FIG. 261.—HARDENING THE PLATE BY JETS OF WATER.
FIG. 262.—OIL TEMPERING.
Making Horse Shoes.—Anthony’s patent, April 8, 1831; Tolles’, of October 24, 1834, and H. Burden’s, of November 23, 1835, were pioneers in horse-shoe machines. Mr. Burden took many subsequent patents, and to him more than any other inventor belongs the credit of introducing machine-made horse shoes, which greatly cheapened the cost of this homely, but useful article. Nearly 400 United States patents have been granted for horse-shoe machines.
Making Screws, Bolts, Nuts, Etc.—Screw-making according to modern methods began between 1800-1810 with the operations of Maudsley. Sloan, in 1851, and Harvey, in 1864, made many improvements in machines, operating upon screw blanks. The gimlet-pointed screw, which allows the screw to be turned into wood without having a hole bored for it, was an important advance in the art. It was the invention of Thomas J. Sloan, patented August 20, 1846, No. 4,704, and was twice re-issued and extended. In later years the rolling of screws, instead of cutting the threads by a chasing tool, has attained considerable importance, and provides a simpler and cheaper method of manufacture. Knowles’ United States patent of April 1, 1831, re-issued March 1, 1833, described such a process, while Rogers, in patents No. 370,354, September 20, 1887; No. 408,529, August 6, 1889; No. 430,237, June 17, 1890, and No. 434,809, August 19, 1890, added such improvement in the process as to make it practical.
In the great art of metal working the names of Bramah, Whitworth, Clements and Sellers appear conspicuously in the early part of the century as inventors of planing, boring and turning machinery for metals. Our present splendid machine shops, gun shops, locomotive works, typewriter and bicycle factories, are examples of the wonderful extensions of this art. In later years the field has been filled so full of improvements and special machines for special work, that only a brief citation of a few representative types is possible, and even then selection becomes a very difficult task. Many special tools, particularly those designed for bicycle work, have been devised, as exhibited by patent to Hillman, August 11, 1891, No. 457,718. In turning car wheels, an improvement consists in bringing the wheel to be dressed into close proximity to the edge of a rapidly revolving smooth metal disk, whereby the surface of the wheel is melted away without there being any actual contact between the wheel surface and the disk. This is shown in patent to Miltimore, August 24, 1886, No. 347,951. In metal tube manufacture three processes are worthy of mention: (1) Passing a heated solid rod endwise between the working faces of two rapidly rotating tapered rolls, set with their axes at an angle to each other, as shown in Mannesmann’s patent, April 26, 1887, No. 361,954 and 361,955. (2) Forcing a tube into a rapidly rotating die, whereby the friction softens the tube, and the pressure and rotation of the die spin it into a tube of reduced diameter, shown in patent to Bevington, January 13, 1891, No. 444,721. (3) Placing a hot ingot in a die and forcing a mandrel through the ingot, thereby causing it to assume the shape of the interior of the die, and greatly condensing the metal, shown in patents to Robertson, November 26, 1889, No. 416,014, and Ehrhardt, April 11, 1893, No. 495,245.
In welding, the employment of electricity constitutes the most important departure. This was introduced by Elihu Thomson, and is covered in his patents Nos. 347,140 to 347,142, August 10, 1886, and No. 501,546, July 18, 1893. In annealing and tempering, electricity has also been employed as a means of heating (see patent to Shaw, No. 211,938, February 4, 1879). It supplies an even heat and uniform temperature, and is much used in producing clock and watch springs. The making of iron castings malleable by a prolonged baking in a furnace in a bed of metallic oxide was an important, but early, step. It was the invention of Samuel Lucas, and is disclosed in his British patent No. 2,767, of 1804.