Page:Popular Science Monthly Volume 92.djvu/622

 606

��Popular Science Monthly

��Dissecting a Rubber Plant to Make It Grow

TO transplant rubber plants success- fully requires careful work on the part of the inexperienced horticulturist. The rubber leaf should be cut off with a part of the plant attached to the leaf stem, as the accompanying illustrations show. The branch is so important that without it the leaf will soon wither and die. The next operation is to fold up the leaf care- fully and to wrap it securely with a piece of string. The plant can now be planted in wet sand in a hot- house or placed under a bell jar in the home. The leaf is folded and tied so that the sun will not absorb the mois- ture from its delicate struc- ture. This moisture, in turn, feeds the stem and branch of the plant until they are able to draw their own moisture soil.

��Cold Rolled Steel and Cold Drawn Steel

ALMOST every person in the me- L chanical trades is familiar with steel that is smooth and has a bright finish. This steel comes in bars, rolls and shafts, and most of us call it "cold rolled steel" or "cold drawn steel." As a matter of fact there is a wide difference between the two, in the process of making, in the nature of the steel, and in its use. To be strictly correct and to avoid mistakes, which may be costly, these differences should be carefully noted.

Cold rolled steel is, as its nature im- plif's, rolled cold under great j)ressure, the material used for the purpose being hot rolled (black) stock. The machine which does this work is called a rolling mill, and consists of a pair of heavy, hard, and highly polished steel rolls mounted in a

��massive frame and suitably driven. The sheet or strip is passed between the rolls, which impart the smooth finish and exact size and shape, whether rectangular, square, round or otherwise. Due to the great pressure, the action of the rolling is also one of squeez- ing, and the stock comes out thinner, wider and longer than when it went into the rolls, and with a rounded edge, which re- tains the black fin- ish of the original. Cold rolled steel may be obtained in "flats" and in strips in a great variety of sizes and in thick- nesses of from .002 in. up. It is relative- ly soft

and is used mostly for bending and stamping purposes where a steel of accurate thickness, bright finish, and easy working qualities is desired. The thin- ner and narrower stock may be obtained in coils or rolls for use on automatic machines that -.vork from a continuous piece. Cold rolled steel is used extensive- ly for drawing operations ; that is, for the making of caps, cups, covers and shells.

Cold drawn steel is finished by an entirely different process. It is this process that gives us shafting, bars, rods and keys, smooth, bright, strong and very accurate. To obtain these desirable qualities a bar of hot rolled steel, slightly larger than the finished size, is run through a machine known as a draw bench, which has a highly polished, heavy and hardened steel die with an opening the exact size of the finished bar. By means of a powerful chain and gripping apparatus, the bar is pulled or drawn through the die.

���Carefully handling the rubber plant for trans- planting. The folding prevents evaporation

��from the

�� �