This is a example how to make a anti-backlash lead screw using 2 nuts and this printed part. The example shown uses 2 m5 nuts and a spring. I have included the CAD file for you to examine in DesignSpark Mechanical. Basically you will only slightly tighten the 2 nuts together so that the free play is taken out and then insert into the nut capture. Too tight and it will have a lot of friction. This design has more drag than ball screws so you will need to use a light lubricant. Preferably containing teflon. You will have to draw a new CAD file with the appropriate bolt holes for mounting and for your particular size threaded rod. Print at 100%. I leave typically a 0.2mm clearance for the nut. so therefore, if you use a m6 threaded rod the nut is 10mm. I draw a 6 sided enclosure for the nut at 10.2mm