In an electric circuit the ends of two pieces of metal brought together form the point of greatest resistance in the electric circuit, and the abutting ends instantly begin to heat. The hotter this metal becomes, the greater the resistance to the flow of current; consequently, as the edges of the abutting ends heat, the current is forced into the adjacent cooler parts, until there is a uniform heat throughout the entire mass. The heat is first developed in the interior of the metal so that it is welded there as perfectly as at the surface.



The electric welder (Figure 42) is built to hold the parts to be joined between two heavy copper dies or contacts. A current of three to five volts, but of very great volume (amperage), is allowed to pass across these dies, and in going through the metal to be welded, heats the edges to a welding temperature. It may be explained that the voltage of an electric current measures the pressure or force with which it is being sent through the circuit and has nothing to do with the quantity or volume passing. Amperes measure the rate at which the current is passing through the circuit and consequently give a measure of the quantity which passes in any given time. Volts correspond to water pressure measured by pounds to the square inch; amperes represent the flow in gallons per minute. The low voltage used avoids all danger to the operator, this pressure not being sufficient to be felt even with the hands resting on the copper contacts.

Current is supplied to the welding machine at a higher voltage and lower amperage than is actually used between the dies, the low voltage and high amperage being produced by a transformer incorporated in the machine itself. By means of windings of suitable size wire, the outside current may be received at voltages ranging from 110 to 550 and converted to the low pressure needed.

The source of current for the resistance welder must be alternating, that is, the current must first be negative in value and then positive, passing from one extreme to the other at rates varying from 25 to 133 times a second. This form is known as alternating current, as opposed to direct current, in which there is no changing of positive and negative.

The current must also be what is known as single phase, that is, a current which rises from zero in value to the highest point as a positive current and then recedes to zero before rising to the highest point of negative value. Two-phase of three-phase currents would give two or three positive impulses during this time.

As long as the current is single phase alternating, the voltage and cycles (number of alternations per second) may be anything convenient. Various voltages and cycles are taken care of by specifying all these points when designing the transformer which is to handle the current.

Direct current is not used because there is no way of reducing the voltage conveniently without placing resistance wires in the circuit and this uses power without producing useful work. Direct current may be changed to alternating by having a direct current motor running an alternating current dynamo, or the change may be made by a rotary converter, although this last method is not so satisfactory as the first.

The voltage used in welding being so low to start with, it is absolutely necessary that it be maintained at the correct point. If the source of current supply is not of ample capacity for the welder being used, it will be very hard to avoid a fall of voltage when the current is forced to pass through the high resistance of the weld. The current voltage for various work is calculated accurately, and the efficiency of the outfit depends to a great extent on the voltage being constant.

A simple test for fall of voltage is made by connecting an incandescent electric lamp across the supply lines at some point near the welder. The lamp should burn with the same brilliancy when the weld is being made as at any other time. If the lamp burns dim at any time, it indicates a drop in voltage, and this condition should be corrected.

The dynamo furnishing the alternating current may be in the same building with the welder and operated from a direct current motor, as mentioned above, or operated from any convenient shafting or source of power. When the dynamo is a part of the welding plant it should be placed as close to the welding machine as possible, because the length of the wire used affects the voltage appreciably.

In order to hold the voltage constant, the Toledo Electric Welder Company has devised connections which include a rheostat to insert a variable resistance in the field windings of the dynamo so that the voltage may be increased by cutting this resistance out at the proper time. An auxiliary switch is connected to the welder switch so that both switches act together. When the welder switch is closed in making a weld, that portion of the rheostat resistance between two arms determining the voltage is short circuited. This lowers the resistance and the field magnets of the dynamo are made stronger so that additional voltage is provided to care for the resistance in the metal being heated.

A typical machine is shown in the accompanying cut (Figure 43). On top of the welder are two jaws for holding the ends of the pieces to be welded. The lower part of the jaws is rigid while the top is brought down on top of the work, acting as a clamp. These jaws carry the copper dies through which the current enters the work being handled. After the work is clamped between the jaws, the upper set is forced closer to the lower set by a long compression lever. The current being turned on with the surfaces of the work in contact, they immediately heat to the welding point when added pressure on the lever forces them together and completes the weld.



The transformer is carried in the base of the machine and on the left-hand side is a regulator for controlling the voltage for various kinds of work. The clamps are applied by treadles convenient to the foot of the operator. A treadle is provided which instantly releases both jaws upon the completion of the weld. One or both of the copper dies may be cooled by a stream of water circulating through it from the city water mains (Figure 44). The regulator and switch give the operator control of the heat, anything from a dull red to the melting point being easily obtained by movement of the lever (figure 45).



Welding.—It is not necessary to give the metal to be welded any special preparation, although when very rusty or covered with scale, the rust and scale should be removed sufficiently to allow good contact of clean metal on the copper dies. The cleaner and better the stock, the less current it takes, and there is less wear on the dies. The dies should be kept firm and tight in their holders to make a good contact. All bolts and nuts fastening the electrical contacts should be clean and tight at all times.

The scale may be removed from forgings by immersing them in a pickling solution in a wood, stone or lead-lined tank.

The solution is made with five gallons of commercial sulphuric acid in 150 gallons of water. To get the quickest and best results from this method, the solution should be kept as near the boiling point as possible by having a coil of extra heavy lead pipe running inside the tank and carrying live steam. A very few minutes in this bath will remove the scale and the parts should then be washed in running water. After this washing they should be dipped into a bath of 50 pounds of unslaked lime in 150 gallons of water to neutralize any trace of acid.

Cast iron cannot be commercially welded, as it is high in carbon and silicon, and passes suddenly from a crystalline to a fluid state when brought to the welding temperature. With steel or wrought iron the temperature must be kept below the melting point to avoid injury to the metal. The metal must be heated quickly and pressed together with sufficient force to push all burnt metal out of the joint.

High carbon steel can be welded, but must be annealed after welding to overcome the strains set up by the heat being applied at one place. Good results are hard to obtain when the carbon runs as high as 75 points, and steel of this class can only be handled by an experienced operator. If the steel is below 25 points in carbon content, good welds will always be the result. To weld high carbon to low carbon steel, the stock should be clamped in the dies with the low carbon stock sticking considerably further out from the die than the high carbon stock. Nickel steel welds readily, the nickel increasing the strength of the weld.

Iron and copper may be welded together by reducing the size of the copper end where it comes in contact with the iron. When welding copper and brass the pressure must be less than when welding iron. The metal is allowed to actually fuse or melt at the juncture and the pressure must be sufficient to force the burned metal out. The current is cut off the instant the metal ends begin to soften, this being done by means of an automatic switch which opens when the softening of the metal allows the ends to come together. The pressure is applied to the weld by having the sliding jaw moved by a weight on the end of an arm.

Copper and brass require a larger volume of current at a lower voltage than for steel and iron. The die faces are set apart three times the diameter of the stock for brass and four times the diameter for copper.

Light gauges of sheet steel can be welded to heavy gauges or to solid bars of steel by "spot" welding, which will be described later. Galvanized iron can be welded, but the zinc coating will be burned off. Sheet steel can be welded to cast iron, but will pull apart, tearing out particles of the iron.

Sheet copper and sheet brass may be welded, although this work requires more experience than with iron and steel. Some grades of sheet aluminum can be spot-welded if the slight roughness left on the surface under the die is not objectionable.

Butt Welding.—This is the process which joins the ends of two pieces of metal as described in the foregoing part of this chapter. The ends are in plain sight of the operator at all times and it can easily be seen when the metal reaches the welding heat and begins to soften (Figure 46). It is at this point that the pressure must be applied with the lever and the ends forced together in the weld.



The parts are placed in the clamping jaws (Figure 47) with 1/8 to 1/2 inch of metal extending beyond the jaw. The ends of the metal touch each other and the current is turned on by means of a switch. To raise the ends to the proper heat requires from 3 seconds for 1/4-inch rods to 35 seconds for a 1-1/2-inch bar.

This method is applicable to metals having practically the same area of metal to be brought into contact on each end. When such parts are forced together a slight projection will be left in the form of a fin or an enlarged portion called an upset. The degree of heat required for any work is found by moving the handle of the regulator one way or the other while testing several parts. When this setting is right the work can continue as long as the same sizes are being handled.



Copper, brass, tool steel and all other metals that are harmed by high temperatures must be heated quickly and pressed together with sufficient force to force all burned metal from the weld.

In case it is desired to make a weld in the form of a capital letter T, it is necessary to heat the part corresponding to the top bar of the T to a bright red, then bring the lower bar to the pre-heated one and again turn on the current, when a weld can be quickly made.

Spot Welding.—This is a method of joining metal sheets together at any desired point by a welded spot about the size of a rivet. It is done on a spot welder by fusing the metal at the point desired and at the same instant applying sufficient pressure to force the particles of molten metal together. The dies are usually placed one above the other so that the work may rest on the lower one while the upper one is brought down on top of the upper sheet to be welded.

One of the dies is usually pointed slightly, the opposing one being left flat. The pointed die leaves a slight indentation on one side of the metal, while the other side is left smooth. The dies may be reversed so that the outside surface of any work may be left smooth. The current is allowed to flow through the dies by a switch which is closed after pressure is applied to the work.

There is a limit to the thickness of sheet metal that can be welded by this process because of the fact that the copper rods can only carry a certain quantity of current without becoming unduly heated themselves. Another reason is that it is difficult to make heavy sections of metal touch at the welding point without excessive pressure.

Lap welding is the process used when two pieces of metal are caused to overlap and when brought to a welding heat are forced together by passing through rollers, or under a press, thus leaving the welded joint practically the same thickness as the balance of the work.

Where it is desirable to make a continuous seam, a special machine is required, or an attachment for one of the other types. In this form of work the stock must be thoroughly cleaned and is then passed between copper rollers which act in the same capacity as the copper dies.

Other Applications.—Hardening and tempering can be done by clamping the work in the welding dies and setting the control and time to bring the metal to the proper color, when it is cooled in the usual manner.

Brazing is done by clamping the work in the jaws and heating until the flux, then the spelter has melted and run into the joint. Riveting and heading of rivets can be done by bringing the dies down on opposite ends of the rivet after it has been inserted in the hole, the dies being shaped to form the heads properly.

Hardened steel may be softened and annealed so that it can be machined by connecting the dies of the welder to each side of the point to be softened. The current is then applied until the work has reached a point at which it will soften when cooled.

Troubles and Remedies.—The following methods have been furnished by the Toledo Electric Welder Company and are recommended for this class of work whenever necessary.

To locate grounds in the primary or high voltage side of the circuit, connect incandescent lamps in series by means of a long piece of lamp cord, as shown, in Figure 43a. For 110 volts use one lamp, for 220 volts use two lamps and for 440 volts use four lamps. Attach one end of the lamp cord to one side of the switch, and close the switch. Take the other end of the cord in the hand and press it against some part of the welder frame where the metal is clean and bright. Paint, grease and dirt act as insulators and prevent electrical contact. If the lamp lights, the circuit is in electrical contact with the frame; in other words, grounded. If the lamps do not light, connect the wire to a terminal block, die or slide. If the lamps then light, the circuit, coils or leads are in electrical contact with the large coil in the transformer or its connections.

If, however, the lamps do not light in either case, the lamp cord should be disconnected from the switch and connected to the other side, and the operations of connecting to welder frame, dies, terminal blocks, etc., as explained above, should be repeated. If the lamps light at any of these connections, a "ground" is indicated. "Grounds" can usually be found by carefully tracing the primary circuit until a place is found where the insulation is defective. Reinsulate and make the above tests again to make sure everything is clear. If the ground can not be located by observation, the various parts of the primary circuit should be disconnected, and the transformer, switch, regulator, etc., tested separately.

To locate a ground in the regulator or other part, disconnect the lines running to the welder from the switch. The test lamps used in the previous tests are connected, one end of lamp cord to the switch, the other end to a binding post of the regulator. Connect the other side of the switch to some part of the regulator housing. (This must be a clean connection to a bolt head or the paint should be scraped off.) Close the switch. If the lamps light, the regulator winding or some part of the switch is "grounded" to the iron base or core of the regulator. If the lamps do not light, this part of the apparatus is clear.

This test can be easily applied to any part of the welder outfit by connecting to the current carrying part of the apparatus, and to the iron base or frame that should not carry current. If the lamps light, it indicates that the insulation is broken down or is defective.

An A.C. voltmeter can, of course, be substituted for the lamps, or a D.C. voltmeter with D.C. current can be used in making the tests.

A short circuit in the primary is caused by the insulation of the coils becoming defective and allowing the bare copper wires to touch each other. This may result in a "burn out" of one or more of the transformer coils, if the trouble is in the transformer, or in the continued blowing of fuses in the line. Feel of each coil separately. If a short circuit exists in a coil it will heat excessively. Examine all the wires; the insulation may have worn through and two of them may cross, or be in contact with the frame or other part of the welder. A short circuit in the regulator winding is indicated by failure of the apparatus to regulate properly, and sometimes, though not always, by the heating of the regulator coils.

The remedy for a short circuit is to reinsulate the defective parts. It is a good plan to prevent trouble by examining the wiring occasionally and see that the insulation is perfect.

To Locate Grounds and Short Circuits in the Secondary, or Low Voltage Side.—Trouble of this kind is indicated by the machine acting sluggish or, perhaps, refusing to operate. To make a test, it will be necessary to first ascertain the exciting current of your particular transformer. This is the current the transformer draws on "open circuit," or when supplied with current from the line with no stock in the welder dies. The following table will give this information close enough for all practical purposes:

K.W. ————————- Amperes at ———————— Rating 110 Volts 220 Volts 440 Volts 550 Volts 3 1.5 .75 .38 .3 5 2.5 1.25 .63 .5 8 3.6 1.8 .9 .72 10 4.25 2.13 1.07 .85 15 6. 3. 1.5 1.2 20 7. 3.5 1.75 1.4 30 9. 4.5 2.25 1.8 35 9.6 4.8 2.4 1.92 50 10. 5. 2.5 2

Remove the fuses from the wall switch and substitute fuses just large enough to carry the "exciting" current. If no suitable fuses are at hand, fine strands of copper from an ordinary lamp cord may be used. These strands are usually No. 30 gauge wire and will fuse at about 10 amperes. One or more strands should be used, depending on the amount of exciting current, and are connected across the fuse clips in place of fuse wire. Place a piece of wood or fibre between the welding dies in the welder as though you were going to weld them. See that the regulator is on the highest point and close the welder switch. If the secondary circuit is badly grounded, current will flow through the ground, and the small fuses or small strands of wire will burn out. This is an indication that both sides of the secondary circuit are grounded or that a short circuit exists in a primary coil. In either case the welder should not be operated until the trouble is found and removed. If, however, the small fuses do not "blow," remove same and replace the large fuses, then disconnect wires running from the wall switch to the welder and substitute two pieces of No. 8 or No. 6 insulated copper wire, after scraping off the insulation for an inch or two at each end. Connect one wire from the switch to the frame of welder; this will leave one loose end. Hold this a foot or so away from the place where the insulation is cut off; then turn on the current and strike the free end of this wire lightly against one of the copper dies, drawing it away quickly. If no sparking is produced, the secondary circuit is free from ground, and you will then look for a broken connection in the circuit. Some caution must be used in making the above test, as in case one terminal is heavily grounded the testing wire may be fused if allowed to stay in contact with the die.

The Remedy.—Clean the slides, dies and terminal blocks thoroughly and dry out the fibre insulation if it is damp. See that no scale or metal has worked under the sliding parts, and that the secondary leads do not touch the frame. If the ground is very heavy it may be necessary to remove the slides in order to facilitate the examination and removal of the ground. Insulation, where torn or worn through, must be carefully replaced or taped. If the transformer coils are grounded to the iron core of the transformer or to the secondary, it may be necessary to remove the coils and reinsulate them at the points of contact. A short circuited coil will heat excessively and eventually burn out. This may mean a new coil if you are unable to repair the old one. In all cases the transformer windings should be protected from mechanical injury or dampness. Unless excessively overloaded, transformers will last for years without giving a moment's trouble, if they are not exposed to moisture or are not injured mechanically.

The most common trouble arises from poor electrical contacts, and they are the cause of endless trouble and annoyance. See that all connections are clean and bright. Take out the dies every day or two and see that there is no scale, grease or dirt between them and the holders. Clean them thoroughly before replacing. Tighten the bolts running from the transformer leads to the work jaws.

ELECTRIC ARC WELDING

This method bears no relation to the one just considered, except that the source of heat is the same in both cases. Arc welding makes use of the flame produced by the voltaic arc in practically the same way that oxy-acetylene welding uses the flame from the gases.

If the ends of two pieces of carbon through which a current of electricity is flowing while they are in contact are separated from each other quite slowly, a brilliant arc of flame is formed between them which consists mainly of carbon vapor. The carbons are consumed by combination with the oxygen in the air and through being turned to a gas under the intense heat.

The most intense action takes place at the center of the carbon which carries the positive current and this is the point of greatest heat. The temperature at this point in the arc is greater than can be produced by any other means under human control.

An arc may be formed between pieces of metal, called electrodes, in the same way as between carbon. The metallic arc is called a flaming arc and as the metal of the electrode burns with the heat, it gives the flame a color characteristic of the material being used. The metallic arc may be drawn out to a much greater length than one formed between carbon electrodes.

Arc Welding is carried out by drawing a piece of carbon which is of negative polarity away from the pieces of metal to be welded while the metal is made positive in polarity. The negative wire is fastened to the carbon electrode and the work is laid on a table made of cast or wrought iron to which the positive wire is made fast. The direction of the flame is then from the metal being welded to the carbon and the work is thus prevented from being saturated with carbon, which would prove very detrimental to its strength. A secondary advantage is found in the fact that the greatest heat is at the metal being welded because of its being the positive electrode.

The carbon electrode is usually made from one quarter to one and a half inches in diameter and from six to twelve inches in length. The length of the arc may be anywhere from one inch to four inches, depending on the size of the work being handled.

While the parts are carefully insulated to avoid danger of shock, it is necessary for the operator to wear rubber gloves as a further protection, and to wear some form of hood over the head to shield him against the extreme heat liberated. This hood may be made from metal, although some material that does not conduct electricity is to be preferred. The work is watched through pieces of glass formed with one sheet, which is either blue or green, placed over another which is red. Screens of glass are sometimes used without the head protector. Some protection for the eyes is absolutely necessary because of the intense white light.

It is seldom necessary to preheat the work as with the gas processes, because the heat is localized at the point of welding and the action is so rapid that the expansion is not so great. The necessity of preheating, however, depends entirely on the material, form and size of the work being handled. The same advice applies to arc welding as to the gas flame method but in a lesser degree. Filling rods are used in the same way as with any other flame process.

It is the purpose of this explanation to state the fundamental principles of the application of the electric arc to welding metals, and by applying the principles the following questions will be answered:

What metals can be welded by the electric arc?

What difficulties are to be encountered in applying the electric arc to welding?

What is the strength of the weld in comparison with the original piece?

What is the function of the arc welding machine itself?

What is the comparative application of the electric arc and the oxy-acetylene method and others of a similar nature?

The answers to these questions will make it possible to understand the application of this process to any work. In a great many places the use of the arc is cutting the cost of welding to a very small fraction of what it would be by any other method, so that the importance of this method may be well understood.

Any two metals which are brought to the melting temperature and applied to each other will adhere so that they are no more apt to break at the weld than at any other point outside of the weld. It is the property of all metals to stick together under these conditions. The electric arc is used in this connection merely as a heating agent. This is its only function in the process.

It has advantages in its ease of application and the cheapness with which heat can be liberated at any given point by its use. There is nothing in connection with arc welding that the above principles will not answer; that is, that metals at the melting point will weld and that the electric arc will furnish the heat to bring them to this point. As to the first question, what metals can be welded, all metals can be welded.

The difficulties which are encountered are as follows:

In the case of brass or zinc, the metals will be covered with a coat of zinc oxide before they reach a welding heat. This zinc oxide makes it impossible for two clean surfaces to come together and some method has to be used for eliminating this possibility and allowing the two surfaces to join without the possibility of the oxide intervening. The same is true of aluminum, in which the oxide, alumina, will be formed, and with several other alloys comprising elements of different melting points.

In order to eliminate these oxides, it is necessary in practical work, to puddle the weld; this is, to have a sufficient quantity of molten metal at the weld so that the oxide is floated away. When this is done, the two surfaces which are to be joined are covered with a coat of melted metal on which floats the oxide and other impurities. The two pieces are thus allowed to join while their surfaces are protected. This precaution is not necessary in working with steel except in extreme cases.

Another difficulty which is met with in the welding of a great many metals is their expansion under heat, which results in so great a contraction when the weld cools that the metal is left with a considerable strain on it. In extreme cases this will result in cracking at the weld or near it. To eliminate this danger it is necessary to apply heat either all over the piece to be welded or at certain points. In the case of cast iron and sometimes with copper it is necessary to anneal after welding, since otherwise the welded pieces will be very brittle on account of the chilling. This is also true of malleable iron.

Very thin metals which are welded together and are not backed up by something to carry away the excess heat, are very apt to burn through, leaving a hole where the weld should be. This difficulty can be eliminated by backing up the weld with a metal face or by decreasing the intensity of the arc so that this melting through will not occur. However, the practical limit for arc welding without backing up the work with a metal face or decreasing the intensity of the arc is approximately 22 gauge, although thinner metal can be welded by a very skillful and careful operator.

One difficulty with arc welding is the lack of skillful operators. This method is often looked upon as being something out of the ordinary and governed by laws entirely different from other welding. As a matter of fact, it does not take as much skill to make a good arc weld as it does to make a good weld in a forge fire as the blacksmith does it. There are few jobs which cannot be handled successfully by an operator of average intelligence with one week's instructions, although his work will become better and better in quality as he continues to use the arc.

Now comes the question of the strength of the weld after it has been made. This strength is equally as great as that of the metal that is used to make the weld. It should be remembered, however, that the metal which goes into the weld is put in there as a casting and has not been rolled. This would make the strength of the weld as great as the same metal that is used for filling if in the cast form.

Two pieces of steel could be welded together having a tensile strength at the weld of 50,000 pounds. Higher strengths than this can be obtained by the use of special alloys for the filling material or by rolling. Welds with a tensile strength as great as mentioned will give a result which is perfectly satisfactory in almost all cases.

There are a great many jobs where it is possible to fill up the weld, that is, make the section at the point of the weld a little larger than the section through the rest of the piece. By doing this, the disadvantages of the weld being in the form of a casting in comparison with the rest of the piece being in the form of rolled steel can be overcome, and make the weld itself even stronger than the original piece.

The next question is the adaptability of the electric arc in comparison with forge fire, oxy-acetylene or other method. The answer is somewhat difficult if made general. There are no doubt some cases where the use of a drop hammer and forge fire or the use of the oxy-acetylene torch will make, all things being considered, a better job than the use of the electric arc, although a case where this is absolutely proved is rare.

The electric arc will melt metal in a weld for less than the same metal can be melted by the use of the oxy-acetylene torch, and, on account of the fact that the heat can be applied exactly where it is required and in the amount required, the arc can in almost all cases supply welding heat for less cost than a forge fire or heating furnace.

The one great advantage of the oxy-acetylene method in comparison with other methods of welding is the fact that in some cases of very thin sheet, the weld can be made somewhat sooner than is possible otherwise. With metal of 18 gauge or thicker, this advantage is eliminated. In cutting steel, the oxy-acetylene torch is superior to almost any other possible method.

Arc Welding Machines.—A consideration of the function and purpose of the various types of arc welding machines shows that the only reason for the use of any machine is either for conversion of the current from alternating to direct, or, if the current is already direct, then the saving in the application of this current in the arc.

It is practically out of the question to apply an alternating current arc to welding for the reason that in any arc practically all the heat is liberated at the positive electrode, which means that, in alternating current, half the heat is liberated at each electrode as the current changes its direction of flow or alternates. Another disadvantage of the alternating arc is that it is difficult of control and application.

In all arc welding by the use of the carbon arc, the positive electrode is made the piece to be welded, while in welding with metallic electrodes this may be either the piece to be welded of the rod that is used as a filler. The voltage across the arc is a variable quantity, depending on the length of the flame, its temperature and the gases liberated in the arc. With a carbon electrode the voltage will vary from zero to forty-five volts. With the metallic electrode the voltage will vary from zero to thirty volts. It is, therefore, necessary for the welding machine to be able to furnish to the arc the requisite amount of current, this amount being varied, and furnish it at all times at the voltage required.

The simplest welding apparatus is a resistance in series with the arc. This is entirely satisfactory in every way except in cost of current. By the use of resistance in series with the arc and using 220 volts as the supply, from eighty to ninety per cent of the current is lost in heat at the resistance. Another disadvantage is the fact that most materials change their resistance as their temperature changes, thus making the amount of current for the arc a variable quantity, depending on the temperature of the resistance.

There have been various methods originated for saving the power mentioned and a good many machines have been put on the market for this purpose. All of them save some power over what a plain resistance would use. Practically all arc welding machines at the present time are motor generator sets, the motor of which is arranged for the supply voltage and current, this motor being direct connected to a compound wound generator delivering approximately seventy-five volts direct current. Then by the use of a resistance, this seventy-five volt supply is applied to the arc. Since the voltage across the arc will vary from zero to fifty volts, this machine will save from zero up to seventy per cent of the power that the machine delivers. The rest of the power, of course, has to be dissipated in the resistance used in series with the arc.

A motor generator set which can be purchased from any electrical company, with a long piece of fence wire wound around a piece of asbestos, gives results equally as good and at a very small part of the first cost.

It is possible to construct a machine which will eliminate all losses in the resistance; in other words, eliminate all resistance in series with the arc. A machine of this kind will save its cost within a very short time, providing the welder is used to any extent.

Putting it in figures, the results are as follows for average conditions. Current at 2c per kilowatt hour, metallic electrode arc of 150 amperes, carbon arc 500 amperes; voltage across the metallic electrode arc 20, voltage across the carbon arc 35. Supply current 220 volts, direct. In the case of the metallic electrode, if resistance is used, the cost of running this arc is sixty-six cents per hour. With the carbon electrode, $2.20 per hour. If a motor generator set with a seventy volt constant potential machine is used for a welder, the cost will be as follows:

Metallic electrode 25.2c. Carbon electrode 84c per hour. With a machine which will deliver the required voltage at the arc and eliminate all the resistance in series with the arc, the cost will be as follows: Metallic electrode 7.2c per hour; carbon electrode 42c per hour. This is with the understanding that the arc is held constant and continuously at its full value. This, however, is practically impossible and the actual load factor is approximately fifty per cent, which would mean that operating a welder as it is usually operated, this result will be reduced to one-half of that stated in all cases.



CHAPTER VII

HAND FORGING AND WELDING

Smithing, or blacksmithing, is the process of working heated iron, steel or other metals by forging, bending or welding them.

The Forge.—The metal is heated in a forge consisting of a shallow pan for holding the fire, in the center of which is an opening from below through which air is forced to make a hot fire.



Air is forced through this hole, called a "tuyere" (Figure 48) by means of a hand bellows, a rotary fan operated with crank or lever, or with a fan driven from an electric motor. The harder the air is driven into the fire above the tuyere the more oxygen is furnished and the hotter the fire becomes.

Directly below the tuyere is an opening through which the ashes that drop from the fire may be cleaned out.

The Fire.—The fire is made by placing a small piece of waste soaked in oil, kerosene or gasoline, over the tuyere, lighting the waste, then starting the fan or blower slowly. Gradually cover the waste, while it is burning brightly, with a layer of soft coal. The coal will catch fire and burn after the waste has been consumed. A piece of waste half the size of a person's hand is ample for this purpose.

The fuel should be "smithing coal." A lump of smithing coal breaks easily, shows clean and even on all sides and should not break into layers. The coal is broken into fine pieces and wet before being used on the fire.

The fire should be kept deep enough so that there is always three or four inches of fire below the piece of metal to be heated and there should be enough fire above the work so that no part of the metal being heated comes in contact with the air. The fire should be kept as small as possible while following these rules as to depth.

To make the fire larger, loosen the coal around the edges. To make the fire smaller, pack wet coal around the edges in a compact mass and loosen the fire in the center. Add fresh coal only around the edges of the fire. It will turn to coke and can then be raked onto the fire. Blow only enough air into the fire to keep it burning brightly, not so much that the fire is blown up through the top of the coal pack. To prevent the fire from going out between jobs, stick a piece of soft wood into it and cover with fresh wet coal.

Tools.—The hammer is a ball pene, or blacksmith's hammer, weighing about a pound and a half.

The sledge is a heavy hammer, weighing from 5 to 20 pounds and having a handle 30 to 36 inches long.

The anvil is a heavy piece of wrought iron (Figure 49), faced with steel and having four legs. It has a pointed horn on one end, an overhanging tail on the other end and a flat top. In the tail there is a square hole called the "hardie" hole and a round one called the "spud" hole.



Tongs, with handles about one foot long and jaws suitable for holding the work, are used. To secure a firm grip on the work, the jaws may be heated red hot and hammered into shape over the piece to be held, thus giving a properly formed jaw. Jaws should touch the work along their entire length.

The set hammer is a hammer, one end of whose head is square and flat, and from this face the head tapers evenly to the other face. The large face is about 1-1/4 inches square.

The flatter is a hammer having one face of its head flat and about 2-1/2 inches square.

Swages are hammers having specially formed faces for finishing rounds, squares, hexagons, ovals, tapers, etc.

Fullers are hammers having a rounded face, long in one direction. They are used for spreading metal in one direction only.

The hardy is a form of chisel with a short, square shank which may be set into the hardie hole for cutting off hot bars.

Operations.—Blacksmithing consists of bending, drawing or upsetting with the various hammers, or in punching holes.

Bending is done over the square corners of the anvil if square cornered bends are desired, or over the horn of the anvil if rounding bends, eyes, hooks, etc., are wanted.

To bend a ring or eye in the end of a bar, first figure the length of stock needed by multiplying the diameter of the hole by 31/7, then heat the piece to a good full red at a point this distance back from the end. Next bend the iron over at a 90 degree angle (square) at this point. Next, heat the iron from the bend just made clear to the point and make the eye by laying the part that was bent square over the horn of the anvil and bending the extreme tip into part of a circle. Keep pushing the piece farther and farther over the horn of the anvil, bending it as you go. Do not hammer directly over the horn of the anvil, but on the side where you are doing the bending.

To make the outside of a bend square, sharp and full, rather than slightly rounding, the bent piece must be laid edgewise on the face of the anvil. That is, after making the bend over the corner of the anvil, lay the piece on top of the anvil so that its edge and not the flat side rests on the anvil top. With the work in this position, strike directly against the corner with the hammer so that the blows come in line, first with one leg of the work, then the other, and always directly on the corner of the piece. This operation cannot be performed by laying the work so that one leg hangs over the anvil's corner.

To make a shoulder on a rod or bar, heat the work and lay flat across the top of the anvil with the point at which the shoulder is desired at the edge of the anvil. Then place the set hammer on top of the piece, with the outside edge of the set hammer directly over the edge of the anvil. While hammering in this position keep the work turning continually.

To draw stock means to make it longer and thinner by hammering. A piece to be drawn out is usually laid across the horn of the anvil while being struck with the hammer. The metal is then spread in only one direction in place of being spread in every direction, as it would be if laid on the anvil face. To draw the work, heat it to as high a temperature as it will stand without throwing sparks and burning. The fuller may be used for drawing metal in place of laying the work over the horn of the anvil.

When drawing round stock, it should be first drawn out square, and when almost down to size it may be rounded. When pointing stock, the same rule of first drawing out square applies.

Upsetting means to make a piece shorter in length and greater in thickness or width, or both shorter and thicker. To upset short pieces, heat to a bright red at the place to be upset, then stand on end on the anvil face and hammer directly down on top until of the right form. Longer pieces may be swung against the anvil or placed upright on a heavy piece of metal lying on the floor or that is sunk into the floor. While standing on this heavy piece the metal may be upset by striking down on the end with a heavy hammer or the sledge. If a bend appears while upsetting, it should be straightened by hammering back into shape on the anvil face.

Light blows affect the metal for only a short distance from the point of striking, but heavy blows tend to swell the metal more equally through its entire length. In driving rivets that should fill the holes, heavy blows should be struck, but to shape the end of a rivet or to make a head on a rod, light blows should be used.

The part of the piece that is heated most will upset the most.

To punch a hole through metal, use a tool steel punch with its end slightly tapering to a size a little smaller than the hole to be punched. The end of the punch must be square across and never pointed or rounded.

First drive the punch part way through from one side and then turn the work over. When you turn it over, notice where the bulge appears and in that way locate the hole and drive the punch through from the second side. This makes a cleaner and more even hole than to drive completely through from one side. When the punch is driven in from the second side, the place to be punched through should be laid over the spud hole in the tail of the anvil and the piece driven out of the work.

Work when hot is larger than it will be after cooling. This must be remembered when fitting parts or trouble will result. A two-foot bar of steel will be 1/4 inch longer when red hot than when cold.

The temperatures of iron correspond to the following colors:

Dullest red seen in the dark... 878 Dullest red seen in daylight... 887 Dull red....................... 1100 Full red....................... 1370 Light red...................... 1550 Orange......................... 1650 Light orange................... 1725 Yellow......................... 1825 Light yellow................... 1950

Bending Pipes and Tubes.—It is difficult to make bends or curves in pipes and tubing without leaving a noticeable bulge at some point of the work. Seamless steel tubing may be handled without very great danger of this trouble if care is used, but iron pipe, having a seam running lengthwise, must be given special attention to avoid opening the seam.

Bends may be made without kinking if the tube or pipe is brought to a full red heat all the way around its circumference and at the place where the bend is desired. Hold the cool portion solidly in a vise and, by taking hold of the free end, bend very slowly and with a steady pull. The pipe must be kept at full red heat with the flames from one or more torches and must not be hammered to produce the bend. If a sufficient purchase cannot be secured on the free end by the hand, insert a piece of rod or a smaller pipe into the opening.

While making the bend, should small bulges appear, they may be hammered back into shape before proceeding with the work.

Tubing or pipes may be bent while being held between two flat metal surfaces while at a bright red heat. The metal plates at each side of the work prevent bulging.

Another method by which tubing may be bent consists of filling completely with tightly packed sand and fitting a solid cap or plug at each end.

Thin brass tubing may be filled with melted resin and may be bent after the resin cools. To remove the resin it is necessary to heat the tube, allowing it to run out.

Large jobs of bending should be handled in special pipe bending machines in which the work is forced through formed rolls which prevent its bulging.

WELDING

Welding with the heat of a blacksmith forge fire, or a coal or illuminating gas fire, can only be performed with iron and steel because of the low heat which is not localized as with the oxy-acetylene and electric processes. Iron to be welded in this manner is heated until it reaches the temperature indicated by an orange color, not white, as is often stated, this orange color being slightly above 3600 degrees Fahrenheit. Steel is usually welded at a bright red heat because of the danger of oxidizing or burning the metal if the temperature is carried above this point.

The Fire.—If made in a forge, the fire should be built from good smithing coal or, better still, from coke. Gas fires are, of course, produced by suitable burners and require no special preparation except adjustment of the heat to the proper degree for the size and thickness of the metal being welded so that it will not be burned.

A coal fire used for ordinary forging operations should not be used for welding because of the impurities it contains. A fresh fire should be built with a rather deep bed of coal, four to eight inches being about right for work ordinarily met with. The fire should be kept burning until the coal around the edges has been thoroughly coked and a sufficient quantity of fuel should be on and around the fire so that no fresh coal will have to be added while working.

After the coking process has progressed sufficiently, the edges should be packed down and the fire made as small as possible while still surrounding the ends to be joined. The fire should not be altered by poking it while the metal is being heated. The best form of fire to use is one having rather high banks of coked coal on each side of the mass, leaving an opening or channel from end to end. This will allow the added fuel to be brought down on top of the fire with a small amount of disturbance.

Preparing to Weld.—If the operator is not familiar with the metal to be handled, it is best to secure a test piece if at all possible and try heating it and joining the ends. Various grades of iron and steel call for different methods of handling and for different degrees of heat, the proper method and temperature being determined best by actual test under the hammer.

The form of the pieces also has a great deal to do with their handling, especially in the case of a more or less inexperienced workman. If the pieces are at all irregular in shape, the motions should be gone through with before the metal is heated and the best positions on the anvil as well as in the fire determined with regard to the convenience of the workman and speed of handling the work after being brought to a welding temperature. Unnatural positions at the anvil should be avoided as good work is most difficult of performance under these conditions.

Scarfing.—While there are many forms of welds, depending on the relative shape of the pieces to be joined, the portions that are to meet and form one piece are always shaped in the same general way, this shape being called a "scarf." The end of a piece of work, when scarfed, is tapered off on one side so that the extremity comes to a rather sharp edge. The other side of the piece is left flat and a continuation in the same straight plane with its side of the whole piece of work. The end is then in the form of a bevel or mitre joint (Figure 50).



Scarfing may be produced in any one of several ways. The usual method is to bring the ends to a forging heat, at which time they are upset to give a larger body of metal at the ends to be joined. This body of metal is then hammered down to the taper on one side, the length of the tapered portion being about one and a half times the thickness of the whole piece being handled. Each piece should be given this shape before proceeding farther.

The scarf may be produced by filing, sawing or chiseling the ends, although this is not good practice because it is then impossible to give the desired upset and additional metal for the weld. This added thickness is called for by the fact that the metal burns away to a certain extent or turns to scale, which is removed before welding.

When the two ends have been given this shape they should not fit as closely together as might be expected, but should touch only at the center of the area to be joined (Figure 51). That is to say, the surface of the beveled portion should bulge in the middle or should be convex in shape so that the edges are separated by a little distance when the pieces are laid together with the bevels toward each other. This is done so that the scale which is formed on the metal by the heat of the fire can have a chance to escape from the interior of the weld as the two parts are forced together.



If the scarf were to be formed with one or more of the edges touching each other at the same time or before the centers did so, the scale would be imprisoned within the body of the weld and would cause the finished work to be weak, while possibly giving a satisfactory appearance from the outside.

Fluxes.—In order to assist in removing the scale and other impurities and to make the welding surfaces as clean as possible while being joined, various fluxing materials are used as in other methods of welding.

For welding iron, a flux of white sand is usually used, this material being placed on the metal after it has been brought to a red heat in the fire. Steel is welded with dry borax powder, this flux being applied at the same time as the iron flux just mentioned. Borax may also be used for iron welding and a mixture of borax with steel borings may also be used for either class of work. Mixtures of sal ammoniac with borax have been successfully used, the proportions being about four parts of borax to one of sal ammoniac. Various prepared fluxing powders are on the market for this work, practically all of them producing satisfactory results.

After the metal has been in the fire long enough to reach a red heat, it is removed temporarily and, if small enough in size, the ends are dipped into a box of flux. If the pieces are large, they may simply be pulled to the edge of the fire and the flux then sprinkled on the portions to be joined. A greater quantity of flux is required in forge welding than in electric or oxy-acetylene processes because of the losses in the fire. After the powder has been applied to the surfaces, the work is returned to the fire and heated to the welding temperature.

Heating the Work.—After being scarfed, the two pieces to be welded are placed in the fire and brought to the correct temperature. This temperature can only be recognized by experiment and experience. The metal must be just below that point at which small sparks begin to be thrown out of the fire and naturally this is a hard point to distinguish. At the welding heat the metal is almost ready to flow and is about the consistency of putty. Against the background of the fire and coal the color appears to be a cream or very light yellow and the work feels soft as it is handled.

It is absolutely necessary that both parts be heated uniformly and so that they reach the welding temperature at the same time. For this reason they should be as close together in the fire as possible and side by side. When removed to be hammered together, time is saved if they are picked up in such a way that when laid together naturally the beveled surfaces come together. This makes it necessary that the workman remember whether the scarfed side is up or down, and to assist in this it is a good thing to mark the scarfed side with chalk or in some other noticeable manner, so that no mistake will be made in the hurry of placing the work on the anvil.

The common practice in heating allows the temperature to rise until the small white sparks are seen to come from the fire. Any heating above this point will surely result in burning that will ruin the iron or steel being handled. The best welding heat can be discerned by the appearance of the metal and its color after experience has been gained with this particular material. Test welds can be made and then broken, if possible, so that the strength gained through different degrees of heat can be known before attempting more important work.

Welding.—When the work has reached the welding temperature after having been replaced in the fire with the flux applied, the two parts are quickly tapped to remove the loose scale from their surfaces. They are then immediately laid across the top of the anvil, being placed in a diagonal position if both pieces are straight. The lower piece is rested on the anvil first with the scarf turned up and ready to receive the top piece in the position desired. The second piece must be laid in exactly the position it is to finally occupy because the two parts will stick together as soon as they touch and they cannot well be moved after having once been allowed to come in contact with each other. This part of the work must be done without any unnecessary loss of time because the comparatively low heat at which the parts weld allows them to cool below the working temperature in a few seconds.

The greatest difficulty will be experienced in withdrawing the metal from the fire before it becomes burned and in getting it joined before it cools below this critical point. The beveled edges of the scarf are, of course, the first parts to cool and the weld must be made before they reach a point at which they will not join, or else the work will be defective in appearance and in fact.

If the parts being handled are of such a shape that there is danger of bending a portion back of the weld, this part may be cooled by quickly dipping it into water before laying the work on the anvil to be joined.

The workman uses a heavy hand hammer in making the joint, and his helper, if one is employed, uses a sledge. With the two parts of the work in place on the anvil, the workman strikes several light blows, the first ones being at a point directly over the center of the weld, so that the joint will start from this point and be worked toward the edges. After the pieces have united the helper strikes alternate blows with his sledge, always striking in exactly the same place as the last stroke of the workman. The hammer blows are carried nearer and nearer to the edges of the weld and are made steadily heavier as the work progresses.

The aim during the first part of the operation should be to make a perfect joint, with every part of the surfaces united, and too much attention should not be paid to appearance, at least not enough to take any chance with the strength of the work.

It will be found, after completion of the weld, that there has been a loss in length equal to one-half the thickness of the metal being welded. This loss is occasioned by the burned metal and the scale which has been formed.

Finishing the Weld.—If it is possible to do so, the material should be hammered into the shape that it should remain with the same heat that was used for welding. It will usually be found, however, that the metal has cooled below the point at which it can be worked to advantage. It should then be replaced in the fire and brought back to a forging heat.



While shaping the work at this forging heat every part that has been at a red heat should be hammered with uniformly light and even blows as it cools. This restores the grain and strength of the iron or steel to a great extent and makes the unavoidable weakness as small as possible.

Forms of Welds.—The simplest of all welds is that called a "lap weld." This is made between the ends of two pieces of equal size and similar form by scarfing them as described and then laying one on top of the other while they are hammered together.

A butt weld (Figure 52) is made between the ends of two pieces of shaft or other bar shapes by upsetting the ends so that they have a considerable flare and shaping the face of the end so that it is slightly higher in the center than around the edges, this being done to make the centers come together first. The pieces are heated and pushed into contact, after which the hammering is done as with any other weld.



A form similar to the butt weld in some ways is used for joining the end of a bar to a flat surface and is called a jump weld. The bar is shaped in the same way as for a butt weld. The flat plate may be left as it is, but if possible a depression should be made at the point where the shaft is to be placed. With the two parts heated as usual, the bar is dropped into position and hammered from above. As soon as the center of the weld has been made perfect, the joint may be finished with a fuller driven all the way around the edge of the joint.

When it is required to join a bar to another bar or to the edge of any piece at right angles the work is called a "T" weld from its shape when complete (Figure 53). The end of the bar is scarfed as described and the point of the other bar or piece where the weld is to be made is hammered so that it tapers to a thin edge like one-half of a circular depression. The pieces are then laid together and hammered as for a lap weld.

The ends of heavy bar shapes are often joined with a "V," or cleft, weld. One bar end is shaped so that it is tapering on both sides and comes to a broad edge like the end of a chisel. The other bar is heated to a forging temperature and then slit open in a lengthwise direction so that the V-shaped opening which is formed will just receive the pointed edge of the first piece. With the work at welding heat, the two parts are driven together by hammering on the rear ends and the hammering then continues as with a lap weld, except that the work is turned over to complete both sides of the joint.



The forms so far described all require that the pieces be laid together in the proper position after removal from the fire, and this always causes a slight loss of time and a consequent lowering of the temperature. With very light stock, this fall of temperature would be so rapid that the weld would be unsuccessful, and in this case the "lock" weld is resorted to. The ends of the two pieces to be joined are split for some distance back, and one-half of each end is bent up and the other half down (Figure 54). The two are then pushed together and placed in the fire in this position. When the welding heat is reached, it is only necessary to take the work out of the fire and hammer the parts together, inasmuch as they are already in the correct position.

Other forms of welds in which the parts are too small to retain their heat, can be made by first riveting them together or cutting them so that they can be temporarily fastened in any convenient way when first placed in the fire.



CHAPTER VIII

SOLDERING, BRAZING AND THERMIT WELDING

SOLDERING

Common solder is an alloy of one-half lead with one-half tin, and is called "half and half." Hard solder is made with two-thirds tin and one-third lead. These alloys, when heated, are used to join surfaces of the same or dissimilar metals such as copper, brass, lead, galvanized iron, zinc, tinned plate, etc. These metals are easily joined, but the action of solder with iron, steel and aluminum is not so satisfactory and requires greater care and skill.

The solder is caused to make a perfect union with the surfaces treated with the help of heat from a soldering iron. The soldering iron is made from a piece of copper, pointed at one end and with the other end attached to an iron rod and wooden handle. A flux is used to remove impurities from the joint and allow the solder to secure a firm union with the metal surface. The iron, and in many cases the work, is heated with a gasoline blow torch, a small gas furnace, an electric heater or an acetylene and air torch.

The gasoline torch which is most commonly used should be filled two-thirds full of gasoline through the hole in the bottom, which is closed by a screw plug. After working the small hand pump for 10 to 20 strokes, hold the palm of your hand over the end of the large iron tube on top of the torch and open the gasoline needle valve about a half turn. Hold the torch so that the liquid runs down into the cup below the tube and fills it. Shut the gasoline needle valve, wipe the hands dry, and set fire to the fuel in the cup. Just as the gasoline fire goes out, open the gasoline needle valve about a half turn and hold a lighted match at the end of the iron tube to ignite the mixture of vaporized gasoline and air. Open or close the needle valve to secure a flame about 4 inches long.

On top of the iron tube from which the flame issues there is a rest for supporting the soldering iron with the copper part in the flame. Place the iron in the flame and allow it to remain until the copper becomes very hot, not quite red, but almost so.

A new soldering iron or one that has been misused will have to be "tinned" before using. To do this, take the iron from the fire while very hot and rub the tip on some flux or dip it into soldering acid. Then rub the tip of the iron on a stick of solder or rub the solder on the iron. If the solder melts off the stick without coating the end of the iron, allow a few drops to fall on a piece of tin plate, then nil the end of the iron on the tin plate with considerable force. Alternately rub the iron on the solder and dip into flux until the tip has a coating of bright solder for about half an inch from the end. If the iron is in very bad shape, it may be necessary to scrape or file the end before dipping in the flux for the first time. After the end of the iron is tinned in this way, replace it on the rest of the torch so that the tinned point is not directly in the flame, turning the flame down to accomplish this.

Flux.—The commonest flux, which is called "soldering acid," is made by placing pieces of zinc in muriatic (hydrochloric) acid contained in a heavy glass or porcelain dish. There will be bubbles and considerable heat evolved and zinc should be added until this action ceases and the zinc remains in the liquid, which is now chloride of zinc.

This soldering acid may be used on any metal to be soldered by applying with a brush or swab. For electrical work, this acid should be made neutral by the addition of one part ammonia and one part water to each three parts of the acid. This neutralized flux will not corrode metal as will the ordinary acid.

Powdered resin makes a good flux for lead, tin plate, galvanized iron and aluminum. Tallow, olive oil, beeswax and vaseline are also used for this purpose. Muriatic acid may be used for zinc or galvanized iron without the addition of the zinc, as described in making zinc chloride. The addition of two heaping teaspoonfuls of sal ammoniac to each pint of the chloride of zinc is sometimes found to improve its action.

Soldering Metal Parts.—All surfaces to be joined should be fitted to each other as accurately as possible and then thoroughly cleaned with a file, emery cloth, scratch bush or by dipping in lye. Work may be cleaned by dipping it into nitric acid which has been diluted with an equal volume of water. The work should be heated as hot as possible without danger of melting, as this causes the solder to flow better and secure a much better hold on the surfaces. Hard solder gives better results than half and half, but is more difficult to work. It is very important that the soldering iron be kept at a high heat during all work, otherwise the solder will only stick to the surfaces and will not join with them.

Sweating is a form of soldering in which the surfaces of the work are first covered with a thin layer of solder by rubbing them with the hot iron after it has been dipped in or touched to the soldering stick. These surfaces are then placed in contact and heated to a point at which the solder melts and unites. Sweating is much to be preferred to ordinary soldering where the form of the work permits it. This is the only method which should ever be used when a fitting is to be placed over the end of a length of tube.

Soldering Holes.—Clean the surfaces for some distance around the hole until they are bright, and apply flux while holding the hot iron near the hole. Touch the tip of the iron to some solder until the solder is picked up on the iron, and then place this solder, which was just picked up, around the edge of the hole. It will leave the soldering iron and stick to the metal. Keep adding solder in this way until the hole has been closed up by working from the edges and building toward the center. After the hole is closed, apply more flux to the job and smooth over with the hot iron until there are no rough spots. Should the solder refuse to flow smoothly, the iron is not hot enough.

Soldering Seams.—Clean back from the seam or split for at least half an inch all around and then build up the solder in the same way as was done with the hole. After closing the opening, apply more flux to the work and run the hot iron lengthwise to smooth the job.

Soldering Wires.—Clean all insulation from the ends to be soldered and scrape the ends bright. Lay the ends parallel to each other and, starting at the middle of the cleaned portion, wrap the ends around each other, one being wrapped to the right, the other to the left. Hold the hot iron under the twisted joint and apply flux to the wire. Then dip the iron in the solder and apply to the twisted portion until the spaces between the wires are filled with solder. Finish by smoothing the joint and cleaning away all excess metal by rubbing the hot iron lengthwise. The joint should now be covered with a layer of rubber tape and this covered with a layer of ordinary friction tape.

Steel and Iron.—Steel surfaces should be cleaned, then covered with clear muriatic acid. While the acid is on the metal, rub with a stick of zinc and then tin the surfaces with the hot iron as directed. Cast iron should be cleaned and dipped in strong lye to remove grease. Wash the lye away with clean water and cover with muriatic acid as with steel. Then rub with a piece of zinc and tin the surfaces by using resin as a flux.

It is very difficult to solder aluminum with ordinary solder. A special aluminum solder should be secured, which is easily applied and makes a strong joint. Zinc or phosphor tin may be used in place of ordinary solder to tin the surfaces or to fill small holes or cracks. The aluminum must be thoroughly heated before attempting to solder and the flux may be either resin or soldering acid. The aluminum must be thoroughly cleaned with dilute nitric acid and kept hot while the solder is applied by forcible rubbing with the hot iron.

BRAZING

This is a process for joining metal parts, very similar to soldering, except that brass is used to make the joint in place of the lead and zinc alloys which form solder. Brazing must not be attempted on metals whose melting point is less than that of sheet brass.

Two pieces of brass to be brazed together are heated to a temperature at which the brass used in the process will melt and flow between the surfaces. The brass amalgamates with the surfaces and makes a very strong and perfect joint, which is far superior to any form of soldering where the work allows this process to be used, and in many cases is the equal of welding for the particular field in which it applies.

Brazing Heat and Tools.—The metal commonly used for brazing will melt at heats between 1350 and 1650 Fahrenheit. To bring the parts to this temperature, various methods are in use, using solid, liquid or gaseous fuels. While brazing may be accomplished with the fire of the blacksmith forge, this method is seldom satisfactory because of the difficulty of making a sufficiently clean fire with smithing coal, and it should not be used when anything else is available. Large jobs of brazing may be handled with a charcoal fire built in the forge, as this fuel produces a very satisfactory and clean fire. The only objection is in the difficulty of confining the heat to the desired parts of the work.

The most satisfactory fire is that from a fuel gas torch built for this work. These torches are simply forms of Bunsen burners, mixing the proper quantity of air with the gas to bring about a perfect combustion. Hose lines lead to the mixing tube of the gas torch, one line carrying the gas and the other air under a moderate pressure. The air line is often dispensed with, allowing the gas to draw air into the burner on the injector principle, much the same as with illuminating gas burners for use with incandescent mantles. Valves are provided with which the operator may regulate the amount of both gas and air, and ordinarily the quality and intensity of the flame.

When gas is not available, recourse may be had to the gasoline torch made for brazing. This torch is built in the same way as the small portable gasoline torches for soldering operations, with the exception that two regulating needle valves are incorporated in place of only one.

The torches are carried on a framework, which also supports the work being handled. Fuel is forced to the torch from a large tank of gasoline into which air pressure is pumped by hand. The torches are regulated to give the desired flame by means of the needle valves in much the same way as with any other form of pressure torch using liquid fuel.

Another very satisfactory form of torch for brazing is the acetylene-air combination described in the chapter on welding instruments. This torch gives the correct degree of heat and may be regulated to give a clean and easily controlled flame.

Regardless of the source of heat, the fire or flame must be adjusted so that no soot is deposited on the metal surfaces of the work. This can only be accomplished by supplying the exact amounts of gas and air that will produce a complete burning of the fuel. With the brazing torches in common use two heads are furnished, being supplied from the same source of fuel, but with separate regulating devices. The torches are adjustably mounted in such a way that the flames may be directed toward each other, heating two sides of the work at the same time and allowing the pieces to be completely surrounded with the flame.

Except for the source of heat, but one tool is required for ordinary brazing operations, this being a spatula formed by flattening one end of a quarter-inch steel rod. The spatula is used for placing the brazing metal on the work and for handling the flux that is required in this work as in all other similar operations.

Spelter.—The metal that is melted into the joint is called spelter. While this name originally applied to but one particular grade or composition of metal, common use has extended the meaning until it is generally applied to all grades.

Spelter is variously composed of alloys containing copper, zinc, tin and antimony, the mixture employed depending on the work to be done. The different grades are of varying hardness, the harder kinds melting at higher temperatures than the soft ones and producing a stronger joint when used. The reason for not using hard spelter in all cases is the increased difficulty of working it and the fact that its melting point is so near to some of the metals brazed that there is great danger of melting the work as well as the spelter.

The hardest grade of spelter is made from three-fourths copper with one-fourth zinc and is used for working on malleable and cast iron and for steel.

This hard spelter melts at about 1650 and is correspondingly difficult to handle.

A spelter suitable for working with copper is made from equal parts of copper and zinc, melting at about 1400 Fahrenheit, 500 below the melting point of the copper itself. A still softer brazing metal is composed of half copper, three-eighths zinc and one-eighth tin. This grade is used for fastening brass to iron and copper and for working with large pieces of brass to brass. For brazing thin sheet brass and light brass castings, a metal is used which contains two-thirds tin and one-third antimony. The low melting point of this last composition makes it very easy to work with and the danger of melting the work is very slight. However, as might be expected, a comparatively weak joint is secured, which will not stand any great strain.

All of the above brazing metals are used in powder form so that they may be applied with the spatula where the joint is exposed on the outside of the work. In case it is necessary to braze on the inside of a tube or any deep recess, the spelter may be placed on a flat rod long enough to reach to the farthest point. By distributing the spelter at the proper points along the rod it may be placed at the right points by turning the rod over after inserting into the recess.

Flux.—In order to remove the oxides produced under brazing heat and to allow the brazing metal to flow freely into place, a flux of some kind must be used. The commonest flux is simply a pure calcined borax powder, that is, a borax powder that has been heated until practically all the water has been driven off.

Calcined borax may also be mixed with about 15 per cent of sal ammoniac to make a satisfactory fluxing powder. It is absolutely necessary to use flux of some kind and a part of whatever is used should be made into a paste with water so that it can be applied to the joint to be brazed before heating. The remainder of the powder should be kept dry for use during the operation and after the heat has been applied.

Preparing the Work.—The surfaces to be brazed are first thoroughly cleaned with files, emery cloth or sand paper. If the work is greasy, it should be dipped into a bath of lye or hot soda water so that all trace of oil is removed. The parts are then placed in the relation to each other that they are to occupy when the work has been completed. The edges to be joined should make a secure and tight fit, and should match each other at all points so that the smallest possible space is left between them. This fit should not be so tight that it is necessary to force the work into place, neither should it be loose enough to allow any considerable space between the surfaces. The molten spelter will penetrate between surfaces that water will flow between when the work and spelter have both been brought to the proper heat. It is, of course, necessary that the two parts have a sufficient number of points of contact so that they will remain in the proper relative position.

The work is placed on the surface of the brazing table in such a position that the flame from the torches will strike the parts to be heated, and with the joint in such a position that the melted spelter will flow down through it and fill every possible part of the space between the surfaces under the action of gravity. That means that the edge of the joint must be uppermost and the crack to be filled must not lie horizontal, but at the greatest slant possible. Better than any degree of slant would be to have the line of the joint vertical.

The work is braced up or clamped in the proper position before commencing to braze, and it is best to place fire brick in such positions that it will be impossible for cooling draughts of air to reach the heated metal should the flame be removed temporarily during the process. In case there is a large body of iron, steel or copper to be handled, it is often advisable to place charcoal around the work, igniting this with the flame of the torch before starting to braze so that the metal will be maintained at the correct heat without depending entirely on the torch.

When handling brass pieces having thin sections there is danger of melting the brass and causing it to flow away from under the flame, with the result that the work is ruined. If, in the judgment of the workman, this may happen with the particular job in hand, it is well to build up a mould of fire clay back of the thin parts or preferably back of the whole piece, so that the metal will have the necessary support. This mould may be made by mixing the fire clay into a stiff paste with water and then packing it against the piece to be supported tightly enough so that the form will be retained even if the metal softens.

Brazing.—With the work in place, it should be well covered with the paste of flux and water, then heated until this flux boils up and runs over the surfaces. Spelter is then placed in such a position that it will run into the joint and the heat is continued or increased until the spelter melts and flows in between the two surfaces. The flame should surround the work during the heating so that outside air is excluded as far as is possible to prevent excessive oxidization.

When handling brass or copper, the flame should not be directed so that its center strikes the metal squarely, but so that it glances from one side or the other. Directing the flame straight against the work is often the cause of melting the pieces before the operation is completed. When brazing two different metals, the flame should play only on the one that melts at the higher temperature, the lower melting part receiving its heat from the other. This avoids the danger of melting one before the other reaches the brazing point.

The heat should be continued only long enough to cause the spelter to flow into place and no longer. Prolonged heating of any metal can do nothing but oxidize and weaken it, and this practice should be avoided as much as possible. If the spelter melts into small globules in place of flowing, it may be caused to spread and run into the joint by lightly tapping the work. More dry flux may be added with the spatula if the tapping does not produce the desired result.

Excessive use of flux, especially toward the end of the work, will result in a very hard surface on all the work, a surface which will be extremely difficult to finish properly. This trouble will be present to a certain extent anyway, but it may be lessened by a vigorous scraping with a wire brush just as soon as the work is removed from the fire. If allowed to cool before cleaning, the final appearance will not be as good as with the surplus metal and scale removed immediately upon completing the job.

After the work has been cleaned with the brush it may be allowed to cool and finished to the desired shape, size and surface by filing and polishing. When filed, a very thin line of brass should appear where the crack was at the beginning of the work. If it is desired to avoid a square shoulder and fill in an angle joint to make it rounding, the filling is best accomplished by winding a coil of very thin brass wire around the part of the work that projects and then causing this to flow itself or else allow the spelter to fill the spaces between the layers of wire. Copper wire may also be used for this purpose, the spaces being filled with melted spelter.

THERMIT WELDING

The process of welding which makes use of the great heat produced by oxygen combining with aluminum is known as the Thermit process and was perfected by Dr. Hans Goldschmidt. The process, which is controlled by the Goldschmidt Thermit Company, makes use of a mixture of finely powdered aluminum with an oxide of iron called by the trade name, Thermit.

The reaction is started with a special ignition powder, such as barium superoxide and aluminum, and the oxygen from the iron oxide combining with the aluminum, producing a mass of superheated steel at about 5000 degrees Fahrenheit. After the reaction, which takes from. 30 seconds to a minute, the molten metal is drawn from the crucible on to the surfaces to be joined. Its extreme heat fuses the metal and a perfect joint is the result. This process is suited for welding iron or steel parts of comparatively large size.

Preparation.—The parts to be joined are thoroughly cleaned on the surfaces and for several inches back from the joint, after which they are supported in place. The surfaces between which the metal will flow are separated from 1/4 to 1 inch, depending on the size of the parts, but cutting or drilling part of the metal away. After this separation is made for allowing the entrance of new metal, the effects of contraction of the molten steel are cared for by preheating adjacent parts or by forcing the ends apart with wedges and jacks. The amount of this last separation must be determined by the shape and proportions of the parts in the same way as would be done for any other class of welding which heats the parts to a melting point.

Yellow wax, which has been warmed until plastic, is then placed around the joint to form a collar, the wax completely filling the space between the ends and being provided with vent holes by imbedding a piece of stout cord, which is pulled out after the wax cools.

A retaining mould (Figure 55) made from sheet steel or fire brick is then placed around the parts. This mould is then filled with a mixture of one part fire clay, one part ground fire brick and one part fire sand. These materials are well mixed and moistened with enough water so that they will pack. This mixture is then placed in the mould, filling the space between the walls and the wax, and is packed hard with a rammer so that the material forms a wall several inches thick between any point of the mould and the wax. The mixture must be placed in the mould in small quantities and packed tight as the filling progresses.



Three or more openings are provided through this moulding material by the insertion of wood or pipe forms. One of these openings will lead from the lowest point of the wax pattern and is used for the introduction of the preheating flame. Another opening leads from the top of the mould into this preheating gate, opening into the preheating gate at a point about one inch from the wax pattern. Openings, called risers, are then provided from each of the high points of the wax pattern to the top of the mould, these risers ending at the top in a shallow basin. The molten metal comes up into these risers and cares for contraction of the casting, as well as avoiding defects in the collar of the weld. After the moulding material is well packed, these gate patterns are tapped lightly and withdrawn, except in the case of the metal pipes which are placed at points at which it would be impossible to withdraw a pattern.

Preheating.—The ends to be welded are brought to a bright red heat by introducing the flame from a torch through the preheating gate. The torch must use either gasoline or kerosene, and not crude oil, as the crude oil deposits too much carbon on the parts. Preheating of other adjacent parts to care for contraction is done at this time by an additional torch burner.

The heating flame is started gently at first and gradually increased. The wax will melt and may be allowed to run out of the preheating gate by removing the flame at intervals for a few seconds. The heat is continued until the mould is thoroughly dried and the parts to be joined are brought to the red heat required. This leaves a mould just the shape of the wax pattern.

The heating gate should then be plugged with a sand core, iron plug or piece of fitted fire brick, and backed up with several shovels full of the moulding mixture, well packed.



Thermit Metal.—The reaction takes place in a special crucible lined with magnesia tar, which is baked at a red heat until the tar is driven off and the magnesia left. This lining should last from twelve to fifteen reactions. This magnesia lining ends at the bottom of the crucible in a ring of magnesia stone and this ring carries a magnesia thimble through which the molten steel passes on its way to the mould. It will usually be necessary to renew this thimble after each reaction. This lower opening is closed before filling the crucible with thermit by means of a small disc or iron carrying a stem, which is called a tapping pin (Figure 56). This pin, F, is placed in the thimble with the stem extending down through the opening and exposing about two inches. The top of this pin is covered with an asbestos, washer, E, then with another iron disc. D, and finally with a layer of refractory sand. The crucible is tapped by knocking the stem of the pin upwards with a spade or piece of flat iron about four feet long.

The charge of thermit is added by placing a few handfuls over the refractory sand and then pouring in the balance required. The amount of thermit required is calculated from the wax used. The wax is weighed before and after filling the entire space that the thermit will occupy. This does not mean only the wax collar, but the space of the mould with all gates filled with wax. The number of pounds of wax required for this filling multiplied by 25 will give the number of pounds of thermit to be used. To this quantity of thermit should be added I per cent of pure manganese, 1 per cent nickel thermit and 15 per cent of steel punchings.

It is necessary, when more than 10 pounds of thermit will be used, to mix steel punchings not exceeding 3/8 inch diameter by 1/8 inch thick with the powder in order to sufficiently retard the intensity of the reaction.

Half a teaspoonful of ignition powder is placed on top of the thermit charge and ignited with a storm match or piece of red hot iron. The cover should be immediately closed on the top of the crucible and the operator should get away to a safe distance because of the metal that may be thrown out of the crucible.

After allowing about 30 seconds to a minute for the reaction to take place and the slag to rise to the top of the crucible, the tapping pin is struck from below and the molten metal allowed to run into the mould. The mould should be allowed to remain in place as long as possible, preferably over night, so as to anneal the steel in the weld, but in no case should it be disturbed for several hours after pouring. After removing the mould, drill through the metal left in the riser and gates and knock these sections off. No part of the collar should be removed unless absolutely necessary.



CHAPTER IX

OXYGEN PROCESS FOR REMOVAL OF CARBON

Until recently the methods used for removing carbon deposits from gas engine cylinders were very impractical and unsatisfactory. The job meant dismantling the motor, tearing out all parts, and scraping the pistons and cylinder walls by hand.

The work was never done thoroughly. It required hours of time to do it, and then there was always the danger of injuring the inside of the cylinders.

These methods have been to a large extent superseded by the use of oxygen under pressure. The various devices that are being manufactured are known as carbon removers, decarbonizers, etc., and large numbers of them are in use in the automobile and gasoline traction motor industry.

Outfit.—The oxygen carbon cleaner consists of a high pressure oxygen cylinder with automatic reducing valve, usually constructed on the diaphragm principle, thus assuring positive regulation of pressure. This valve is fitted with a pressure gauge, rubber hose, decarbonizing torch with shut off and flexible tube for insertion into the chamber from which the carbon is to be removed.

There should also be an asbestos swab for swabbing out the inside of the cylinder or other chamber with kerosene previous to starting the operation. The action consists in simply burning the carbon to a fine dust in the presence of the stream of oxygen, this dust being then blown out.

Operation.—The following are instructions for operating the cleaner:—

(1) Close valve in gasoline supply line and start the motor, letting it run until the gasoline is exhausted.

(2) If the cylinders be T or L head, remove either the inlet or the exhaust valve cap, or a spark plug if the cap is tight. If the cylinders have overhead valves, remove a spark plug. If any spark plug is then remaining in the cylinder it should be removed and an old one or an iron pipe plug substituted.

(3) Raise the piston of the cylinder first to be cleaned to the top of the compression stroke and continue this from cylinder to cylinder as the work progresses.

(4) In motors where carbon has been burned hard, the cylinder interior should then be swabbed with kerosene before proceeding. Work the swab, saturated with kerosene, around the inside of the cylinder until all the carbon has been moistened with the oil. This same swab may be used to ignite the gas in the cylinder in place of using a match or taper.

(5) Make all connections to the oxygen cylinder.

(6) Insert the torch nozzle in the cylinder, open the torch valve gradually and regulate to about two lbs. pressure. Manipulate the nozzle inside the cylinder and light a match or other flame at the opening so that the carbon starts to burn. Cover the various points within the cylinder and when there is no further burning the carbon has been removed. The regulating and oxygen tank valves are operated in exactly the same way as for welding as previously explained.

It should be carefully noted that when the piston is up, ready to start the operation, both valves must be closed. There will be a considerable display of sparks while this operation is taking place, but they will not set fire to the grease and oil. Care should be used to see that no gasoline is about.



INDEX

Acetylene filtering generators in tanks piping properties of purification of Acetylene-air torches Air oxygen from Alloys table of Alloy steel Aluminum alloys welding Annealing Anvil Arc welding, electric machines Asbestos, use of, in welding

Babbitt Bending pipes and tubes Bessemer steel Beveling Brass welding Brazing electric heat and tools spelter Bronze welding Butt welding

Calcium carbide Carbide storage of, Fire Underwriters' Rules to water generator Carbon removal by oxygen process Case hardening steel Cast iron welding Champfering Charging generator Chlorate of potash oxygen Conductivity of metals Copper alloys welding Crucible steel Cutting, oxy-acetylene torches

Dissolved acetylene

Electric arc welding Electric welding troubles and remedies Expansion of metals

Flame, welding Fluxes for brazing for soldering Forge fire practice tools tuvere construction of welding welding preparation welds, forms of Forging

Gas holders Gases, heating power of Generator, acetylene carbide to water construction Generator location of operation and care of overheating requirements water to carbide German silver Gloves Goggles

Hand forging Hardening steel Heat treatment of steel Hildebrandt process Hose

Injectors, adjuster Iron cast grades of malleable cast wrought

Jump weld

Lap welding Lead Linde process Liquid air oxygen

Magnalium Malleable iron welding Melting points of metals Metal alloys, table of Metals characteristics of conductivity of expansion of heat treatment of melting points of tensile strength of weight of

Nickel Nozzle sizes, torch

Open hearth steel Oxy-acetylene cutting welding practice Oxygen cylinders weight of

Pipes, bending Platinum Preheating

Removal of carbon by oxygen process Resistance method of electric welding Restoration of steel Rods, welding

Safety devices Scarfing Solder Soldering flux holes seams steel and iron wires Spelter Spot welding Steel alloys Bessemer crucible heat treatment of open hearth restoration of tensile strength of welding Strength of metals

Tank valves Tapering Tables of welding information Tempering steel Thermit metal preheating preparation welding Tin Torch acetylene-air care construction cutting high pressure low pressure medium pressure nozzles practice

Valves, regulating tank

Water to carbide generator Welding aluminum brass bronze butt cast iron copper electric electric arc flame forge information and tables instruments lap malleable iron materials practice, oxy-acetylene rods spot steel table thermit torches various metals wrought iron Wrought iron welding

Zinc

THE END