I bought some rods of 12mm bronze a while ago for scrap price. This thing makes nice bushings and things that need to slide with low friction. I drilled a 4.2mm hole, tapped to M5 and then machined to 10mm. Then I machined it to 8mm so it has a flange.
They were cut off using a cut-off tool (lacking picture, sorry). The original RepRap plastic parts are supposed to fit a M5 so I disassembled the x-carriage and drilled out this hole to 8mm and hammered it in. I should have been more gentle as the x-motor mount cracked a bit. No worries, a bit of superglue would fix that. I just have to assemble everything together and... F*** The smooth rods are at an odd angle in the x-idler plastic. Not sure whether this is due to the printer that printed the part or me being a little too rough with the nut insertion (no pun intended). I fixed it a bit by drilling out the holes on a drill press to make it closer to 90°. It not quite there but it's better than before.