【正文】 Classes of grinding machines include the following: cylindrical grinders, centerless grinders, internal grinders, surface grinders, and tool and cutter grinders. The cylindrical and centerless grinders are for straight cylindrical or taper work。 on some parts. Bores and singlepoint finishes can be held to 177。 singlespindle automatics, multiplespindle automatics and automatic chucking machines. Originally designed for rapid, automatic production of screws and similar threaded parts, the automatic screw machine has long since exceeded the confines of this narrow field, and today plays a vital role in the mass production of a variety of precision parts. Quantities play an important part in the economy of the parts machined on the automatic to set up on the turret lathe than on the automatic screw machine. Quantities less than 1000 parts may be more economical to set up on the turret lathe than on the automatic screw machine. The cost of the parts machined can be reduced if the minimum economical lot size is calculated and the proper machine is selected for these quantities. Automatic Tracer Lathes Since surface roughness depends greatly upon material turned, tooling ,and fees and speeds employed, minimum tolerances that can be held on automatic tracer lathes are not necessarily the most economical tolerances. Is some case, tolerances of 177。s production shops by a wide variety of automatic lathes such as automatic of singlepoint tooling for maximum metal removal, and the use of form tools for finish and accuracy, are now at the designer39。s freedom, and hence are a part of the implied specifications. A small plant, for instance, may not own coldworking machinery. Knowing this, the designer selects other metalprocessing methods which can be performed in the plant. The labor skills available and the petitive situation also constitute implied specifications. After the problem has been defined and a set of written and implied specifications has been obtained, the next step in design is the synthesis of an optimum solution. Now synthesis cannot take place without both analysis and optimization because the system under design must be analyzed to determine whether the performance plies with the specifications. The design is an iterative process in which we proceed through several steps, evaluate the results, and then return to an earlier phase of the procedure. Thus we may synthesize several ponents of a system, analyze and optimize them, and return to synthesis to see what effect this has on the remaining parts of the system. Both analysis and optimization require that we construct or devise abstract models of the system which will admit some form of mathematical analysis. We call these models mathematical models. In creating them it is our hope that we can find one which will simulate the real physical system very well. Evaluation is a significant phase of the total design process. Evaluation is the final proof of a successful design, which usually involves the testing of a prototype in the laboratory. Here we wish to discover if the design really satisfies the need or needs. Is it reliable? Will it pete successfully with similar products? Is it economical to manufacture and to use? Is it easily maintained and adjusted? Can a profit be made from its sale or use? Communicating the design to others is the final, vital step in the design process. Undoubtedly many great designs, inventions, and creative works have been lost to mankind simply because the originators were unable or unwilling to explain their acplishments to others. Presentation is a selling job. The engineer, when presenting a new solution to administrative, management, or supervisory persons, is attempting to sell or to prove to them that this solution is a better one. Unless this can be done successfully, the time and effort spent on obtaining the solution have been largely wasted. Basically, there are only three means of munication available to us. There are the written, the oral, and the graphical forms. Therefore the successful engineer will be technically petent and versatile in all three forms of munication. A technically petent person who lacks ability in any one of these forms is severely handicapped. If ability in all three forms is lacking, no one will ever know how petent that person is! The petent engineer should not be afraid of the possibility of not succeeding in a presentation. In fact, occasional failure shoul