Originally Posted by
miriam
I don't know the correct terms but it sounds like it might be the same or similar. There is also a needle feed - some of the Davis machines work that way. I've not used one of them. They do have a better ability to evenly feed layers of fabric through a machine. I had a couple nice walking foot sewing machines when I had my tent making business. Other than the foot they are just a sewing machine.
Here's the literature I've been able to find on the 21w180:
http://www.sil.si.edu/DigitalCollect...ines/SIL/0029/
Sounds like a combination of the Davis vertical feed and a normal feed dog feed.