The may be regarded as a great advance upon the grind stone, and, for certain purposes, as greatly superior to the emery- and corundum-wheels, particularly for unnecessary masses of metal and for bringing pieces down to a desired profile. It may be considered as a rotating planer or shaper-tool. By its use the cheap and rapid production of desired profiles may be effected by power with great uniformity and per fection of result. Its cut is usually in straight lines; as a general rule, the object to be milled is not rotated. In some machines the cutters have only a rotating movement and the work is fed to them in straight lines; in oth ers the cutter has a traverse and the work remains fixed; while in some machines both the cutter and the work are fed. The metal-milling ma chine finds its high-speed counterpart in the planing, matching, moulding, and tenoning wood-working machines employing cutters upon a rapidly rotating shaft, the blades having a working length equal to, or greater than, the width of the surface to be removed, and their profiles effectively corresponding to the outline of surface to be produced. The milling-cut ter as sometimes used is akin to the rotating drill; again it resembles in its operation and product the routing-machine. Countersinking-machines show good examples of both such resemblances, some of them working both with the cylindrical periphery and with the end of the rotating cutter-bit. Mill ing-cutters are either solid—in which case they always lose their size as they are worn by work and sharpening (sometimes losing in effectiveness or working diameter and thickness for the same reason)—or have their cut ting-edges so disposed with regard to the mass and the cutter, and with reference to the body to be worked, that even as they are ground down they make the same size and profile of cut. The latter is a most desir able feature, and exists nowhere in greater perfection and to greater advan tage than in cutters for working out the spaces between the teeth of gear wheels.
Afiging r to 24 (pl. 29), which the following ex planation will enable the reader to understand fully, are exceedingly inter esting. Figurer shows how hexagon nuts or heads of bolts are milled with a single cutter; Figure 2, how a number of nuts while strung ou a mandrel are milled at one time with two cutters; Figure 3, how a number of caps are milled, and how at the same time their sides and bottoms are accurately finished; Figure 4, how a T-slot is milled having a groove milled or planed to the proper depth; Figure 5, how a V-slot is milled; and Figure 6, how the guides of a housing are milled. This can be done with a cutter the width of the guide or with a saw about inch thick, finishing one side and then the other. A small cutter should then be applied to finish the inside bear ings. The housing requires but one chucking. Figure 7 shows how to turn out a hole with a boring-bar arbor. Various work can be drilled and bored out to advantage in this way, either by bolting the work on the table, by gripping it in a vise, or by holding it between centres. Fig ure 8 shows how to mill a key-seat in a vise or between centres; Figure 9, how to mill a taper-reamer; Figure TO, how to cut a number of gear wheels when strung on a mandrel; Figure rr, how to mill a tap; and Figure 12, how to hob a worm-wheel after the teeth are cut. The latter operation gives the teeth the proper shape, so that the shafts will stand at right angles to each other. Figure i3 shows how to cut off pieces of metal, and Figure 14 how to mill a tool, the milling-cutter to be V-shaped and at an angle of 6o°. First one side and then the other can be milled without re-chucking. Figure 15 shows how to mill an angle, finishing, at the same time, the sides and bottoms; Figure 16, how to mill a slot with a small cutter; Figure 17, how to mill a fork true with its round shank, one end being held in a universal chuck, which is screwed on the spindle of the indexing centre, and the other in a steady-rest; Figure 18, how to cut a rack; Figure 19, how to mill boxes perfectly true with the hole; Figure 20, how to mill an angular cutter; Figure 21, how to index dial-plates, the tool not revolving; Figure 22, how to mill a cam; and Figure 23, how to mill a friezing,-bit for wood-work. First the sections are milled out with a square-faced cutter, and then the cutting edges are milled by placing a right-and-left angular cutter on the milling arbor. These bits can be milled complete before removing them from the
mandrel. Figure 24 shows how to cut off round or square stock by placing the universal chuck on the main spindle and using the overhanging ann for a length-gauge.
The Automalic shown in Figure 8 (6/. 23), is used for automatically cutting or milling teeth upon the periphery of blank wheels for cog-wheels, or, as they are more properly termed, gear-wheels. To cut gears it was formerly necessary, when the means of the manufacturer were limited, for the operator to put in his entire time at the machine, since, after having the blank wheel and cutter in position, he had to feed the cutter through by hand, withdraw it, and then give the divisions on worm-gear or dial, repeating this operation as each tooth was cut on the wheel. With the gear-cutters known as " half-automatic " the operator goes through the same work, with the exception that the cutter feeds itself through the wheel and then stops. The workman then withdraws the cutter, gives the required divisions by hand, sets the self-feed, and then procelds, repeating the operation for each tooth on the wheel. Nearly his whole time and attention must be given to this machine when in operation, because it feeds the cutter only through the teeth.
With the automatic gear-cutter the workman can without attention cut either bevel-, spur-, worm-, or face-gears, and after the machine has been set and started it can be run at a slight expense. He sets the blank to be cut, adjusts the machine and starts it running, and then can go about other work and let the machine take care of itself. The machine feeds the cut ter through the wheel, draws out the cutter, and makes every change or division of the worm-wheel itself. It makes the divisions with perfect accuracy, the dividing-disc making only one revolution for any number of teeth; and when properly set, mistakes are impossible. In a hand machine mistakes are liable to, and often do, occur. When done cutting a wheel, the machine strikes a gong, thus notifying- the workman to come and put in another blank. It is constructed of the following principal parts. The main frame is in the shape of the letter L, upon, the front face of the vertical portion of which are two V-tracks, placed for the align ment of a vertically movable head, which contains the barrel and spindle for holding the work, this spindle or work-mandrel being inside the barrel. To the outer or rear end of this barrel is fastened a worm dividing- or master-wheel. Alongside this master-wheel, but fastened to the movable head, is suspended a back or frame. The worm-shaft, engaging with the master-wheel, is supported from this back, as are also the bracket for placing the various combinations of change-wheels for dividing purposes and a one-revolution stop-shaft cam and trip. To the end of the worm shaft, opposite to the end on which the change-wheels are placed, is a slipping friction-wheel, which is driven from the counter-shaft, and which has a tendency to cause the shaft to revolve; but it is kept from doing so by the stop-shaft cam. This worm-shaft is permitted to revolve only for dividing purposes. The entire movable head and parts attached are raised and lowered by a screw with a hand-wheel, which is graduated for accu rate adjustment. The cutter is driven by a counter-shaft with a three- or four-step cone pulley, belted to a cone-stand on the floor, motion being given to the train of gearing driving the cutters by two universal joints with a slipping sleeve. This sleeve enables the cutter-slide to be placed in any position for either bevel- or worm-gears without affecting the length of the belts. For moving the cutter-slide in and out, motion is brought to its front part by means of a V-belt or light train of gearing from the train driving cutter-arbor. The in-and-out motion is obtained by two clutches, one for feeding, which revolves at a slow speed, the return motion being much quicker. These clutches run loose upon the shaft, but between them is a single clutch, which has teeth on each side, and which slides back and forth between the opposite running clutches on a key or feather, fastened in the same shaft. Thus, as this central clutch is made to engage with one or the other of the clutches, a back or a forward motion is im parted to the feathered shaft, which is connected to the screw operating the cutter-slide.