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).
Letter from Hoffmann Manufacturing Co. Ltd. concerning hardness testing on a returned bearing.
| Identifier | ExFiles\Box 9\7\ 07-page156 | |
| Date | 5th March 1938 | |
| BRANCHES: LONDON, BIRMINGHAM, MANCHESTER, LEEDS, GLASGOW. AGENTS IN PRINCIPAL COUNTRIES THROUGHOUT THE WORLD. HOFFMANN Registered Trade Mark BALL-AND-ROLLER-BEARINGS STEEL-BALLS-AND-ROLLERS THE HOFFMANN MANUFACTURING Co. LTD. CONTRACTORS TO THE ADMIRALTY, WAR OFFICE AND INDIA OFFICE. CHELMSFORD. TELEPHONE: 3151 (Five Lines). TELEGRAMS: HOFFMANN, CHELMSFORD CODES USED: A.B.C. 5TH EDITION, BENTLEY'S PHRASE, BENTLEY'S 2ND PHRASE, MARCONI AND WESTERN UNION 5 LETTER. MESSRS. ROLLS-ROYCE LTD., DERBY. 5th March 1938. YOUR REF. Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}9/MH.{M. Huckerby} IN YOUR REPLY PLEASE QUOTE OUR REF. JLH/WAH. Dear Sirs, For the attention of Mr. F.J. Hardy. Your letter dated February 3rd has been carefully considered by our Technical Manager, Mr. C.H. Smith and the Writer and we have carefully examined the N.2790 bearing which you returned. We normally employ for hardness testing the Vickers machine, but in view of the readings given in your letter, we attempted to carry out a check on the outer race of the bearing on our Rockwell machine. The results of this check were not at all satisfactory, as due to the conical surfaces of the race, difficulty was experienced in supporting it rigidly with the result that the race moved under the testing load, so causing a low reading. On the Vickers machine, we obtained readings of H.D. 746 - 761 which are equivalent to Rockwell C.60 - 60.5 which is within the range of hardness you specify. As, however, we wish to be quite certain that this conversion from one scale to the other was correct, we have sectioned the race so that direct readings with both types of test could be obtained without risk of movement of the specimen and find that the Rockwell hardness mentioned above is confirmed. We are returning the sectioned race to you under separate cover, in case you may like to verify our readings and are arranging to replace the outer race prior to returning the other parts to you. We note your instructions regarding frictional resistance in the assembled bearings which are, of course, confirmed in your letter of the 2nd instant and are looking closely into this on the parts/ | ||