Fourth. Heavy Turning

For turning very large and heavy work such as rolling mill work, crank shafts, etc., the heavy triple geared lathes are best adapted. Special lathes are built for such work as roll turning, locomotive driving wheels, and similar work. Recently the vertical boring mill has been much used on many circular castings formerly machined on the face plate of a lathe, and with much greater economy. Several boring and turning tools are used simultaneously, and the work is more advantageously handled on a horizontal table than a vertical face plate.

Fifth. Medium Class Of Turning

This class of work in the form of shafts, etc., is very economically handled on the so-called "Rapid Reduction Lathes," the "Lo-swing Lathe," and similar highly developed types of the engine lathe, although much of this work is still done on the ordinary type of engine lathe, with various labor-saving attachments, gauges, and the like.

Sixth. Small Turned Cylindrical And Flat Work

This class, including a great variety of small shafts, studs, pins, collars, flanges, stuffing box glands, gear blanks, and similar machine parts are economically made in hand or automatic turret lathes, automatic screw machines, and similarly designed special machines, as well as engine lathes having special attachments for doing this class of work.

Seventh. Gear And Rack Cutting

This work is rapidly becoming of more importance in machines of modern design; so much so that there are many shops organized for the sole purpose of doing this class of work. In manufacturing concerns doing their own gear cutting automatic gear cutters, gear shapers, and gear planers are almost exclusively used, while hobbing machines for worm gears have an adjustable power feed device whereby very accurate work is turned out. Spiral gears, now so much used, are very generally cut on a universal milling machine, of which there are several of exceptionally good design and construction.

Eighth. Drilling And Boring

There has been much development in this class of work in recent years, two of the most important results having been the production of the radial drills and the multiple spindle drills. The former is much used for heavy work and that which is large and awkward to handle, as the drilling device, being movable to any desired point within a quite large radius, while the work remains in a fixed position, is capable of a very large range and various angles of operation. The multiple spindle drill is particularly adaptable to jig work where several different sized holes are to be drilled at one operation. A special design of this form of drill provides a special location of a spindle for each hole to be drilled in the same direction in the piece, and all are drilled simultaneously, or in the time occupied in drilling one hole. Horizontal and vertical boring machines are used, not only for drilling large holes, but for boring out cylinders and other like castings requiring large and heavy boring work.

Ninth. Grinding

Great accuracy, efficiency, and economy have been realized in the use of grinding operations. This work may be divided into three classes: (a) cylindrical grinding; (b) surface grinding; and (c) disk grinding. In the first the piece is usually placed on centers, and revolves in the opposite direction to the grinding wheel. In the second the work, or the wheel, travels to and fro on a table similar to a planer table, while the wheel revolves above it and is gradually moved across it. Disk grinding is a kind of surface grinding, but is mainly used for the purpose of finishing or polishing the surface of machine parts having flat surfaces. In this form the grinding surfaces are composed of flat cast iron disks whose surfaces are cut with a shallow spiral line. The surface is covered with emery cloth cemented to it. The work to be ground is laid upon a table normally located at right angles to the face of the disk, but capable of being adjusted to any desired angle when angular surfaces are to be finished. Two of these disks arranged facing each other, and one of them made adjustable, are used for grinding opposite surfaces of flat pieces.