Spiral step twist drill bit

A spiral step twist drill bit, comprising:

• a shank;
• and
• a cutting portion;
• wherein the cutting portion is provided with a spiral flute and a body clearance;
• a tip of the cutting portion is provided with a chisel edge and a cutting edge;
• a flank face connected to the cutting edge is provided with a spiral cutting groove;
• a spiral direction of the spiral cutting groove is the same as a spiral direction of the spiral flute;
• a slope of the spiral cutting groove is the same as a slope of the flank face;
• the spiral cutting groove is configured to divide the cutting edge into a plurality of segments to form a plurality of first edges and a plurality of second edges;
• the spiral cutting groove is configured to divide the flank face into a plurality of first annular surfaces and a plurality of second annular surfaces, wherein the plurality of first annular surfaces are perpendicular to the plurality of second annular surfaces;
• the plurality of first edges are respectively located on the plurality of first annular surfaces;
• and the plurality of second edges are respectively located on the plurality of second annular surfaces;
• wherein a spiral chip removal groove is provided in a right-angle recess formed by each of the first annular surface and a corresponding second annular surface;
• and a spiral direction of the spiral chip removal groove is the same as the spiral direction of the spiral flute.