GB609504A - Improvements in or relating to self-locking threaded fastening devices - Google Patents

Abstract

609,504. Making nuts. WATSON, F. (Elastic Stop Nut Corporation of America). Dec. 28, 1945, No. 35078. [Classes 83 (ii) and 83 (iv)] [Also in Groups V and XXV] Powder metallurgy.-Self-locking nuts of the type in which the bolt impresses the thread either wholly or in part in the locking section of the nut are made by the powder metallurgy process. A mould corresponding to the hexagonal or other shape of the nut is formed in a member 18, Fig. 2, movable from station to station, and contains a hollow punch 22 fitted with a thin sleeve 24 and mandrel 26. The thickness of the sleeve determines the amount by which the bore of the locking part 10, Fig. 1, exceeds the root diameter of the threaded part 12. With the parts in the position of Fig. 2, the powder for the section 10 is filled in to the mould space. At the next station, the parts 22, 24 are lowered and the powder for the part 12 is added. Next, a punch similar to 22, but bored to fit the mandrel, is advanced into the mould and at the same time the punch 22 and sleeve 24 are differentially raised.. After compression, the parts 22, 24, 26 are all raised so that their end surfaces are level with the top of the mould and the compacted nut is ejected. The punch 22 preferably forms the chamfer on the nut and the upper punch both forms a chamfer and countersinks the bore. The nut is then sintered and the part 12 is tapped. In a modification, the punch 22 is in two concentric sections shaped to form the part 46, the inner punch part applying a greater pressure than the outer. In some cases, the tap may be such as to tap an incomplete thread in the locking section. When the metal is uniform throughout the nut, the first filling stage is omitted and all the powder is inserted with the parts in the position of Fig. 3. Electrolytic iron powdered to pass 100 mesh is compressed at from 50 to 150 tons per square inch, preferably 100, and is sintered at from 1700‹ to 2100‹ F. Carbon may be added up to 0.2 per cent or more. When a full thread is to be impressed, in the locking part, by the bolt, up to five, but preferably three per cent of lead is added to this powder for this part. Silicon and manganese may be added to the metal for the threaded part. A brass or copper locking part may be used with a ferrous threaded part or brass and bronze may be used. Brass with 60 to 80 per cent copper is compacted at 50 tons per square inch and sintered at from 1500‹ to 1700‹ F. The bronze has a copper content of from 90 to 95 per cent.