[mvoltin]

Lots have been written about the Delrin DIY nut by boring and melting it around the acme screw. The problem most, including myself, experience is that the nut comes out very tight and reheating and rolling up and down does not help. I found a solution that seems to address this issue and will let you know how it works out in a long run:

Spray part of the screw with a primer or something else that will provide a thin uniform layer and make sure it dries for at least 24 hours. Then, reheat the screw few inches from the painted area and thread the Delrin nut so that it goes over the hot portion first and then force it over the painted area to cool down. After cooling down you will have to wrestle it off but the nut seems to move freely after that while maintaining zero backlash properties.

Good luck.

[Mogal]

I haven't hads an issue with the delrin nuts I use (DumpsterCNC)
The acme rods I got are the generics from Roton(1/2"x10 double start)
I use a way oil on the rods (k68)
Not sure how many miles are on them now, but there is minimal wear.
They have been in place for about 5yrs now. Still maintain minimal/zero backlash.

Not sure if I like the idea of painting the rods, getting an even coat on them would be tricky.
And if/when the paint starts to wear and flake off, would generate grit and wear the nuts even quicker.

[mvoltin]

Sorry, I was not clear. the painted part is only used during the molding to make sure the nut does not come out too tight (I had some extra - same as yours - 1/8 with 8 pitch and 2 starts). Definitely not suggesting to use the painted ACME rod for CNC. This is only for DIY nut which is made by heating the rod and using a vise to squeeze the bored Delrin piece around it. Off-the-shelf nut would not have that issue. Here is one thread talking about the process and there are tons like that with many having same type of issue as I described below: Nylon(instead of delrin) for a feed nut? [Archive] - The Home Shop Machinist & Machinist's Workshop Magazine's BBS