Material to be worked in face driving and method for working the same

A material to be formed in a shape of column, to be worked by a working device that includes a face driver, a tailstock spindle and a tool bit, and to be worked in face driving with one end surface of the material in an axial direction held by the face driver haying a center pin and a plurality of driving claws arranged around the center pin, comprising:

• a center hole into which the center pin is fit, and which is formed on the one end surface;
• and
• a recess or a protrusion formed to exist in every phase in a circumferential direction of the one end surface around the center hole, which is formed on the one end surface,
• wherein the driving claw is formed as a pillar,
• wherein a tip part of the claw has a pair of tapered surfaces next to each other toward the tip thereof,
• wherein a linear claw part is formed at the tip defined by the tapered surfaces,
• wherein the face driver holds the one end surface of the material in the axial direction thereof by driving the plurality of driving claws into the one end surface and by making the plurality of driving claws bite into the one end surface of the material,
• wherein the tailstock spindle supports the other end surface of the material in the axial direction thereof,
• wherein a tool bit is a cutting tool for turning the outer circumferential surface of the material,
• wherein the outer circumferential surface of the rotating material is turned by the tool bit while holding the one end surface of the material in the axial direction thereof with the face driver in the face driving, and
• wherein the recess or the protrusion is arranged within an area of the one end surface in a radial direction of the one end surface, into which the plurality of driving claws are driven.