To provide a throw-away hob enabling the fixing of a tip with a wedge piece irrespective of the size of a module and having high tip strength and clamp rigidity, and also reduce its outer diameter by stabilizing a tip mounting accuracy and reducing a finishing allowance for post-machining.

A worm 3 spirally machined on the outer periphery 2 of a hob body 1, pockets 4 dividing the worm equally around the axis thereof and entirely in the axial direction, and the crests of the worm are formed by disposing tip holding crests 7 fixing the tip to a tip seat by threadedly fixing the wedge piece 10 holding the tip 20 by the tip seat 9 supported by a face forming the pockets to a screw hole 11 with a tightening bolt 12 and relief crests 8 having relief parts 13 not coming into contact with the tip seat side faces 21 of the tip and the corner parts 22 thereof alternately in the axial direction and a lead direction. The tip seat side faces 26 and the lower surface 27 of the rectangular parallelepiped part 25 of the tip are brought into contact with the tip seats of the tip holding crests, and both side faces 28 are fitted to the side faces 8a of the relief crests.