Pulleys are typically pressed onto the shafts on which they mount. The outside diameter of the shaft is slightly larger than the inside diameter of the pulley hole, resulting in an interference or "press" fit that makes removal by hand impossible. Pulley pullers have fingers that hook onto a convenient edge and are supported by a hub. A large threaded arbor runs through the center of the hub and bears on the end of the pulley shaft, which allows the components to be supported and provides a slow, steady and even pressure to be applied to the pulley.
Set up the puller. Model-specific pullers will be ready to use, but the more common "generic" puller will have several options. Orient the puller fingers to pull on the outside or inside (whichever is appropriate for the application) of the pulley and tighten the finger-mounting bolts. Install the threaded arbor into the hub, pointed end on the finger side of the hub.
Position the puller in front of the pulley and engage the fingers with the pulley. Hold the puller in place with one hand and screw the arbor in until it makes contact with the end of the pulley shaft.
Hold the hub in position against the torque of the arbor with one of the wrenches. Most pullers have a nut-shaped boss with flats to facilitate this. Apply torque to the arbor shaft with the other wrench at the nut-shaped area on the end of the puller opposite the pointed end. Slowly torque the arbor while opposing the puller's tendency to rotate with the first wrench. As the arbor presses on the shaft, the hub and its fingers move away from the shaft and carry the pulley with it. Keep turning the arbor until the pulley pops free, then disengage the pulley from the fingers.
