PURPOSE: To permit a number of ring bodies to be held stably by installing a plurality of cutting tools in one time and using a chuck with which a plurality of ring bodies can be cut at a same time in accordance with the number of cutting tools, when a number of ring bodies are obtained by cutting a metal pipe into round slices.

CONSTITUTION: A back plate 4 and a front plate 5 which have center holes 2 and 3 respectively are fixed at the opening parts on the both sides of a cylindrical body 1 which is fixed concentrically onto the driving shaft of a lathe etc. On the side surface of the front plate 5, a hooked part 12 is formed on the peripheral edge of a base cup 11 which is fixed, keeping away from an operating shaft 6. A chuck is constituted so that the operating shaft 6 which revolves with the body 1 is supported onto the body 1, and cup members 131, 132,...13n are held onto the body 1. Since in said chuck, each hook piece 23 is arranged, pressed onto the inner surface of the pipe, the pipe is held by each hook piece 23 and can be cut easily and certainly at a same time, even if round cutting is performed at a same time by positioning each cutting blade at the position corresponding to the hook piece 23.