ACME 8mm Tr8*8-2p + Tr8*4-2p leadscrew nut / 4 and 2 start/

basically this is the same nut as here http://www.thingiverse.com/make:186226

I am designing a printer from scratch so because of customisation i needed the nut in some solid format, but it was next to impossible to find it.

Following the instructions from link above i managed to make it in OpenScad. Then exported it to .CSG. Downloaded and imported it in FreeCad. exported from there to STEP but whatever i did it did not work properly, tens of thousands of small bodies.
At the end exp