MACHINES. Brown cf. Sharpe's Automatic Gear Cutter, shown in Fig. 1, is automatic in all its motions, cutting through for each tooth. and revolving the wheel until all the teeth are cut. thus enabling the operator to attend to other work. The indexing is done by a worm and worm-wheel moved by change-gears. The blank being, put in place. and the cutter-head adjusted for length of i stroke, the wheel is lowered by a screw having a dial reading to thousandths of an inch, until the proper depth of cut is obtained, when the cutter passes the blank and back by a return movement ; the wheel is then moved the proper distance for the next tooth, and so on until finished. The cutter-head is adjustable at any for bevel-wheels, the being marked on a are, no other There is also pro vision for the cutter out of center each way, for bevel-wheels, lievel-(iear Cutler is shown in 2 and 8. The principle of the machine is explained as fellows: It is possible to make with any system of a rack which will correctly with any wheel of the set. Any wheel that correctly with this rack must therefore also correctly with any Other wheel of the set and from this it follows that if any number of wheels are made to enrreetly with this rack. they mast :also correctly with one another. If the wheels were made of some soft material, say wax, the teeth could be formed by simply the blank into the rack. care taken that the pitch-line of the blank will roll on dial of the rack without slip. The desiralde clearance van be obtained by this rack just the converse of clearance. Gears are. how ever, made of material that can not he removed by pressure. and the process must therefore he modified. The teeth of the rack be made of hardened steel, with sharp at the ends ; and by giving them Wend motion the material could he 1-iit away instead of pressed 10 one side. The 2) shows how the tooth of an involute rack would col its way the blank. I lins one of the spaces between two teeth.
This is. in fact. the process by which this gear-caller nevomplishes its work. The
tool represents one tooth of a rack to an set of and it obtains mot Mu in the manner of a shaper-tool. while the blank receives a movement as it were rnllitig ou its pitch snrfnee. In the tool the rack toot It, while passes the depths or piteltes: therefore the line or involute rack-toeth is the only available one for this purpose. The tool, instead of parallel with the line. Mils! NW parallel with the 'Raton) of the space. This will he more readily understood if it is considered that the rack of n is else lint it bevel-gear a pitch of ISO° at the apex. or a flat. eireular disk. with teeth con fr the eireumferenee toward the center. The look should rim. Ihe outline of lhe or lids pfini,whi,i: mid it is evident, therefore, that only tale side of the 14)11VCrgillg space can be hirmed ciirreelly at n limn.
The machine, then, consists of two principal parts—the shaper, which holds and operates the tool. arid what may be called the evolver, which holds and moves the blank. In order that the blank shall imitate the movement of a rolling cone, the axis must, in the first place, be moved in the manner of a conical pendulum. To accomplish this, the bearing of the arbor which carries the blank is secured in an inclined position between two uprights to a semi circular horizontal plate, which can be oscillated on a vertical axis passing through the apex of the blank. To complete the rolling action, the arbor must, in the second place, receive simultaneously the proper rotation, and this effect is produced in the machine by having a portion of a cone (corresponding with the pitch-cone of the blank) attached to the arbor, and held by two flexible steel bands stretched in opposite directions, thus preventing this cone from making any but a rolling motion when the arbor receives the before-described conical swinging motion. One end of each of the two bands, of course, is attached to the cone, while the other is attached to the framework of the evolver.