We manufacture case work using fluted dowels. They are very consistent in size, snug fitting. All the flutes allow some of the trapped glue that gets pressed to the bottom to be squeezed back up the flutes, better locking the dowel than the more traditional spiral flute ones. We mostly use 8 x 35mm, beech or birch. I think they are available in small quantities for home shop use. Ours come 4000 to the box, but we use automated bore and insert machines that are quite intolerant of over sized dowels. Slick machines if you ever get to the point of using a lot of dowels. 1.2 seconds to drill, blow the dust out, inject glue, drive the dowel and move to the next location (CNC.) Another option for you if you want to size imperial dowel rod is to buy one of the steel dowel fluting/sizing plates and just drive the dowels through with a hammer.