Hollow drill bit

A hollow drill bit comprising a drill head located at a distal end of the hollow drill bit, wherein the drill head is provided with a plurality of cutting teeth distributed around a working rotation axis of the hollow drill bit, each cutting tooth comprising a plurality of cutting segments arranged in sequence in an axial direction,

• wherein while being distributed sequentially towards a proximal side in an axial direction, the plurality of cutting segments is also distributed sequentially towards a radially outer side in a radial direction, thereby forming a stepped structure,
• wherein the plurality of cutting segments comprise one end segment and one or more circumferential step segments, the end segment is located at a distalmost end of the corresponding cutting tooth in an axial direction and comprises an end cutting edge, the circumferential step segments are located at an proximal side of the end segment in an axial direction, and each circumferential step segment extends substantially in a circumferential direction and comprises a major cutting edge and a minor cutting edge, and
• wherein in an axial direction, a total length of the plurality of cutting segments of each cutting tooth is not less than half of a depth of a slot between said cutting tooth and any adjacent cutting tooth.