Below is the basic setup. An ER32 collet chuck and 16mm replacable carbide tip slot mill in the spindle, and the toolmakers vice from my pillar drill mounted on the vertical slide.
There is a fair bit of overhang on the cross slide. A lower profile vice would reduce this.
Countering this, the mill bit is mounted close to the spindle bearings and is immensely rigid.
Work is brought up to the cutter, the opposite of what happens with a combination or stand alone mill, where the quill is extended towards the work. Column and quill flex are therefore not an issue, as occurs with all light mill setups.
The end result is that the lathe setup can be more accurate and effective than a small dedicated mill head. Obviously a big heavy industrial mill is the best method of all.Here's a video of it milling some medium to high carbon steel with a carbide cutter.
Care must be taken to eliminate any backlash in the slides and feed systems, and the carriage locked down on each pass to get a good finish.
Adjust out any slop in the rear way adjuster on the carriage, to reduce any tendency for the carriage to lift at that point.
Cross slide lock
It's also desirable to lock the cross slide where possible, to eliminate the lash that exists on most lathes. This will minimize shudder and movement when plunging with an endmill.
Below is a
photo showing a simple cross slide lock (red arrow) and
hexagonal head of the carriage lock - both essential items.
The cross slide lock is simply a threaded hole with a 6 mm bolt (recess the end slightly) and a ball bearing pressing against the side of the gib blade. Dead easy to fit.
It also has the advantage that when feeding with the cross slide, light pressure can be applied to the gib plate to dampen out backlash and further improve the finish.