speed of screws

Two years ago I had never heard of CNC then I saw a patern that was
cut in to a peice of wood. Being a woodworker I said if it will do
that Imagine what I could make it do!
I bought a 60oz stepper kit from HobbyCNC and got set of plans for a
small router table.I started out making the table and went to buy
leadscrews and stoped building becouse of cost of screws. well I
started up once more after buying a leadscrew from one of the Surplus
places. Then I made one from threaded rod 24tpi. It works great has
tought me more that my wife cares to talk about. But I only can get
10"per min feed rate. Now is this becouse I am stepping 6400 times to
get a Inch or have I reached the torq limit of the stepper. or a
little of both. I want to take what I have learned and make a larger
router table and faster, and maybe speed up the first one I built.
Or do I need to start playing with motors with encoders and Geco
drives?