PURPOSE: To prevent swing of an arm despite of that a fillet part being a work is situated on the one side as a result of the fillet part being a work being situated on the one side by a method wherein swing preventing parts on which the reaction force in an axial direction of a journal part occasioned by resting the fillet part on a roll is exerted are mounted on both sides of an arm.

CONSTITUTION: When a fillet part F of a journal part J1 is rested on a roll, an arm 5 is about to escape in the direction of an antifillet part F by means of the reaction force of a fillet roller 12. But, the arm 5 is regulated and constrained by pressure contact between a pad plate 14 and a swing preventing plate 19 and pressure contact between a pad 13 and a swing preventing plate 20. A spindle head 1 is finally burdened with a reaction force, produced occasioned by resting on a roll, through the swing preventing plates 19 and 20. As a result, escape of the arm 5 and in turn swing of the arm 5 can be prevented from occurring despite of a roll being rested only on the fillet part F on the one side.