Discussion on "Screw threads" at the Western Section of the Institution

MR. DAUNCEY : We have all been interested in what Mr. Kenworthy has told us to-night, but we are sorry that he has not touched upon the manufacturing side of screw threads, which I think is one of the biggest problems, to get them to agree with the elaborate gauge system which he has described, and in use to-day. We should very much like to have some of his ideas on machining threads on various materials, particularly duralumin and stainless steel. We have found considerable difficulty with dies on duralumin. We use the Coventry diehead and dies and they screw the threads quite well, but the dies do not seem to stand up to the work. We also have difficulty in screwing up to the shoulder to the limits allowed by the authorities. Another difficulty is to machine a thread on stainless steel. With regard to the development of ground threads, I should like to know why it is thought advisable to grind threads. I appreciate the necessity for having a perfect fit in some instances. Would he recommend it for commercial work¿the better class work and aircraft work¿and is there all that practical difference and advantage in having ground threads ?