For a small lathe, why not build this small milling attachment for your metal turning lathe?
You can mount this milling attachment to the cross slide and do milling, surfacing, and keyway cutting. A handy unit for small metal turning lathes. It consists simply of a drill-press vise mounted on the cross slide of the carriage.
The vise is mounted on a disk similar to the index disk of the compound rest. Thus you utilize both the lateral and traverse feeds and the depth of the vise jaws gives a considerable range of vertical adjustment.
Also the unit can be swiveled to any degree desired to handle angular work.