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).
Notes on steel types, machinability, hardening processes, and crankshaft manufacturing.
| Identifier | ExFiles\Box 178\2\ img107 | |
| Date | 5th January 1940 guessed | |
| Notes on Visit to Harvey, Illinois. Page 5. Carbon steel at 3.1 is considerably less machinable than chrome-moly. steel at 380. An alternative is air-quench normalized 1045 steel at 217-241 Brinell. This is in the experimental stages with W.G. but grain size is much finer than from oil quench and it is thought they may be recommending this practice shortly. The Derby hardness of 321-341 on carbon steel for PL.72 is considered to be above commercial machineability for carbon steels. Note: It was equally recommended that nickel alloys be avoided for the same reason. For a given range of physical properties, hardness, etc. they are even more difficult to machine than carbon steels. The adherent scale on all nickel and nickel-chrome steels also makes them undesirable for forgings such asthese. The 4100 series of chrome-moly. steels are much preferred for economical manufacture. An example quoted was the use of 2515 steel (5% nickel, case hardening) for the Pratt & Whitney crank-shaft. This causes so much trouble that a "drive" is on to persuade P. & W. to use a nitriding steel. 1050 Tocco. This is a variation on SAE.1050 used almost universally for Tocco hardening. Contains C .45 - .55 MN .70 - 1.00 CR{Mr Cra???ster / Mr Chichester} .18 Minimum .20 - .25 Average. McQuaid - EHN grain size - 6 to 8. Heat treat for Brinell range - 241 to 269. Tocco hardening can be carried out on a crank like this with large dia. bores in pins and journals provided the boring is done after the hardening. A crank (6 throw, 7 bearing) which is very close to the design PL.72 is being made now by W.G. for International Harvester. It has similar bores in pins and journals. The material and procedure are as outlined above. In Tocco hardened cranks care is necessary for careful machine chamfering around the oil holes, to avoid chatter marks. Magnaflux test after Tocco hardening is essential, for detection of occasional minute cracks around oil holes or in billets. Jackson Crankshaft could probably do the complete machining of this crank at a reasonable price, and have the Tocco equipment. | ||