Patent GB-640142-A (GB)
Title: Screw-cutting machine working with a tool
IPC: B23G1/02
Filed: 1946-01-05
Abstract: 640,142. Screw-cutting lathes. SOC. CRIDAN. Jan. 5, 1946, No. 480. Convention date, Jan. 9, 1945. [Class 83 (iii)] An automatic lathe for cutting screws by a number of traverses controlled by a cam has a second cam for controlling the. depth of cut and an automatic stop when the predetermined numbers of cuts have been made. The saddle is adjustably fixed on the bed during operation, the feed mechanism being mounted in the apron and the traverse being obtained from a slide rest mounted on the saddle and in turn mounting a cross slide for applying and removing cut and a top slide for adjusting the initial position of the tool. The lathe is driven from a motor 4, Fig. 1, by belt to a continuous change speed gear 6 transmitting by belt 30 to a pulley 29, Fig. 7, mounted in ball bearings 31 and roller bearing 32 on a sleeve 15 fixed in the headstock. The spindle 8 is mounted, independently of the pulley, in bearings 17, 18 and has splined to it at 37 a combined clutch 35 and brake 47 engaging the pulley and splined sleeve 16, respectively. A ring 39 mounted on the clutch by a ball race 38 provides for operation by a yoke 40 and lever 43, Fig. 6, actuated through a spring 45a and lever 45 by a screw 62 in one arm 61 of a lever having another arm 60 opposed by a finger 59, Fig. 4, on a rockshaft 50 controlled by a handle 49 and spring 51. A second finger 54 on the shaft 50 cooperates with a lever 55, Fig. 8, having another -armconnected by a rod 57, Fig. 4, to a lever 28, 27 controlling the draw spindle 21, Fig. 7, of the bevel closing chuck 19 in opposition to the closing spring 25. A pin 58, Fig. 8, limits the movement of the finger 54. The chuck is opened by movement of the lever 49 in the direction f<SP>1</SP>, Fig. 4. Movement of the lever in the direction f<SP>2</SP> permits the chuck to close and causes the finger 59 to bear on the lever 60 to release the brake and engage the clutch, in which position an arm 63 of the lever 60 is locked by a spring bolt 64 operated by a rockshaft 67 when release is required. Feed is transmitted from the spindle at 69 through change gears 76 to 77 and reversing gear 83 to a shaft 88 splined to a pinion 120 mounted on the saddle. Bevel pinions 89 drive an indicator for the spindle speed. The saddle 9, Fig. 11, slides on ways 1a, 1b on the bed under the control of gibs 95, 96, provided with locking bolts 97, Fig. 4, operated by eccentrics on a hand-operated cross-shaft 101. A plate 103 fixed to the saddle carries ways engaged by rollers on a traversing slide 105, the rollers being journalled on eccentric pins to provide adjustment for wear. Springs 128 mounted between the plate 103 and the slide 105, and confined by lugs on these parts, maintain a roller 127 on the slide against a cam 126 that controls the length of pitch of the threads cut. The cam is mounted to permit interchange. The means for removing the tool from the cut at the end of the stroke, returning the slide, for applying depth of cut feed, returning the tool to the cut and stopping the lathe at the end of a cycle are as described in Specification 640,141. The tailstock is split at its base for clamping on to the ways on a sole-plate 193, Fig. 4, secured to the bed by means of a handled screw 196. The spindle is advanced to the work by a spring 198 and is retracted by a lever 201 on a rock-shaft 200, Fig. 25, having arms 199 engaging in shaped notches 197a cut in the spindle, a cam surface 197b co-operating with the ends of the arms 199. After the lever 201 has been moved in the reverse direction tc move the arms 199 to a clear position, and allow the spring 198 to advance the back centre, linkage 203, Fig. 4, rocks a screwed spindle 205 to clamp the spindle by pads 206. Specifications 624,612 and 636,664, [Group XXIV], are referred to.