|(That's copper grease BTW not rust!)|
The shaft of the steering column joins with the steering worm gear via a parallel key and two cotter bolts through an outer sliding sleeve. The column shaft is tubular with about an 1/8" wall thickness. The keyway is neatly machined through the column tube and corresponding worm shaft. This means the key is fitted after the shaft has engaged, then a split sleeve or collar slips over the key and the cotter bolts retain everything tightly. No stress raising keyways demanding over size hollow shafts, just very neat simple and innovative design.