Mathematically speaking, a cone does not terminate at the apex. but is extended beyond, and thus consists of two opposite sides or surfaces meeting in the apex. Basing on this prin ciple. the rolling cone above described is placed on the side of the apex opposite that on which the blank is placed, in order to avoid an interference with the tool.
The feed mechanism effects a slow intermittent movement of the semicircular plate which supports the inclined arbor, thereby producing a slowly progressing rolling of the blank while the reciprocating tool forces its way through the metal. The feed can be reversed or disengaged altogether, permitting the blank to be rolled to the one or the other side by a hand-crank.
The arbor carrying the blank can be rotated independent of the rollinA. cone by means of a worm-wheel, worm and index plate, which enables the blank to be presented to the cutting de vice at properly spaced divisions corresponding with the number of teeth of the desired wheel.
It is essential that the tool should be so adjusted that the lowest point of the cutting side should move exactly toward the apex of the blank, and, in order to set the tool, a gauge is provided by which the tool can lie adjusted. A distance-block is used between this gauge and the tool this mode ;Willits of a high degree of accuracy, since variations of distances can readily be detected by the touch when the eve ceases to discern.
When a wheel is to be cot out of the solid, the tool is at first adjusted at a slight distanee from its correct position, and cater each cut the of the evolver causes the blank to slowly roll, and allows the tool to cut out the stuck in the manner shown in the diagram. All spaces are now treated in the same manner by using the index device, whereat con the tool is properly adjusted for one and then for 1he other side, each adjustment being followed by a repetition of the process in order to finish both of the teeth.
In securing the blank to the arbor, great care must be exercised in placing its apex exactly in the center of the evolver. A special device tandlles the operator to gauge the distance of the ends of the teeth from the center of the evolver, and whenever this distance agrees with that calculated from the drawing. the apex of the blank is in its right place.
The ineinnition of the arbor which holds the blank is made adjustable. so as to adapt it to
the angle of the desired gear. This adjustment must be exactly concentric with the center of the evolver—i. P.. the apex of theblank. The rolling cone is made detachable, in order that it may lie replaced by such cones as correspond with the angle of the blank to be cut : but as the number of cones required would be unlimited, 11leallS have been devised to make a hunted of cones suffice.
The tool consists of 1 triangular liar of hardened steel, forming, at the point an angle of on each side. and held by a special holder. By grinding, it can be more or l s, truncated to suit the pitch of the gear to he cut. liy this form of tool a higher degree of accuracy is attainable than with tools having curved faces made to a gauge. The proper up-and-down and sidewise adjustment is effected by two slides working it right angles. and operated by screws. The clamp which fastens the tool-holder is so constructed that it also clamps the slides to the apron, securing the necessary stability. The box in which the apron works is !node in parts, and the faces are turned true with the pin-holes, in order to get these faces exactly at right angles with the pin. The latter is fast in the apron, and revolves in the two sides, in which it has taper fits that the wear may be taken np. A device for lifting the apron during the return-stroke prevents the dragging, of the tool.
The tool-bar is moved by a Whitworth quick-retinal motion, which is attached directly to the belt-pulley. A double counter-shaft con nected by cone pulleys is employed to change the speed, if a shorter or longer stroke is desired.
1;'Lrritardf's A otomatie Gear-Culler (Fig. 4) shows a machine fur cutting gears only. made by Gould & Eberhardt. Newark, N..f. It is designed to cut gears of a pitch as coarse as and 20-in, face in steel; and is arranged so that two cut ters, one blocking and one finishing, may he placed and run through tog,etlwr. The cutter-spindle has ample bearings on each side of the cutters. The wheels to he cut are held on the I1(11'i 711111111 111/111111TI. WhiCh has a rigid outward support and bearing. (miter is hold by a spindle lit right angles to the work-mondrel. on a slide which' is fed :nit onnit i eolly by the screw seen in t he cut.