.004 is a reasonable feed rate for parting with a low hp less than rigid machine. Like Joshua said, you have to keep the parting tool in the cut and moving on flexible machines or the chatter starts, once the chatter starts on a light weight machine, you are done for, either lousy finish, broken cutter or worse. If .004 feels to fast practice hand feeding with the lathe off, to master a steady feed. Dead on center, dead square and power thru, using either carbide or HSS. If using HSS make sure its sharp with a little relief to one side, that lets the cutter start with less than a full bite. If the part that matters is in chuck , I like that side of cutter to start first, just a slight relief is all that is needed. A great way to practice parting with less drama is to use aluminum or plastic, a bit more forgiving and the principles are the same. From there I would move up to 12L14 steel.
michael