Cutting insert for percussion drill bit

Abstract

A cutting insert for a percussion hammer bit. The cutting insert includes a base portion for coupling to a bit face of the percussion hammer bit. An extension portion is coupled to the base portion and axially offset therefrom along a longitudinal axis extending through the base portion and the extension portion. The extension portion includes at least three lobes that are circumferentially offset from one another around the longitudinal axis. The lobes extend axially away from the base portion, and the lobes extend radially outward from the longitudinal axis.

What is claimed is: 
     
         1 . A cutting insert for a bit, comprising:
 a base portion adapted to be coupled to a bit face of the bit; and   an extension portion coupled to the base portion and axially offset therefrom along a longitudinal axis extending through the base portion and the extension portion, the extension portion including at least three lobes that are circumferentially offset from one another around the longitudinal axis, the at least three lobes extending axially away from the base portion and radially outward from the longitudinal axis.   
     
     
         2 . The cutting insert of  claim 1 , the extension portion including three lobes. 
     
     
         3 . The cutting insert of  claim 2 , at least two of the three lobes being circumferentially offset from one another by an angle between about 100° and about 140° with respect to the longitudinal axis. 
     
     
         4 . The cutting insert of  claim 1 , the extension portion including four lobes. 
     
     
         5 . The cutting insert of  claim 4 , at least two of the four lobes being circumferentially offset from one another by an angle between about 70° and about 110° with respect to the longitudinal axis. 
     
     
         6 . The cutting insert of  claim 1 , the extension portion further including a relief between two of the at least three lobes, an outer surface of the extension portion proximate the relief being positioned nearer the base portion than an outer surface of the at least three lobes. 
     
     
         7 . The cutting insert of  claim 1 , a width of the at least three lobes being greater proximate an outer radial edge portion of the extension portion than proximate the longitudinal axis. 
     
     
         8 . The cutting insert of  claim 1 , a width of the at least three lobes being greater proximate the longitudinal axis than proximate an outer radial edge portion of the extension portion. 
     
     
         9 . The cutting insert of  claim 1 , a height of an outer axial surface of the at least three lobes being greater proximate the longitudinal axis than proximate an outer radial edge portion of the extension portion. 
     
     
         10 . The cutting insert of  claim 1 , the at least three lobes being integral with one another proximate the longitudinal axis. 
     
     
         11 . A percussion hammer bit, comprising,
 a body having a bit face; and   a cutting insert coupled to the body, the cutting insert including:
 a base portion; and 
 an extension portion extending from the bit face and including at least three lobes circumferentially offset from one another around a longitudinal axis extending through the base portion and the extension portion, the lobes extending radially outward from the longitudinal axis, and the extension portion including a relief between two of the at least three lobes such that an outer surface of the extension portion proximate the relief is positioned closer to the base portion than an outer surface of the lobes. 
   
     
     
         12 . The percussion hammer bit of  claim 11 , two of the at least three lobes being circumferentially offset from one another by an angle between about 100° and about 140° with respect to the longitudinal axis. 
     
     
         13 . The percussion hammer bit of  claim 11 , two of the at least three lobes being, circumferentially offset from one another by an angle between about 70° and about 110° with respect to the longitudinal axis. 
     
     
         14 . The percussion hammer bit of  claim 11 , a width of the at least three lobes being greater proximate an outer radial edge portion of the extension portion than proximate the longitudinal axis. 
     
     
         15 . The percussion hammer bit of  claim 11 , a width of the at least three lobes being greater proximate the longitudinal axis than proximate an outer radial edge portion of the extension portion. 
     
     
         16 . A percussion hammer bit, comprising,
 a body having a bit face; and   first and second cutting inserts coupled to the body and each including:
 a base portion coupled to the bit face; and 
 an extension portion integral with the base portion and including at least two lobes, the at least two lobes of the first and second cutting inserts being oriented with respect to one another to increase linkage of cracks in a subterranean formation contacted by the first and second cutting inserts. 
   
     
     
         17 . The percussion hammer bit of  claim 16 , the first and second cutting inserts being in a same circumferential row on the bit face. 
     
     
         18 . The percussion hammer bit of  claim 17 , the first and second cutting inserts being in a circumferential gage row. 
     
     
         19 . The percussion hammer bit of  claim 16 , the first and second cutting inserts being in adjacent circumferential rows on the bit face. 
     
     
         20 . The percussion hammer bit of  claim 19 , the first cutting insert being in a circumferential gage row and the second cutting insert being disposed in a circumferential adjacent-to-gage row. 
     
     
         21 . The percussion hammer bit of  claim 16 , the at least two lobes being oriented to increase linkage at locations of lower cutting insert density.