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).
Cracking issues found in camshafts made from low carbon case hardening mild steel (UBAS type) after grinding.
| Identifier | ExFiles\Box 93\5\ scan0043 | |
| Date | 23th July 1937 | |
| 307 [Handwritten Note] Sewell - See me Perles Rm{William Robotham - Chief Engineer} [Stamped Initials] H.H.S. C.E.P. C.B.T. G.Rm.{William Robotham - Chief Engineer} C.F.F. BY/HM.{Capt. W. Hallam - Head Repairs}16/J.23.7.37. ------------------- CAMSHAFTS IN LOW CARBON CASE HARDENING MILD STEEL (UBAS TYPE). ------------------------------------------------- As you are aware, we have completed a number of camshafts made in Fox's Steel to Spec. 3.S.14 which is a low carbon case hardening mild steel which has been suggested for various applications both on chassis and aero engines. We have kept in touch with the progress of these camshafts and the material appears to be free from longitudinal flaws or inclusion such as were found in the UBAS Steel. Upon Magnetic test after completion however, the shafts were found to be full of cracks of a transverse type which are not associated with flaws in the material but in the opinion of our Laboratory are associated with grinding. It would therefore, appear that special precautions are necessary in finally grinding this type of steel and we would suggest that if it is desired to proceed further with the use of this class of material, it will be necessary to introduce a special stress releasing treatment of two to four hours at 130°C. before grinding. This will not soften the "case" but should prevent any cracking occurring during the grinding operation. We doubt whether it will be possible to save the existing shafts as it is very difficult to remove these cracks once they are formed, but it is worth while trying one shaft by stress releasing as above and then regrinding all over, both cams and bearings. We shall be pleased to learn the result of the experiment. BY/HM.{Capt. W. Hallam - Head Repairs} | ||