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).
The required blade sizes for a feeler gauge for the SS. unit.
| Identifier | ExFiles\Box 16\6\ Scan012 | |
| Date | 12th August 1928 | |
| H.R. } FROM R.{Sir Henry Royce} BY.{R.W. Bailey - Chief Engineer} } (crossed out) X.7580 R1/M8.12.28. Copy to BJ. " EFC. FEELER GAUGE. X.7580 The feeler gauge for the SS.{S. Smith} unit we think should have the following blades: .004 .005 .010 .020 .025 .050 Some of the older ones, such as .018 and .030 have no meaning now, and the latter is too wide we think for sparking plugs with the present compression pressures. .020 and .025 are useful for ignition plugs and many other clearances. .004 and .005 are for valve tappet clearances "go", and "not go". .010 and .050 are useful for adding up for other tests such as clearances on switch unit. R.{Sir Henry Royce} | ||