Input: orange shaft carrying workpiece.
Violet slider carrying green rack moves longitudinally thanks to pink screw.
Red slider has traversal motion thanks to blue screw and turns yellow bar.
Yellow bar makes green rack move in traversal direction and the latter turns yellow gear that has sliding key joint with grey shaft.
Green screw turns irregularly makes pink tool post moving irregularly to create helix groove of variable lead.
Two black closed lines represent chains of two chain drives.