It looks like a fair amount of Blown polyethylene foam ( the stuff milk crates are made from) Which is a fine material all by itself and may be great for this low stress, zero blunt force impact, application.
It's not like there are a lot of machining forces exerted in the process.
It offers some interesting elements:
1) you can take up the back lash by tightening the nuts.
2) you can double thread. Multi lead threads are used for very expensive applications The old school expensive Parker Pens from the 1960s used double lead threads because it seats better ( more squarely) guiding the parts together from multiple positions on the diameter.
3) it can create different thread pitches without a set up change
I have seen a couple videos of it in use but they didn't give me any real sense of the thing.
It's not like there are a lot of machining forces exerted in the process.
It offers some interesting elements:
1) you can take up the back lash by tightening the nuts.
2) you can double thread. Multi lead threads are used for very expensive applications The old school expensive Parker Pens from the 1960s used double lead threads because it seats better ( more squarely) guiding the parts together from multiple positions on the diameter.
3) it can create different thread pitches without a set up change
I have seen a couple videos of it in use but they didn't give me any real sense of the thing.