After looking through various alternative designs, Paul & I decided to go ahead building a hydraulic knurling tool. Based on Paul’s initial design I went off and refined the details to come up with a specific plan and draw the CAD design (which I’ll eventually publish when I get it all finished).

After that, I figured I would start on the easy parts (the arms) and leave the rest to Paul ;-)
You can see some photos of the work here and here. The final result is:

Not too bad, although a little rought, and perhaps not quite as accurate as I might hope. Still, at the very least they should work as a proof of concept and hopefully will work adequately for the finished tool.