for work that would be unusual, as very effective results may be obtained by using a gap bed lathe which can be purchased at but slight extra cost over that of the regular tools. The advantages of this type of lathe will be considered in proper sequence. A lathe that will swing 16 or 18 inches will be sufficiently large for most shops, though it can be supplemented by a smaller size adapted for lighter work if the funds permit. In buying lathes, especially for a small shop where the machine tool equipment is necessarily limited, it is well to remember that small work can be handled in a large lathe much easier than large work can be turned in a smaller one, and where it is imperative that but one tool be purchased, it will be the best economy to install a substantial machine. If a drill press is included, one that will swing 24 inches has been found large enough to handle nearly all parts of automobiles. The sensitive drill press is used for drilling small holes, and should have a capacity so that it will handle drills up to a half inch diameter, at least. Machine Tool Equipment for Complete Repair Shop.-An unusually complete machine tool outfit is shown in the shop plans at Figs. 5 and 6. With an equipment of this nature all kinds of repair work may be accomplished economically and, in fact, the outfits shown are sufficiently complete so competent mechanics will be able to build an automobile without outside assistance. As the lathe is the king of machine tools, the major portion of the equipment consists of these useful machines. Seven lathes are provided, two being ten inch swing, three fourteen inch swing, one eighteen inch swing and one capable of handling work up to twenty-four inches in diameter. A universal milling machine upon which a wide variety of work may be done is a useful adjunct to the lathe. A milling machine can finish flat or irregular surfaces which a lathe cannot do unless fitted with a milling attachment. It will make Woodruff keyways or straight splines, it can cut gears, cams and do a variety of other work that cannot be done on the simple lathe. A small shaper having about sixteen inches stroke is also useful, because it will do much of the work done on a milling machine and require simpler tools. While a milling machine has a greater range of work and will do it more economically than the shaper, the latter can be used to advantage in many cases where the cost of milling cutters would be much more than that of making the shaper tool and doing the work besides. Both milling machine and shaper should be provided, if possible. Three drilling machines are provided, one a sensitive drill for light work, the intermediate size, a back-geared drill press, and for extremely large work, such as drilling frames, boring cylinders, axle housings, etc., a radial drill is very useful, as it will handle any part of a motor car irrespective of size. A power hack saw, two emery grinders, one used for roughing purposes and the other for tool grinding, and an arbor press, complete the equipment of this machine shop. Power for the Shop.-Just as electric current is superior for lighting, it also has many advantages as a source of power. The electric motor is an ideal power generator, because it is clean, efficient, economical, easily started and stopped, compact and capable of standing considerable overload. It makes possible individual motor equipment of machine tools in large shops and can be used very effectively for driving the line shafting of the smallest establishment, because it can be suspended out of the way on a platform hung from the ceiling or in the smaller sizes placed on a shelf attached to the wall or some convenient post. Where electric current is not available and where it is not profitable to install a generating plant, the gasoline engine is an economical method of supplying power. The marked advantage of electric current is that it may be employed not only for lighting, but for operating various portable drills, polishing machinery, air compressors, etc., and it also has a great advantage of generating current that can be used for charging storage batteries, which are now included in the equipment of all up-to-date automobiles, as a source of current for the electric self-starter and lighting system. Where electric current is not available from a municipal central station, a garage or repair shop of any size will find it more economical to install a generating plant and make its own electricity for lighting and power than to use a steam or gasoline engine which can only fur nish power and then depend upon kerosene and acetylenę lamps for lighting, which naturally increase the fire risk. Small Generating Sets.-A typical generating set consisting of a four cylinder gasoline engine driving a direct current dynamo is shown at Fig. 20. The equipment is furnished in various sizes, and an outfit can be purchased that will furnish current econ Fig. 20.-Isolated Power Plant for Generating Electric Current. omically for even the smallest shop. The outfits include switchboards and all necessary governing and control appliances, and once the engine is started it requires no further attention, as it will perform the various functions incidental to controlling its speed and power automatically. Instead of using the line shaft, as would be necessary with a gas engine belted direct, it is possible to install individual motor drive on the various machine tools, an example of which is shown at Fig. 21. When one considers that the average line shaft consumes from 20 to 30 per cent. of the power delivered to it in journal friction, if any number of hangers are used, or if the shaft is not absolutely aligned, it will be apparent that the use of individual motor drive will reduce this power loss appreciably. When only two or three machines are to be driven, it is, of course, more profitable to drive these from a short length of shafting than it would be to provide a separate motor Fig. 21.-Form of Lathe Adapted for Direct Drive from Electric Motor. for each machine tool, as one motor may be made to serve them all where the power requirements are not great. The writer does not mean to imply that the internal combustion motor in its various stationary forms is not adapted for power delivery in small units, because many repair shops, some having a very complete equipment, obtain their power directly from an oil engine which is the most economical of the various power-generating units. When a generating set is used it is necessary to use an engine of greater power than would be needed if belted directly to the shaft line, but as in most installations |