I think I used something like 2" bearings, 6" is going to the extreme. The only bearings that big (and cheap), would be truck wheel bearings, or 'Catipillar' (expensive). From my experience with this (and a lami trimmer), you would need something solid like roller bearings, because of the harmonics/vibration. Vibration was one of the problems I had.
I'm testing the memory now, but I think I used tube and 2" bearings. As long as you are not turning the chuck too fast, I reckon you could use 6" tube and 3 bearings, placed evenly around the tube, so the tube rolls evenly inside the bearings - or even 5 bearings, see below??????????????. pete
