Rotatable cutting tool for breaking hard material

Abstract

A rotatable cutting tool for applications such as road resurfacing work includes a cutting bit insert and a tool body. The cutting bit insert includes an insert body and an inner tiered protrusion integrally formed from the insert body. The inner tiered protrusion has multiple tiers. The tool body has a tiered recess that corresponds to the inner tiered protrusion to hold the inner tiered protrusion. A combination of the inner tiered protrusion and the tiered recess provides a strong connection for the cutting bit insert and the tool body and keeps stress from concentrating at a single point.

1 . A rotatable cutting tool comprising: 
 a cutting bit insert comprising 
 an insert body having a conical tip and an inner flat end; and  
 an inner tiered protrusion integrally formed on the inner flat end;  
   a tool body having an outer end and a tiered recess defined in the outer end of the tool body to firmly hold the inner tiered protrusion and the inner flat end of the insert body; and    a resilient retainer attached to the tool body.    
   
   
       2 . The rotatable cutting tool as claimed in  claim 1 , wherein the inner tiered protrusion comprises 
 a proximal tier with a top protruded perpendicularly from the inner flat end of the insert body; and    a distal tier protruded perpendicularly from the top of the proximal tier;    wherein the proximal tier, the distal tier and the inner flat end of the insert body are welded in the tiered recess of the tool body.