Dave,
Having looked at the commercial line boring equipment available from the US, a lot of them are based simply on mag-based drills, with an arbor with the single point cutter moved by action of the magdill handle. At least one of the companies reckons that a bungee cord provides a reasonable feed, its not exactly smooth/accurate control but probably good enough. Its the approach we plan to take when line boring out the third-shaft bearings on the Aveling.
pic here:
http://www.tractiontalkforum.com/sho...ht=line+boring
Dave