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).
Redesign of standard bolt heads for improved production and usability.
| Identifier | ExFiles\Box 181\M11\ img210 | |
| Date | 1st September 1919 | |
| E MULTUM IN PARVO. ORIGINAL 2 To BA. from E.{Mr Elliott - Chief Engineer} Copy to C. " " BN.{W.O. Bentley / Mr Barrington} " " BH. " " BY.{R.W. Bailey - Chief Engineer} " " W.. " " EFC. X. 3645 E3/G12/9/19. RECEIVED 1919 RE BOLT HEADS. Referring to the design of our present standard bolt heads, Mr. Royce thinks that this might be considerably improved with a view to:- (1) Making the bolt head neater so that it can be accommodated more easily in a design. (2) Conforming to existing spanner sizes. (3) Facilitating and cheapening production. The new bolt heads should still be of square form, but with the corners removed. The width of the square on any bolt is to be equal to the width of the hexagon (on the standard hexagon list) which is the next size smaller than used for the Rolls-Royce nut for that bolt. Thus, a .312 bolt head would be .448" over the flats, which is one size smaller than the size over the flats of our standard .312" nut, e.g. .525". The bolts are to be turned from round bar of a diameter which is smaller than the diagonal of the square for the heads, so that these latter will appear as in the sketch. It is desired that the diameter D shall be fixed as far as possible to conform with obtainable sizes of bar, but the side S should be slightly longer than the side of a hexagon of width across flats M.{Mr Moon / Mr Moore} If it be possible to obtain round bar in the material we require, having a sufficiently smooth surface finish, then the diameter D can be left unmachined, provided of course, it conforms to the bar size. It will be seen that condition (1) mentioned in the beginning of the letter is satisfied by these new bolt heads requiring very much smaller circular facings than the old and further, where required to engage with a flat feature to prevent turning, they can be tucked in more closely to the job, owing to their smaller width. (Contd.) | ||