PURPOSE: To improve the efficiency of attachment/detachment processes, and to prevent abrasion and loss of a tray by fixing the base end of a spiral member on the outside surface of the end of a cylindrical member, forming a recessed part for receiving a driving shaft on the side surface in the base end of the cylindrical member, and by fixing the cylindrical member and the driving shaft so as to be attached to or detached therefrom.

CONSTITUTION: A flange 3 whose cross section is L-shaped, is mounted on the inner surface of the base end of a cylindrical member 1, by welding and so on, and a small size part 4a of a driving shaft 4 is fitted in the inside of the cylindrical member 1, while a large size part 4b is fitted in the L-shaped cross section of the flange 3. It is fixed through an installing means 5 such as a screw. The base end of a spiral 2 is fixed on the outer surface of the cylindrical member 1. In this structure, the efficiency of the attachment/ detachment operations can be improved, and the stay of chips can be prevented, whereby the abrasion and loss of a tray can be prevented.