Isaac,
You probably need to check all the Kerk data sheets etc. for setting and adjustment of their screws / nuts.
http://www.haydonkerk.com/Portals/0/files/lead_screw_technology_engineering_data.pdfAlso check your machine for rigidity / tightness of all components and also for any lateral movement at the tool tip when stationary (and disconnected from the supply

)
The problem with backlash is that the total amount is very dependant on tool loading. You can set up a machine for zero backlash with a D.T.I but as soon as it is put into operation, the deeper the cut or greater the tool loading then the greater the backlash that starts to appear. Another important factor here is having good quality and sharp tooling (dull cutters are best consigned to the bin, unless they can be resharpened cheaply enough).
Tweakie.