;所述圆弧状角刃7A和两个侧切削刃7B低于端面(即上端面3或下端面4)。本实施例中,第一前刀面11与上端面3(或下端面4)的夹角不变,且0°≤α1≤10°,12°≤α2≤25°,0.02mm≤L1≤0.15mm,0.25mm≤L2≤0.5mm。本实施例中,楔形断屑部顶面811与上端面3(或下端面4)形成的夹角为β,3°≤β≤10°。812夹角为γ,75°≤γ≤125°。本实施例中,楔形断屑部81与第二前刀面13连接的过渡圆弧为r2,0.3mm≤r2≤0.5mm,楔形断屑部81与凸台壁面151连接的过渡圆弧与r3,0.3mm≤r3≤0.8mm,楔形断屑部81与凸起部82的过渡圆弧与r4,0.3mm≤r4≤0.8mm。H,0.2mm≤H≤0.5mm。2逐渐增大,且侧切削刃的宽度L2逐渐减小。1不变,且0°≤α1≤10°,12°≤α2≤25°,0.02mm≤L1≤0.15mm,0.25mm≤L2≤0.5mm。170°≤β≤178°。75°≤γ≤125°。r4,0.3mm≤r4≤0.8mm。H,0.2mm≤H≤0.5mm。R,且25mm≤R≤125mm。W,且0.05mm≤W≤0.3mm。examination。