plugs removed, a short piece of pipe may then be inserted and perfectly soldered. In five minutes the ice in the pipes may be thawed and the water set to flowing freely again. TO JOIN WATER PIPES Water pipes may be united by using a preparation made by combining four parts of good portland cement and one part of unslaked lime mixed together in small portions in a stout mortar, adding enough water to permit it to be reduced to a soft paste. WELDING METALS Welding together two pieces of metal of any kind can be accomplished only when the surfaces to be joined are equally heated, and both surfaces must be brought to such a temperature that the particles will form a perfect continuity between the pieces united. This embraces the entire theory of welding, soldering or brazing metallic substances of any kind. In addition, however, to the equal and adequate heating of the surfaces to be united, every particle of coal dust, cinders or scales of oxide must be removed, so as to present two perfectly clean surfaces at the very moment when the union is to be effected. The piece of metal that would fuse at the lower temperature must be the guide, when bringing the surfaces of conjunction up to the proper heat. If, for example, two pieces of wrought iron are to be welded, the part that will melt at the lower temperature must be brought just to a welding heat, and the surface of the other piece must be heated quite as hot, or a trifle hotter than the first piece. Then, if the surfaces are clean when the parts are brought together, the union will be satisfactory. The degree of heat aimed at must be, not to produce a fluid, but simply to bring the metal into a condition between the fluid and plastic. GRINDING TOOLS All steel is composed of individual fibers running lengthways in the bar and held firmly together by cohesion. In almost all farm implements of the cutting kind the steel portion which forms the edge, if from a section of a bar, is welded to the bar lengthwise, so that it is the side of the bundle of fibers hammered and ground down that forms the edge. So, by holding on the grindstone all edgetools, as axes, scythes and knives of strawcutters, in such a manner that the action of the stone is at right angles with the edge, or, this is to say, by holding the edge of the tools square across the stone, the direction of the fibers will be changed, so as to present the ends instead of the side as a cutting edge. By grinding in this manner a finer, smoother edge is set, the tool is ground in less time, holds an edge a great deal longer, and is far less liable to nick out and to break. Plane irons should be ground to a level of about 35 degrees-chisels and gouges to 30. Turning chisels may sometimes run in an angle of 45. Molding tools, such as are used for ivory and for very hard wood, are made at from 50 to 60 degrees. Tools for working iron and steel are beveled at an inclination to the edge of from 60 to 70 degrees, and for cutting gun and similar metal range from 80 to 90. |