US 12,285,809 B2
Hard-film-coated drill
Junichi Noshiro, Toyama (JP); and Ryo Hayashi, Toyama (JP)
Assigned to NACHI-FUJIKOSHI CORP., Tokyo (JP)
Filed by NACHI-FUJIKOSHI CORP., Tokyo (JP)
Filed on Apr. 8, 2021, as Appl. No. 17/225,351.
Application 17/225,351 is a continuation of application No. PCT/JP2019/039597, filed on Oct. 8, 2019.
Claims priority of application No. 2018-192830 (JP), filed on Oct. 11, 2018.
Prior Publication US 2021/0291279 A1, Sep. 23, 2021
Int. Cl. B23B 51/02 (2006.01); C23C 28/04 (2006.01)
CPC B23B 51/02 (2013.01) [C23C 28/044 (2013.01); B23B 2224/08 (2013.01); B23B 2224/36 (2013.01); B23B 2228/105 (2013.01); B23B 2251/125 (2013.01); Y10T 408/89 (2015.01)] 4 Claims
OG exemplary drawing
 
1. A hard-film-coated drill having a drill body with a surface coated with a hard film, the drill body being made of a cemented carbide and having two or more cutting edges, a flank surface, a rake surface, and a margin,
wherein the drill body is provided with a chamfered surface adjacent to the flank surface and the rake surface,
a surface hardness of the hard film is within a range of 2000 to 2500 HV in Vickers hardness,
a first ridgeline where the chamfered surface and the flank surface intersect and a second ridgeline where the flank surface and the margin intersect are formed in a round shape in cross section,
a radius r1 (in μm) of curvature of the round shape of the first ridgeline is within a range represented by a formula r1=0.45×D+a1 (10≤a1≤25), where D is a diameter (in mm) of the drill body and a1 is a constant (in μm) to keep r1 within an upper limit and a lower limit, and
a radius r2 (in μm) of curvature of the round shape of the second ridgeline is within a range represented by a formula r2=0.65×D+a2 (39≤a2≤67), where a2 is a constant (in μm) to keep r2 within an upper limit and a lower limit,
wherein the hard film includes a first layer formed of a first hard film containing a nitride that includes Al and Ti, a second layer formed by alternately stacking second and third hard films having different compositions, and a third layer formed of a fourth hard film containing a nitride that includes Ti and Si, and the first to third layers are stacked in this order from a drill body side, and
wherein the second hard film contains a nitride that includes Ti, Al and Si, and the third hard film contains a nitride that includes Ti, Al, Cr and Si.