Drill in particular masonry drill

Abstract

The invention relates to a drill bit ( 1 ), in particular a masonry drill bit comprising an elongated shaft ( 15 ) and a cutting plate ( 2 ), one end of which has inclined cutting edges ( 3, 3′;4, 4 ′) that form a point. Each cutting edge ( 3, 3′; 4, 4 ′) is formed by the abutment of a cutting face ( 5, 5′; 6, 6 ′), lying in front of the cutting edge ( 3, 3′; 4, 4 ′) in the rotational direction ( 17 ) of the drill bit ( 1 ) and a flank ( 7, 7′; 8, 8 ′), lying behind the cutting edge ( 3, 3′; 4, 4 ′) in the rotational direction ( 17 ) of the drill bit ( 1 ), each cutting face and flank respectively forming a wedge angle y. In the central region of the drill bit ( 1 ), the cutting plate ( 2 ) has a centring tip that is stepped in relation to the marginal regions, the cutting edges ( 4, 4 ′) of said tip being set back in the rotational direction ( 17 ) in relation to the cutting edges ( 3, 3 ′) of the marginal regions. The cutting edges ( 4, 4 ′) of the centring tip have a cutting angle α ranging between 70 and 90 and a wedge angle γ ranging between 50 and 70, at least in the immediate vicinity of said eges ( 4, 4 ′).

1 - 10 . (canceled)  
   
   
       11 . A drill bit, comprising: 
 an elongated shaft;    a cutting plate disposed on said elongated shaft, said cutting plate having a centering tip and lateral regions formed with cutting edges;    a rake face disposed ahead of a respective said cutting edge in a direction of rotation of the drill bit, and a flank disposed behind said cutting edge in the direction of rotation of the drill bit, said rake face and said flank face enclosing a wedge angle γ with one another and defining said cutting edge therebetween;    said cutting edges at said centering tip being offset with respect to said lateral regions, with said cutting edges being set back in the direction of rotation relative to said cutting edges of the lateral regions; and    said cutting edges at said centering tip, at least in a region directly adjacent said cutting edges, having a rake angle a ranging from 70° to 90° and a wedge angle γ ranging from 50° to 70°.    
   
   
       12 . The drill bit according to  claim 11 , wherein said cutting edges of said centering tip are set back approximately by one third of a thickness s of said cutting plate and run parallel to said cutting edges of said lateral marginal regions.  
   
   
       13 . The drill bit according to  claim 11 , wherein said the centering tip has a width b ranging from 25% to 50% of a drill bit diameter d.  
   
   
       14 . The drill bit according to  claim 11 , wherein an envelope of said cutting edges of said centering tip is offset with respect to an envelope of said cutting edges of said lateral regions in a drill bit center by a distance a in a direction of a drill bit axis.  
   
   
       15 . The drill bit according to  claim 14 , wherein said distance a ranges from 10% to 15%of said drill bit diameter d.  
   
   
       16 . The drill bit according to  claim 14 , wherein a point angle δ 1  of said cutting edges of said centering tip is smaller than a point angle δ 2  of said cutting edges of said later regions.  
   
   
       17 . The drill bit according to  claim 16 , wherein said the point angle δ 1  is approximately 130°.  
   
   
       18 . The drill bit according to  claim 16 , wherein said point angle δ 2  is approximately 150°.  
   
   
       19 . The drill bit according to  claim 11 , wherein said rake faces of said cutting edges of said centering tip have a flat region directly adjacent said cutting edges, and said flat region merges into curved faces that peter out centrally and downward, wherein said flat region has a rake angle α of approximately 90° and a wedge angle γ of approximately 60°.  
   
   
       20 . The drill bit according to  claim 11  configured as a masonry drill bit.  
   
   
       21 . A cutting plate for a drill bit, comprising: 
 cutting edges formed on a centering tip in a rotational center of the cutting plate and on lateral regions laterally of said centering tip;    a rake face disposed ahead of a respective said cutting edge in a direction of rotation of the drill bit, and a flank disposed behind said cutting edge in the direction of rotation, said rake face and said flank face enclosing a wedge angle γ with one another and defining said cutting edge therebetween;    said cutting edges on said centering tip being offset with respect to said lateral regions, with said cutting edges on said centering tip being set back in the direction of rotation relative to said cutting edges of said lateral regions; and    said cutting edges on said centering tip, at least in a region directly adjacent said cutting edges, having a rake angle a ranging from 70° to 90° and a wedge angle γ ranging from 50° to 70°.    
   
   
       22 . The cutting plate according to  claim 21  configured for a masonry drill bit.