OK, now, about this collar.
It's just a 3/16" slice off the ⅜" mild steel bar (previously reduced to 0.350" OD, drilled axially 0.150" then cross-drilled and tapped 8 BA. Doesn't sound difficult, does it?!?! Still, I bet some of you are thinking 'I know which bit of this goes wrong for him!'.
Well, the first operation mostly went well, like this:

What you see in that photo is raw ⅜" mild steel bar, I omitted to previously reduce it to 0.350" OD! Mistake #1!! Not too serious, that one, I can skim the OD just before parting-off the slice.
In weighing up how I would approach this job, the principal difficulty I had anticipated was cross drilling the tapping size hole for the 8 BA grub screw. If I parted-off the 3/16" slice first, it would be difficult to hold. I wrote off any idea of cross drilling the hole using my drilling machine (it's only a drilling machine, not a vertical mill, so no tables with graduated lead-screws). So, how was I going to ensure that the cross hole was accurately on a diameter? The answer to both of those problems was to drill the cross hole using the lathe and
before parting-off the collar from the stock - this would give plenty of material to hold while positioning and drilling.
First thoughts were to use the vertical slide and the little Myford machine vice. But rigging that seemed to be a cumbersome process.
Then I realised that maybe I had the answer right there in my Dickson pattern quick-change tool-post! I fitted the length of rod in a boring bar tool-holder, the type with a vee-groove, with a fair length extending out of the holder. I could then adjust the height of the tool-holder to bring the centre of the rod to the lathe centre height. The conventional way to set this up would be to use a clock gauge, again a rather fiddly procedure.
Instead of that, I used a Myford accessory comprising a 2 Morse taper shank with a Vee pad. I fitted this in the lathe mandrel taper and turned the mandrel to level the vee. Then, having checked that the rod was square to the lathe axis, I offered the rod into the vee groove, adjusting the tool-holder height as necessary. When I thought that was OK, I turned the lathe mandrel through 180° and checked the alignment again. It turns out that, on my drill-pad, the vee-groove is slightly off so I 'split the difference'. I then repositioned the rod in the tool-holder with just enough overhang for the drilling operation. I then replaced the vee-pad with a drill chuck.
I forgot to take photos of these operations - in the one I did take the camera auto-focus locked-on to the cross-slide rather than on the cross-drilling operation.
Next time I get in the workshop, I'll restage these operations and take more photos.
To summarise, the cross-drilling went well, as did the parting-off of the 3/16" slice. However, catastrophe struck when I tried to tap the cross hole. Maybe I drilled too small a hole, maybe I was just clumsy. The bottom line is I have to do it again! Watch this space.