Rotary percussion drill with a hard material bit

Abstract

A rotary-percussion drill, includes a hard material bit ( 2, 2 ′) having at least one cutting edge ( 3, 3 ′), and a shaft having an end ( 7, 7 ′) with an axial base surface ( 6, 6 ′) provided with a chamfer ( 8, 8 ′) at least on its outer radial rim, the bottom surface ( 4, 4 ′) of the bit ( 3, 3 ′) which lies opposite the cutting edge ( 3, 3 ′), being secured to the base surface ( 6, 6 ′) of the shaft end ( 7, 7 ′) by brazing alloy in a material-locking manner.

1 . A rotary-percussion drill, comprising a hard material bit ( 2 ,  2 ′) having at least one cutting edge ( 3 ,  3 ′) and a bottom surface ( 4 ,  4 ′) located opposite the at least one cutting edge ( 3 ,  3 ′); a shaft having an end ( 7 ,  7 ′) with an axial base surface ( 6 ,  6 ′) provided with a chamfer ( 8 ,  8 ′) at least on an outer radial rim thereof; and brazing alloy means ( 5 ,  5 ′) for securing, in a material-locking manner, the bottom surface ( 4 ,  4 ′) of the bit ( 3 ,  3 ′) to the base surface ( 6 ,  6 ′) of the shaft end ( 7 ,  7 ′). 
   
   
       2 . A rotary-percussion drill according to  claim 1 , wherein an axial thickness (D) of a layer of the brazing alloy means ( 5 ,  5 ′) provided between the base surface ( 6 ,  6 ′) of the shaft end ( 7 ,  7 ′) and the bottom surface ( 4 ,  4 ′) of the bit ( 2 ,  2 ′) overall is smaller than 0.6 mm. 
   
   
       3 . A rotary-percussion drill according to  claim 1 , wherein the hard material bit ( 2 ′) has an X-shape with four radially extending blades ( 11 ), and the base surface ( 6 ′) has a corresponding X-shaped mortise ( 9 ′) in which the bit ( 2 ′) is brazed, with the bottom surface ( 4 ′) being butt-brazed to the base surface ( 6 ′) of the shaft end ( 7 ′) in a sector of two diametrical free surfaces ( 10 ), and wherein the base surface ( 6 ′) is provided with a radial chamfer ( 8 ′) for each blade ( 11 ). 
   
   
       4 . A rotary-percussion drill according to  claim 3 , wherein in a radially middle region of the sector of two diametrical free surfaces ( 10 ), there are provided two additional radial chamfers ( 12 ) between each two circumferentially adjacent blades ( 11 ).