Screw rotor processing method and screw rotor lead correction calculation device

A screw rotor processing method for correcting a lead error of a screw rotor to process the screw rotor, comprising:

• grinding a material of the screw rotor;
• measuring, as a distance, the lead error with respect to a reference lead at an axial position of a rotor groove portion of the screw rotor produced by grinding;
• wherein a lead correction amount for correction of the lead error and a lead correction starting position as an axial position of the screw rotor for starting the lead correction are calculated based on the lead error measured as the distance, including
• obtaining a rotation angle θ on the reference lead at the axial position of the rotor groove portion and a rotation angle dθ corresponding to a lead error at the position with the rotation angle θ,
• obtaining a correction point, by means of a rotation angle −dθ obtained by inverting a sign of the rotation angle dθ corresponding to the lead error, as a difference from the rotation angle θ, and
• obtaining the lead correction amount from a correction lead passing through the correction point and the lead correction starting position from the rotation angle θ;
• and
• grinding the screw rotor based on the calculated lead correction amount and the calculated lead correction starting position.