Stepped drill bit assembly

Abstract

A wet drill bit assembly and a dry drill bit assembly for cutting a borehole in the earth strata of a mine wherein the borehole has a reduced dimension interior region and an enlarged dimension exterior region. The wet drill bit assembly includes an axial forward spade-style cutting member, which has a spade hard cutting member with a first transverse cutting dimension, and an axially spaced apart axial rearward reamer cutting member, which has a hard insert with a second transverse cutting dimension, which is greater than the first transverse cutting dimension. The dry drill bit assembly includes an axial forward cutting member, which has an axial forward hard cutting insert with a first transverse cutting dimension, and an axially spaced apart axial rearward hard cutting insert that has a second transverse cutting dimension which is greater than the first transverse cutting dimension. An elongate sleeve is adapted to receive cutting debris from the operation of the axial forward hard cutting insert.

What is claimed is: 
     
         1 . A wet drill bit assembly for cutting a borehole in the earth strata of a mine wherein the borehole has an interior region with a reduced transverse dimension and an exterior region with an enlarged transverse dimension, the drill bit assembly comprising:
 an axial forward spade-style cutting member having a spade hard cutting member with a first transverse cutting dimension;   an axial rearward reamer cutting member having a hard insert with a second transverse cutting dimension;   the axial forward spade-style cutting member being axial spaced apart from the axial rearward reamer cutting member; and   the first transverse cutting dimension being less than the second transverse cutting dimension.   
     
     
         2 . The wet drill bit assembly according to  claim 1  further comprising an upper section of tubing having an axial forward end and an axial rearward end, and the axial rearward reamer cutting member having a central axial bore with an reduced diameter section, and a section of the tubing adjacent the axial rearward end being received within the reduced diameter section of the central axial bore. 
     
     
         3 . The wet drill bit assembly according to  claim 2  wherein an upper mechanical fastener engages the upper section of tubing to retain the upper section of tubing within the reduced diameter section of the central axial bore. 
     
     
         4 . The wet drill bit assembly according to  claim 2  further including a lower section of tubing having an axial forward end, and the lower section of tubing being received within an enlarged diameter section of the axial rearward reamer cutting member. 
     
     
         5 . The wet drill bit assembly according to  claim 4  wherein a lower mechanical fastener engages the lower section of tubing to retain the lower section of tubing within the enlarged diameter section of the central axial bore. 
     
     
         6 . The wet drill bit assembly according to  claim 1  wherein the axial rearward reamer cutting member including a plurality of the hard inserts being spaced-apart. 
     
     
         7 . The wet drill bit assembly according to claim I wherein the axial forward spade-style cutting member having a single one of the spade hard cutting member. 
     
     
         8 . The wet drill bit assembly according to  claim 1  wherein the axial forward spade-style cutting member containing an outlet opening for the exit of drilling fluid. 
     
     
         9 . A dry drill bit assembly for cutting a borehole in the earth strata of a mine wherein the borehole has an interior region with a reduced transverse dimension and an exterior region with an enlarged transverse dimension, the drill bit assembly comprising:
 an axial forward cutting member having an axial forward hard cutting insert with a first transverse cutting dimension;   an axial rearward hard cutting insert with a second transverse cutting dimension;   the axial forward hard cutting insert being axial spaced apart from the axial rearward hard cutting insert;   the first transverse cutting dimension being less than the second transverse cutting dimension; and   an elongate sleeve adapted to receive cutting debris from the operation of the axial forward hard cutting insert.   
     
     
         10 . The dry drill bit assembly according to  claim 9  wherein the axial forward cutting member further including a mediate helical region defining helical flights with hard edging inserts, and the mediate helical region having a third transverse cutting dimension. 
     
     
         11 . The dry drill bit assembly according to  claim 10  wherein the third transverse cutting dimension being equal to or less than the first transverse cutting dimension. 
     
     
         12 . The dry drill bit assembly according to  claim 9  wherein the axial forward cutting member further including a base region containing a dust port through which debris can travel under a vacuum. 
     
     
         13 . The dry drill bit assembly according to  claim 12  further including a vacuum chuck operatively attached to the base region. 
     
     
         14 . The dry drill bit assembly according to  claim 13  further including a tube operatively attached to the vacuum chuck, and an adjustable clip adjustably attached to the tube to provide an abutment for the elongate sleeve. 
     
     
         15 . The dry drill bit assembly according to  claim 9  wherein the elongate sleeve being movable between a forward position in which the elongate sleeve fully encompasses the axial forward cutting member and a rearward position in which the elongate sleeve fails to encompass any of the axial forward cutting member. 
     
     
         16 . The dry drill bit assembly according to  claim 9  wherein the elongate sleeve having a reduced axial rearward section with an inside transverse rearward dimension and an enlarged axial forward section with an inside transverse forward dimension, and where the inside transverse forward dimension is greater than the inside transverse rearward dimension. 
     
     
         17 . The dry drill bit assembly according to  claim 16  wherein the inside transverse forward dimension is greater than the second transverse cutting dimension. 
     
     
         18 . The dry drill bit assembly according to  claim 16  wherein the inside transverse rearward dimension is less than the second transverse cutting dimension.