| 摘要 |
<p>Rotary shaping blades (20) for forming rack teeth (2) by cutting into rack formation surfaces (16) of pipe bodies (11) are arranged in parallel to one another in a row in the longitudinal direction of pipe bodies (11). The direction in which rotary shaping blades (20) are arranged is maintained parallel to the length of pipe bodies (11). Numerous rack teeth (2) are simultaneously formed on rack formation surfaces (16) of respective pipe bodies (11) by rotary shaping blades (20). At that time, the center of trough portion (2a) of one of rack teeth (2a) being formed on rack formation surface (16) of each pipe body (11) is cut through by rotary cutting blade (22) simultaneously with formation of rack teeth (2). Even in a state where rack teeth (2) of pipe body (11) are separated, their undulations reliably correspond to each other, and the strength of rack teeth (2) are maintained so that they are prevented from chipping.</p> |
