Oldbones,

Glad you had good luck duplicating the results.

I tried a piece of small anhydrous hose today. Had to modify my feed a little bit so the knife did not cut clear through. While it did cut the spiral. Its not very good I think the material was too soft and rubbery. Trying to drive with the drill it wanted to twist up and kink instead of just turning. I used a longer piece of PVC pipe to lead it in and keep it more contained prior to the knife but it did not really self feed like the black poly.  You had to maintain forward pressure while running the drill to keep it advancing. Then if you went to fast it sort of wadded up after the knife. Had to take time to untwist the knotted mass and get the spirals oriented correctly afterwards . I don't think you could cut a very long piece of this with the long lead in PVC pipe.

The black poly is the best for cutting and feeding mainly because it is not so thick and it is fairly stiff and not so rubbery.