Making your own flex shaft

Hello, folks I have been trying to make my own flex shaft and the challenge seems to be in the covering like Rick says. I have tried the 1/2" pex B plastic tubing for 3/8" cable. I made a 35' and a 75'. I lubed one with lube grease and the other with marine lube. What I have found is when I run the drill if forward it binds up momentarily that springs and the cutter spins. I was trying an dewalt drill that spins at 1500 rpm's. Than I was trying to use 5/16" inner core cable for kitchen drain lines I tried very flexible pvc air hose and it just twisted up. Today I tried clear plastic 3/8" id water tubing for the 5/16" cable it ran in reverse OK not if forward. I believe that the cable is torquing up around the inner core and this makes it thicker so it binds in the tubing.

Via RSSMix.com Mix ID 8247361 http://www.rssmix.com/