I use the lathe as a broach. Even works on tapered holes. Grind a toolbit so it looks like a cutoff tool. put it on it's side in the tool holder and shim it up so it's centred with the chuck. Lock the chuck. run it in and out of the hole, backing out the crossfeed a few thou. at a time. Grind the toolbit so it's the same width as the woodruff key your going to use. Takes a while but does a nice job.