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).
Revised procedure for reaming hollow stem valves to reduce manufacturing costs for the Kestrel engine.
| Identifier | ExFiles\Box 96\2\ scan0080 | |
| Date | 27th November 1935 | |
| To Wor.{Arthur Wormald - General Works Manager} from RHC.{R. H. Coverley - Production Engineer} c.c. Sft.{Mr Swift} HY.{Tom Haldenby - Plant Engineer} Hs.{Lord Ernest Hives - Chair} DY.{F R Danby} TS. x354 RHC.{R. H. Coverley - Production Engineer}2/ETM27.11.35. REAMING OF HOLLOW STEM VALVES. Investigation into the process of boring exhaust valve stems has been carried out with the object of reducing cost of manufacture and eliminating the internal polishing to remove tool marks. Whilst in principle the procedure is unaltered, a modified reaming process is introduced to give the required standard of finish and accuracy without the necessity for polishing. The revised procedure, as applying to the Kestrel exhaust valve is as follows - 1. Rough bore 2.500 deep .265 diameter, using ordinary twist drill .... 5 minutes 2. Bore full depth .281 diameter, using ordinary twist drill .... 7 minutes 3. Bore .296 diameter using flat bottomed drill ... 5 minutes 4. Ream .307 diameter using R.H. spiral reamer ... 15 minutes 5. Ream .312 diameter using special reamer ........ 15 minutes Total actual time .. 47 minutes The corresponding total actual time for the production operations is 1 hr. 7 minutes which means that an appreciable reduction in cost of manufacture can be effected, as shown by the following figures - Cost of boring and reaming by production methods .. £6. 14. 0 per set Cost of internal polishing ....................... £5. 8. 0 " " Total £12. 2. 0 " " Cost of boring and reaming by revised method ..... £ 4. 14. 0 " " Total cost reduction per set £ 7. 8. 0d " " Representing a saving of 61% of cost of Production Boring, Reaming, and polishing operations. | ||