A axis?
It will depend on how your turret works as to how you connect it, mine id hydraulic and uses combinations of limit switches to show the tool position and other limits to show when its clamped, unclamped, rotated etc etc. I need quite a lot of I/O between the turret, Front Toolpost, Gearchange etc so I got a PLC. You may not need so much so maybe the parallel ports will provide enough. Not sure what the combo board is, better have a look see LOL
Hood