Drawing the chuck, the bore, and the 3 spider components.
Using CAD to measure the dimensions. The main requirements are that the 3 components are identical, and the 30/120 degree angle. (360/3).
Transfer the dimensions to Vcarve pro, to generate the G code. (not essential to use Vcarve pro. This simple shape could have been entered directly into the CNC mill)
Simulation of the process, using VCarve pro. Again, not essential, but it is fun.
I use an iphone App called FS Wizard to calculate the feeds and speeds.
Milling the components.
The aluminium sacrificial holding plate, and the components. I tried a wooden sacrificial holding plate, but it was just not adequately rigid, and the finish was poor. The aluminium plate worked well. It will now join the growing pile of sacrificial plates from other CNC projects. You can also see the result of an extra milling step which removed the rounded fillet, allowing the spider to sit snug against the chuck jaws.