Stepped cutter and inner cooling hole position design method thereof

The invention discloses a stepped cutter and an inner cooling hole position design method thereof. The stepped cutter comprises a small-diameter cutting part, a stepped cutting part and a handle part which are sequentially arranged, the stepped cutting part is provided with a stepped cutting edge, at least one set of spiral grooves and spiral inner cooling holes corresponding to the spiral grooves, the stepped cutting edge is arranged at the transition position of the small-diameter cutting part and the stepped cutting part, the spiral groove extends to the rear cutter surface of the small-diameter cutting part from the connection position of the stepped cutting part and the handle part, the spiral inner cooling hole extends to the stepped cutting part from the handle part, and a water outlet is located in the spiral groove and is adjacent to the stepped cutting edge, cooling is sufficient, chip removal is smooth, and the quality of the machined surface is good; and the step cutter inner cooling hole position