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Numbering System for Standard Drills, Standard Taps, and Reamers

This hands-on manual provides a systematic method for identifying standard drills, standard taps, and various types of hand, machine and shell reamers used in industrial applications. Complete contents include: J2122 - Numbering System for Standard Drills; J2123 - Numbering System for Standard Taps; and J2124 - Numbering System for Reamers. A complete appendix section listing numerous examples of standard tool designations using the numbering scheme is also included. A valuable reference that will help OEMs and suppliers effectively communicate tool descriptions, as well as more efficiently catalog and supply tools!
Technical Paper

The Use of Trailers with Motor-Trucks

TRAILER registration figures for the entire United States are given to show the rapid increase in the use of trailers in the last seven years, and, for comparison, State registrations of all motor-vehicles in 1931 are given. To account for the relatively more rapid increase in trailers than in trucks, factors favoring the use of trailers are mentioned and illustrative examples of operation are briefly described. The factor of first importance is legislation, which in general is stated to have promoted the use of trailers to distribute the weight of heavy loads over more axles and wheels; but in some States the laws and regulations have a serious adverse effect. Next to legislation, savings in hauling costs through the use of trailers account for the increase in their numbers, and comparative figures of the cost of hauling per 100 lb. per 100 miles by truck, by truck and trailer and by rail are given to show the economy.
Technical Paper


When the volume and the variety of the parts produced by a plant increase beyond the point at which the shop mechanic is capable of devising the methods and building the tools for accomplishing the desired results, it becomes necessary to make a division of labor, and a special department on tool division is needed to determine the proper sequence of operations and the suitable equipment to produce the required quantity with the required degree of accuracy. It is necessary that the men be informed regarding the daily and the ultimate numbers of parts to be produced and the tolerances that will be allowed. The foremost consideration of the production engineer should be economy of production. In this phase of tool engineering, the ultimate number of parts to be produced plays an important role and equipment should be selected that will give the maximum production. All known methods of production should be compared and the most economical one chosen.
Technical Paper


A practical method of nickel-plating is outlined and the various processes are described by which the Packard Motor Car Co. has been successful in producing a durable coating of nickel on automobile parts in general, and the radiator shells, the rim plates and the tire-carrier plates, in particular. These are the parts of greatest exposure, and for plating them a new system of moving-cathode tanks was installed. The three problems to which special attention was devoted were rusting, pitting and peeling. No effort was made to secure a coating of any designated depth but reliance was placed solely on the results indicated by a 24-hr. salt-spray test, which was considered to be the equivalent of 2 years' exposure to the usual weather conditions. Peeling was overcome by thoroughly cleaning the parts before plating. New equipment was purchased and laid out in accordance with the system decided upon, namely, copper-plating, buffing and nickel-plating.
Technical Paper


Principal stresses in one type of eye-bolt have been determined in the laboratory of photoelasticity at the Massachusetts Institute of Technology by the photoelastic method. In the test, an eye-bolt, designed in accordance with a method suggested for circular eyes in a course in machine design by the Institute, was made of celluloid 0.25 in. thick, 1 in. wide on either side of the eye, with a 1.405-in. diameter of eye, and a 1.333-in. width of shank. Steel loading-plates were pinned to the broadened end of the shank and a load of 100 lb. was suspended from the bolt, which gave a mean stress of 300 lb. per sq. in. in the shank. Plain polarized light was passed through the celluloid model and the isoclinic lines, or lines of equal inclination of principal stress, were observed and recorded. Two families of lines of principal stress, designated as P and Q stresses, were determined graphically from these isoclinic lines.
Technical Paper


The question as to whether a part should be made or bought is one that must be settled by the individual maker according to the value of his product, the nature of the part, his capital available for manufacturing purposes and the price at which his product is sold. The author describes the practice followed by some of the large companies, showing that in spite of their being quantity producers, they have found it desirable to buy a number of important parts. Certain parts are rarely made by automobile manufacturers, either because they can be bought more cheaply or because the machinery to produce them is intricate. The author sums up the problem by stating that a manufacturer makes the unit on account of not getting deliveries or because he does not get a fair price from the parts maker or an article good enough to satisfy his conditions. In order to give individuality to the product, the car maker often produces certain parts, such as the engine, himself.
Technical Paper


PROBLEMS of suspension spring design that have been of major interest in recent years, such as spring life and reliability, hardness and settling, fatigue, shot peening, and presetting, are presented here. Various types of springs are discussed by Mr. Schilling, who concludes that no one type is superior in all respects, hence commercial applications of different types have remained competitive. He feels that this picture will not change in the future, that is, no one type will be used exclusively. Considering the great superiority of some types in economy of material, however, he expects that the less economical springs will gradually be replaced unless their weight can be substantially reduced.
Technical Paper

Effect of Weight/Power Ratio on Highway Transportation

THE purpose of this presentation is to focus attention upon the need for improving commercial highway vehicles in order to keep pace with the new standards of comfort and operation now prevailing in passenger-car design. The tendency to reduce the number of motions and the physical effort required to perform a task has led to the use of automatic transmissions in automobiles. Passenger-car manufacturers have designed higher-output engines without materially increasing weight, thereby providing a horsepower reserve which eliminates uneconomical operation of the engine at peak output at all times. Streetcars have been improved so that the operator need only apply foot-treadle pressure to start, accelerate, and stop the vehicle. This appears to be in direct contrast to the trend in bus and truck design.
Technical Paper

Temperature Gradients and Heat Stresses in Brake Drums

The main purpose of this paper is to show that the phenomena classed under the generic thermal failure are not due to excessive temperature alone, but to a combination of high stresses and high temperature; other factors of importance are brake design, geometry, physical properties of brake lining, and those of the drum. Concerning stresses, it will be shown that temperature gradients alone can cause them to reach well into the plastic state, even in a comparatively cool drum. Such heat stresses are known to give rise to crazing of the track, but in addition it is explained here that they are also responsible for heavy scoring, heat checks, or outright fracture. A detailed analysis indicates why and how certain purely mechanical design aspects lower stresses and heat concentrations, thereby mitigating or even preventing the onset of thermal failure.
Technical Paper

The New Packard Lightweight Diesel Engines

THE new Packard automotive diesel engine is reported to feature reductions in weight and space occupied, while maintaining good life expectancy. It is available in 6-cyl in-line, V8, V12, and V16 models. These models all have a large number of interchangeable parts. They all have the same bore and stroke. According to the authors, noteworthy points of these engines include: 1. Extensive use of aluminum. 2. Turbosupercharging. 3. One-piece cylinder and head assembly. 4. Four valves per cylinder, with stellite seating surfaces on valves and seats in the head.
Technical Paper

Effect of Temperature on Endurance Limit and Relaxation of Spring Materials

ENDURANCE limits and load losses at various temperatures from -75 F to 650 F for several spring materials are reported in this paper. The materials tested were in the form of helical springs, both shot peened and unpeened. Some general observations made by the authors include: 1. Shot-peened springs had higher endurance limits and greater relaxation than unpeened springs at -75 F and 75 F. 2. As test temperatures rose above atmospheric, endurance limit of all unpeened springs tended to hold steady or increase somewhat, while that of shot-peened springs tended to decrease. 3. Except for high-speed steel and stainless steel, chrome-silicon steel showed lowest load loss in both static and dynamic tests in the temperature range from atmospheric to 450 F. 4. Both unpeened and shot-peened high-speed-steel springs showed high endurance limits at all test temperatures. 5. Endurance limits at -75 F were similar to those at atmospheric temperature, but the amount of set was less, on the average.
Technical Paper

Effect of Shot-Peening Variables and Residual Stresses on the Fatigue Life of Leaf-Spring Specimens

RESULTS of an investigation into the effect of shot-peening variables and the resulting residual stresses on fatigue life are reported in this paper. Leaf springs were the simple specimens heat-treated, cold worked, and tested in this study. Some of the conclusions reached are: 1. There is a minimum shot velocity for each shot size to obtain best fatigue life, and this value is much lower than that normally used. 2. Exposure time for this type of shot-peened specimen beyond some minimum value is wasteful and costly. 3. Shot size has little influence on fatigue life for these specimens. 4. Shot peening specimens while under tensile strain greatly increases fatigue life at 200,000 psi nominal stress over that of nonpeened or strain-free-peened specimens. 5. Shot peening these specimens gave residual compressive stresses 50% of yield strength, and these stresses can be increased to more than 50% by strain peening. 6.
Technical Paper


THIS paper deals with cavitation pitting where vacuum bubbles exist. Experiments are described which attempt to correct this condition where plating of liners varied in composition and thickness. It was concluded that a nickel-chrome plating has very good resistance to cavitation-pitting attack. Investigation of cylinder-wall vibration was made to find out about the cause of cavitation. Minimum liner wall vibration results with use of a 2-piece heavy wall liner and a piston with 20% less clearance. Endurance tests prove that on these pitting has been eliminated.