291,478. Garrard, C. G. Dec. 4, 1926. Nuts.-In a machine for cutting an annular recess or groove in the bore of a nut, two tools are inserted from opposite ends of the bore and operate on different parts of the recess. The tools are spaced preferably 180‹ apart. and may rotate in the same direction while the work remains stationary, or the tools may be stationary while the work rotates, or the tools and work may both rotate in opposite directions. As applied to a machine for cutting an annular groove in nut blanks to form self-looking nuts, a nut is gripped between members 17, 18, Fig. 1, operated by a rod 21 attached to a pedal 22. The two tools are carried by barrels 26 fed axially to and from each other by toothed racks 30, toothed bell-crank levers 31, links 34 and a rod 35 attached to the pedal, the tools being rotatably mounted in the barrels and their cutting edges being 180‹ apart so that they operate on opposite ends of a diameter of the work. Each barrel 26 is slidably mounted in a casing 16 and carries, by means of ball bearings 28, Fig. 3, a sleeve 27 having keyed thereon a pinion 29 driven by a pinion 26<a>, the two pinions 26<a> being keyed at opposite ends of a shaft 24 belt driven at 25. Each sleeve 27 has at one end a guideway 38 preferably inclined at 45‹ to the axis, in which slides a tool-head 37 carrying a tool 44. A pin 43 in the tool-head engages an inclined recess 42 in a plunger 39 passing through the sleeve and rotatable therewith. In operation nut blanks are inserted and removed by hand and depression of the pedal 22 first clamps the work 20 and next feeds the barrels 26 towards each other. A spring 45 normally retains the plunger 39 in a retracted position so that the head 37 is concentric with the sleeve 26, as shown in Fig. 5, and the tool can pass freely into the work. When the tool reaches the position of the desired recess, however, adjustable nuts 40 on the plunger engage a ball-bearing washer 41 on the casing 16 and prevent further movement of the plunger, whereupon the sleeve 27 slides relatively thereto and the head 37 is displaced along the guide 38, the line of movement of the point of the tool being parallel to the pin 43 and determining the angle of the side of the recess being formed. Each tool acts on one side only of the recess which is completed when the tools reach the apex as shown in Fig. 10. In order to limit both the depth of feed of the tools and the rate of feed, a worm 50, Fig. 11, driven by a chain from the shaft 24, drives a worm wheel 51 having an annular recess on one face in which is mounted a concentric disc 53 freely rotatable on the spindle 32 to which the bell-crank levers 31 are keyed. The disc has ratchet teeth, or balls and ratchet recesses, engaging the worm wheel, the arrangement being such that the worm wheel may be driven in the direction of the arrow 56 without rotating the disc. A spring 54 normally maintains a stop 57 on the disc in contact with an adjustable stop 58 on the casing 49, but when the pedal 22, is depressed to feed the tools towards each other a lever 59 keyed to the spindle 32 is oscillated in the direction of the arrow 56 and carries the stop 57 with it, thus rotating the disc at any desired speed less than that of the worm wheel and limiting the maximum rate of feed of the tools. Stops 60 on the casing 49 limit the oscillation of the lever 59 and thus limit the depth of feed. The cutting tools may be lubricated by slurry circulated by a pump driven from a countershaft. The shape of the groove formed by the machine may be varied, e.g. U-shaped, channel or dove-tailed grooves may be cut by arranging the guide pins 43 at the corresponding angle. The operation performed by the machine may be one of the operations to be carried into effect on an entirely automatic machine for making nuts, in which case bar stock of hexagonal or other section is fed by a reciprocating gripper against a stop, whereupon it is automatically gripped in an index plate and prevented from receding by a non- return gripping device whilst it is operated upon by a twist drill. Simultaneously with the action of the drill, the faces of a nut are machined and chamfered and the nut is cut off by cutters rotating around the work and fed by cams on a common cam shaft. The index plate is then rotated through 60‹ and the cut-off blank is grooved by the tools 44 whose feed is controlled by cams. At the next station of the index plate the nut is threaded and at a further station it is held on one side whilst indications such as a number, name or trade mark are rolled into the face by a marking tool. According to the Provisional Specification, two diametrically opposed cutting- off tools are mounted out arbots adapted to swing to and from the centre of the work, each arbor carrying a pinion engaging an internally toothed wheel also provided with external teeth, the external teeth and similar teeth on a wheel which drives the cutting-off head being engaged by two coaxial driving pinions which are keyed to a shaft by straight and helical keys respectively so that endwise movement of the shaft by a cam will cause the tools to be fed radially whilst the head is rotating. The spindle of the tap for threading the nuts carries a screwed sleeve rotating in a nut and its rotation in opposite directions is controlled by a pair of clutches on a shaft geared thereto, the clutches being actuated by a camoperated lever which fulcrums on one! end of the tap-spindle. This clutch shaft may also rotate a crank frictionally, the crank serving to oscillate a ratchet cam for feeding the index plate and operating the work-gripping devices thereon.