Sawppy the Rover’s design included several uses of 8mm steel rods to transfer motion while supported by a pair of 608 bearings. While I could personally ask nicely and access a metalworking lathe, not everyone would be so lucky. So I wanted to prove the rover could be built with basic tools, like this jury-rigged lathe.
In this setup, our 8mm steel workpiece is rotated by a drill. To help hold the shaft steady, one of the earlier iterations of a wheel steering knuckle (more specifically, the pair of 608 bearings already installed in it) was used as a crude steady rest. A Dremel tool with cutting wheel will create the features we want in steel.
One feature we want to create is to cut a groove for a retaining clip.
A retaining clip wants a groove with a squared-off bottom. A Dremel cutting wheel will inevitably round off itself (especially if we fail to hold it square to the workpiece.) To restore the squared-off profile of a cutting wheel, almost every Dremel tool kit comes with a stone that is strong enough to stand up to the cutting wheel. We can then spin up the Dremel and use this stone to reshape wheel profile back to our desired square.
The other feature we want to cut is a flat in the shaft as a detent for set screw to bite and hold position. This can be done by leaving the shaft static (not spinning) and running the cutting wheel back and forth on one side. For a set screw to hold position, it does not need to be perfectly flat, it just needs to be not round.
Some sharp edges may remain after steel cutting operations. Protect against cutting our fingers by cleaning up edges with a file. Alternatively, for people with a nice heavy vise available, use the file to create set screw detents instead of Dremel. (More details on this option later.)
Two retaining clip grooves plus two detents later – we have a steering shaft!