Homebrew PCBs

>For lead screw applications I'd keep the encoder on
>the screw. Doing so allows the screw to be driven
>indirectly and velocity/torque/rotational-precision
>to be scaled via simple friction coupling without
>introducing slippage error.

A DC gearhead motor is best for lead screw applications as it allows 
the screw to be driven "directly" without any complications provided 
speed and torque requirements are met. It doesn't get much simpler 
than this;

http://www.pbase.com/eldata/image/45200286

http://www.pbase.com/eldata/image/45200509