Saginaw Recirculating Ball Worm & Nut-Manual Steering Gears

Fig. 1 Sectional view of Saginaw recirculating ball-worm & nut steering gear:

Fig. 2 Cross-sectional view of Saginaw recirculating ball-worm & nut gear:

As shown in Fig. 1, the wormshaft on the lower end of the steering shaft and the ball nut which is mounted on the worm have mating spiral grooves in which steel balls circulate to provide a low friction drive between wormshaft and ball nut.
Two sets of balls are used, ranging in number from approximately 20 to 30 to a set, depending upon the size of the gear unit. Each set of balls operate independently of the other. The circuit through which each set of balls circulates includes the grooves in the worm and ball nut and a ball return guide attached to the outer surface of the nut.
When the wheel and steering shaft turn to the left, the ball nut is moved downward by the balls which roll between the worm and nut. As the balls reach the outer surface of the nut, they enter the return guides which direct them across and down into the ball nut where they enter the circuit again.
When a right turn is made, the ball nut moves upward and the balls circulate in the reverse direction.
The teeth of the ball nut engage teeth on the sector which is forged integral with the pitman shaft, Fig. 2. The teeth on the ball nut are made so that a ``high point'' or tighter fit exists between the ball nut and pitman shaft sector teeth when the front wheels are in the straight-ahead position. The teeth on the sector are tapered slightly so that a proper lash may be obtained by moving the pitman shaft endwise by means of a lash adjuster screw which extends through the gear housing side cover.
The head of the last adjuster and the selectively fitted shim fit snugly into a T-slot in the end of the pitman shaft so that the screw also controls end play of the shaft. The screw is locked by an external lock nut.