Patent ID: 11865627
Assignee: nan
Field: Machine tools (Mechanical engineering)
Classification: CPC B | IPC B

Claim 6:
7. A twist drill, comprising:
an operation portion comprising a cone portion and a cylinder portion axially fixed to the cone portion;
a shank portion axially fixed to the cylinder portion opposite the cone portion;
a spiral flute formed on an exterior surface of the operating portion extending from a front end of the cone portion and at least partway up the cylinder portion, the spiral flute having a sidewall;
a plurality of composite cutting blade groups formed sequentially on a cone portion exterior from the front end of the cone portion to a rear end of the cone portion, each of the plurality of composite cutting blade groups comprising:
a first step surface;
a second step surface adjacent to the first step surface,
a major cutting edge defined by an intersection of the first step surface and the sidewall of the spiral flute;
a minor cutting edge defined by an intersection of the second step and the sidewall of the spiral flute; and
a cutting tip defined by an intersection of the major cutting edge, the minor cutting edge, and the sidewall of the spiral flute; and
a top blade provided on the front end of the cone portion;
wherein a diameter of each of the plurality of composite cutting blade groups increases sequentially from the front end of the cone portion to the rear end of the cone portion;
and each of the plurality of composite cutting blade groups is configured to cut fine chips and the spiral flute is configured to shunt the fine chips; and
wherein a diameter of a composite cutting blade group located at the rear end of the cone portion immediately adjacent to the cylinder portion is less than or equal to a diameter of the cylinder portion.