An electrode apparatus for an electric arc vapor deposition machine has an electrode body with a coaxially aligned stud threaded into its rear surface and projecting substantially perpendicularly thereto. The distal end of the stud is threaded for rapid detachable fastening to an electrode support means such that the periphery of the rear surface of the electrode is uniformly drawn toward engagement with the electrode support means. A seal member forms a fluid tight seal between the peripheral rear surface of the electrode body and the electrode support means, which cooperatively define a coolant cavity for actively and efficiently cooling substantially the entire lower surface of the electrode. The electrode support means includes means for directly bathing the seal with liquid coolant from the coolant cavity. The simple threaded stud mounting configuration allows a spent cathode to be rapidly replaced.