I think you're going to find that the 10 TPI acme screw gives you way more resolution than you can take advantage of. For example with a 10 micro step drive (2000 pulses per revolution) the theoretical resolution is 0.00005" (.1/2000). Stepper motor torque is high at low rpm and diminishes rapidly as rpm increases. I use 600 rpm as my target maximum motor speed. At 600 rpm you're only getting 60 ipm feed rate with the 10 TPI screws. I use a target feed rate of between 100 and 200 ipm minimum for routing wood. (I don't know what you would want as a target feed rate for engraving metal.) To get the target feed rate of 100-200 ipm (actually 120-240 ipm) I would choose a screw with a lead of between .2 and .4 inches per revolution.
Chris