Patent ID: 6898853
Filing Date: 2005-05-31
Classification: B21C,B21K,B62D,Y10S,Y10T

Abstract:
1. A method for manufacturing a hollow rack shaft comprising: a first step for forming a substantially flat and rectangular plate workpiece into a gutter-like shaped workpiece, said gutter-like shaped workpiece having a flat bottom portion, a pair of semi-circular bottom portions extending from each longitudinal side of said flat bottom portion and a pair of leg-like side walls extending upwardly in parallel from each lateral side of said fiat bottom portion and said semi-circular portions; a second step for forming a row of rack teeth on said flat bottom portion of said gutter-shaped workpiece; and a third step for forming said workpiece into a hollow shape by bending said leg-like side walls by butting edges of said walls against each other; wherein said second step further comprises a preliminary forming step and a main forming step; wherein, at said preliminary forming step, a row of intermediate rack teeth substantially equal to a finally required pitch and smaller than a finally required pressure angle is formed; wherein, at said main forming step, a row of rack teeth with required tooth shape is formed; and wherein, a surface of the die set used in said main forming step is provided with a plurality of recesses for releasing surplus material of said workpiece in a die clearance at a stroke end; and wherein, each die of said die set is divided into a plurality of segments at said recess.