Power Required for Machine Tools.-The amount of power to be provided in a repair shop depends entirely upon the character and number of machines to be driven. If a line of shafting is to be used to turn the machinery, and especially if there are individual countershafts for each machine, as is needed for most machine shop tools, it will be necessary to double the power requirements of the tools used, as given in the accompanying tabulation, to take care of loss of power through belt slip, journal friction, lack of machine alignment and other causes. The figures given are taken from the best mechanical authority and are an average of some widely different estimates for the same class of machine.

Energy Consumption of Common Machine Tools

Installation of Machine Tools.-The placing of the machinery will depend entirely upon the ideas of the master mechanic and the best method of installing line shafting will, of course, depend upon the character of the building and the materials of which the

wall or ceiling to which it is attached is constructed. If the floor space permits, the machinery should be arranged so that all may be driven from a single main line of shafting. It is well to remember that a reduction of the length of the shaft and the number of hangers for its support decreases journal friction and consumes less of the shop power. If the machines are on the ground level, as is the case with most small shops, the floor may be made of heavy planks, attached to substantial beams laid over a foundation of cinders or well grouted crushed stone. A floor of cement should always be planked over because the wood flooring is much easier on the feet of the workmen. It seems almost unnecessary to mention that a perfectly level floor should be sought for. It is imperative that the floor be substantial enough so it cannot vibrate and have sufficient strength so it will not deflect under the weight of the machine tools. There is some danger from this source, if the machine room is placed on an upper floor of a converted building that has not been especially constructed for automobile repair work. All machinists and millwrights agree that the foundation for the bed of a machine should have no deflection, if the life of the machines and the accuracy of the work performed upon them is to be given consideration. The problem is considerably simplified when one considers that in automobile repairing, machine tools of great weight are not used, so there should be no difficulty due to either floor vibration or deflection in any ordinarily well constructed building.

The floor plans presented at Figs. 3, 4, 5 and 6 inclusive show logical arrangements of machine tools that can be followed to advantage. The lathes, milling machines and shapers should be installed where there will be plenty of light upon them, and it is well to group all lathes together, if possible. Drilling and boring machines must be installed with ample floor space around them so the large work can be handled to advantage. Ample room should be allowed around each individual machine, and there should be sufficient space between the benches and tools to allow the workmen at the bench to pass between the operator at the machine and the bench with room to spare. An ideal method of installing an electric motor, if this is used as a source of

power, as would be the case in any city or town where central station current was available, is to support it on a stout platform suspended from the ceiling at any convenient point and to make a direct belt connection with the main driving pulley of the line shafting. The proportions between the motor armature pulley and that on the line shaft should be such that the speed of the shafting will not exceed 300 R. P. M. The switches, starting rheostats and fuse blocks should be placed on one panel at a convenient height on the wall. As an electric motor needs but little attention, in some shops it is hung directly from the ceiling, i.e., the base is securely attached to the beams by lag screws. If precaution is taken to change the location of the lubricating oil wells under the main journals, a motor can be operated just as well upside down as in any other position. Where central station current is procurable and but few machines are used, the individual motor equipment does not have the advantages in a small establishment that are presented in its favor when used in the large manufacturing enterprises. While an individual motor for each machine eliminates a large amount of overhead shafting, belting, etc., and conduces to a lighter and cleaner shop, it is doubtful if the advantage of rendering each tool or machine independent of the others as regards power would compensate for the cost of such an equipment. It is doubtful if individual motor drive would be an economy in the repair shop if one considers that most companies supplying current make a fixed service charge, this being figured so closely that it is almost as cheap to keep a low power motor going all day as to keep shutting it off and on or using a varying number of smaller motors having in the aggregate somewhat less power. Besides, in a repair shop of any size, it is not likely that there will be any lull in the work, and power would be required from morning to night.

The Lathe, Types and Accessory Equipment.-Two very simple forms of lathes which are better adapted for the private garage repair shop than for general work are shown at Fig. 25. That at A is a foot power machine that is capable of doing very fine work, and that is well adapted for experimental and light repair purposes. It will swing nine inches and has a space of 25 inches

between centers. The tail stock can be set over for taper turning, and a swivel tool carriage permits a wide range of work. It is provided with a lead screw and is suitable for thread cutting. The lathe at B is a small speed lathe that is shown with a tool rest adapted for hand-turning tools. This can be replaced by the usual form of cross slide rest, making it suitable for metal turning work. A small lathe of this nature is included in many repair shops for wood turning and is often fitted with a drill chuck and used in place of a sensitive drill for light drilling. A machine of this kind is inexpensive and very useful. The light screw-cutting lathe shown at A is also furnished with a countershaft, making it suitable for power drive, though a surprising quantity of accurate work may be accomplished without unduly fatiguing the operator, if the foot power form is utilized.

All lathes, with the possible exception of the speed lathe, in order to be thoroughly practical for repair shops, should have screw-cutting attachments, elevating compound rests, hollow spindles and a good outfit of auxiliary attachments. Several sizes of chucks and face plates, and a steady rest and back rest for long work, should also be provided. A lathe that will cut from four to forty threads per inch has sufficient range for all ordinary shop work. A number of different designs of lathes of latest pattern suitable for repair shop use are shown at Fig. 26. That at A is the conventional form of engine lathe that has been so universally applied in the machine shops of the world. It is back geared and provided with a complete set of gears for screw cutting. The difference between this lathe and that shown at B is in the change speed gear box provided, by which any desired speed of travel of the carriage may be obtained by merely shifting a lever. In the form shown at A it is necessary to remove the driving and stud gears, and in some cases the lead screw gears, and replace them with others for varying classes of work. In the form at B any desired gear ratio within the range of the tool may be obtained by the simple movement of a gear-shifting lever.

The lathe at C is a gap bed type, one of which should be included in the equipment of practically all repair shops, and if