Drill Head for Deep-Hole Drilling

Abstract

Provided is a drill head for deep-hole drilling in which a cutting blade tip is mounted to face a cutting chip discharge port opened at a head distal end surface and a hollow inside is made into a cutting chip discharge passage communicating with the cutting chip discharge port, wherein high cutting efficiency based on good cutting chip dischargeability can be achieved and the cutting blade itself is also easily processed in terms of form. The drill head for deep-hole drilling is configured such that an inner end 20 a of a blade edge 20 of a center cutting blade tip 2 A is spaced apart from a head shaft center axis O and forms a non-cutting zone Z in the vicinity of the head shaft center axis O, an inner side surface of the cutting blade tip 2 A constitutes an axially rearwardly inclined side surface 21 inclined from an inner end side to the head shaft center axis O side, an uncut core C of a work material W generated in the non-cutting zone Z is broken off by press-contact of the inclined side surface 21 of the cutting blade tip 2 A during deep-hole drilling work.

1 . A drill head for deep-hole drilling, comprising:
 a head main body having a head shaft center axis (O) defining a forward-to-rear axial direction;   a head distal end surface provide at a forward end of the head main body;   one or more cutting blade tips mounted on the head main body and positioned to face a cutting chip discharge port opened at the head distal end surface; and   a hollow portion constituting a cutting chip discharge passage which communicates with the cutting chip discharge port; wherein:   at least one of said one or more cutting blade tips serves as a center cutting blade tip which is responsible for cutting a center portion of a hole, the center cutting blade tip comprising:
 a blade edge having an inner end spaced apart from the head shaft center axis of the head main body, whereby the inner end forms a non-cutting zone in the vicinity of the head shaft center axis upon rotation of the drill head during drilling operations; and 
 an inner side surface at an inner end side of the blade edge, the inner side surface having an axially rearwardly inclined surface which is inclined from the inner end to the head shaft center axis side; 
   wherein the axially rearwardly inclined surface of the cutting blade inner side surface is configured to press-contact and break off an uncut core generated in the non-cutting zone upon rotation of the gun drill during drilling operations.   
     
     
         2 . The drill head for deep-hole drilling according to  claim 1 , wherein:
 the axially rearwardly inclined surface of the center cutting blade tip forms an angle of 75 to 90 degrees with respect to a tip front surface.   
     
     
         3 . The drill head for deep-hole drilling according to  claim 1 , wherein:
 the center cutting blade tip has an inner end of a blade edge spaced 0.05 to 0.5 mm apart from the head shaft center axis; and   an inclination angle of the inclined side surface with respect to the head shaft center axis is 5 to 30 degrees.   
     
     
         4 . The drill head for deep-hole drilling according to  claim 1 , wherein
 the center cutting blade tip has a blade edge arranged in parallel with a radial line passing through the head shaft center axis and in a center-raised position 0.2 to 1.5 mm more forward in a cutting rotation direction than the radial line.   
     
     
         5 . The drill head for deep-hole drilling according to  claim 1 , wherein the at least one or more cutting blade tips is brazed to a recessed portion provided to the head main body. 
     
     
         6 . The drill head for deep-hole drilling according to  claim 1 , wherein:
 the whole of the blade edge of the center cutting blade tip is inclined in a radially inward and axially forward direction towards the head shaft center axis side; and   a guide pad is provided on a head outer circumferential surface at a position opposite to a mounting side of the center cutting blade tip.   
     
     
         7 . The drill head for deep-hole drilling according to  claim 1 , wherein:
 the whole of the blade edge of the center cutting blade tip is inclined in a radially inward and axially forward direction toward the head shaft center axis side.   
     
     
         8 . The drill head for deep-hole drilling according to  claim 1 , wherein:
 the inner end constitutes the forwardmost portion of the drill head.   
     
     
         9 . The drill head for deep-hole drilling according to  claim 1 , wherein:
 the head shaft center axis intersects the axially rearwardly inclined surface of the center cutting blade tip.   
     
     
         10 . The drill head for deep-hole drilling according to  claim 1 , wherein:
 the whole of the blade edge of the center cutting blade tip is inclined in a radially inward and axially forward direction toward the head shaft center axis side.   the inner end constitutes the forwardmost portion of the cutting head; and   the head shaft center axis intersects the axially rearwardly inclined surface of the center cutting blade tip.   
     
     
         11 . The drill head for deep-hole drilling according to  claim 10 , wherein:
 a guide pad is provided on a head outer circumferential surface at a position opposite to a mounting side of the center cutting blade tip;   the center cutting blade tip is brazed to a recessed portion of the cutting head; and   the cutting blade tip and the guide pad are devoid of clamping bores suitable for receiving a clamping screw.   
     
     
         12 . The drill head for deep-hole drilling according to  claim 1 , further comprising:
 a circumferential cutting blade tip and an intermediate cutting blade tip, both of which are radially outward of the center cutting blade tip; wherein:   the circumferential cutting blade tip, the intermediate cutting blade tip and the center cutting blade tip are all brazed to respective recessed portions of the drill head; and   the circumferential cutting blade tip, the intermediate cutting blade tip and the center cutting blade are all devoid of clamping bores suitable for receiving a clamping screw.   
     
     
         13 . The drill head for deep-hole drilling according to  claim 1 , wherein:
 the center cutting blade tip is the only blade tip on the drill head; and   the center cutting blade tip is retained to the drill head by a clamping screw.   
     
     
         14 . A drill head for deep-hole drilling comprising:
 one or more cutting blade tips mounted to face a cutting chip discharge port opened at a head distal end surface; and   a hollow inside made into a cutting chip discharge passage communicating with the cutting chip discharge port; wherein:   a center cutting blade tip, which is responsible for cutting a center portion of a hole, has an inner end of a blade edge spaced apart from a head shaft center axis, the inner end positioned to form a non-cutting zone in a vicinity of the shaft center axis;   an inner side surface of the cutting blade tip constitutes an axially rearwardly inclined surface which is inclined from the inner end to the head shaft center axis side, and   the axially rearwardly inclined surface is configured to press-contact and break off an uncut core of a work material generated in the non-cutting zone during deep-hole drilling work.   
     
     
         15 . The drill head for deep-hole drilling according to  claim 14 , wherein:
 the axially rearwardly inclined surface of the center cutting blade tip forms an angle of 75 to 90 degrees with respect to a tip front surface.   
     
     
         16 . The drill head for deep-hole drilling according to  claim 14 , wherein:
 the center cutting blade tip has an inner end of a blade edge spaced 0.05 to 0.5 mm apart from the head shaft center axis; and   an inclination angle of the inclined side surface with respect to the head shaft center axis is 5 to 30 degrees.   
     
     
         17 . The drill head for deep-hole drilling according to  claim 14 , wherein
 the center cutting blade tip has a blade edge arranged in parallel with a radial line passing through the head shaft center axis and in a center-raised position 0.2 to 1.5 mm more forward in a cutting rotation direction than the radial line.   
     
     
         18 . The drill head for deep-hole drilling according to  claim 14 , wherein the at least one or more cutting blade tips is brazed to a recessed portion provided to a head main body. 
     
     
         19 . The drill head for deep-hole drilling according to  claim 14 , wherein:
 the whole of the blade edge of the center cutting blade tip is inclined in a radially inward and axially forward direction towards the head shaft center axis side; and   a guide pad is provided on a head outer circumferential surface at a position opposite to a mounting side of the center cutting blade tip.   
     
     
         20 . The drill head for deep-hole drilling according to  claim 14 , wherein:
 the whole of the blade edge of the center cutting blade tip is inclined in a radially inward and axially forward direction toward the head shaft center axis side.   the inner end constitutes the forwardmost portion of the cutting head; and   the head shaft center axis intersects the axially rearwardly inclined surface of the center cutting blade tip.