PURPOSE: To minimize the length of a residual material by a sure operation with a simple structure and to feed out a bar rod by moving a spring collect provided movably in the axial direction on the center hole of a chuck main body in the axial direction in relation to the closing of a chuck holding claw.

CONSTITUTION: When working of a bar rod W held by a chuck claw 10 is completed and a cutting tool post is retreated, press oil fed to the cylinder 5A of a double cylinder 5 is changed over and fed from an oil pass 15b. Then a piston 15 is advanced and a spring collet 13 is advanced by a connection rod 16, so that the bar rod W is fed out. On completion of the delivery, a piston 6 is retreated, the chuck claw 10 is closed to hold the bar rod W, the piston 15 is retreated and the spring collet 13 is returned by its retreat by sliding on the bar rod W.