The precision with which steam-hammers operate is no less wonder ful than the wide range of force with which they may be made to work and the titanic energy which the greatest of them exert. Some ham mers which are capable of striking a blow of from fifty to one hun dred tons are so accurate in their adjustment that they may be made to crack a walnut or may be brought down, without breaking the delicate crystal, to within a small fraction of an inch above the face of a watch placed upon the anvil.
Tendencies in illetal-working ilfachinoy.—The tendency of manufac turers of metal-working machinery in general, and machine-tools in par ticular, is in two lines, leading from the previous direction of thought and work. Two distinct classes of machines are becoming more and more common each year: special tools for effecting from one to twenty opera tions at a time upon one article, where such article is manufactured in large quantities, and what might be called "universal" machines, having a wide range of adjustment and being capable of doing many kinds of work. Of the universal machines, the boring- and turning-mill pre viouslv mentioned is a good type, an important variant being a machine which not only bores and turns the cylindrical surfaces of large cylinders, but also planes their flanges, faces-off their valve-seats, and drills bolt holes in flanges and seats without removing the cylinder from the machine, and with little if any change of place while being worked. Such a machine has a wide range in the dimensions of cylinders which it takes in and in the arrangement of their parts; in this respect it differs greatly from the special machine proper, which is intended to take in one or more articles at a time, but permits of little if any variation in design, construction, dimension, or finish in the articles produced.
The modern machine-tool is an instrument of precision, and its work is characterized by its greatly increasing accuracy and finish. The in creasing exactitude of lead-screws and index-plates, due to the loving and intelligent labors of a few master minds in machine-tool building, has induced an increasing degree of accuracy in all other machine-tools and in all machines built thereby; and the standard having been thus raised, the demand has gone out from machine-builders for a higher grade of work manship in all their machine-tools and metal-working machinery, so that all along the line, from bloom-squeezer and steam-hammer to delicate milling-machine and gear-cutter, the grade has been improved. Thus do demand and supply, desire and its fulfilment, go hand in hand, opening and smoothing the way of human progress.
It is to be regretted that the wide range of operations and the wonder ful accuracy of modern machine-tools have done so much to lower the standard of personal dexterity in mechanical manipulations. The milling machine and the emery-wheel have nearly supplanted the wonderful skill once exercised by the file and the scraper. The machinist is lapsing into a specialist, able to operate but one class of machines and to do but one class of work, and the working force of the machine-shop has become merely an assemblage of machine-tenders. (R. G.)