GB617905A - Improvements in or relating to screw blanks - Google Patents

Abstract

617,905. Making screw blanks. WATERBURY FARREL FOUNDRY & MACHINE CO. April 2, 1946, No. 10167. Convention date, April 21, 1945. [Classes 83 (ii) and 83 (iv)] Forging; extruding; cupping; dies.-A method of making a screw blank with a socketed head comprises cutting a workpiece from a length of solid stock, heading the workpiece and extruding the body thereof while forming a socket in the head with flattened areas on the side walls of the socket. The forming of the blank is carried out in a machine comprising a die holder with a number of dies which co-operate with a number of punches carried by a reciprocating gate. The blank is transferred from station to station by known mechanism. At the first station a length of rod stock is severed and then moved into the path of a punch 20 at the second station, Fig. 2, by which it is pushed into a die 17 and upset to form a conical head portion 23. After ejection by a pin 19 the blank is moved to the third station, Fig. 3, where the head is again upset to the form shown and in addition is indented at 34 by the coned end 30 of a pin 29 operating within the punch 28. At the fourth station is a further heading-die 35, a backing-die 36, an extruding- die 37 and another backing-die 38, while the punch 41 has a conical tip 44 on a hexagonal or other polygonal base, the sides of the polygon constituting the ends of flat faces 43 tapering at an angle of approximately twelve degrees relatively to the cylindrical outline of the punch. The tip 44 engages the indentation 34 and pushes the blank into the dies so that the forward end is extruded through the throat 46 of the die 37 to form the portion 45 to be screwthreaded. In addition, the head is further shaped externally by the die 35 and is formed with a conical socket of roughly polygonal cross-section by the punch 42 as shown in Fig. 4. At the fifth and last station, Fig. 5, the punch 54 has a cylindrical end of polygonal cross-section adapted to enter the previously formed socket and to push the head through a die 51 having a throat 52 by which the head is drawn to cylindrical form externally and is closed in over the punch to form a cylindrical socket of polygonal cross-section. During this operation, the stem of the blank is supported within a tubular guide 53 which moves rearwardly with the work. On the withdrawal of the punch, the blank is stripped by a member 57.