The recirculatingball steering gear contains a worm gear. You can image the gear
In two parts. The first part is a block of metal with a threaded hole in it. This block has gear teeth cut into the outside of it, which engage a gear that movesthe pitman arm (see diagram above). The steering wheel connects to a threadedrod, similar to a bolt, that sticks into the hole in the block. When the steering wheel turns, it turns the bolt. Instead of twisting further into the block theway a regular bolt would, this bolt is held fixed so that when it spins, it moves the block, which moves the gear that turns the wheels.