Material：Catalpa plating board
In a rotary shearing line in which sheet stock is fed by a feeder to a rotary shear for fast cutting by its rotating cutting shear, a synchronous speed and a synchronization length are calculated by an arithmetic unit. It is supplied with the cutting length and the average feed rate of the sheet stock, Reference pulses of a frequency corresponding to the synchronous speed. The synchronization length is provided to a first numerical controller for controlling the feeder. The second numerical controller is for controlling the rotary shear. The first numerical controller controls the feeder to feed the sheet stock at a speed higher, or lower than the synchronous speed in such a manner that when the sheet stock is fed at the synchronous speed, the length of the sheet stock short or excessive of the cutting length before its cutting is compensated for within a cutting period.