Hi Guys,
I take it you are referring to END Float on the shaft and not backlash on the thread.
This can be eliminated using a ball bearing on either end of the screw, shimmed to be a close fit for length and just "lightly" tensioned with a nyloc nut on the floating end of the screw, opposite the motor.
You also can have both bearings back to back with each other at the motor end with a small shim between them to allow for lightly compressing the bearings together to eliminate the end float, but remember, you only need a light pressure on them just to eliminate the float otherwise you will get bearing heating which will increase the pre-load and make things tighter than they should be which will cause drag and premature failure of the bearings or loss of steps on your motors etc
Have fun with the build.
Rich.