| 摘要 |
A twist drill has fastening elements and a cutting part that comprises helical grooves and two cutting edges with a spherical radius of a cutting wedge. The spherical radius of cutting wedge is variable on the length of main cutting edges. The spherical radii of main cutting edges on the periphery of drillare equal to (0,004-0,005)R, where R- radius of a drill bit, mm. The spherical radii of the edges near a bridge are defined by formula, mm, where- spherical radii of the main cutting edges on the periphery of drill. The spherical radius along the length of main cutting edges is fromto. The tool strength is provided. |
