Pcd percussion drill bit

Abstract

The invention is embodied in a percussion drill bit which comprises a steel body with a working front head portion having a front central zone and plural wing zones radiating from the central zone and being spaced at the outer circumferential edges thereof; first gauge-cutting PCD inserts are secured in the wing zones to extend forwardly at an angle relative to the axis of the bit, and of at least one second core-cutting PCD insert is non-axially secured to extend forwardly from the central zone.

1 . A percussion drill bit for drilling bore holes in hard rock and mineral, comprising:
 (a) a steel body having a working front head portion and a rearward shank portion for connection to an impact driving force;   (b) said head portion having a front facing central zone and plural wing zones extending radially from the central zone and being spaced apart at the outer circumferential edges thereof by grooves in the outer wall of the front head portion;   (c) a first gauge-cutting PCD insert secured in the steel head portion of at least two wing zones and being constructed and arranged to extend at a predetermined angle to the axis and have a gauge-cutting PCD surface operable for forming the bore hole dimension; and   (d) at least one second PCD insert non-axially secured in the central zone to project forwardly of the first PCD inserts and being operable for impact at the core area of the bore hole to pilot the boring hole effort of the first PCD inserts.   
   
   
       2 . The drill bit of  claim 1  in which the head portion has an outer side wall that tapers inwardly from the circumferential edges of the wing zones to the shank portion of the steel body. 
   
   
       3 . The drill bit of  claim 1  wherein there are three side wing zones each having a first gauge-cutting PCD insert secured therein. 
   
   
       4 . The drill bit of  claim 3 , in which there are plural second core-cutting PCD inserts projecting forwardly from the central zone and being asymmetrically and non-axially disposed. 
   
   
       5 . The drill bit of  claim 4 , in which the wing zones have front faces sloping at a predetermined angle rearwardly from the front facing central zone to the outer circumferential edge of the head portion, and a primary socket extending into each sloping front face and being recessed normal thereto for seating said first gauge-cutting PCD insert therein. 
   
   
       6 . The drill bit of  claim 5 , wherein the sloping surfaces of the side wing zones are formed at an angle in the range of 15° to 35° relative to a plane perpendicular to the axis of the drill bit. 
   
   
       7 . The drill bit according to  claim 6  wherein the gauge cutting inserts have cylindrical body sections and parabolic head sections, the cylindrical body sections being press-fit into said first sockets to a depth of about 0.250 to 0.390 inches. 
   
   
       8 . The drill bit according to  claim 7  in which the cylindrical body sections extend outwardly from the sloping surface of each side wing zone to space the domed head sections of these inserts forwardly of the plane of the front facing central zone. 
   
   
       9 . The drill bit according to  claim 8 , wherein there are at least two second PCD inserts non-axially secured in the front facing central zone and extending forwardly from the plane thereof. 
   
   
       10 . The drill bit of  claim 9 , wherein the central zone lies on a plane perpendicular to the axis of the drill bit, and second socket means formed in the central zone for seating the second PCD inserts therein. 
   
   
       11 . The drill bit according to  claim 10  wherein the first and second socket means are formed in said head portion to open outwardly at the wing zones and front-facing central zone on different radius lines from the axis of the drill bit. 
   
   
       12 . The drill bit according to  claim 11  wherein said first and second socket means are formed to extend into said head portion and have bottoms that are offset axially from each with the bottoms of the first socket means being below the bottoms of the second socket means. 
   
   
       13 . The drill bit according to  claim 10  in which the second PCD inserts are constructed and arranged as core-cutters for the bore hole being formed, the second PCD inserts having parabolic working surfaces extending forwardly beyond the parabolic head sections of the first PCD inserts. 
   
   
       14 . The drill bit of  claim 3  in which said head portion of said steel body is armored with a hard cladding material tougher than the steel body to thereby reduce outer body wear at the side wing zones and thereby prolong the PCD insert integrity with a substantially longer drill bit life. 
   
   
       15 . The drill bit of  claim 14 , in which the hard cladding material covers the front face of the head portion around the first and second PCD inserts and circumscribes the outer side wall of the head portion. 
   
   
       16 . The drill bit of  claim 15  in which the hard cladding material includes chromium (CR) and is plated to a hardness of at least 60 Rc and a thickness in the range of 0.001 to 0.030. 
   
   
       17 . The drill bit of  claim 16  in which the plated chromium material has a Rockwell hardness of 65 to 68 and a thickness in the range of 0.005 to 0.015. 
   
   
       18 . A percussion drill bit comprising:
 (a) a head portion having a front-facing central zone and multiple wing zones radiating symmetrically therefrom and being spaced apart at the outer circumferential edges thereof;   (b) first gauge-cutting PCD inserts secured in at least two of said wing zones and being constructed and arranged to extend angularly relative to the axis of the drill bit and being operable for forming the fore hole dimension; and   (c) at least one second PCD insert non-axially secured in the central zone to project forwardly of the first PCD inserts and being operable for piloting the bore hole formation.   
   
   
       19 . The drill bit of  claim 18 , in which said first and second PCD inserts are seated in primary and secondary angularly related socket means extending into the head portion, said primary socket means being deeper than said secondary socket means. 
   
   
       20 . The drill bit of  claim 18  wherein the first PCD inserts are relatively large and sized to do the principle drilling work while the smaller second PCD insert initiate the bore-hole and then work in conjunction with the first PCD inserts. 
   
   
       21 . The method of making an armored percussion bit with PCD inserts
 (a) forming a steel bit body having a shank portion and a working head portion with a central zone and plural spaced wing zones extending radially from the central zone and being separated circumferentially by spaced grooves in the outer head portion wall;   (b) bonding a hard cladding material to cover the exposed surface areas of the head portion;   (c) boring the shank portion axially to provide a threaded means for connecting the drill bit to an impact driving force, and providing axial passageways for flushing fluid;   (d) boring the head portion to provide flushing fluid passages from the axial passageway to each of the spaced grooves in the outer head portion wall   (e) forming sockets through the hard cladding material into the central zone and wing zones of the head portion to accommodate PCD inserts; and   (f) press fitting the PCD inserts into the sockets.   
   
   
       22 . The method according to  claim 21 , in which the cladding material comprises chromium. 
   
   
       23 . The method according to  claim 21  including the step of constructing and arranging the PCD inserts so that the central zone PCD inserts project forwardly of the wing PCD inserts whereby to initiate and pilot the bore hole drilling operation.