Abstract: A butterfly-valve disc (10) is reconstituted by applying welding metal about its edge, rotating the disc with a lathe, and working the disc edge with a lathe tool. A spinner apparatus adapts the butterfly valve disc to be turned on the lathe. The spinner apparatus comprises two spinner mechanisms (A and B) for respectively attaching to opposite sides of the disc. Each of the spinner mechanisms includes a block (38), an elongated centering shaft (42) slidably mounted on the block, a spinner bar (48) fastened to the block for extending into a boss hole (22 or 24) on a side of the valve disc on which the spinner mechanism is to be mounted, and aligning bars (70 and 72) attached to the block for making contact with the side of the valve disc on which the spinner mechanism is to be mounted for holding a valve-disc axis (88) aligned with an axis (43) of the centering shaft.