Got to admit here that I have built this very 4th axis. I use it on a router and have cut oak, beech and Iroko, it works perfectly well with a 6:1 reduction and a 3Nm stepper. Although the materials I have cut are a little harder than cheese, and I intend to try PVC an HDPE soon, you'd be mad to think of using it to cut metals.

It cost more to build than buying a rotary table and converting it; even given I am in the happy position of getting the main shaft, backplate and ally plates etc for free. I used my router to machine the plates and the lathe at work to bore the backplate for the chuck and it STILL cost more than a bought solution but I'm happy as it was a good excersise.

Jeff.