| 摘要 |
A twist drill (1), in particular for machining wrought aluminium alloys, has a drill shaft (2) and a cutting part (3) that extends to a drill point (6), spiral chucking grooves (4) extending along the cutting part (3), forming a drill core (15), the thickness (D k) of the core at the drill point (6) being equal to (15 ~ 3) % of the drill diameter (D), the drill diameter (D) and/or core thickness (D k) diminishing from the drill point (6) to the shaft (2), the twist drill having a primary clearance angle ($g(a)1) equal to (19 ~ 3)° and a secondary clearance angle ($g(a)2) equal to (26 ~ 4)°. |
