Processing block, holder for processing block, and method of positioning processing block

A system comprising:

• a disk-shaped processing block;
• a holding device for holding the disk-shaped processing block in a predetermined position in a processing machine during processing the disk-shaped processing block into a product in a desired shape, wherein:
• the holding device includes:
• a ring-shaped holding member that includes a receiving-side holding member disposed, with respect to the processing block, on one side of the processing block in an axial direction thereof,
• a pressing-side holding member disposed, with respect to the processing block, on the other side of the processing block in the axial direction thereof, and
• an engagement mechanism for freely engaging and disconnecting the receiving-side holding member and the pressing-side holding member with each other;
• the disk-shaped processing block is held detachably by engaging and disengaging the engagement mechanism while the disk-shaped processing block is between the receiving-side holding member and the pressing-side holding member;
• the disk-shaped processing block comprising:
• a columnar workpiece;
• a flange protruding from a peripheral surface of the workpiece and having, on an upper surface thereof, a holding surface provided so as to form a part of a side surface of a cone, wherein
• the system is configured such that, when the disk-shaped processing block is held by the holding device, the holding surface abuts a facing peripheral edge, which is an end portion on a processing-block side of an inner peripheral surface of the pressing-side holding member, thereby positioning an axial center of the disk-shaped processing block.