Machining a large shaft with fins - GIF

Machining a large shaft with fins. Not really sure what I'm looking at here.

<video controls autoplay loop> <source src="https://diqn32j8nouaz.cloudfront.net/machining_giant_impeller_shaft_jl23.mp4" type="video/mp4"> Your browser does not support the video tag. </video>


Previously:

https://www.homemadetools.net/forum/...263#post227643
https://www.homemadetools.net/forum/...177#post227330
https://www.homemadetools.net/forum/...333#post227888
https://www.homemadetools.net/forum/...786#post223613
https://www.homemadetools.net/forum/...223#post218356

Perhaps some kind of material moving device. Reminds me of a grain auger.

Maybe some kind of mixer? It's big!
That tool post is almost as big as my lathe.

If you look real close at the very end you can tell that it is flighting, but I'm curious as to why the spiral gap unless due to the length and number of flights the gaps are to prevent compaction of the material in the flights.
Also noted is that lathe is special poupous for that particular type of job. The ways are a crazy distance apart and the ribs or girts are recessed very deep.