coating every part thereof and insinuating itself into every crack and corner. Between surfaces, capillary attraction fills all the space and makes a solid filling after the work has cooled.

In this kind of brazing, parts of the work which must not be adhered to by the spelter, are covered with graphite specially prepared for the purpose in such a manner that the brass will never adhere where the "anti-flux" graphite has been applied. This substance is made up into a paste

and applied with a brush to parts which must not be covered by the spelter. The graphite is not affected by the intense heat of the spelter, and if care is used in painting on the graphite, little or no filing will be necessary after the brazing operation has been finished.

The proper flux to use with one of these furnaces, is pretty hard to determine. Some operators use pure borax, and keep it from three-eighths of an inch, to over two

inches deep on top of the spelter, while other people who do excellent brazing, use three parts boracic acid and one part borax, while others use exactly the opposite proportion of borax and acid. Other people use boracic acid straight, without anything else with it. Again, some use soda mixed with borax, and, in fact, almost any compound which has borax in it, seems to work well as a flux in the dipping process of brazing.

The other method of brazing, alluded to above, as being a great advance in the process of brazing, is known as the "Pich Process of Brazing Cast Iron." Cast iron can be brazed by the methods described above, but it is very delicate business, as the iron melts, or at least softens so it will break under the least strain, at a temperature pretty near that at which the spelter melts, so that it is almost impossible to melt the brass without "burning" up the cast iron which is being brazed.

By the Pich method, the surfaces to be brazed are first brushed over with a varnish made of oxide of copper mixed with any liquid which will allow of the copper being spread with a brush, and which will afterwards hold the oxide when dry.

After this application, the brazing is carried out the same as in the ordinary method. The brass or spelter is placed in position, and the flux applied, then a gas-air flame is applied as in ordinary brazing. It is assumed that the metallic oxide acts as a reducer on the surface of the cast iron to be brazed. Without the oxide, the carbon above noted acts much like the graphite used in the dipping method of brazing as an anti-flux as described in the description of the dipping process of brazing. It is claimed that the metallic oxide is reduced, removing during the process of reduction, the carbon on the surface of

the metal, and, it is claimed, often penetrating for a distance of three or four inches into the metal itself, thereby making the cast iron stronger at and near the joint, than it was before. Of this matter, the writer has no personal knowledge. The process has been described very fully in a paper by Wilifred Lewis, read before the American Society of Mechanical Engineers.

It is claimed that both the joint and the casting itself is made from 5% to 10% stronger by the treatment with oxide. This, if correct, is a pointer of value to the iron worker, aside from in the process of brazing, for, if in certain cases, cast iron can have its strength increased 10%, it will be of inestimable value to the designing engineer to know thereof.

Soldering.

Soldering is much like brazing in some of its details. In fact, some kinds of soldering are done exactly like some kinds of brazing, but other varieties of soldering are totally unlike any brazing operations. Soldering, therefore, may be taken to mean the uniting of two or more pieces of metal, with fusible alloys of lead and tin. Sometimes, lead areas are united by melting their surfaces without the use of solder, the surfaces being fluxed. This form of soldering differs slightly from welding, and is called "burning" by the trade. The method is usually employed in uniting the edges of sheets of lead used in the lining of acid tanks or similar apparatus.

The particular kind of soldering usually employed is by the use of the so-called "soldering iron," which is really a copper bit placed on the end of an iron handle.

An alloy of lead and tin is used which readily adheres to the surface of the bit, which must be clean, free from oxide, etc. The operation of coating a copper bit with solder is known as "tinning," and will be described elsewhere. The theory of soft soldering is: that as the soft metal adheres to, and unites with the surface of the copper bit, so will the soft metal, under certain conditions, ad

a

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The Derry-Collard Co. NY.

Figs. 11 and 12. Forms of soldering "irons."

here to, and unite with the surface of the metals to be soldered. In fact, soft soldering, as well as brazing, consists of welding together two or more pieces of similar or dissimilar metals by means of another metal of lower melting point. That constitutes soldering; all the rest of the operation, is detail, which may be varied to suit conditions.

The form of copper bit usually employed, is shown by

Fig. 11, herewith. There are also many other shapes in common use, and those represented by a, b, c and d, in Fig. 11, are frequently seen. In the latter illustration, a is the "hatchet" bit, used perhaps more frequently than any of the others, except that shown by Fig. 11, which is the tool with which nearly all jobbing and repairing is done. The "hatchet" form of bit is also shown by b, Fig. 12, and differs only that the handle is swivelled so that the edge of the bit may be turned in any direction as made necessary by the work in hand. This tool is used for long, straight seams, and for heavy work generally. The bit shown at c, is one of the many shapes used for special work. Tools of any shape can be easily made by the workman who simply forges the copper when cold, to the size and shape desired. Copper forges on the anvil pretty well and if the precaution be taken to anneal the bit frequently, almost any desired shape can be made with little if any filing or cutting-simply by forging alone. The annealing operation for copper, consists of heating to a dull red heat, and then quenching in water—the reverse of the steel hardening operation.

The shape shown by C, is a very useful tool where soldering has to be done in corners or small places. It is of the same shape as form A, except that it is smaller, and round in section, instead of "hex." The handle is screwed into the bit, and three holes are drilled and tapped so that the handle can be put in as shown, or with the flat end either "hatchet," or "cross," as the work to be done may demand. The swivel hatchet bit, B, is one of the most useful tools. It ranks next to form A. Fitted with the two tools, Fig. 11, and B, Fig. 12, all kinds of large work can be done. With the addition of C, the stock is complete.