done more than two times. 
     After heat treating, the tool bits  100 ,  200 ,  400  and bit holder  300  can have a final hardness greater than or equal to 61 on the Rockwell C scale (HRC). In some embodiments, the hardness can be between about 61 and about 63 HRC. In certain embodiments, the hardness may be about 61, about 61.1, about 61.2, about 61.3, about 61.4, about 61.5, about 61.6, about 61.7, about 61.8, about 61.9, about 62, about 62.1, about 62.2 about 62.3, about 62.4, about 62.5, about 62.6, about 62.7, about 62.8, about 62.9, or about 63 HRC. In further embodiments, the hardness may be greater than 63 HRC. 
     Coating 
     In certain embodiments, the tool bits  100 ,  200 ,  400  and bit holder  300  are coated to improve corrosion resistance. The bits are preferably nickel plated, although other suitable coatings are well known in the art, such as phosphating or oxidize coatings, for example. M4 steel is a particularly good base for chemical vapor deposition (CVD) or physical vapor deposition (PVD) coatings, but these are comparatively expensive. 
     Data and Test Results 
     As shown in the table below, analysis was performed on PM HSS tool bits (i.e., tool bit #1—PM) and wrought HSS tool bits (i.e., tool bit #2—Wrought). In particular, tool bit #1 is composed of powdered metal (PM) material having a grade of M4. Tool bit #2 is composed of wrought material having a grade of M2. The analysis was conducted to determine the size and the shape of the carbide particles of tool bit #1 compared to the size and the shape of the carbide particles of tool bit #2. For each tool bit, three cross sections were taken in which the cross-sectional sample was mounted polished, and etched for two minutes with five percent nital. Ninety carbide particles were analyzed from the three cross-sections at 2000× magnification. Specifically, the size and the shape was determined for all of the analyzed carbide particles. The area of each carbide particle was measured, and the circularity of each carbide particle was also determined. Circularity is defined as 
               C   =       4   ⁢   π   ⁢           ⁢   Area       Perimeter   2         ,         
where C=1 is perfectly round. The average, standard deviation, minimum, and maximum was determined for the area and the circularity for each tool bit.
 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                 Std. 
                   
                   
               
               
                 Tool Bit 
                 Size/Shape 
                 Average 
                 Dev. 
                 Minimum 
                 Maximum 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 #1 - PM 
                 Area 
                 1.585 
                 0.644 
                 0.55 
                 4.697 
               
               
                   
                 (micron 2 ) 
               
               
                   
                 Circularity 
                 0.89 
                 0.123 
                 0.31 
                 0.991 
               
               
                 #2 - Wrought 
                 Area 
                 10.182 
                 24.26 
                 0.371 
                 148.136 
               
               
                   
                 (micron 2 ) 
               
               
                   
                 Circularity 
                 0.78 
                 0.232 
                 0.206 
                 0.991 
               
               
                   
               
            
           
         
       
     
     With continued reference to the table of  FIG.  7   , the carbide particles of tool bit #2 had an average area of 10.182 micron 2  and an average circularity of 0.78. In contrast, the carbide particles of tool bit #1 had an average area of 1.585 micron 2  and an average circularity of 0.89. The standard deviation of the carbide particles of tool bit #2 was 24.26, while the standard deviation of the carbide particles of tool bit #1 was 0.644. As such, the carbide particles of tool bit #1 are substantially uniform (i.e., each of the carbide particles are about the same size and the same shape). In comparison to tool bit #1, the carbide particles of tool bit #2 do not have generally the same size or the same shape. Specifically, the area of most of the carbide particles of tool bit #1 is less than 2.55 micron 2 , in which most of the carbide particles is defined as 85 carbide particles out of the 90 carbide particles analyzed. 
     Tool bits embodying the invention were tested to determine a hardness and impact durability of the tool bits in comparison to conventional tool bits currently in the market. In one test, Phillips #2 tool bits were used with various screws, materials, and tools to simulate everyday use. The tool bits were used until failure (e.g., the tool bit wore out and was no longer suitable for use). The conventional tool bits ranged, on average, from about 168 to about 1369 uses before wearing out. In contrast, the tool bits embodying the invention made of PM HSS ranged, on average, from about 2973 to about 3277 uses (depending on the size/length of the tool bit) before wearing out. 
     In another test, T25 tool bits were used with an impact driver to drive screws into double-stack laminated veneer lumber (LVL) with pre-drilled sheet steel over the top. The tool bits were used until failure. The conventional tool bits ranged, on average, from about 557 to about 2071 uses before failure. In contrast, tool bits embodying the invention made of PM HSS all lasted until the test was stopped at 3000 screws driven without any of the tool bits failing, showing improved impact durability over the conventional tool bits. 
     In another test, PH2 tool bits were used with an impact driver to drive screws into a double-stack LVL. The tool bits were used until failure. The conventional bits ranged, on average from about 178 to about 508 uses before failure. In contrast, tool bits embodying the invention made of PM HSS ranged, on average, from about 846 to about 953 uses (depending on the size/length of the tool bit) before failure, with many tool bits lasting until the test was suspended at 1000 screws driven. This test also showed improved impact durability over conventional tool bits. 
     Thus, the invention provides, among other things, a tool bit having markedly improved wear resistance. While specific configurations of the tool bit have been described, it is understood that the present invention can be applied to a wide variety of tool components and that the tool bit could take on a variety of other forms, for example, cutting components of other hand or power tools. Various features and advantages of the invention are set forth in the following claims.