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).
Forced fit knurled assemblies, comparing the methods of knurling and surface broaching for hydraulic shock dampers.
| Identifier | ExFiles\Box 151\2\ scan0314 | |
| Date | 12th November 1936 | |
| 12972 1292 To H. {Arthur M. Hanbury - Head Complaints} from Rm {William Robotham - Chief Engineer} /Les. c.c. to Sft. {Mr Swift} c.c. to HEC. c.c. to Da. {Bernard Day - Chassis Design} c.c. to Hdy. {William Hardy} c.c. to HV. FORCED FIT KNURLED ASSEMBLIES. Referring to E.S/RP.6.11.36. Gordon Armstrong can sell a set of four hydraulic shock dampers for 27/6d. including three fixtures of levers to the main shafts by cutting serrations both in the lever and on the shaft. Knurling the shafts was tried, but it was found impossible to obtain a tight fitting lever. The method used for serrating the shafts is surface broaching. This operation needed some development work but is now no more expensive than knurling. It is necessary to have an undercut on the shaft at the end of the serration. The attached sketch shows the approximate shape of the cutter used by Gordon Armstrong. The serrations are cut in one operation, but a first and second cutters ensure a better finish. Difficulty was originally experienced from the teeth breaking in the cutter. The interference fit is such that four tons are required to press the lever on the shaft. More interference causes the levers to work loose. We recommend that we should copy Gordon Armstrong's method rather than continue to test knurled shafts which Delco's have also deleted. Rm {William Robotham - Chief Engineer} /Les. Sketch attached. | ||