To vary an axial core of a work to a spiral shape by adjusting a space between a pair of feed rolls and a pair of tensile rolls according to an outer diameter measurement of the work, setting zigzagingly arranged rolls to fit a curvature twisted measurement and adjusting discrepancy and spacing of rolls from a passing position of the work against a certain range of roll groups.

A pair of feed rolls 1, 10 and a pair of tensile rolls 5, 6 comprising a pair of drum type rolls being oppositely crossed are installed. They nip a work and advance if forward keeping an angle of 45° against the work, while circularly rotating the work in 360° and, making a contacting face with the work small. Between those pairs of rolls 1, 10 and 5, 6, the drum type rolls 2, 3, 4, 7, and 8, 9 are arranged in zigzag and in fitting to the curvature measurement against the work alternately. A crashing (compressing) volume to be determined by discrepancy from the work passing position and a space between the rolls is adjusted for deciding a spiral shape.