Cutting tool inserts

Abstract

An insert ( 10 ) for a cutting tool ( 100 ) for use down a well bore comprises a body of a hard material (tungsten carbide) suitable for cutting steel. The body is shaped for formation in a mould that comprises a die ( 70 ) and first ( 74 ) and second ( 78 ) punches and arranged so that the first punch can eject the body after formation from an opening of the die closed during formation by said second punch. The insert has first ( 12 ) and second ( 14 ) ends whose faces are defined, at least in part, by corresponding faces of the first and second punch. Between them is a longitudinal axis ( 24 ) of the insert. The area of the first end is less than the area of the second end. The body has flanks ( 16 ) that form ridges ( 18 ) extending between the first and second ends. The ridges form cutting edges of the insert. They are separated by V-shaped troughs ( 20 ) of said flanks. The ridges taper and spiral about the axis.

1 . An insert for a cutting tool for use down a well bore, comprising:
 a body of a hard material suitable for cutting steel, the body being shaped for formation in a mould that comprises a die and first and second punches and arranged so that the first punch can eject the body after formation from an opening of the die closed during formation by said second punch, said body having:   first and second ends whose faces are defined, at least in part, by corresponding faces of the first and second punch and which between them define a longitudinal axis of the insert, the area of the first end being less than the area of the second end, and   flanks of the insert extending between the first and second ends comprising ridges, said ridges forming cutting edges of the insert and being separated by troughs.   
     
     
         2 . An insert of  claim 1 , wherein the insert has a plurality of tiers that are of different cross sectional area with steps between them, each tier having said ridges and troughs that extend between first and second faces of the tier. 
     
     
         3 . An insert of  claim 1 , wherein said ridges taper from said second end to said first end. 
     
     
         4 . An insert of  claim 1 , wherein said ridges spiral about said axis. 
     
     
         5 . An insert of  claim 4 , wherein the degree of spiral is sufficiently limited, the degree of taper is sufficiently large, and the angular separation of a ridge and trough in the radial plane of the axis is so arranged, that the insert is not required to rotate on ejection from the die. 
     
     
         6 . An insert of  claim 1 , wherein said troughs are V-sections. 
     
     
         7 . An insert of  claim 1 , wherein said troughs diminish in depth, and said ridges correspondingly diminish in height, from said second end to said first end. 
     
     
         8 . An insert of  claim 7 , wherein said ridges terminate at or before said first end. 
     
     
         9 . An insert of  claim 3 , wherein the tapering is not linear. 
     
     
         10 . An insert of  claim 9 , wherein said tapering is convexly curved with respect to the axis. 
     
     
         11 . An insert of  claim 2 , wherein said tapering is not linear and is at least partly caused by said steps in the ridges forming said tiers. 
     
     
         12 . An insert of  claim 2 , wherein the cross section of each tier is constant along said axis. 
     
     
         13 . An insert of  claim 2 , wherein the ridges of each tier taper between said first and second faces. 
     
     
         14 . An insert of  claim 2 , wherein the steps between adjoining ridges form additional cutting faces. 
     
     
         15 . An insert of  claim 2 , wherein there are three tiers. 
     
     
         16 . An insert of  claim 2 , wherein the profiles of the tiers are the same. 
     
     
         17 . An insert of  claim 16 , wherein adjacent tiers are rotationally offset about said axis with respect to one another. 
     
     
         18 . An insert of  claim 1 , wherein said hard material comprises sintered tungsten carbide in a binder matrix. 
     
     
         19 . An insert of  claim 18 , wherein said binder comprises cobalt. 
     
     
         20 . A tool comprising:
 a substantially cylindrical body having a working face,   wherein the working face has applied thereto within a fixing matrix a plurality of cutting inserts of said body of  claim 1  disposed on the face in a random distribution.   
     
     
         21 . A tool of  claim 20 , wherein the working face is arranged in a radial plane of the tool. 
     
     
         22 . A tool of  claim 21 , wherein the working face is arranged substantially perpendicularly to a radial plane of the tool. 
     
     
         23 . A tool of  claim 22 , wherein said working surface may comprise blades attached to the tool. 
     
     
         24 . A tool of  claim 21 , wherein said working surface may comprise flutes formed in the side of the tool. 
     
     
         25 . A tool of  claim 20 , wherein said fixing matrix is braze material. 
     
     
         26 . (canceled)