30mm diameter, 11mm thick, a rail groove on the edge, circular divots on the faces. Simple!
I decided to make them from stainless steel. And tonight I have multiple small cuts on my fingers to prove it.
Stainless steel is a bugger to machine. It requires slow feeds, deepish cuts, COOLANT, and sharp tools. Carbide is OK for roughing, but for accurate final surfaces, sharp high speed steel is required. And it produces razor wire. Copious amounts of it.
First I machined some 40mm stainless rod down to 31mm. Too late I realised that was too big.
Then I used a HSS form tool bit to cut the edge groove. But got too much chatter. So spent some time getting the coolant pump and nozzle working. Some improvement, but still some chatter. So I switched to a HSS parting tool 3mm wide, and that seemed to work well. The DRO was handy to achieve the final groove depth of 2.5mm, and 6mm wide. And then to take 0.5mm off each face to produce a boss 12.7mm wide and 0.5mm deep.
Then completed the parting off. Oh. Forgot to mention the 5mm shaft hole which was drilled.
But when I tried to install the wheels in the wheel brackets I realised that I need to remove about 0.1mm from each boss. This is the setup which I used.
So, the first pic is the current situation, . Next steps are to make the washers for the axles, trim the axles to length, and drill/install retaining pins. These steps always seem to require at least double the predicted workshop time.