PURPOSE: To securely feed even a headless bolt to the front of a driver bit by means of air feeding by fixing a shuttle body to a chuck body and providing a parts guide passage and a parts entering passage on said shuttle body.
CONSTITUTION: A headless bolt 18 is fed by air, passes through the parts entering passage 27a of a hose mounting fitting 27, and is fed to the parts guide passage 26a of a shuttle body 26. In this condition, when a small cylinder 29 is operated, its rod 29a is advanced along the parts guide passage 26a and pushes out the headless bolt 18. As the headless bolt 18 is moved with its end face sliding along the parts guide passage 26a and when it reaches a guide groove 17c on the ends of chuck claws 17, the peripheral face of the headless bolt 18 is brought into contact with the chuck claws 17 and spreads the chuck claws 17. After the headless bolt 18 is further moved and has completely spread the chuck claws 17, the headless bolt 18 reaches on a parts holding hole and is held in this position while being interposedly held by the chuck claws 17.