The typical step pulley consists of three to five grooves. This type of step pulley is found on equipment such as drill presses, lathes and milling machines where different operational speeds can be produced simply by changing the belt to a different pulley size. The step pulley is always operated in pairs, and when the belt is changed on one pulley, it is also changed on the corresponding pulley on the other side of the belt.
When it has been determined that the speed should be regulated on a particular step pulley equipped machine, the process of adjusting the speed is usually an easy one. With the motor in the off position, open the belt cover. Take note of where the belt is currently positioned on the pulleys. Remember, a large pulley driving a smaller pulley will result in more power but less speed output. Conversely, a small pulley driving a large pulley will have more speed output but less power.
Dimensional information can be found here