1939: Machine Development

As is usually the case, machine development in 1939 consisted mostly in gradual improvement of previous designs and practices. There are few if any, startling changes that can be credited strictly to this particular year. Most noticeable in the machine tool field, and this also applies to machinery in general, is the change in outward appearance. Many of the new machine outlines bear little resemblance to the same type of machine built a few years ago. Except for a few projecting handles and a familiar name cast in the frame, a modern grinding machine might be almost any machine for an entirely different purpose. Everything possible is enclosed and the outward contour gives little hint of the operations performed. While much of this has been called 'streamlining,' the term really has little application to such stationary objects as machine tools.

There is also an increase in the number of machines with frames built up from steel plates by welding. Improvements in welding technique produce welded seams that do not detract from the appearance of the machine. There are now numerous machines in which steel plates up to 3 inches in thickness enter into the frame construction.

Hydraulic Machines.

Hydraulic control of both tool and work movements has increased in nearly every kind of machine. Even comparatively small milling machines now have hydraulic feeds. Hydraulic mechanisms are also used in connection with some screw feeds to prevent backlash, so as to permit 'climb' milling, which has advantages on many kinds of work. Hydraulic variable speed drives are also finding their way into use on a larger scale, one having a speed range of from 10 to 3000 r.p.m., which is far in excess of the usual speed ranges of other forms of variable speed transmissions. Hydraulically operated planers, shapers and similar machines continue to grow in favor, and are being experimented with by several builders.

Gearing Precision.

Greater precision in gearing is being constantly demanded, largely due to the automobile manufacturers' desire for transmissions that will be more quiet when in gear. How far this will be affected by the introduction of the so-called fluid flywheel, or hydraulic drive, remains to be seen. In the meantime more care is being taken to secure greater accuracy in tooth form and spacing, and smoother surfaces on the mating teeth. One marked departure is known as the Zerol curved tooth as a substitute for plain or straight, level teeth. This new gear has a curved tooth but without any angle as in the cases of spiral-bevel gears which are now common in automobile rear axles and in other places. The Zerol tooth transmits power more uniformly and with less noise than the straight tooth.

Cutting Oils and Compounds.

The effect of cutting oils on both the cost and quality of machined work is receiving more attention, especially by the larger oil companies. This much disputed subject now plays a more important part in the economical production of machine parts than seemed possible before it received such careful attention, both by oil company laboratories and by users of different grades of steels, both for tools and products.

Clarification of oils and cutting compounds is also receiving attention. The process is similar to that used in dairies for separating cream from milk, the equipment being made by the same people. The clarification not only increases the life of the cutting compounds but also improves the quality of the work, especially in the case of fine grinding. Ball bearing manufacturers find that in addition, the life of the grinding wheels is materially increased.

Increase in Motor Driven Machines.

More and more machines of all kinds are being equipped with motor drives, not only for the main spindles but for such functions as feeds, rapid traverse of carriages, clamping cross rails on planers, and for both lubricant and cutting compounds. Some of the new larger machines have a dozen motors. One recent design of lathe has a flange-type motor mounted on the end of the headstock. Multi-spindle machines frequently have a motor for each spindle beside those for other functions.

A new engine lathe has special devices for turning unusual shapes such as are used in making molds for glassware and the similar products. Another has a new screw cutting method which includes a micrometer adjustment that corrects minute inaccuracies in the lead screw, for precision work. This has previously been a laboratory operation.

Machine Bearings.

Machine bearings continue to receive attention from both bearing manufacturers and machine builders. Greater demand for precision in products necessitates increased accuracy in the bearings of the machines in which they are made. This is true of ball, roller and needle bearings as well as plain or sleeve bearings on grinding and other machines. One advance in this line is the fitting of the sleeve bearings of a new grinding machine with such small clearance that kerosene is used for lubricant instead of the heavier oils usually recommended. Bearing clearance plays such an important part in machines of this kind that it is customary to let the machine run idle long enough to heat up the spindle and bearing to working temperature before starting it to work. The effect of temperature on accurate work is shown by the practice of boring automobile cylinders in rooms with constant temperature to secure uniformity. Recent developments in securing extra fine finishes on bearing surfaces is also playing its part in this advance. Super-finish, developed last year, has helped to increase the life of bearings in automobiles.

Higher Cutting Speeds.

As a result of constant improvement in cutting tools, machines are being designed with higher cutting speeds to utilize the advantages of these new materials. Planers for example, are now made to run at a cutting speed of 240 feet per minute. They can also be run as slow as 8 feet per minute. This wide range of speeds necessitates improved mechanisms, with more speed changes. It is one reason for the increased use of speed-changing devices of various kinds. The continued use of gearing, special-coned pulleys and belts indicate that none of the previous hydraulic variable speed transmissions completely meet all requirements. Perhaps the device mentioned previously may prove satisfactory.

New Alloys.

New developments on metals are playing their part in machining progress. Steel makers have devoted much time to alloys that will not only have the highly desirable physical qualities of strength to resist stresses and hardness for long life in bearing surfaces, but what is most important, that can also be machined economically. This phase of the problem has been greatly aided by the new cutting tools such as Stellite and cemented carbides of various kinds, in addition to the aforementioned research work in cutting compounds.

By carefully selecting the materials to meet the requirements of the parts to be made, and choosing the proper cutting tools and coolants to machine these materials and the best machine tools for the operations to be performed, we secure the greatest economy in metal production. More than ever before we are dependent on many different branches of industry for success in our own line.

Machines for Molding and Forming Plastics.

The growing use of plastics in nearly all industries has developed a variety of special machines for molding and forming the new materials into their desired shape. These machines are of two types; injection molding machines where the material is heated so as to be forced into dies or molds under heavy pressure, and forming machines of the press order, where the sheet material is formed to shape or where powder is put into molds and formed to shape, as in small handles and knobs.