A rotary die cutter mechanism for cutting and/or creasing corrugated boards including a rotatable die cylinder with a cutting die, and a rotatable anvil against which the corrugated boards are cut as they pass between the die cylinder and the anvil. A computer is used to determine how much the speed of the anvil should be changed to compensate for changes in the diameter of the anvil so that the boards are cut to the desired dimension. A fine adjustment of the size of the boards to be cut is made by providing information to the computer representative of the specific die being used. The computer then calculates an adjusted speed of the anvil to cut the boards to the desired dimension, and then sends a signal to a motor for changing the speed of the anvil to the adjusted speed calculated by the computer.