| 摘要 |
PURPOSE:To improve dimensional accuracy of products by holding a plank holder having diameter equal to the bottom face of a plank against the bottom face of the concave side of the plank after forming the vicinity of central part of the plank. CONSTITUTION:A plank 3 is held between a main shaft 6 and a tail stock. While rotating the plank 3, the plank 3 is held between a working roller 8 and a holding roller 9, and the rollers 8, 9 are moved in oblique direction. When working of the plank 3 is progressed in this way and the holding roller 9 advances to a position in radial direction where it does not interfer with the plnak holder, a plank holder 7 having contacting face equal in diameter with the bottom face of the plank 3 is pressed against the bottom face of the plank 3. By this way, working is progressed by holding the plank 3 between the plank holder 7 and tail stock. |
