...yeah, well, as predicted, progress has been slower than I would have liked. BUT, we do have the various shafts for the machine sorted now!
Picture below is my own version of the "lathe" required to cut the shafts to length and to lay down the grooves for the retaining clips. Drill in a vice. Angle grinder with 1mm cutting disc. I tried the Dremel but the geometry was not quite conducive to accurate grooves.
Tip for anyone following - the grooves really don't need to be very deep at all. Shaft OD is 8mm. Retaining clip ID is 7.5mm. So the groove only needs to be 0.25mm deep.
I came close to going too deep on the fist shaft. We bought chromed shafts (not just straight mild steel) and leaned a bit too hard to break through the chrome the first time. Lesson learned - not probs after that.
Very useful thing was the old kitchen chair I used as a tool rest of sorts. Hard to be very accurate when going free hand.
Another problem with chrome shafts is that you can't mark the measurements on the steel very easily - had to wrap a piece of masking tape around the blanks so that I could set out the marks.
And - big news - we got washers in the mail (!!!) so we can finish most of the mechanical build. Still waiting for the threaded inserts though :(
We have all the electrical / power bits now too, so overall we're pretty much sorted for having all the pieces of the jigsaw sitting ready to go.
Raspberry Pi capability is rising. Been reading, taking notes, watching & mucking about.
Just need time and sufficient intent now :)