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).
Letter from Aubert & Duval discussing the grinding of nitro-hardened steel components.
| Identifier | ExFiles\Box 22\1\ Scan314 | |
| Date | 20th August 1923 guessed | |
| Aubert & Duval, Freres, 62, Avenue de la{L. A. Archer} Republique, Paris. Messrs. Rolls-Royce Ltd., Derby. Sirs, We are in receipt of your letter of the 28th. ult. It is quite unnecessary to grind the surface of steels that have been nitro hardened in order to eliminate the brittle surface. Nitro steel should have no tendency to peel off under ordinary working conditions. Therefore for this particular complaint for gear wheels always in mesh, for shafts and cylinder liners, there is no necessary to provide for final grinding. Nevertheless it is necessary to provide a certain margin for grinding in the case of cyl. liners because one cannot foretell exactly what distortion will take place. One is therefore forced to allow a small margin for truing up by grinding, but we always advise our customers to make this allowance as small as possible and to remove the minimum quantity of metal, for the outer layer is the hardest, and it is desired that the working face shall be composed of this outer layer. In the case of small dia. cyl. liners of (60 to 80 mm. bore) (2.36" to 3.150") in which a variation in dia. of 2 to 3/10 mm. (.0008 - .0012") is not considered of vital importance, the liners are usually erected without any final truing up by grinding. We would remind you that shafts and gears are never finally ground after nitro hardening. Tappets alone have their surfaces ground to a depth of from .002 to .0035". In this case the surface blows are violent and one is obliged to remove this depth of outer layer. Yours faithfully, FOR AUBERT & DUVAL. | ||