I have a design for woodturning that I haven't quite finished yet for a 170mm centre height lathe. This will provide for a max 110mm diameter workpiece. However, it really requires a milling machine to make, although some patient work with a file would do it. The "ring" in the photo attaches to the piece of steel angle which then bolts to the lathe bed. The ring is just a 12mm section from a large diameter steel pipe, cut to length by the supplier. If you want a dimensioned 2D drawing I can send you one. Very simple design really. Parts so far:-