The Use And Care Of The Soldering Iron Fluxes Making Different Soldering Joints

The Soldering Iron.—The soldering iron is one of the first tools a plumber has to master. This tool is sometimes called a "copper bit" as it is made of copper; and so throughout this book the words "soldering iron," "copper bit," "iron," and "bit" are used synonymously. There are several different-shaped irons in common use today, but an iron shaped like the one in Fig. 13 is the one for use in the following work. Take the iron as it is purchased, having a wooden handle and the copper exposed on pointed end. Before it can be used the point must be faced and tinned. To do this, proceed as follows:

  1. First, heat the iron on the furnace.

  2. Second, place in vise and file the four surfaces of the point.

  3. Third, run a file over edges and point.

  4. Fourth, heat the iron until it will melt solder.

  5. Fifth, put 6 or 8 drops of solder and a piece of rosin the size of a chestnut on an ordinary red brick. (This rosin is called a flux.)

  6. Sixth, take the hot iron and melt the solder and rosin on the brick.

  7. Seventh, rub the four surfaces of the point of the iron on the brick keeping the point in the melted solder.

Fig. 13.--Copper. Fig. 13.—Copper.

The solder will soon stick to the copper surfaces and then the iron is ready for use.

Another way to tin the iron that is in common use is to rub the point of a hot iron on a piece of sal-ammoniac, or dip the hot iron in reduced muriatic acid, then rub the stick of solder on the iron. The use of muriatic acid in tinning the iron is not recommended. In the first place, it is not always possible to carry it, and in the second place it eats holes in the surface of iron, which makes it necessary to file and smooth the surfaces again. The constant use of muriatic acid on the copper soon wears it away and makes it unfit for use. Rosin is easily carried and applied and is by far the best to use in regular work.

Points to Remember in the Care of the Soldering Iron.

  1. First, proper tinning is absolutely necessary for rapid and good work.

  2. Second, do not allow the iron to heat red hot.

  3. Third, keep the point of the iron properly shaped.

  4. Fourth, use the same flux in tinning as is to be used in soldering.

  5. Fifth, when filing iron, file as little as possible.

  6. Sixth, keep in use two irons of the same size.


A flux is used to clean the surfaces of joints and seams to be soldered, also to keep them from oxidizing and to help the metals to fuse.

The following list gives the names of various fluxes in common use, how they are applied, and on what material they are most commonly used:

Flux How applied Used on
Rosin Sprinkled on Lead, tin, and brass
Tallow Melted Lead and brass
Muriatic acid (reduced) With swab Copper, galvanized iron
and brass
Muriatic acid (raw) With swab Dirty galvanized iron

Rosin.—Rosin is purchased by the pound and comes in chunks. It is very brittle and powders easily. Plumbers generally take a piece of 11⁄4 N. P. brass tubing, solder a trap screw in one end and a cone-shaped piece of copper on the other. The point of the cone is left open. Rosin is put into this tube and is easily sprinkled on work when needed.

Tallow.—A plumber's tallow candle answers the purpose for tallow flux. Some plumbers carry a can for the tallow, making it cleaner to handle.

Muriatic Acid.—Muriatic acid or hydrochloric acid is used both raw and reduced. Raw acid is not diluted or reduced. Reduced acid is made as follows: Put some zinc chips in a lead receptacle and then pour in the muriatic acid. The acid will at once act on the zinc. The fumes should be allowed to escape into the outer air. When chemical action ceases, the liquid remaining is called reduced acid.


It is necessary when soldering or wiping a joint to cover the parts of pipe adjoining the portion that is to be soldered or wiped so that the solder will not stick to it. There are a number of preparations for this. The one used by the best mechanics today is paste, made as follows:

  • 8 teaspoons of flour.

  • 1 teaspoon of salt.

  • 1 teaspoon of sugar.

  • Mix with water and boil down to a thick paste.

The advantages of paste as a soil are many:

  1. First, it is made of materials easily obtained.

  2. Second, solder will not stick to it.

  3. Third, if pipe is thoroughly cleaned, the paste will not rub off easily.

  4. Fourth, poor workmanship cannot be covered up.

  5. Fifth, when the work is completed, a wet cloth will wipe it off and leave the work clean.

Another soil used is lampblack and glue. A quantity of glue is melted and then lampblack is added. This needs to be heated and water added each time it is used. This soil is put on pipes with a short stubby brush. The work when completed with the silvery joint and jet black borders appears to the uninitiated very artistic and neat, but when the black soil is worn away the uneven edges of the joint appear, disclosing the reason for using a black soil that covers all defects. The mechanic of today who takes pride in his ability for good workmanship will not cover his work with black soil.

It can readily be seen that the use of lampblack soil encourages poor workmanship, while the use of paste forces, to a certain extent, good workmanship on the part of the mechanic.

Before soil or paste is applied, the pipe needs to be cleansed. Grease and dirt accumulate on the pipe. The methods employed to remove all foreign matter are simply to scrape the surface with fine sand or emery paper; sand and water will also answer for this purpose. This cleans the surface and allows the soil or paste to stick to the pipe.


The tools used in making the different solder joints as described and illustrated in this chapter are shown in Fig. 14.

Cup Joint.—The materials necessary for the work (Fig. 15): 12 inches of 1⁄2-inch AA lead pipe, paste, rosin, 1⁄2 and 1⁄2 solder.

If a gas furnace is not on the bench to heat the iron, then a gasoline furnace is necessary.

Each of the following operations must be done thoroughly to insure a perfect job:

  1. First, with the saw cut off 12 inches of 1⁄2-inch AA lead pipe from the coil. When cutting off a piece of lead pipe from a coil or reel, always straighten out 1 foot more than is needed. This leaves 1 foot of straight pipe always on the coil.

Fig. 14.--Tools used for making solder joints. Fig. 14.—Tools used for making solder joints.

  1. Second, with the flat side of the rasp, square the ends of the 12-inch piece of pipe. (A good way to do this is to hold the pipe at right angles with the edge of the bench, run the rasp across the end of the pipe, keeping the rasp parallel with the edge of the bench. Apply this to all work when necessary to square the ends of pipe.)

    Third, cut the pipe with the saw, making two pieces each 6 inches in length.

    Fourth, square the ends just cut.

    Fifth, rasp the edges of one end as shown in the cut. Hold the work in such a way that the stroke of the rasp can be seen without moving the pipe.

    Sixth, take the other 6-inch piece of pipe and with the turn pin spread one end of it. The turn pin must be struck squarely in the center with the hammer, the point of the turn pin being kept in the center of the pipe. The pipe should be turned after each blow of the hammer. The pipe must not rest on the bench but should be held in the hand while using the turn pin. If the pipe bends, it can be straightened with bending irons. If the pipe is spread more on one side than the other, the turn pin should be hit on the opposite side so as to even the spread.

Fig. 15. Fig. 15.

Fig. 16.--Cup joint. Fig. 16.—Cup joint.

  1. Seventh, when the pipes are properly fitted, moisten the tips of the fingers with paste and rub the paste on parts of pipe marked "paste." Put the pipe aside to allow the paste to dry.

    Eighth, put the soldering iron on to heat.

    Ninth, with the shave hook scrape off the paste and surface dirt as shown in the figure. The inside of the cup will look bright, but must be scraped.

    Tenth, place the two pieces into position as shown in Fig. 16, sprinkle rosin on the joint, melt a few drops of solder on the joint and with the iron melt the solder on the joint, drawing the iron around the pipe keeping the solder melted around the iron all the time.

    Eleventh, fill the joint with solder and continue to draw the hot iron around the joint until a smooth and bright surface is obtained. To master the correct use of the soldering iron in this work, considerable practice will be necessary.

Overcast Joints.—(Fig. 17.)

Note.—Each operation must be performed thoroughly.

  1. First, saw off from a coil of 11⁄2-inch D lead pipe a 10-inch piece of pipe.

    Second, square the ends with the rasp, as previously explained.

    Third, take a 11⁄2-inch drift plug and drive through the pipe (Fig. 18).

    Fourth, saw the pipe into two pieces of 5 inches each.

    Fifth, square the ends of the pipe with the rasp.

    Sixth, rasp off the outside edge of one end of the pipe as shown.

    Seventh, rasp off the inside edge of one end of the pipe.

    Eighth, finish rasped surfaces with a file. Both surfaces should have the same angle.

Fig. 17. Fig. 17.
Fig. 18. Fig. 18.
Fig. 19.--Overcast joint. Fig. 19.—Overcast joint.

  1. Ninth, with a shave hook scrape the outside surface of each pipe for about 1 inch from the end.

    Tenth, put the soldering iron on to heat.

    Eleventh, paste paper on the joint as shown in the cut.

    Twelfth, fit the pieces together and lay on the bench. Drop some melted solder on the joint and with the hot iron proceed to flow the solder around the joint by turning the pipe. Use plenty of flux (rosin). The pipes must be tacked in three or four places at first or they will have a tendency to spread.

    Thirteenth, to finish the joint, lift the iron straight up.

This joint when finished will have a bright smooth finish. The two foregoing joints need considerable practice and should be perfectly mastered before going on to the next job.


A description of the making of wiped seams for lead-lined tanks will not be attempted as very few are made now. The plumber, however, is often called upon to make a seam joining two pieces of sheet lead. The beginner will do well to go over the following exercise carefully and practice it thoroughly.

Fig. 20.--Flat seam. Fig. 20.—Flat seam.

Materials.—Two pieces of 8-pound sheet lead, 6 by 10 inches each; one bar of 1⁄2 and 1⁄2 solder; paste, paper, and rosin.

Tools.—Rasp, shave hook, and soldering iron.

The 10-inch side of each piece is rasped and fitted together. The edges are cleaned and paper is pasted on leaving 1⁄4 inch for solder. Paste without the paper can be put on. This will make a joint 1⁄2 inch wide.

Apply the rosin to the joint, then with the heated iron and some solder tack the seam on the top, then on the bottom and middle. This will prevent the seam from spreading when the lead is heated. Solder and rosin can now be put on the full length of the joint. With a hot iron proceed to float the solder down the seam. The soldering iron must not rest at full length on the pieces of lead or it will melt the lead and render the work useless. The solder will flow and form a clean neat seam, if the iron is at the right heat and the right amount of solder is put on. If the iron is too hot, the solder will flow instantly when the iron is laid on it and the solder will disappear as it runs through the seam. If the iron is too cold the solder will not melt enough to flow. Too much solder on the seam will cause it to overflow, that is, the solder will spread beyond the papered edges. After a little practice this surplus solder can be drawn in on the seam with the iron and carried along the seam to some point that has not enough solder. When the seam is completed the edges should be perfectly straight and even. The iron is carried along the seam with one stroke which makes the seam appear smooth and bright.

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