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).
Comparing hexagon and square headed bolts, concluding not to standardize on the hexagon type.
| Identifier | ExFiles\Box 148\5\ scan0169 | |
| Date | 2nd July 1937 | |
| 1360 HS.{Lord Ernest Hives - Chair} c. Rm.{William Robotham - Chief Engineer} HPS.{Horace Percy Smith - Experimental Factory Mgr} Ds. E/NS.{Norman Scott} E.5/HP.2.7.37. Rolls-Royce Standard Parts. Hexagon versus Bolt Heads. We have investigated the question of using hexagon headed bolts as against square headed bolts, and cannot find a case for standardising the former. The difference in factory cost is negligible, material and machining figures for both types being practically identical. We have moreover carried out tests of the doubtful feature of the hexagon headed bolt, that is, the location against an aluminium shoulder to prevent the bolt from turning, and the hexagon type has definitely failed under the tests reported in HPS.{Horace Percy Smith - Experimental Factory Mgr}1/VS.{J. Vickers}2.6.37. The single disadvantage we know of the square head is that it demands a somewhat larger circular facing when the seating for the bolt head is machined in this way, but this has not proved serious in practice. In view of the foregoing we are not proceeding any further with the hexagon head type. E.{Mr Elliott - Chief Engineer} | ||