Rotating ring disk electrodes (RRDEs) are a powerful and versatile tool for mechanistically investigating electrochemical reactions at electrode surfaces, particularly in the area of electroanalysis and catalysis. Despite their importance only limited electrode materials (typically glassy carbon, platinum and gold) and combinations thereof are available commercially. In this work we present a method employing 3D printing in conjunction with machined brass components to produce housing which can accommodate any electrode material in e.g. pressed powdered pellet, wafer, rod, foil or vapor deposited onto a conductive substrate, form. In this way the range and usability of RRDEs is extended. This custom DIY approach to producing RRDEs, also enables RRDEs to be produced at a significant fraction of the cost of commercial RRDEs. To illustrate the versatility of our approach, co-planar boron doped diamond (BDD) RRDEs are fabricated for the first time, using the approach described. Experimental collection efficiencies for the redox couple FcTMA+/FcTMA2+ are found to be very close to those predicted theoretically. BDD electrodes serve as an ideal electrocatalyst support due to their low background currents, wide solvent window in aqueous solution and chemical and electrochemical stability in acid and alkali solutions. The BDD RRDE configuration is employed to investigate the importance of surface incorporated non-diamond carbon in BDD on hydrogen peroxide generation via the oxygen reduction reaction in acid solutions.