Another part for the machine helping from roguetoolpath on Tormach CNC machine.
“Lathe 3 jaw chuck material stop. Another lathe accessory useful for holding large diameter short stock in 3 jaw chuck. Can be made with a mill, router or 3d printed. Optional magnet insets shown. Models uploaded to grabcad and fit a 4 inch 8l lathe 3 jaw chuck or other 4 inch chucks.”
You can watch tutorials about milling in SprutCAM.