Fig. 219.

The use of drilling and profiling machines has long been associated with the manufacture of small arms and sewing machines.

The chief application of the profiling machine was the formation of gun and pistol trigger action, the milling machine being chiefly employed in the preparation of the various cutters used in shaping the members of the gun, pistol, and sewing machines. Recent developments in milling operations have extended their use in many directions, and the advantages of this class of machine are worthy of receiving more attention from the sheet-metal worker and others not directly associated with mechanical engineering than they hitherto have done.

The milling machine, fig. 220, is an example of a modern machine fitted with the latest improvements and conveniences, suitable for the production of articles of smallarms, cycle components, brass work, and for general engineering purposes. The headstock has a hardened and . ground spindle running in conical bearings, a hole being bored through the entire length of the spindle, which facilitates the holding and removal of the cutter mandrel, the taper hole in the front end of spindle being bored to the Morse standard.

Fig. 220.

Two solid projections are formed on the end of the spindle, and these tit freely in milled slots in the mandrel collar, thus providing a positive drive, so that the driving of the cutter mandrel is not dependent upon the friction of the taper. The mandrel steady is an internal cone bush of suitable taper, and the steady arm is cylindrical and can be easily removed when necessary.

An effective brace is provided to tie the cylindrical steady-bar rigidly to the knee bracket of the machine for reducing the vibration to a minimum. The work-table has tee slots to receive the holding-down bolts, and the table has ample space to allow of several gangs of work being milled side by side, as is in some instances required. The knee bracket is fitted with screw and bevel gear for elevating, and has vertical stops and indicated discs for the purpose of setting on the cuts accurately. Automatic feed devices are provided with a trip gear, which stops the feed at any desired position, and adjustments are provided to enable the feed belts to be shortened or lengthened within reasonable limits without cutting them. When suitable cutters are at hand ordinary cutting beds may be cheaply milled top, bottom, and edges, besides such tools as those seen at figs. 87, 94, and similar work. A typical profiling machine is represented at fig. 221. The vertical slide has a central stop-motion, and the lever for working the slide is also placed in a central position. The transverse slide runs on rollers, thereby making it very free to handle; it can be actuated by a screw and worm feed motion in addition to the ordinary lever, and is furnished with two locking bolts, to clamp it in any fixed position, and stops are provided to allow for milling to definite lengths. The work-table is actuated by wheels and pinion, and is provided with compensating devices to take up wear and ensure perfectly steady rutting. The principle of the profiling machine is indicated at fig. 222. A cutting-out bed D is fixed upon the work-table M T, and the milling cutter c is carried by a vertical spindle attached to the slide. A steel pattern P is fixed by the side of the die D; this pattern is also known as a template or former, and is made the exact contour as required to be formed upon the die D. At one side of the spindle which carries the cutter a tracing or feeling peg t is fixed; this peg is turned taper, so that by lowering or raising the peg the cutter c will be drawn to or from the die D, as the case may be. The feeler is kept hard up against the former P by means of a chain and weight attached to the slide; and since the distance between the feeler t and the cutter c is always the same, it will be readily understood that as the feeler t travels over the contour of the pattern P, so the cutter c will travel round the die D, thereby producing the required contour thereon. Another example of die that may be easily formed by profiling is the die S D, intended for cutting spoon blanks, and the profiling machine may be as readily used for external as internal work. A study of the various and peculiar shapes of cutting dies to be met with in any sheet-metal works will give an idea as to the machine's usefulness. In a tool room, where large quantities of small screws are required for joining up the various parts of dies, punches, and bolsters, the screw-nicking machine, fig. 223, will be a useful addition for milling the slits in the heads of screws; and the screw-polishing machine, fig. 224, may be used for polishing the small screws, pins, and piercing punches, which would otherwise occupy the lathe.

Fig. 221.

Fig. 222.

Fig. 223.

The ordinary machine vice, owing to the uplift of the loose jaw and unreliability of the fixed jaw, has hitherto not been of much use for dealing with tool work of any great accuracy, and the special machine vice, known as Taylor's patent, has many advantages. In making this vice great care is taken as regards parallelism of the upper and lower faces of the vice. Any work done upon the upper surface of the article may be depended upon to be true with its under surface, and the necessity of hammering down the article held in the vice is abolished.

Fig. 224.

The direct action of the screw enables the necessary degree of tightness to be obtained with the expenditure of less force than is required with an ordinary vice, and, in consequence of its favourable position, the screw escapes the dirt and swarf of the cuttings. The"Taylor"vice is represented at figs. 225 and 226. It will be seen that the loose jaw is free to slide backwards and forwards in the longitudinal slot of the vice, as is also the grip plate when tilted slightly forward, thereby disengaging the two strong teeth from those on the body of the vice. Fig. 226 is a section of part of the vice, showing that the rear faces of the steel jaw plates C, C are inclined, thus causing them-when an article is gripped-to slide downwards for a very short distance, carrying with them the article held, the pin holes in the jaws being slotted to allow of this motion. E, E are screws and springs holding jaw plates back. These plates are raised again when the article being held is released, by simple springs working in the recesses D, D, shown at the bottom of each plate. The small cap screw F keeps water and dirt from entering the pin hole. A piece of hardened steel is fixed in the centre at the back of the moveable jaw to receive the pressure of the screw. These vices are sometimes provided with special vertical tilting adjustable angle plates, forming a convenient attachment for use on milling and shaping machines when employed on general tool work.

Fig. 225.

Fig. 226.

Fig. 227.

Fig. 228.

The dividing headstocks, represented at figs. 227, 228, and 229, are for general use on either milling or shaping machines. Fig. 227 is a 6 in. centre plain set of heads, and admits 15 inches between the centres, a notched dividing plate being attached thereto. Fig. 228 is a set of 4 1/2 in. plain heads, admitting 12 inches between the centres. This apparatus is provided with a drilled drum of large diameter, having nine rows of divisions, with the following numbers-120, 100, 90, 88, 72, 64, 42, 36, 26.

The quadrant dividing headstock, fig. 229, is fitted with a switching block, graduated to set the spindle to any angle, from a horizontal to a vertical position, and provided for cutting cutters of any angle. The divisions are obtained by means of worm and worm wheel, and with the plate supplied most numbers can be obtained from 2 to 360 divisions. The index fingers can be set to any division, and by their use the necessity of counting and the danger of mistake are entirely avoided.

Fig. 229.