297,263. Shaw, J. C., and Shaw, R. D. Dec. 24, 1927. Milling-machines.-In a, die-sinking machine or an electric copying machine for milling cams of face, edge or drum type, a tracer engages a template which is a development of the cam profile and controls two pairs of electro magnetic clutches, one pair actuating a forward and reverse linear feed between the tool and work and a selected one of the other pair actuating rotation of the work. The linear and rotary motions take place intermittently and alternately. The machine comprises a bed 1, Fig. 1, on which is mounted a work-table 20 slidable on guides 19 and a stationary pillar 2 carrying the cutter 6 and tracer 18. Driving machine-spindles; axial spindle feeds. -The cutter 6 is carried by a spindle 5 mounted in a bearing sleeve 4 which is axially adjustable by a rack and hand operated pinion 8, the spindle being rotated by reduction gearing 10, 13 from an electric motor 16. Work-holders; work-table feeds; headstocks; revening-mechanism.-The blank 49, Fig. 1, from which a face or edge cam is to be cut is mounted on a shaft 33 adapted to be rotated through double worm gearing 34, 38, and spur gearing 2 from one of a pair of electro-magnetic clutches 44, Fig. 2, which are continuously rotated in opposite directions by a bevel gear 46 and an electric motor 47. The clutch armature 45, keyed to the spur gear 42, is actuated by the tracer to engage either of the clutches for rotating the work. The shaft 33 is mounted in a. headstock 32 adjustable on the table 20 by a hand-operated screw 30. For cutting edge and face cams the head-stock is secured by bolts 63 in the position shown in Figs. 1 and 2, but for cutting drum cams the headstock is rotated about the bolt 62 through an angle of 90‹, the bolts 63 then entering prepared holes in an intermediate table 28. The table 20 is traversed by a screw 21 having a clutch armature 25, Fig. 2, slidably keyed thereon and under the control of the tracer to engage either of a pair of electro-magnetic clutches 24 continuously rotated in opposite, directions by bevel gearing 27 and an electric motor 26. The screw may also be rotated by a handle 23. Copying-mechanism.-The template 54, Fig. 3, consists of a flat. plate of standard size graduated horizontally to indicate linear measurements and vertically to indicate angular measurements on the cam to be produced. The desired cam profile is set out on the graduated plate and cut to form an edge 57 against which the tracer 18 acts. The template is secured tc bars 53 on a member 55 attached to a vertical rack 50 which engages a pinion 52 on the work-spindle 33 and slides in vertical guides 51, Fig. 1, on a. bracket 48 attached to the headstock 32. When cutting face or edge cams the template is mounted as shown in Figs. 1 and 2, but when cutting drum cams, angle brackets are attached to the member 50 so that the template may still be mounted in a plane perpendicular to the axis of the tracer 18. The tracer comprises a spindle 67, Fig. 7, universally pivoted at 68, and similar in construction to the tracer described in Specification 233,747. The rear end of the spindle seats in a conical recess in a lever 69, pivoted at 70 and carrying an electrical contact 73 normally engaged with a fixed contact 74 by a spring 72. A further contact 78 on the lever is adjacent a contact 79 on a second lever 80 pivoted at 81 and influenced by a spring 82 to maintain a second contact 84 thereon against a fixed contact 83. The pairs of contacts 73, 74, and 78, 79 are in circuit with relay magnets 76, 91, and 88, 92 respectively, supplied by a low tension generator 94, the return leads being earthed through the frame of the machine at 71 and 95. The relays 76, 88 actuate a switch 77 controlling a high tension. supply from mains 96 97 to the electro-magnetic clutches 24 and 44 which effect the traversing and rotation of the work respectively, while the relays 91, 92 actuate switches 110, 111, connected in series in the high tension circuit of the clutches 44. A manually operated switch 107 closes the circuit to one or other of the clutches 44 in order to determine the direction of rotation of the work. At the commencement of the cutting operation the template is at the top of its stroke and the tracer contacts are in the position shown in Fig. 7 with the contacts 73, 74 closed so that the relays 76, 91 are energized. The, relay 76 throws over the switch 77 to energize the clutch 24 (L) and cause the work to be traversed in the direction of the arrow L in Fig. 2, while the relay 91 opens the switch 111 and prevents rotation of the work. When the tracer meets the template the spindle 67 is rocked and displaces the lever 69 to open the contacts 73, 74, de-energizing the relays 76, 91 and allowing the switch 77 to be brought into a neutral position by springs, while the switch 111 is closed by a spring 117 and the work commences to rotate. As a rising portion of the template increases the side pressure on the tracer, the lever 69 is rocked further so as to close the contacts 78, 79, thus energizing the relays 88, 92 and stopping rotation of the work while putting into operation the clutch 24 (R) to cause the work to move away from the cutter. Intermittent rotation and traverse in the direction of the arrow R in Fig. 2, continue until the rise in the cam has been surmounted, whereupon the pressure on the tracer is relieved, the contacts 78, 79 are opened and rotation alternates with traverse, in the direction of the arrow L while a receding part of the cam is being cut. When cutting a dwell on the cam both sets of contacts 73, 74, and 78, 79 remain open and rotation of the work proceeds uninterruptedly. After the work has made a complete revolution a tappet 50, Fig. 3, on the template rack 50 engages a limit switch 59 or 60 Figs. 3 and 7, according to its direction of movement, and breaks the circuit of the respective clutch 44 to prevent further rotation. If it should happen that the contacts 78, 79 of the tracer fail to act to stop rotation of the work the pressure on the tracer spindle will build up sufficiently to cause the lever 69 to rock the second lever 80 and open the contacts 83, 84, thus breaking the circuit to the clutches 44. When cutting face or drum cams the cutter is first fed the required distance into the work by the hand operated screw 30 and the intermittent rotation and traverse then proceed as before. Instead of having the tracer and cutter fixed, the traversing movement may be imparted to them and the work will then rotate only.