How to make a 4th Axis for my CNC Router - YouTube
Bantam Tools Desktop CNC 4th Axis
4th Axis CNC Rotary Module for Genmitsu 4040 Pro | CNC 3D Wood Carving
BuildYourCNC - 4th Axis with Tail Stock
4th axis jig for CNC machine: fine-tune it once, then set it and forget it. Easily re-mount it square to your t-slot table so you don't have to re-tram/tune/shim it each time. :