Drill assembly

Abstract

A drill assembly ( 1 ) comprising a cutter arrangement ( 50 ) and a guide member ( 2 ), the guide comprising a longitudinal axis (A-A), the arrangement of the assembly being such that, in use, the cutter arrangement engages with the guide and the cutter arrangement being caused to rotate about the longitudinal axis and the guide being shaped so as to pivot cutter blocks ( 51 ) of the cutter arrangement generally laterally of the longitudinal axis as the cutter arrangement is urged in a direction which is generally parallel to said longitudinal axis. In a preferred embodiment the guide is of a frusto-conical profile ( 6 ) so as to form a hole ( 20 ) of a corresponding shape. Advantageously the shape of the hole formed with the assembly can be accurately controlled. The inventive assembly finds particular application in reaming preformed holes which are used to locate anchor bolts.

1 . A drill assembly comprising cutter means and guide means, the guide means comprising a longitudinal axis (A-A), the cutter means being mounted for pivotal movement which is generally lateral of the longitudinal axis of the guide means about respective pivot axes which are substantially parallel to the longitudinal axis of the guide means, the arrangement of the assembly being such that, in use, the cutter means engages with the guide means, and the cutter means being caused to rotate about the longitudinal axis of the guide means and have a component of movement in a direction which is generally parallel to said longitudinal axis, and the guide means comprising a variable diameter portion which portion is of variable diameter in a direction which is parallel to the longitudinal axis of the guide means and in use said guide means causing the cutter means to move generally laterally of the longitudinal axis.  
   
   
       2 . A drill assembly as claimed in  claim 1  in which the guide means comprises a generally elongate member which is adapted to be positioned in a pre-formed hole.  
   
   
       3 . A drill assembly as claimed in  claim 1  in which the guide means comprises a guide surface and in use the cutter means engages with the guide surface so as to determine the lateral movement of the cutter means.  
   
   
       4 . A drill assembly as claimed in  claim 1  in which the guide means comprises a first substantially frusto-conical portion.  
   
   
       5 . A drill assembly as claimed in  claim 4  in which the guide means comprises a second substantially frusto-conical portion, the direction in which the second frusto-conical portion tapers being opposed to that in which the first frusto-conical portion tapers.  
   
   
       6 . A drill assembly as claimed in  claim 5  in which the second substantially frusto-conical portion is provided towards a distal end of the guide means.  
   
   
       7 . A drill assembly as claimed in  claim 1  in which the cutter means is resiliently biased against the guide means.  
   
   
       8 . A drill assembly as claimed in  claim 1  in which the cutter means comprises a plurality of pivotally mounted cutters.  
   
   
       9 . A drill assembly as claimed in  claim 1  in which the cutter means comprises a substantially arcuate cutter surface.  
   
   
       10 . A drill assembly as claimed in any preceding  claim 1  in which the cutter means comprises a cutter surface which is formed from diamond dust in a metal matrix.  
   
   
       11 . A drill assembly as claimed in  claim 1  in which the guide means comprises locating means which is adapted to receive a pivotal portion of the cutter means, such that in use the locating means allows for movement of the cutter means in a direction which is substantially parallel to the longitudinal axis of the guide means and pivotal movement of the cutter means.  
   
   
       12 . A drill assembly as claimed in  claim 11  in which the locating means comprises a longitudinal channel.  
   
   
       13 . A drill assembly as claimed in any of the preceding claims in which the cutter means comprises an array of pivotally mounted cutters the radically inner surface portions of which are arranged to engage with the guide means which is centrally located of the array of cutters.  
   
   
       14 . A method of forming a hole comprising the steps of: 
 inserting guide means into a pre-formed hole, the guide means comprising a longitudinal axis (A-A) and comprising a variable diameter portion which variable diameter portion varies in diameter in a direction which is parallel to the longitudinal axis of the guide means;    arranging that cutter means engages with the guide means:    causing the cutter means to rotate about the longitudinal axis of the guide means and to have a component of movement in a direction which is substantially parallel to said longitudinal axis and the shape of the variable diameter portion causing the cutter means to move generally laterally of the longitudinal axis about the pivot axes which are substantially parallel to the longitudinal axis.    
   
   
       15 . A method as claimed in  claim 14  in which both the cutter means and the guide means are caused to rotate about the longitudinal axis.  
   
   
       16 . A drill cutter assembly comprising cutter means for engaging with guide means the guide means comprising a longitudinal axis (A-A) and a variable diameter portion, the variable diameter portion varying in diameter in a direction which is parallel to the longitudinal axis, the cutter means being adapted to rotate about the longitudinal axis of the guide means, and being adapted to move generally laterally of the longitudinal axis about pivot axes which are substantially parallel to the longitudinal axis, the drill cutter assembly being adapted to move longitudinally along the guide means, which guide means is located in a pre-formed hole and in use as a result of engagement with an outer surface of said guide means, as the cutter means moves longitudinally along said guide means said cutter means is pivoted laterally about respective axes.