GB1489512A - Screw thread cutting device for a centre lathe - Google Patents

Abstract

1489512 Screw-cutting DUPLOMATIC MECCANICA APPLICAZIONI OLEODINAMICHE SpA 2 Oct 1975 [4 Oct 1974] 40337/75 Heading B3T A thread cutting device for a centre lathe comprises a base 1 which is mountable on the lathe carriage, a slide 7 mounted on the base for movement parallel to the main axis of the lathe, a control mechanism 2 which derives its movement from the lead screw of the lathe and causes reciprocating movement of the slide on the base, and a first resilient member 10 for urging the slide into engagement with the mechanism. A tool carriage 14 is mounted for sliding movement transverse to the main axis on the slide 7 and is cyclically moved by a control rod 17 displaceable axially of the slide to disengage the tool at the end of each thread cutting press and re-engage the tool at the end of the return movement, a second resilient biasing member 22 urging one end of the rod into engagement with means 19 for cyclically moving the rod axially. The other end of the rod is connected by an inclined plane coupling 27, 28 with the tool carriage and causes transverse movement thereof, the coupling comprising a sliding block 27 engaging a groove 28 in an insert member fixable in one or other of two positions, the movement of the carriage being limited by one or other of two sets of stops 41, 42 according to the position of the insert member. The arrangement permits either internal or external screw threads to be cut with the tool always operating on the same side of the main axis of the lathe. The control mechanism 2 has an input shaft 3 driven by the lead screw of the lathe and an output shaft 4 driving a cam 5 having faces 6, 19. Cam face 6 engages a follower 8 on the slide 7 to effect reciprocation thereof parallel to the main axis of the lathe, the member 10 in the form of a spring maintaining the follower 8 in engagement with the face 6. The cam face 19 co-operates with a follower 20 on one end of the rod 17 which is guided for axial movement in the slide 6, the second member 22, also in the form of a spring urging the follower 20 into engagement with the face 19. The other end of the rod has a sliding block 27 which engages the groove 28 of the insert 29 which is mounted in the carriage 14 guided for transverse movement along guideways 13 in the slide, the carriage having a tool support 15 for an internal or external screw-cutting tool. The insert can be secured in the carriage in one or other of two positions so that the groove is inclined in one direction or the other to cause movement of the carriage towards or away from the main axis of the lathe upon movement of the rod 17 away from the cam 6 depending on whether internal or external screw-cutting is to be effected. The movement of the carriage towards or away from the axis during external or internal screw cutting, respectively, is limited by engagement of a locator 44 on the carriage with one or other of sets of stops 41, 42 formed on opposite sides of a groove 43 in a member 37 mounted in the slide and rotatable by a knob 40 or in steps by a trip mechanism 38, 39 actuated upon reciprocation of the slide so that the tool is given an increment of feed for each reciprocation of the slide.