Patent GB-227465-A (GB)
Title: Improvements in method of and machine for milling threads
IPC: B23G1/32
Filed: 1925-01-10
Abstract: 227,465. Mirfield, G. E. Jan. 11, 1924, [Convention date]. Milling screws.-In a thread-milling machine, particularly for milling tapered or parallel threads on the ends of pipes or tubes, a roughing cutter, arranged in front of the threading-cutter is first brought into operation to trim up the end of the work, the threading-cutter being subsequently fed in tangentially to depth and both cutters then continuing in operation until, after slightly more than a complete revolution of the work, the threading is completed. The machine is provided with an adjustable bracket 5 supporting the outer end of the arbor 7 driven from the main-shaft 8 and carrying the threading-cutter T which is preferably of taper form and has annular teeth without pitch. The table 11, adjustable by a screw 12 carries a slide 10 which supports a longitudinal slide 4 provided with the usual automatic feed and a quick-return manual feed operated from a hand-wheel 13. The slide 4 carries a base 20 secured by bolts 21 and provided with an adjustable block 23 having bearings for the spindle of the roughing-cutter R and a housing 24 in which is journaled the work-spindle 25. Further bracket supports are provided in the base for a counter-shaft 27. The block supporting the roughing cutter is movable on ways 22 and is traversed by a cam 39 mounted on a pivot 40 carried at the rear of the bed. The spindle of the roughing-cutter is driven from a gear 140 on the arbor 7 through gearing carried by links 143 while further gearing from the spindle serves to drive the countershaft 27. The cam 39 is driven from the countershaft through worm-gearing 55. A segment 60 secured to the rim of the cam effects the positive withdrawal of the roughing- cutter at the required time. The hollow workspindle 25 is driven from the countershaft through worm gearing 100. Axial movement of the spindle during thread-cutting is effected through a master thread 110 which is of greater pitch than the thread to be formed and which coacts with a nut 112 driven from a gear 114. The latter is mounted on a sleeve having a clutch portion 120 engageable with a wheel 121 driven from the work spindle, the clutch being normally engaged by a spring 123. The nut 112 is thus driven in the same direction as the spindle at a relative speed depending on the pitch of thread to be cut. On completion of the threading, a ratchet wheel 117<1> is automatically actuated to rotate the gear 114 reversely to return the workspindle to its starting position. The axis AB, Fig. 13, of the work-spindle is slightly inclined so 'as to be parallel to the tapered sides of the threading cutter, but the axis of the work and cutter are parallel to each other. The ball connection 76 permits of this adjustment. In operation the outer end of the work is rotatably supported and the roughing cutter is first brought up and fed radially by its cam into the work (Fig. 12b). At a predetermined point, a dog 63 on the cam actuates a trip rod 29 tu engage the automatic table feed to carry the pipe beneath the threading cutter, which attains its full depth when the position shown in Fig. 12<c> is reached. At this point the automatic feed is disengaged by means of an adjustable dog 150 and the pipe is moved axially and its rotation continued through rather more than a further revolution to complete the threading operation. Mandrels; lathe and like drivers and carriers. -The work spindle is journaled in a split bushing 70 adjustable by a ring 71, the forward end being provided with a cupped head 72 carried in a similar bushing 73 and accommodating a ball 76 driven with the spindle by means of a stud 79. A rotatable collar 93 is retained on the front end of the ball by a cover plate 95 and is provided with cam tracks so that by rotatirg the collar, spring pins 92 may be pressed forward to engage a groove 91 in a chuck member 88 which is therebv drawn onto a centre 81. The chuck comprises a number of balls 85 and by screwing the member 88 into its carrier 86, the balls are caused to actuate blades 87 to grip the work. For driving the work the plate 95 is provided with a dog entering between spaced lugs 99 on the chuck.