It's been a while since I was able to update this thread. I reprinted the rear wheels fixing the hex pockets, it's shown here along with the donor axles that need to be modified for the center axle.
I finished modifying the second set of axles that will be used for the center axle, this is the modified axles.
The only difference between the center axle and the rear axle shown in the previous picture, is that the center axle uses the pinion housing for both the front and rear of the diff.
The right end of the 6" rule in the attachment shows the length of the original axle shaft. The original axle was parted off about 29mm from the inboard end of the shaft. The remaining piece of the donor axle was parted off 39mm from the outboard end of the shaft. Both the parted off ends were turned from 5mm down to 3mm. The turned stubs were about 14mm in length, this length isn't critical. What is critical is the location of the shoulder. On the inboard section this shoulder is 15mm from the inboard end, on the outboard section the shoulder is 25mm from the outboard end. These two sections are joined together with a piece of 3mm ID x 5mm OD brass tubing with a length of 30mm. These 3 parts are then glued together with the HF equivalent of red Loctite using a vee-block as an alignment jig. If I did everything right, I should end up with axles 70mm long. One measures 69.95mm, and the other is 69.97mm.
Is there an easier way to do this? You betchya! You could just cut the axle shaft with a hacksaw and glue the pieces into a piece of 5mm ID tubing, The only reason I chose the method I did is because of the way the outboard axle bearing will be installed. When I use these donor axles to build a powered steer axle, the CV joint that will be glued into the outboard end of the shaft is over 5mm in diameter. In order to install the outboard rear axle bearing it will need to be slid onto the axle shaft from the inboard end.
I've still got problems with the Sherline. First the headstock bearings are stiff and noisy. These are the original shielded bearings and I suspect that the factory grease isn't exactly greasy anymore. I've been dousing them with light oil to try to reconstitute the grease but so far without much luck. I'm thinking new bearings are probably needed.
The second problem is with the carriage lead-screw, it binds up. But only when moving the carriage toward the headstock, and only when the hand-wheel is between the 2:00 and 5:00 positions. I suspect that this is a left over boo-boo from when the Sherline took a nose-dive off the bench onto the end of the threading attachment drive dog.