From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Informational brochure detailing the TOCCO PROCESS for the surface hardening of crankshaft bearings by induction.
| Identifier | ExFiles\Box 132\4\ scan0051 | |
| Date | 8th January 1937 guessed | |
| HOURS Reduced to SECONDS BY THE TOCCO PROCESS Surface Hardening by Induction Above left is shown the standard motor and special generator installed to produce the high-frequency current for TOCCO hardening. The output of this frequency-changer set is regulated automatically and is accurately controlled. The illustration on the right shows the simple method designed for securing the automatic control for the surface-hardening of different crankshafts. Once one of the revolving cylinders has been properly prepared to control the time cycle for any given crankshaft specification it is always available and may be quickly inserted in the machine at any time duplicate crankshafts are to be treated by the TOCCO PROCESS. A Description of the TOCCO PROCESS of Hardening Crankshaft Bearings A brief description of the method used in hardening crankshaft bearings by the TOCCO PROCESS will be of interest to manufacturers and production men as well as to engineers and metallurgists. The heat of steel to be used on a crankshaft which is to be TOCCO-hardened must be one which passes the usual inspection tests and in addition should be of the fine-grained type. After forging, the crankshaft is properly cooled, this alone producing the necessary normalizing. Then without further normalizing or heat treating it is machined, radial oil holes drilled and the journals rough ground. The final grinding operation follows the TOCCO surface hardening. For the TOCCO-hardening a high-frequency current at high voltage is transformed into low voltage with high amperage. This current passes into inductor blocks which surround but do not actually touch the bearing area it is desired to harden. The inductor block current induces a current in the surface of the metal. This induced current is the heating factor. When the area to be heated has been thus subjected to an accurately controlled, high-frequency current for the correct length of time the electrical circuit is opened and simultaneously the heated surface is quenched by a spray from a water jacket built into the inductor block. When all the main, intermediate and pin bearings are hardened the entire shaft is drawn at a low temperature to remove strains. Then a final grind completes the shaft. The combination of instantaneous pressure quenching and a split-second heating cycle produces a surface hardened zone of from 58 to 60 Rockwell C scale, blending gradually into the core with no sharp line of demarcation and consequently no opportunity for flaking or spalling. Ever since man first fashioned metal he has known the need for a harder, wear-resisting surface on a softer, resilient core. That heating metal and quenching it instantly hardened its surface was learned long before science discovered the reason why. The armorers of ancient Damascus and those later masters who forged the fabled sword of Richard Coeur de Lion and Saladin's scimitar, knew much the same processes that industry is still using on crankshafts, gears and wearing parts of modern machinery. The old process was good enough in the days when each halbert, each cuirass, each sword was an individual masterpiece produced by hand and patience. But industry has searched long and hard, since mass production of machines began, to find a more modern, more rapid and efficient and less costly means of producing hardened metal surfaces. That new method has been found, a method which not only reduces hours of surface-hardening time to seconds, but produces a scientifically regulated, exact result—superior in many ways to the surface produced by the old, wasteful, time-consuming, furnace treating—as customary in carburizing, nitriding, cyaniding and other processes. This new method requires no furnace, no fuel—only a few cents worth of electric current. It is the TOCCO PROCESS, developed by the Ohio Crankshaft Company. The following pages give more details on this interesting process—which already has been welcomed and widely adopted by leading manufacturers. Advantages of the TOCCO PROCESS for Producing Hard Bearing Surfaces ADAPTABILITY—Localized heating may be controlled with ease, thus permitting the hardening of only the areas desired. UNIFORMITY—Absolute duplication of results. DUCTILITY—Unusual ductility of the hardened area is evidenced by lack of flaking or spalling in service. BOND—Cohesion between the hardened area and the core is well diffused. TIME CYCLE—Split-second heating cycle permits process to be included in the production machine line. ECONOMY—TOCCO-hardening permits use of a normalized crankshaft in place of a heat-treated crankshaft with consequent saving in heat-treating, machining, tool and straightening costs. Also permits the use of higher crankshaft speeds and bearing pressures than are customary with the heat-treated crankshaft. Hence horsepower per cubic inch of engine displacement can be increased. LONGER LIFE—TOCCO-hardened bearing surfaces (58 to 60 Rockwell C scale) wear from five to ten times as long as those produced by automotive heat-treating methods. THE OHIO CRANKSHAFT CO. Cleveland, Ohio | ||