No, so far the heaviest cuts were on the side of its faceplate, and that wasn't too heavy at about 10 thou. I think I might run into limitations of the 3-jaw chuck before limitations of the gearbox. My plan is to make a secondary faceplate that mates to this one in place of the chuck and has T-slots, which would permit some heavier milling. I might mill the T-slots with it mounted on the 4th axis so they align with the center, haven't decided about that yet. Actually most of the projects I have in mind for it in the near future would be in wood on the CNC router, where it would be unlikely to push the limits of stiffness. I just built it heavily so I can use it on the mill too, but it won't be much more than an indexing head until I get the CNC conversion done on the mill.