Rotary tool and its cutting part

Abstract

A rotary tool (T) has a rotary segment ( 10 ) with an opposed surface opposed to a work surface and a plurality of cutting parts ( 20 ) arranged on the opposed surface. Some cutting parts ( 20 ) include tips ( 22 a ) made of a grinding tool segment obtained by binding abrasive grains by a metal binder and the other cutting parts ( 20 ) include tips ( 24 a ) made of a sintered material harder than the grinding tool segment, and the respective cutting parts ( 20 ) are arranged such that the tips ( 24 a ) are located at positions more outward than the tips ( 22 a ) with respect to radial directions of the rotary segment.

1 . A cutting part for use in a rotary tool including a rotary segment having an opposed surface opposed to a work surface, comprising a tip for scratching off a surface portion of the work surface when the rotary segment is pressed against the work surface while being drivingly rotated about an axis extending in a direction normal to the opposed surface, wherein an inner part of the tip with respect to a radial direction is made of a grinding tool segment obtained by binding abrasive grains by a metal binder and an outer part of the tip with respect to the radial direction is made of a sintered material harder than the grinding tool segment.  
   
   
       2 . A cutting part according to  claim 1 , wherein the outer part of the tip with respect to the radial direction is made of a polycrystalline diamond sintered material or polycrystalline cubic boron nitride sintered material.  
   
   
       3 . A cutting part according to  claim 1 , wherein the entire tip excluding the tip part made of the sintered material is made of a grinding tool segment obtained by binding abrasive grains by a metal binder.  
   
   
       4 . A cutting part according to  claim 1 , wherein the length of the tip made of the sintered material is set within a range of 1% to 67% of the entire length of the tip.  
   
   
       5 . A rotary tool, comprising: 
 a rotary segment having an opposed surface opposed to a work surface; and    a plurality of cutting parts arranged on the opposed surface and each having a tip for scratching off a surface portion of the work surface in a peripheral direction, the rotary tool scratching off the surface portion of the work surface by pressing the respective cutting parts against the work surface while the rotary segment is drivingly rotated about an axis extending in a direction normal to the opposed surface,    wherein:    the opposed surface is arranged with a grinding tool segment obtained by binding abrasive grains by a metal binder;    each of the cutting parts includes a tip made of a sintered material harder than the grinding tool segment; and    the tip made of the sintered material is provided at a position more outward than the grinding tool segment with respect to radial direction of the rotary segment.    
   
   
       6 . A rotary tool according to  claim 5 , wherein some cutting parts include tips made of the grinding tool segment and the other cutting parts include tips made of the sintered material harder than the grinding tool segment, and the respective cutting parts are arranged such that the tips made of the sintered material are located at positions more outward than the tips made of the grinding tool segment with respect to the radial directions of the rotary segment.  
   
   
       7 . A rotary tool according to  claim 5 , wherein the grinding tool segment has such a shape continuous along a peripheral direction of the rotary segment, and the cutting parts having the tips made of the sintered material are provided at positions more outward than the grinding tool segment with respect to the radial directions of the rotary segment.  
   
   
       8 . A rotary tool, comprising: 
 a rotary segment having an opposed surface opposed to a work surface; and    a plurality of cutting parts arranged on the opposed surface and each having a tip for scratching off a surface portion of the work surface in a peripheral direction, the rotary tool scratching off the surface portion of the work surface by pressing the respective cutting parts against the work surface while the rotary segment is drivingly rotated about an axis extending in a direction normal to the opposed surface, the plurality of cutting parts including at least one cutting part having a tip whose inner part with respect to the radial direction is made of a grinding tool segment obtained by binding abrasive grains by a metal binder and whose outer part with respect to the radial direction is made of a sintered material harder than the grinding tool segment.    
   
   
       9 . (canceled)  
   
   
       10 . A rotary tool according to  claim 8 , wherein the plurality of cutting parts include a first cutting part having a tip made of sintered material and a second cutting part having a tip made of grinding tool segment, the second cutting part being arranged such that the tip thereof is located at a position more inward than the tip of the first cutting part made of sintered material with respect to the radial direction of the rotary segment.  
   
   
       11 . A rotary tool according to  claim 8 , wherein all the cutting parts of the rotary tool are cutting parts have a tip whose inner part with respect to the radial direction is made of a grinding tool segment obtained by binding abrasive grains by a metal binder and whose outer part with respect to the radial direction is made of a sintered material harder than the grinding tool segment.  
   
   
       12 . A rotary tool according to  claim 11 , wherein the outer part of the tip with respect to the radial direction is made of a polycrystalline diamond sintered material or polycrystalline cubic boron nitride sintered material.  
   
   
       13 . A rotary tool according to  claim 11 , wherein the entire tip excluding the tip part made of the sintered material is made of a grinding tool segment obtained by binding abrasive grains by a metal binder.  
   
   
       14 . A rotary tool according to  claim 11 , wherein the length of the tip made of the sintered material is set within a range of 1% to 67% of the entire length of the tip.  
   
   
       15 . A rotary tool according to  claim 11 , wherein all the cutting parts having a tip whose inner part with respect to the radial direction is made of a grinding tool segment obtained by binding abrasive grains are peripherally arranged at even intervals.  
   
   
       16 . A rotary tool according to  claim 8 , wherein the outer part of the tip with respect to the radial direction is made of a polycrystalline diamond sintered material or polycrystalline cubic boron nitride sintered material.  
   
   
       17 . A rotary tool according to  claim 8 , wherein the entire tip excluding the tip part made of the sintered material is made of a grinding tool segment obtained by binding abrasive grains by a metal binder.  
   
   
       18 . A rotary tool according to  claim 8 , wherein the length of the tip made of the sintered material is set within a range of 1% to 67% of the entire length of the tip.