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).
Cadmium plating inducing brittleness in small screwed parts and proposing a special heat treatment.
Identifier | ExFiles\Box 30\6\ Scan067 | |
Date | 14th December 1928 | |
H1. c. Hs.{Lord Ernest Hives - Chair} X1360 BY2/G.14.12.28. CADMIUM PLATING ON SMALL SCREWED PARTS. --------------------------------------- Referring to H11/EA.13.12.28. it is evident from your experience that generally speaking there is no increased tendency to brittleness after plating. In regard to the final suggestion that it was a tight thread. This I had personally tested, and am satisfied was not the case. The original fractures took place on four connecting links with screwed ends. They were all made at the same time from the same material, and all failed on the engines very rapidly. We then took some screwed rod and tried it as produced from the machines, and secondly after plating. The plated piece on these particular samples only bent through approximately 2/3rds. of the angle of the unplated parts. From your experience and the foregoing, I should be inclined to draw the conclusion that it is only material in a certain condition which is likely to suffer, but the fractures which occurred on the engine and the similar discrepancy on the plated parts when I checked the position with some screwed rod, certainly makes it clear to me that there is a condition of the material which does occur in practice, which if combined with cadmium plating induces brittleness. I am quite prepared to concede that in most cases the brittleness would not occur, but I think it is a parallel case to the soft steel used for petrol tank ends. You will remember that whilst these in the tinned condition as received from Messrs. Nicholls & Lewis were all brittle, we were unable to reproduce the brittle condition on similar material when we tried to do so in the Lab. By heat treatment of the parts this fault was eliminated at that time, but after two deliveries we found they had cut out the heat treatment and the next delivery was brittle. As a precautionary measure I therefore propose to add to the drawings of all screwed parts which are cadmium plated that they must be given a special heat treatment. I think you will agree that this precaution is the only possible course under the circumstances. BY.{R.W. Bailey - Chief Engineer} B4 | ||