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).
Manufacturing methods for Bakelite threads, hard rubber inserts, and a cost analysis for a synthetic molding department.
| Identifier | ExFiles\Box 39\3\ Scan097 | |
| Date | 24th May 1921 guessed | |
| -4- (4) THREADS. Threads of great accuracy and fine finish are produced in Bakelite by use of a hardened steel insert in the die, which is threaded externally for an internal thread and vice versa. These threads can be in the line of pressure or at any angle to the line of pressure. The insert comes away with the job and is then screwed out of it and replaced in the die. Such loose pieces add seriously to the cost of dies and are avoided if possible by using a screwed brass insert which is left in the mold. (5) HARD RUBBER INSERTS. All distributors with rubbing contacts have hard rubber inserts molded in them. The Eisemann magneto has a hard rubber track and hard rubber collector post molded into the distributor head. It is impossible, however, to distinguish the two materials, since they are the same color. The rubber is formed and vulcanized in preform dies, before molding. (6) COST. A pair of presses suitable for our work of say 500 tons (for big work like the steering wheel) and 100 tons with hydraulic accumulator for 5000 lbs. water pressure, would cost, with necessary equipment (according to the Bakelite Co.) about £5,000 or £6,000. The cost of dies mentioned in my letter of May 19th. totals £4,000, and represents probably less than the cost of making these by expert die-makers trained to the job, since all our suppliers have given us prices which charge up a fair proportion of the die cost on the parts produced. With the difficulties in die construction, etc. which might be expected in starting up a synthetic molding department at Derby, one would expect the cost to be greatly in excess of the two thousand pounds indicated above. As suggested in my letter of April 9th on this subject, we think it would be best to purchase Bakelite moldings required from the Damard Lacquer Co. of Birmingham, or Condensite moldings from J.{Mr Johnson W.M.}& F.Hill of Sheffield, rather than to undertake such a new and specialized branch of manufacture at Derby. This would be strictly along the lines which are found best by manufacturers of electrical machinery in this country, where the Westinghouse Co., the General Electric and the Delco Co. | ||