I have dumpster CNC antibacklash delrin nuts on an acme 8 2 start screw.

I ordered the screw with a black oxide finish which I had to sand off in order to get it into the bearings.

I think it is kind of difficult to turn the screws in the nuts.

About how hard should it be to turn the screws in the nut?

Analogies might help, as I have no idea how to measure the pressure needed.

Right now, if i lay the 3 foot screw on the table with the nut... that has a 2 inch flange.. and try to turn it. As opposed to the screw turning the nut... the whole nut assembly turns over.

They will feel rather tight on an uncoated or anodized single start acme rod. That is the spring tension forcing the white delrin part against the face of one side of the two screw threads and the black delrin body against the other side of the two threads. The delrin parts are in effect pinching the threads. My 1/2-10 single start rods and DumpsterCNC ABNs worried me at first also. I have new 1/2-10 5 start rods in hand and the ABNs will arrive by Friday. I expect the tightness to be almost 5 times greater.

The spring that DumpsterCNC uses seems kinda tight to me, but once the delrin wears in a little it should ride on the rod a little easier during operation. You can help it by spraying or brushing a light oil on the rod, letting the excess run off, and let the remainder dry a few minutes to evaporate any solvents that allow it to spray. Then try screwing the ABN onto the rod again. Delrin is not harmed by most light general purpose oils.

CarveOne