For my 3d Printer table I used something called Creform, commonly used for tables and shelves in manufacturing environments. Creform is a very useful tool, its basically like an adult erector set. I have a bunch of this stuff and use it for everything. If you want to get some of see how it works check out their website. creform.com If you want to buy their stuff you need to sign up for an account on diy.creform.com/Default.aspx.
The standard diameter of the tubing is 28mm, so I made this bushing to help my filament roll better on the creform. It is threaded inside and on the end end so the filament does not come off of the bushing. It fits most standard 1kg rolls of filament.
Print one of each for each roll on the creform spool holder. In my case just a tube running along the side of the machine.