The grinding of duplicate machine parts efficiently was impossible during the earlier stages of grinding practice, because only light machines and slow-cutting wheels were available; but this condition has been changed by the development of artificial abrasives, improved bonding processes, and powerful machines that make it possible to use the fast-cutting modern wheels effectively in the production of precision work. Therefore, successful grinding practice now depends mainly upon the way in which this high-grade equipment is used. The machine may be perfect and the wheel faultless as to cutting qualities, but to grind successfully, it is necessary to follow approved methods.

Much has been published regarding the constructional features of different types and designs of grinding machines, but there has been a lack of definite information on modem grinding practice. This treatise deals almost exclusively with subjects of especial value to the user of grinding machines. The chapters on "Cylindrical Grinding," "Form Grinding," "Internal Grinding," "Surface Grinding," "Cylinder Grinding," "Crankshaft and Camshaft Grinding " and "Disk Grinding," all contain information that is fundamental and of practical value to the man in the shop. Throughout the book there are many typical examples which indicate what can be done, by showing what has been done. These examples are accompanied by data arranged in compact form and covering wheel and work speeds, grade and grain of wheels used, and other important points.

Careful attention has been given to the subject of grinding wheel selection, and the tables accompanying this chapter list the grain and grade of wheels recommended by various wheel manufacturers for grinding different materials. While such information must necessarily be general, it will often serve as a guide and enable efficient results to be obtained without needless experimenting. Various types of wheel-truing devices and fixtures for holding work on different classes of machines are also described and illustrated in separate chapters.

The aim has been to present useful information and to exclude unimportant details. It is not expected that the practice described will invariably meet with approval, since opinions differ greatly in regard to grinding methods. A special effort has been made, however, to present average practice, and to show exactly how various classes of work are ground in different shops.

The cooperation of various automobile, grinding machine and wheel manufacturers, in supplying illustrations and data, has greatly increased the value of this treatise.

Grinding machines were originally used almost exclusively for truing tool steel parts which had been distorted by hardening, and they are still indispensable for work of this class. The great improvements which have been made, both in grinding machines and abrasive wheels, however, have resulted in the application of the grinding process to the finishing of a great many unhardened parts. In either case, the work, as a rule, is first reduced to nearly the required size by turning in some form of lathe, and then it is ground to the finished dimension. After a part has been hardened, grinding is the only practicable method of truing it. On the other hand, unhardened pieces can be finished by other means, but grinding is preferable for most cylindrical work, because it enables parts to be finished accurately to a given diameter in less time than would be required by any other known method.

Several different types of grinding machines have been developed for handling the various kinds of work to which the grinding process is applicable. The machines used for grinding cylindrical parts such as shafts, piston-rods, etc., are called cylindrical grinders, whereas the type used for grinding holes in bushings, gears, milling cutters, etc., are known as internal grinders. There are also surface grinders for finishing flat or plane surfaces, and, in addition, types that are specially designed for sharpening cutters, reamers, etc. As cylindrical grinders are the type most commonly used, they will be considered first.

A Cylindrical Grinding Machine - From the foregoing, it will be seen that a cylindrical grinding machine must be arranged to rotate both the grinding wheel and work. In addition, either the work or the wheel must be traversed longitudinally. The wheel must also be fed in automatically for taking successive cuts, and provision must be made for varying the traversing movement and the rotative speed of the work to suit different conditions. The way these various movements and adjustments are obtained with the type of cylindrical grinder illustrated in Fig. 2 will be explained. It should be understood, however, that the mechanical details vary with grinders of different makes, although all cylindrical grinding machines operate on the same general principle. Other machines for cylindrical grinding will be referred to later.


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