Skate bearings have to be the best all round DIY solution for me, low cost, the effectiveness of them, 8mm shaft.....the tubing is a little harder to find (for free) I'm up to 38 skate bearings now with 4 more shortly on the drive reduction

Another thing that has worked well for me is the 12mm threaded rod across the table as this way only needs sides making - crude but easy to adjust and mount things from etc

Cheers Shaun