Patent GB-568234-A (GB)
Title: Improvements in or relating to apparatus for cutting internal screw threads
IPC: B23G1/16
Filed: 1943-04-12
Abstract: 568,234. Taps. PIPE MACHINERY CO. April 12, 1943, No. 5831. Convention date, June 29, 1942. [Class 83 (iii)] A taper threading collapsable tap has an inner slide for moving the chasers by axial movement thereof in the body, an outer slide movable axially on the body and engageable with the work to move the inner slide rearwardly, for taper threading, as the body is advanced, and means connecting the inner and outer slides for moving the former forwards and the latter backwards to disengage the inner slide from the chasers to permit removal thereof. The tap comprises a body 1 attached to a rotary machine spindle 2 and having a head 1b accommodating the chasers 7 in slots 1g. The wedge core 8 constituting the inner slide has grooved connection with the chasers for positive actuation in both directions and is attached to a sleeve 9 splined within a worm-wheel 11. A plunger 10 engages the sleeve 9 by screw-threads 10a and is connected by the taper-forming cam 34 to an abutment 14 slidable within the body and normally locked, against the action of a spring 39, by a spring detent 41. The outer slide consists of a sleeve 16 splined on the body and provided with and end flange 20 for engaging the work W. A cam bar 27 is pivoted inside the sleeve at 28 and may be given various inclinations to the vertical by a selflocking screw 30 to adjust the taper produced on the work, a scale.33, Fig. 3, on the outside of the sleeve indicating the setting. In operation, the diameter of cut is adjusted by rotating a worm 12, through an aperture in the sleeve 16, to rotate the sleeve 11 and vary the axial position of the wedge 8 relatively to the abutment 14. As the spindle 2 is advanced the flange 20 engages the work to arrest further movement of the sleeve 16, whereupon continued advance of the body 1 causes a roller 26 on a transverse slide 22 in the body to ride along the inclined cam 27, thereby moving the slide laterally and carrying with it the splined cam 22 which retracts the wedge 8 progressively through an inclined cam bar 34b. When the desired length of thread has been cut, an adjustable stop 49 on the sleeve 16 engages a spring- pressed trigger 46 which is then moved rearwardly on the body to release the latch 41 arid allow the spring 39 to withdraw the abutment 14, carrying with it the wedge 8 to collapse the chasers. To reset the tap, feed of the spindle 2 is. reversed by mechanism actuated by a ring 55 moving with the abutment 14 and the spindle is raised until a bracket 60, resting on the top of the sleeve 16 and slidable in a guide 61 on the machine frame, contacts a fixed stop 62 to arrest further upward movement of the sleeve 16. Keys 58, Fig. 3, which form the splined connection of the sleeve 16 on the body, then arrest upward movement of the ring 55 to which is attached a transverse bar 54 passing through the abutment 14, whereby the abutment is moved relatively to the body against the spring 39 until again locked by the latch 41, the trigger 46 then returning to the position shown in Fig. 1. Parallel threads may be cut by adjusting the cam bar 27 to a vertical position and the length of thread cut is indicated by graduations on the wrench 53 used for setting the stop 49. The tap may be collapsed at any time by movement of the trigger 46 through a handle 48 thereon and the tap may be reset by moving the ring 55 upward manually. To remove the chasers from the body without affecting any of the settings, the wedge 8 is advanced through the body until the chasers become detached from the rear end thereof, as shown in Fig. 12. This is accomplished by withdrawing a key 66 which normally secures two rings 59, 64 together, the ring 59 having a fine-pitched screw connection with the sleeve 16 and the ring 64 having a coarserscrewed connection, of opposite hand, with the ring 59 and being splined at 65 to the sleeve 16. Rotation of the ring 59 by a tommy-bar, whilst upward movement of the ring is prevented by the bracket 60, will move the flange 20 upwardly clear of the chasers and the ring 55 downwardly, through the keys 58, thereby advancing the wedge 8 to release the chasers. Lubricant or coolant is fed to the chasers during operation by a pipe 69 and a non- rotatable ring 68 attached to the lower end of the sleeve 16 by rings 17, 18 which are apertured at 17a, 18a to deliver fluid to an annular passage 18b leading to radial ports 18c. Specification 577,452 and U.S.A. Specification 2,265,764 are referred to.