Diamond tip point-attack bit

Abstract

A rotatable point-attack bit retained for rotation in a block bore, and used for impacting, fragmenting and removing material from a mine wall. An improved elongated tool body having at the front end a diamond-coated tungsten carbide wear tip that is rotationally symmetric about its longitudinal axis and contiguous with a second section steel shank at the rear end. The two distinct parts are joined by a high impact resistant braze at ratios that prevent tool breakage. The method of making such a diamond-coated section comprises of 1) placing within a reaction cell, the diamond powder and the carbide substrate and 2) simultaneously subjecting the cell and the contents thereof to temperature and pressure at which the diamond particles are stable and form a uniform polycrystalline diamond surface on the tip of the carbide substrate thus forming a diamond-coated insert providing both cutting edge and steel body protection for increased durability and extended cutting tool life.

What I claim as my invention is:  
     
         1 . A rotatable cutting bit for impacting, fragmenting and removing material such as asphalt, concrete, rock, and minerals, the rotatable cutting bit comprised of: 
 a polycrystalline diamond tip, affixed to a cemented carbide substrate by high temperature and pressure bonding, forming a diamond-coated unitary body, positioned at the forward central axis extremity of the cutter bit, having coaxially aligned, rotationally symmetric about its longitudinal axis a tip section, and a base section, having a maximum diameter at said base section, and having a flat surface or a convex protrusion or partial continuously varying radiused extension at its rearward section.    a ferrous body with a head section and elongated shank having a circular cross section, said body depending from said protective diamond-coated unitary body along a longitudinal axis, said head portion having a flat surface or concave seat or partial continuously varying radiused socket at the forward end.    
     
     
         2 . The rotatable cutting tool of  claim 1  wherein the forward section is coated with polycrystalline diamond, cubic boron nitride, wurtzite boron nitride or mixtures thereof formed by a method that comprises the placing within a reaction cell pre-pressed forms of abrasive particles affixed to the tip of the cemented carbide substrate and simultaneously subjecting the cell and the contents thereof to temperature and pressure conditions at which the diamond, cubic boron nitride or wurtzite boron nitride particles form a super hard abrasion resistant polycrystalline layer permanently sinter reaction bonded to the tip of the cemented carbide substrate.  
     
     
         3 . The rotatable cutting tool of  claim 1  wherein the forward section has a cemented carbide substrate, which at its forward end has from 1-5 staggered concentrically layered rounded radiused protuberances that serve to support the diamond layer.  
     
     
         4 . The rotatable cutting tool of  claim 1  wherein the forward end of the steel shank contains a flat surface or seat or partial continuously radiused socket defining a surface area, having an overall depth of 0.001 to 2.00 inches.  
     
     
         5 . The rotatable cutting tool of  claim 1  wherein the axially rearward section of said diamond-coated insert has a flat surface or protruding or radiused extension that generally corresponds to, and fits into the shape of the flat surface or seat or partial continuously radiused socket of said steel shank.  
     
     
         6 . The rotatable cutting tool of  claim 1  with a braze joint joining the surface area of the flat or protruding or radiused extension axially rearward section of said diamond-coated insert body to the flat surface, mating seat or radiused socket of the axially forward section of said ferrous shank by means of a medium to high impact resistant braze alloy.  
     
     
         7 . The brazed surface areas in  claim 6  of said steel shank axially forward section flat surface, seat or radiused socket and said rearward diamond-coated insert body section flat surface, protruding or radiused extension to be at a ratio of steel shank surface area to diamond-coated insert body lateral cross sectioned area of 1.0 to 6.5.  
     
     
         8 . The rotatable cutting tool of  claim 1  wherein the tip is made of a polycrystalline diamond affixed in situ to the carbide substrate by high temperature and high pressure.  
     
     
         9 . The rotatable cutting tool of  claim 1  wherein the tip is made of a polycrystalline cubic boron nitride affixed in situ to the carbide substrate by high temperature and high pressure.  
     
     
         10 . The rotatable cutting tool of  claim 1  wherein the diamond-coated insert cemented carbide substrate is made of a composition containing grains of carbide of group IVB, VB, or VIB metals pressed and sintered in the presence of a binder such as 5.0 to 18.0% cobalt, nickel, iron or alloys thereof.  
     
     
         11 . The rotatable cutting tool of  claim 1  wherein the diamond-coated insert cemented carbide substrate is made of a composition containing carbide of group IVB, VB, or VIB metals having grain sizes from 0.01 to 30 microns as measured on a sintered, polished and etched part at 100 to 1500× optical magnification.  
     
     
         12 . The rotatable cutting tool of  claim 1  wherein said diamond-coated insert protective cemented carbide substrate has an overall length of 0.01 to 3.0 inches.  
     
     
         13 . The rotatable cutting tool of  claim 1  wherein said diamond-coated insert cemented carbide substrate section has a plurality of even numbered peripherally spaced, laterally projecting surfaces or vanes extending generally longitudinally along the bit, each surface or vane being substantially triangular with a narrow leading end and a wider trailing end, and having relatively diverging sides that extend from the leading end to the trailing end, the purpose of which is to effect a positive rotation of the bit upon contact with material being impacted, fragmented or removed.  
     
     
         14 . The rotatable cutting tool of  claim 1  wherein said steel shank has a means for holding a loosely resilient retainer on the steel body that allows the cutter bit to rotate about its longitudinal axis in a mounting block.