POLYCRYSTALLINE DIAMOND EDGE QUALITY AND AND SURFACE INTEGRITY FOLLOWING ELECTRICAL-DISCHARGE GRINDING

The edge quality of various grades of polycrystalline diamond (PCD) cu tting tool blanks has been examined after electrical discharge grindin g (EDG) on either the face or periphery of a rotating graphite wheel e lectrode, using a range of operating conditions. Edge roughness was as sessed using a Rank Taylor Hobson Talysurf 10 with a chisel edge diamo nd stylus and sub-surface damage by optical and scanning electron micr oscopy. Peak current, on-time, polarity and direction of wheel rotatio n, were found to have a significant influence on blank surface integri ty and edge finish. Blanks with a fine grain size were easier to fabri cate in that they had higher material removal rates, higher grinding r atios (G-ratios) and lower surface and edge roughness. Coarse grain PC D products in general showed a higher depletion of material at the dia mond/carbide interface and extremely coarse grain products, >50 mu m, suffered cracking of the PCD layer. Similar results were obtained when sparking on the face and periphery of the wheel.