Please see the [Transcriber’ Notes] at the end of this text.

Soldering, Brazing
and Welding

EDITED BY
BERNARD E. JONES
Editor of “Work”

With 78 Illustrations

FUNK & WAGNALLS COMPANY
NEW YORK and LONDON
1917

EDITOR’S PREFACE

This handbook, which explains in detail a variety of processes common to general metalworking, has been written by a number of thoroughly practical men, by whom it was contributed in another form to “Work,” the illustrated weekly journal of handicrafts and mechanics. Its appeal is to everybody who makes any attempt at working in metals, inasmuch as at least one of the processes—soldering, brazing or welding—will be met at a very early stage in the beginner’s experience. This handbook will be found a complete workshop guide to the usual methods of soldering and brazing, and will form an excellent introduction to the modern electrical and oxy-acetylene welding processes, to do complete justice to which, however, a separate handbook would, of course, be necessary. If readers encounter difficulty in any of the matters treated in this book, they have only to write to “Work,” in whose columns (but not by post) help will be willingly afforded.

B. E. J.

CONTENTS

SOLDERING, BRAZING AND WELDING

CHAPTER I
The Various Processes of Joining Metals

Apart from the use of rivets, screws, etc., metal is commonly joined by soldering, brazing, or welding, three groups of processes that have one thing in common—the use of heat to fuse either the metals themselves or an alloy which is interposed to consolidate the joint. The word “solder” is derived through the French from a Latin word meaning “solid.”

Soldering may be “soft” or “hard.” Soft-soldering uses lead-tin alloys which are easily melted in a bunsen gas flame or with a hot iron or bit; while hard-soldering employs a silver-copper alloy, to melt which a mouth blowpipe at least is necessary. Brazing is hard-soldering with spelter (brass), and a forge or a heavy blowlamp or a powerful blowpipe must be employed to provide the heat.

Welding is a fusion process which in the past was almost entirely confined to wrought-iron and steel, these metals possessing the property of weldability to an extent unknown in the case of any other metals. The blacksmith’s process of welding is to heat the iron or steel until the surface of the metal becomes pasty, and then to bring the two pieces into intimate contact by hammering on the anvil. Of late years the welding of iron, steel, copper and some other metals has been rendered possible by the use of certain electrical and chemical methods and—most important of all—by the use of the oxy-acetylene blowpipe, the process being known as “fusion welding” or “autogenous soldering,” the word autogenous implying that the process is complete in itself and independent of the use of any extraneous substance such as solder. The thermit process, of which so much has been heard, and which is briefly dealt with [later], is the fusion welding of iron and steel by means of the intense heat produced by the combustion of a special chemical compound. Perhaps the oldest of the autogenous soldering processes is “lead-burning,” in which the flame of an airo-hydrogen blowpipe is brought to bear upon the lead, the joint being fed with a strip of the same metal.

Soft-soldering is an operation that the beginner will not find nearly so difficult as hard-soldering or brazing, and although the strength of joints made by it is not nearly equal to that produced by the methods named, it fills a useful place within its scope. It is purely a surface union—that is, the solder adheres to the faces in contact in much the same manner as an adhesive sticks to metal; but with the assistance of fluxes, the contact is made so intimate that some force is necessary to break the joint. Soft-soldering is also of use where brazing would simply mean the ruin or destruction of the metals, as in the cases of lead, poor-quality brass, pewter, tin, zinc, and in tinplate and galvanised iron.

In silver-soldering and brazing, the silver or spelter that fuses to form the joint alloys itself so intimately with the copper or brass that it actually becomes part of the piece itself, and for all practical purposes cannot be distinguished from it. But soft-soldering is not always inferior to hard-soldering. Indeed, the surface nature of the soldering often constitutes its value.

The strongest joints of all are produced by fusion welding, as will be duly understood from later chapters.

CHAPTER II
Soft Solders

A solder should melt at a slightly lower temperature than the metals which it unites, and should possess the quality of alloying with the two surfaces, thus effecting a sound and true metallic joint. Ordinary soft solders are lead-tin alloys, and the larger the proportion of lead the commoner is the solder said to be. At an extreme is plumber’s solder, consisting of 2 parts of lead to 1 part of tin, and, at the other, the best blowpipe soft solder, which contains 2 parts of tin to only 1 part of lead. In the ordinary way, a “coarse” or “common” solder is 2 parts of lead to 1 part of tin; a “fine” or “medium” solder, 1 part of lead to 1 part of tin; and a “very fine” or “best” solder, 1 part of lead to 2 parts of tin.

Eutectic Alloys.

—Lead-tin solders are eutectic alloys—that is, they are examples of the phenomenon of a combination of two metals melting at a temperature lower than one of them would if melted separately. Thus, lead melts at about 328° C., and tin at about 232° C., yet reference to the following table, given by Mr. A. H. Hiorns, will show that the “commonest” solder mentioned fuses at 303° C., and the “best” at 175° C.

Melting points of lead-tin alloys

Hardness of Solders.

—According to the before-mentioned authority, Saposhniko, in 1908, determined the hardness of various lead-tin alloys by Brineli’s method, by which a steel cone is forced into the metal. The results he obtained are as follow:

These results, says Mr. Hiorns, show that the hardest alloy is the one with 66% (about 2 parts) of tin and 34% (about 1 part) of lead, which also is the one having the lowest melting point of all the lead-tin alloys. The results also show that tin is slightly harder than lead.

Compositions of Soft Solders.

—As already shown, solders vary in fusibility according to their composition, and the choice should be determined by the nature of the work and the properties of the metal to be soldered. Should a solder be used of too high a melting-point, the metal will itself be fused before the solder begins to flow.

A point to be particularly observed is that the introduction of a foreign substance into the solder—for example, the addition of a little zinc to a pot of “very fine” solder—will utterly spoil it and render it unworkable. To remove zinc from solder, melt the solder in a pot, take it off the fire and stir in powdered sulphur or brimstone until the whole is of the consistency of wet sand. Replace the pot on the fire and melt, but do not stir the contents. The sulphur and zinc will rise to the surface and form into a cake. Now take the pot off the fire and carefully remove the cake without breaking by employing two pieces of hoop iron with bent ends.

It is false economy to use a rough solder for fine work on the score of cheapness, since more solder is required for a given job on account of the rough particles of solder clinging to the work; moreover, the rough appearance of the soldering may completely spoil the job.

The [table] on the opposite page gives the fluxes and the compositions of soft solders suited to a number of different metals.

Making Solder Strips, Wire, Tears, etc.

—Only clean, pure tin and pure lead should be employed. The lead is first melted and then the tin added. When all is melted, place a piece of resin on the molten metal to act as a flux, and after well stirring, the solder is made into strips by pouring from a ladle. Solder should not be poured into sand. It may be poured into strips on an oiled sheet of black iron, preferably corrugated to accommodate the strips. In the absence of a corrugated iron sheet, some workers use a ladle resembling a large spoon with a hole about ¹⁄₁₆ in. in diameter near the end. To form the strips, get a ladle full of solder, place it on a flat iron sheet; then, tilting the ladle to allow the solder to flow over the hole, quickly draw the ladle across the sheet. A thin strip of solder should thus be formed, and the thickness of the strip may be varied by increasing or decreasing the diameter of the hole in the ladle. A button of solder usually forms at one or both ends of the strip, and this excess should be melted off the strips by just dipping the ends into the molten solder in the pot.

Soft Solders for Various Metals

Solder wire is very handy for small work, and can be made in the following way: Roll a sheet of stiff writing or drawing paper into a conical form, rather broad in comparison with its length; make a ring of stiff wire to hold it in, attaching a suitable handle to the ring. The point of the cone should first of all be cut off to leave an orifice of the size required. It should then be filled with molten solder, and held above a pail of cold water, and the stream of solder flowing from the cone will solidify as it runs and form the wire. If held a little higher, so that the stream of solder breaks into drops before striking the water, it will form handy elongated “tears” of metal; when it is held still higher, each drop forms a thin concave cup or shell, and each of these forms will be found to have its own peculiar uses in blowpipe work.

The method adopted for granulating tinman’s solder, which is very rarely called for, is as follows: Place a piece of wood, well greased, over a tub containing water, and by gently pouring the molten alloy from a distance in a small stream on to the greased board, the metal is broken up into a large number of very fine shots, which run off the board into the water and are immediately cooled. The fine shots are then taken from the water and gently dried.

Making Solder from Pewter.

—This alloy is composed of variable proportions of tin and lead, the average composition being about 4 parts of lead to 1 part of tin. If old pewter is to be utilised for making solder, tin will have to be added to the molten pewter. Thus, to convert 5 lb. of average pewter to “coarse” or “common” solder, add 1 lb. of tin; to “fine” or “medium,” add 3 lb. of tin; and to “very fine” or “best,” add 7 lb. of tin. The respective proportions of lead and tin will then be 2 and 1; 1 and 1; and 1 and 2. After the proper quantity of tin has been added, mix some powdered sal-ammoniac with the molten metals, and well stir the alloy; it is then ready for pouring into the moulds.

Making Coarse Solder from Composition Piping.

—Good composition piping is made of nearly all tin, or an alloy of tin and lead, in which the former metal is in excess, and formerly was much used by plumbers in the making of coarse solder, as the material consisted of odd pieces of small value. As, however, a great deal of composition tubing is made out of old metals of which lead, tin, antimony, arsenic, and zinc form the alloy, it is not advisable to introduce it into solder. Should it be done, the melting point of the solder would be raised, and in applying it to the lead to be joined together, would probably partly melt it. Neither do the metals named alloy in a thorough manner, but partake more of the nature of a mixture in which the constituents partly separate when making the joints, and some, especially zinc, show as small bright lumps on the surface. Joints wiped with what is usually called “poisoned metal” are difficult to make, almost invariably leak when on water service pipes, and are dirty grey, instead of bright and clean. The zinc could be removed from the mixture by the method already given.

Combined Solder and Flux.

—This consisted of equal parts of lead and tin made into fine tubing and afterwards filled with flux having resin as a base. “Tinol” is a paste made of finely powdered solder and a special flux, and there is also “Tinol wire” having a core of flux.

A “magic” solder, sold by hawkers, consists of the above tubular flux-filled solder of such low melting point that it can be fused in the flame of a lighted match.

Soft Solders that Melt in Boiling Water.

—The following soft solders melt at a temperature lower than that of boiling water: 1 part tin, 1 part lead, and 2 parts bismuth, melting point about 200° F.; 8 parts lead, 4 parts tin, 15 parts bismuth, and 3 parts cadmium, melting point 140° to 150° F.; 6 parts lead, 7 parts bismuth, and 1 part cadmium, melting point about 180° F. To ensure the alloys melting at the temperatures stated, the metals of which they are formed should be free from impurities, and care should be taken to prevent oxidation while making the alloys. When melting the metals, that having the highest melting point should be melted first, with a layer of resin over it, the other metals being added in the order of their melting points. The alloy should then be well stirred with a wooden stick, and poured quickly into moulds.

Re-melting and Overheating Solder.

—After solder has been re-melted a number of times or has been overheated, its content of tin will be reduced, and the solder will become poorer and coarser. The tin melts earlier than the lead and, being the lighter of the two, floats over it, and is thus fully exposed to the air, the oxidising effect of which on heated, molten metal is extremely active. The oxidised tin forms a dross, from which most of the tin may, however, be recovered by melting it with powdered charcoal, which combines with the oxygen and frees the tin. The addition of a little fresh tin is desirable.

CHAPTER III
Fluxes Used in Soft-soldering

Why a Flux is Required.

—The great essential to successful soldering is the chemical cleanliness of the surfaces to be united, and the proper use of a flux. Although work may be filed or scraped perfectly bright and clean, this is not the kind of cleanliness which is alone sufficient; there is always in course of formation a film of oxide present, and the duty of the flux is to dissolve this and keep any more from forming. Then, and not until then, will the molten solder “run” and spread over faces in the intimate contact necessary. If this vital precaution of cleaning and fluxing is always observed, the difficulties which many beginners experience in effective soldering will vanish.

Variety of Fluxes.

—There are a good many fluxes employed, including tallow (largely used for lead and pewter), resin (used for lead, compo-pipe, and tinned metals), hydrochloric acid, diluted (for zinc and galvanised iron), and chloride of zinc (the well-known “killed spirit”). The last-named is the most generally used, being suitable for tinplate, tinned iron, new zinc, copper, and brass. Sal-ammoniac is also utilised, sometimes in conjunction with chloride of zinc. The small worker who does but a moderate amount of soldering will find it convenient to use a soldering paste such as “Fluxite,” which is sold in a tin, and can be kept handy and applied to the work with a sliver of wood. “Tinol” is a paste flux in combination with a solder.

Preparing Zinc Chloride (“Killed Spirit”).

—Make this flux at home from finely snipped new sheet-zinc and pure hydrochloric or muriatic acid. (This is sufficiently cheap at any working druggist’s stores, and infinitely preferable to the contaminated oil-shop quality known as “spirits of salt.”) Stand the acid outdoors in a stoneware crock, add the zinc cuttings a few at a time at first, and when the first violent ebullition moderates, put in the rest. Be sure to provide an excess of metallic zinc, observing that a quantity remains undissolved after all chemical action ceases. Leave the metal in the liquor for twelve hours (covering the crock with a pane of glass), then decant and filter into a wide-mouth glass jar of handy size. Do not add water to the concentrated zinc chloride solution; dilution is sometimes recommended, but should never be done; the heavy, slightly syrupy, water-bright liquor should be used as it is. The alleged “cleaning” qualities of this chloride can scarcely be admitted to exist, and its principal function is to shield the surfaces of the work from oxidation; this it fulfils by the formation of a viscid glaze on the heated metal when the salt reaches its anhydrous (waterless) condition by evaporation. The addition of water to the flux, therefore, only uselessly prolongs the period occupied by evaporation, and wastes heat.

Always remove all trace of flux from finished work, first by soaking in water, and afterwards by washing with soda, soap, and water. Otherwise, there is the risk of the work being corroded.

Special “soldering solutions,” obtainable ready prepared, should not be used in preference to zinc chloride made as before explained or to the well-known paste fluxes.

Applying the Flux.

—A short heavy bottle about 3 in. or 4 in. high is best for bench use as a flux container. It should be particularly noted that soldering and soldering tackle should be kept as far away from other work (and iron and steel goods and tools) as possible.

A pointed wooden stick is not a good tool for applying killed spirit, because the acid acts on the wood, which becomes unpleasant to handle, and the liquid does not leave the wood readily enough to place the right quantity on the exact spot to be soldered. A galvanised iron wire is better. Another good tool is a thin steel or iron “spit,” about 12 in. long, and a steel knitting-needle is also excellent. Should a brush be preferred, take a few hairs from a broom, place them in one end of a thin metal tube, and then flatten the end with a blow from a hammer.

A brush made by hammering the ends of a short length of cane until the fibres are like bristles is frequently used for the purpose, the handle end being soaked in molten wax before using the cane brush the first time.

Fig. 1.—Wire for Applying Flux

A convenient method of applying liquid flux is to have a bottle with a screw cap sprinkling top such as is often used for perfumes, and to push a length of thick galvanised iron wire through the orifice in the stopper, leaving about 1¹⁄₂ in. projecting above. The lower end should just reach the bottom of the bottle, and may be flattened and pointed. The lead nipple is squeezed round the wire to hold it firmly, and the projecting end bent into a ring to form a handle, as shown in [Fig. 1]. The cork part should be thinned a little to render it an easy fit in the bottle neck. The flux can be quickly applied with the wire exactly where it is wanted, and in very small quantity; for a long seam the wire can be run along with one dip in the solution. The fingers need not be brought into contact with the flux; the cork will not go soft and will not sink down owing to the lead flange supporting it.

Flux Used on Food Containers.

—Killed spirits is objectionable as a flux for soldering vessels intended to contain food of any kind. Not only is this flux a poison, but it is liable to produce subsequent rusting wherever used unless all traces of it are thoroughly removed immediately after soldering. A good non-poisonous flux suitable for tin boxes may be made by dissolving resin in oil. Place a quantity of powdered resin in an iron vessel, add colza, olive, or any similar oil, and apply gentle heat, meanwhile stirring it until the resin is dissolved. Dissolve as much resin in the oil as possible without making the flux too thick (when cold) to apply with a brush. One or two small experiments will soon decide the required proportions. The resin is really the base of the flux; but the oil is added to facilitate its application and removal before and after the soldering process.

CHAPTER IV
Soft-soldering with the Copper Bit

Choice between Blowpipe and Bit.—The method of heating depends on the size of the work, or rather the area to be soldered, and the conveniences at the command of the worker. The soldering bit, although so commonly used, is not necessarily the best for the beginner to use for small work. A blowpipe flame—from a bunsen burner or a spirit lamp—is far more convenient and neat, and its effects can be applied and localised with the greatest precision, down to the merest pin point of heat applied at a definite spot. The bit is chiefly useful for long joints such as in tinplate work, and for pieces bound together to which the bit is applied to heat up and melt solder between them. But for work where the soldering area does not measure more than an inch or so (and there is a vast amount of this kind), the blowpipe flame is far preferable. It must be admitted, though, that this is a matter in which some workmen might have two distinct opinions; and, as already remarked, the bit is far more commonly used.

Fig. 2.—Soldering Bit

Fig. 3.—Pivoted Soldering Bit

Copper Bits.

—The soldering bit or bolt (miscalled an “iron”) carries a pointed lump of copper at the end ([Fig. 2]), riveted in, or alternatively, in small sizes, screwed on to the shank. Some bits are pivoted (see [Fig. 3]) to enable them to point at various angles for dealing with difficult situations.

A home-made bit ([Figs. 4] and [5]) may be made by drilling and tapping a short length of 1¹⁄₂-in. or 2-in. square copper to receive the screwed end of a rod of ⁵⁄₁₆-in. iron, the copper being afterwards heated and drawn to a point or to a blunt edge as preferred. This forms a good bit for most ordinary purposes. An axe-head or hatchet bit is shown in [Fig. 6]; the copper bolt is riveted in the eye of the iron rod, the bit, however, being free to revolve, as this is essential when making joints in heavy lead pipe, for which purpose it is principally used. [Fig. 5] represents a bit which is a combination and modification of the two others, and it is largely used for the internal soldering of bottoms of large drums, milk churns, etc., where great local heat is required.

Fig. 4.—Home-made Soldering Bit

Fig. 5.—Bit for Internal Soldering, etc.

Fig. 6.—Hatchet Soldering Bit

As to the size of bit required, for ordinary small work the straight type should not be less than 8 oz. or 10 oz. (weight of the actual copper).

Two bits are very useful in doing a large job, as the work can then be arranged to progress continuously, one bit heating while the other is in use.

A bit suitable for quite light work can be easily made by drilling and tapping a piece of copper, say ¹⁄₂ in. by ¹⁄₂ in. by 1¹⁄₂ in. long, either in the end or in the side, for a ³⁄₁₆-in. steel rod 12 in. long, a handle being then fitted at the other end.

In the “Tinol” telescopic soldering bit for amateurs’ use, the handle is in three parts: (a) the actual wooden handle bushed with metal, and provided with a set-screw shaped like a screw eye, and therefore easily turned; (b) a steel tube which telescopes into the first part, and which is also provided with a set-screw; and (c) a short rod, having at one end a hatchet-shaped copper bit. The extreme length of the tool is 12 in., and the length, when the parts are telescoped together, is about 5 in.

The “Fluxite” bit is larger and heavier. It has a hollow cast-iron handle, perforated to dissipate the heat, threaded internally at one end to receive the screwed end of the iron stem, only 5 in. or so in length, which at the other end screws into an adapter or holder which, in turn, receives the screwed end of the copper bolt, itself about 4 in. long. The bit is taken to pieces in a few moments, and is quite a workmanlike tool.

Fig. 7.—Spirit-heated Bit

Spirit-Heated Soldering Bits.

—Bits heated by benzoline or spirit may be made with a small barrel-shaped reservoir which also forms the handle. One end of the reservoir is fitted with a filling cap, and from the opposite end protrudes the tube carrying the burner. To the tube end of the reservoir an iron clip is attached, and this secures an iron bar which stands out over the burner head. At the end of this bar the copper bit is attached and held either vertically or horizontally in the flame. Tool merchants’ catalogues show a variety of such implements. [Fig. 7] illustrates one of the most elaborate of them all, the weight complete being 2¹⁄₄ lb. It has a polished brass container A, of ¹⁄₅ pint capacity—sufficient for 45 to 60 minutes, whence the benzoline flows to the burner B, the flame from which heats the copper bit C. This bit may be of any of the regular shapes, and weighs about ¹⁄₂ lb. The position shown is that for heating the bit preparatory to soldering. The tray D catches any drips that might occur at starting, E is the stand, F the filler cap, G is the regulating handle, and H is the clamp that holds the bit in place.

Fig. 8.—Bit attached to Blow-lamp

A writer in Popular Mechanics has stated that the ordinary blow-lamp, with the burner end equipped with a copper bolt (see [Fig. 8]), makes an excellent soldering device. The point can be easily kept at the proper heat, and there will be no want for hot coppers. The end of the burner is threaded on the outside, and a hole is drilled in the copper point and threaded to match. Small holes are drilled in the copper in the same manner as in the burner, to make vents for the flame.

Fig. 9.—Gas-heated Bit

Gas-heated Bits.

—These are largely used in factories, and are cleanly, expeditious, safe, and convenient. The type shown by [Fig. 9] is very handy, and the illustration and description are due to F. X. Sommers, Jun., in the American Machinist. A mixture of air and gas enters the pipe at about 10 lb. pressure, or enough to give a hot, blue flame. The part A is of cast-iron, which, on experiment, has been found to last longer without corroding than steel, although copper would be better. The soldering bolt B was made of steel because it kept the correct shape point much longer than cast-iron or copper, although the latter metal is better for transmitting the heat. The point should be tinned before using. This form of soldering head is being used on automatic can-soldering machines, and does the work effectively. It also saves gas. It will heat to the correct temperature in about 1¹⁄₂ minutes.

Fig. 10.—Gas-heated Bit complete

Fig. 11.—Air Inlets in End of Air Chamber

Fig. 12.—Section through Air Chamber and Gas-reducing Valve

Fig. 13.—Details of Cones or Needles

A gas-heated bit invented by W. G. Ryan is shown in [Figs. 10] to [13]. The actual bit A is held in a steel sheath B having a space underneath the bit to allow the gas to pass. The sheath has a row of holes on each side to allow the gas to come through, the flame enveloping the bit when in use. The gas, supplied through a flexible tube, passes through the tube that forms the handle, at the end of which is a small chamber C to admit air, which mixes with the gas to cause it to burn atmospherically, the supply of gas passing through a small cone valve D and thence through the air chamber. In the air-inlet holes E at the end of the air chamber are fitted small cones F to regulate the quantity of air. All the cones, including the gas-valve cone, are connected rigidly together, so that when cutting down the gas supply temporarily, the air supply is automatically reduced, and the gas flame remains in being, although its size is much reduced. It has been found that, in some gas-heated bits, the cutting down of the gas seriously interferes with the proportion of the gas and air mixture, resulting in a back-fire. The device here described has been invented especially to obviate that trouble. To reduce the gas supply and, with it, the air supply also, all that is necessary is a slight forward movement of the fitting to which the cones or needles are attached. The copper bit is kept in position by the sheath or clip, the small bolt in which can be taken out in a moment when special attention to the bit becomes necessary. The connection to the flexible gas tubing is at G, while H indicates a guide and stuffing box for the gas-valve cone or needle.

Fig. 14.—Gas-stove for Heating Bits

Stoves for Heating Soldering Bits.

—Although a copper bit may be heated in any fire, it is better to avoid the dirt, smoke and tarry stickiness which are often present in a coal fire. In the absence of gas, a bright, clear coke fire or a charcoal fire should be used whenever available. Portable oil stoves of the wickless type can also be employed, but the ideal fuel is gas, which may be regulated at will to give a uniform temperature. Two gas-stoves specially constructed for copper bits are shown by [Figs. 14] and [15].

Fig. 15.—Gas-stove for Heating Bits

Tinning a Bit.

—Before a bit can be used, it must be “tinned,” that is, coated with solder in a smooth complete covering, for which purpose—by one method, not the best, but the most general—the end is heated to a dull red, rubbed quickly with the file on the facets, dipped in killed spirit or “fluxite,” or rubbed against a piece of sal-ammoniac, and then applied to a stick or lump of solder, the facets being quickly wiped or rubbed on a piece of tinplate so as to spread the solder evenly. When properly done, the nose of the bit is coated with a smooth film of solder. This must always remain so, or the bit will not act, and when it is honeycombed, or the “tinning” is present in patches, it must be re-tinned. A bit must never be raised to a red heat sufficient to melt the tinning. The bit does not operate well at such a heat, because its contact makes solder too fluid and apt to run too quickly.

When dipping a hot bit, prepared for tinning, into killed spirit, a sharp pop, without smoke or spluttering, denotes the right temperature. If, on withdrawing the bit, it is damp and still unclean, it had not been heated sufficiently.

Another method of tinning may be mentioned. Into a small and clean tin box (a 2-oz. tobacco tin about ³⁄₄ in. deep) put some scraps of solder and powdered resin. Heat the bit to a very dull red, quickly file up clean on one side of the point, and then plunge into the solder and resin and rub about; it will at once take on a coat of the alloy. A second side of the bit may be tinned by then repeating the operation, re-heating if necessary. The bottom of the box should be covered with solder, which adheres easily enough, with a film of resin on top. It is probably most convenient to tin the under side and the left-hand working face of the bit. “Tinol” could be used in this way without admixture with anything.

Still another method is to use a firebrick having a hollow in which the solder and resin are placed; but the tin box plan is thought to be better.

Undoubtedly the best method of tinning a bit is that in use by the plumber who well knows the invaluable qualities of sal-ammoniac (ammonium chloride) for the purpose. He has no wish to squander energy on those vigorous rubbings of the bit—on paving-stone, bath brick, tinplate, etc. etc., and he believes that the habit of dipping the bit into zinc chloride is both slovenly and wasteful, for not only is this corrosive stuff sprayed about broadcast, but the remainder is soon rendered unfit for its purpose by contamination with copper chloride and dirt from the fire. The outlay of a few halfpence on a sizable slab of sal-ammoniac will keep the bit in the best condition for years, and save hours of superfluous labour. Commercial sal-ammoniac is obtainable in large, rugged crystals of a tough, fibrous texture. A piece weighing upwards of ¹⁄₄ lb. can be trimmed to a roughly rectangular slab, a few inches long and wide and about 1 in. thick; and a cavity should be scooped in one of the flat sides to accommodate the bit.

Fig. 16.—Tinning Bit in Sal-ammoniac Block

Let the bit-faces be made shapely and filed bright and the tool thoroughly heated in a clean fire, removed, flicked free of ash, and then held down firmly in the cavity of the sal-ammoniac block (see [Fig. 16]). Profuse white fumes will arise, and the surface of the salt will fuse. Bear heavily on each facet in turn, and then melt a few beads of solder into the cavity along with the bit, and the latter will become brightly tinned in a moment or so. The bit should be applied to the “ammonia block” every few heats, or as required, as the work progresses, and flicked with a tuft of dampened cotton-waste.

The sal-ammoniac has one great disadvantage—it is deliquescent (collecting moisture from a damp atmosphere), and its near proximity to most metals oxidises and corrodes them. Iron and steel, particularly, it rusts rapidly and deeply. Therefore the tools (saw and chisel) used to shape the block must be washed, dried, warmed, and greased before they are laid by, and the waste fragments must be carefully swept up and disposed of. The block itself must always be kept apart from tools. Plumbers enclose it in a sheet-lead box wrapped in a greasy rag; amateurs may store it on a dry shelf, parcelled in waxed paper secured by a rubber band, or in a length of motor-tyre inner tube, rolled up.

Simple Soldering.

—Scrupulous cleanliness in everything connected with the process of soldering is essential to success. The ordinary procedure in making a joint is to clean the surfaces first by filing or scraping with a scraper or a knife or a plumber’s shave-hook ([Fig. 17]). In some cases, dirty metal is cleansed with dilute hydrochloric acid. With or without preliminary heating of the work, flux is then applied to the joint, and the heated bit is held in one hand and a stick of solder in the other, and the stick drawn along the joint while the bit touches it (or “drops” of solder may be transferred to the work by means of the bit). This will cause a line of molten solder to run, and some skill and care are necessary to get just the right amount of solder without wasting it and allowing it to spread in a lumpy fashion beyond the necessary area. The bit is next worked up and down the joint to spread the solder, and by the transmitted heat to make it thoroughly penetrate the joint. This is an outline of the process, and there is a number of points requiring special instruction or a few words of caution.

Fig. 17.—Shave-hook

Note that the work must be filed, scraped, or otherwise mechanically cleaned, and then chemically cleaned by coating with the flux just where the soldering is required. In heating the copper bit do not let it reach even a dull red heat. Lightly dip it into the flux to clean the point; then, with a small button or blob of solder resting on the work, place the bit momentarily upon it to cause the solder to flow, and draw the bit where the solder is required.

Many beginners try to draw along the solder with an insufficiently heated bit. The result is a series of lumps—“putting it on with a trowel,” as it is sometimes termed. A good joint cannot be made this way, however much solder may be used.

Some beginners fly to the other extreme, and try to make a neat job with a red-hot bit, which results in the solder assuming a sandy appearance and in the work being discoloured.

Others try to solder uphill—that is, they hold or place the work in such a way as to cause the solder to flow away from where it is required. The correct method is to solder downhill by tilting or inclining the work, so that the solder will always collect around and travel with the point of the bit. This, besides facilitating the work, makes a strong joint, and imparts a clean and neat appearance to the job.

Figs. 18 and 19.—Incorrect and Correct Methods of Holding Bit

A common mistake is to hold the bit in a cramped and awkward way, as in [Fig. 18], the hand being twisted under the handle, the thumb being brought to the top, and the elbow forced to the side. The correct positions of arm and fingers are shown in [Fig. 19]; the elbow is held well out from the body, and the thumb is placed directly under the handle of the bit, forming a fulcrum over which the bit may be slightly raised or depressed at will. This is all-important when soldering very fusible metals such as pewter, tin, etc., on which the weight of the copper bit should never be allowed to rest, as otherwise a hole will suddenly be made in the work. The whole weight of the bit should be supported and balanced on the thumb by the downward pressure of that part of the hand close to the little finger. The worker should not for a moment lose control of the copper bit, and control is always assured when the thumb is underneath the handle.

There is but little strength in a butt joint with the edges of the metal only just touching—that is, without a lap; to take the example of a small cylinder, the body seam should have at least a ¹⁄₄-in. lap. [Fig. 20] represents an example of internal grooved seam soldering, which may be executed in the following way:—After applying the flux, place a small button of solder inside the cylinder on the seam, rest the bit momentarily on the solder to melt it, and then draw it gently along the seam. The cylinder should be slightly tilted to allow of the solder travelling with the point of the bit. The hand should avoid touching any part of the work that comes directly into contact with the copper bit, as otherwise the hand would be badly burned.

Fig. 20.—Soldering Internal Grooved Seam

Fig. 21.—Soldering on Can Bottom Internally

The method of internally soldering the bottom on a canister, etc., is shown in [Fig. 21]. The bottom is held in position by gently pressing it against (but not placing it on) the bench during the soldering process, while the tilt of the canister and the position of the bit cause the solder to travel with the bit.

In soldering all such articles, the soldering should be done with one sweep of the bit, the left hand meanwhile making the necessary revolution. This saves time and solder, and avoids the unsightly appearance of a series of starts and stops.

In work of a larger and more substantial nature, as, for example, galvanised or tinned iron work, the bottom of the article is first “knocked up,” and then soldered internally. [Fig. 21] represents an example of internal soldering where the whole weight of the bit is shown resting on the molten solder inside; this provides the local heat required to “sweat” the solder into the four thicknesses of metal which constitute the bottom seam; and for this work the bottoming bit shown in [Fig. 3] is often used. Pewter, lead, zinc and tin—the latter should not be confused with tinplate—do not require sweating, on account of their low fusibility, and any attempt even to solder them with a very hot bit will probably end disastrously.

Fig. 22.—Soldering Can Externally

[Fig. 22] shows an example of external seam soldering. The method there shown is invariably adopted for simple lap seams, although grooved seams are similarly soldered. A grooved seam, however, should preferably be soldered internally. The position of the worker’s elbow and thumb should be noted, as should also the tilt of the cylinder (more pronounced in this case than the other) in order to secure the downflow of the solder.

Sweating has already been mentioned. It should be said that one of the easiest ways in which a beginner may make a reliable joint is to prepare both faces of the joint by fluxing and covering with a thin film of solder, and then pressing the two parts together with the hot bit until the top part “floats” and then settles down. The advantage of this way is that one can be sure of perfect application of the solder to the joint faces, since each is dealt with first and thoroughly coated, with no faulty patches. Sweating is also done in the flame of a bunsen burner or blowpipe, as explained later.

Reinforced and Filled-in Soldered Joints.

—The bottoms of square or cylindrical vessels should, preferably, be soldered from the inside, and “buttons” of solder may be melted to assume a stout triangular-shape stud in the corners of the square vessels. A tinned rivet is sometimes riveted or just placed in a corner, and sufficient solder floated over it to strengthen the corner. Solder is always liable to run through an improperly closed seam at the corner when external soldering is resorted to; but in cases where this is the only practical method, a tinned rivet may be inserted from the outside, and then soldered over. It sometimes happens that two “raw” edges require soldering together without a lap. Where a strong joint is required a good plan is to place a length of tinned wire over both edges and solder the lot together. In addition to strengthening the joint, the wire considerably improves the general appearance. A simpler joint may be made by “skimming” the solder over with a copper bit heated only just sufficiently to melt the solder. The quick and skilful touch is required to perform this operation satisfactorily; but a little practice will soon bring the necessary proficiency. The idea is to “draw” the solder across the joint quickly, before it has time to run through. This method is useful when soldering thin metal goods of a lower degree of fusibility than that of the solder employed. No preparation for filling cracks previous to soldering can be recommended, beyond such small pieces of metal that may be afterwards soldered over and effectively hidden. It is much better to endeavour to produce work of such quality that this expedient is altogether unnecessary.

Soldering Heavy Milk Churns.

—When soldering the bottom rims on large milk churns, sufficient heat cannot be maintained with only one soldering bit. At least two heavy bits are required, so that one may be getting hot while the other is in use. The rims are usually tinned before being fixed by first pickling them in dilute hydrochloric acid, washing, and then dipping in a bath of molten tin. When repairing and resoldering the rims, remove all dirt and rust with a file, use a few brushfuls of raw spirits further to assist the cleaning process, then wash with clean water and solder in the usual way, using killed spirits as a flux.

Soldering Hole in Enamelled Ware.

—First scrape or file away the enamel quite clear all round the hole, apply a little raw spirit to the surface of the iron, and coat it with solder in the usual manner. Then cut out a tin disc large enough to cover the hole, and solder this in, using killed spirit as the flux.

Soldering Leaded Lights.

—For soldering the calmes of a lead-light window, the calmes having been fitted properly together, shave a small round dot at the point of junction, sprinkle a little powdered resin on the shaving, and with a copper bit or with a glazier’s iron having a tinned face, melt a small piece of tinman’s ordinary solder on the shaved part so that it tins to the lead and forms a round button.

Soldering Catch on Gun-barrel.

—In soldering a catch on a gun barrel it will first be necessary to tin both barrel and catch, and then to wire them together, in addition binding the barrels for some distance from each side of the catch, making the ribs secure with wedges. To melt the solder, use heaters; these are generally made of copper with iron handles; or iron rods can be used, the ends being made red hot and inserted in the barrels. Cut some small slips of thin solder and place them on each side of the catch, using powdered resin. As soon as the solder melts, remove the heaters and cool the barrels.

CHAPTER V
Soft-soldering with Blowpipe or Bunsen Burner

Fig. 23.--Mouth Blowpipe
Fig. 24.--Black’s Mouth Blowpipe
Fig. 25.--Fletcher’s Mouth Blowpipe

Fig. 23.--Mouth Blowpipe

Fig. 24.--Black’s Mouth Blowpipe

Fig. 25.--Fletcher’s Mouth Blowpipe

Fig. 26.—Section through Blowpipe Flame

The Mouth Blowpipe.

—Although soft-soldering is usually associated with the use of a copper bit, quite a number of jobs can be done without one, using instead a bunsen burner or, more generally, a mouth blowpipe, which is an inexpensive appliance, useful for both hard and soft soldering, and with either gas, candle, or a methylated-spirit flame. Three shapes of mouth blowpipe are shown in [Figs. 23] to [25]. In a blowpipe flame there are three cones, X, Y, Z ([Fig. 26]). X is a non-luminous cone, consisting of a mixture of atmospheric air and unburnt combustible gases (each with a low temperature); Y is a luminous cone, composed of burning gases (carbon and carbonic acid being in excess); and Z is a cone the oxygen in which renders it less luminous and free from combustible materials, its temperature being exceptionally high, especially where the cone comes in contact with the point of the cone Y. Because of its properties, Z is termed the oxidising or outer flame, whilst Y is known as the inner or reducing flame, because when it is applied to some easily reducible substance—say, lead oxide—the oxygen in the substance heated mingles with the unburnt carbon in the cone of the flame and produces carbonic oxide, the lead being thus separated or reduced. The blowpipe flame is one of intense heat, even that produced by blowing a common candle being capable of melting metallic fragments when they are supported on a bed of charcoal. The pointed flame gives the greatest heat, and this can be produced simply by increasing or decreasing the space between the flame and the article to be soldered or the metal to be melted.

The particular advantage of a blowpipe is that it gives a fierce heat at a very localised area, beyond which the solder does not run, and it enables spots to be soldered, or parts to be unsoldered, adjusted and re-soldered without allowing heat to stray and cause trouble at other places. A useful little addition to the ordinary blowpipe is a small washer soldered on near the mouth end (see [Fig. 23]), the object of this being to raise this part off the bench and so keep it from contamination with dirt, filings, etc., which are unpleasant to the lips. Sometimes the washer is made elliptical and slightly concave to fit the lips, so that it forms a convenient stop or steady when the blowpipe is held between the teeth without help from either hand.

Bunsen Burner, Spirit Lamps, etc.

—The bunsen burner is, of course, the most convenient device for heating (when the bit is not in question); but failing a gas supply, a spirit-lamp must be employed. This is a small glass bottle with wick, methylated spirit being used. Plumbers and gasfitters make use of metal tubular lamps fed with spirit poured on cotton-wool, and having a blowpipe tube attached and coupled up to the lips with a rubber tube; they also use wax tapers.

Fig. 27.—Home-made Spirit-lamp

Fig. 28.—Another Home-made Spirit-lamp

Fig. 27.—Home-made Spirit-lamp

Fig. 28.—Another Home-made Spirit-lamp

A methylated wick lamp may be easily made out of a small “self-opening” canister, as shown in [Fig. 27]. The holes near the top increase the efficiency of the flame. Another spirit soldering-lamp is shown by [Fig. 28]. The container for the spirit can be made about 3 in. in diameter by about 1¹⁄₂ in. deep, with a handle soldered on. A glance at the [illustration] will explain the burner. An outer wick surrounds a piece of tube, which itself contains another wick. The spirit in the inner tube is vaporised by the heat from the burner when the outside wick is lit. The spirit vapour issues from a ¹⁄₃₂-in. hole at A. At B a ring is slipped over the outer wick, holding it to the central tube. By lifting the central tube the height of the vaporising flame can be adjusted. The vaporising tube is a piece of ³⁄₈-in. brass tube with a ³⁄₈-in. gas cap screwed on the end, or a brass disc can be brazed in. The total cost should not exceed sixpence.

Fig. 29.—Swivelling Gas-burner for Bench Soldering

Bench Blowpipes.

—The best form of gas bracket for bench use is one having a horizontal swivelling arm, and screwed to the bench by a flange, as shown in [Fig. 29]. The swivelling head is also a cock, which shuts off the gas when the jet arm is pushed over at right angles to the edge of the bench, as indicated, and the gas is connected by an iron or compo pipe under the bench. A second gas tap should be arranged in the supply to regulate the amount of gas, and for reasons of safety. A simple device (see [Fig. 30]) may be made by anyone, and connected to a rubber-pipe connecting head on the gas bracket supplying light to the bench and workshop.

Fig. 30.—Simple Bench Burner

Fig. 31.—Gas Blowpipe for Bench

A design of gas blowpipe which leaves one hand free is shown by [Fig. 31]. This enables the worker to apply the solder to the work (holding the end of a strip against it), after it has been brought to the melting heat of the solder. The blowpipe is arranged so that it can be held in the hand or dropped into a hole in the bench.

Tapers.

—Tapers for a blowpipe flame are made by untwisting cotton rope until the threads of the individual strands are straight. These are then dipped in melted wax made by melting two wax candles over a gas stove in a jam jar. They are repeatedly dipped until sufficient thickness of wax is obtained. The wax should be just sufficiently hot to keep melted.

Catching-tray for Bunsen Burner.

—The blowpipe is not essential for some kinds of work, such as when the job can be held wholly in the flame without causing any damage. When solder is being melted to drop on to a surface, the plain bunsen or atmospheric flame is also sufficient, though in this case it is well to tilt the burner over so as to prevent the solder dropping down the tube. An elbow fitted on the top of the tube is handy in this connection, to deflect the flame at an angle, and [Figs. 32] and [33] show this, with the addition of a tray to catch the dripping solder which otherwise would splash on the bench and cause untidiness. The tray is riveted to a strip of brass bent round to slip over the outside of the elbow, and a small pin riveted into the tube prevents the tray from falling down.

Figs. 32 and 33.—Bunsen Burner and Solder-catching Tray

Fig. 34.—Section through Blowlamp for Soldering, Brazing, etc.

Blow Lamps.

—A soldering lamp is used sometimes in the place of a blowpipe, and it should combine perfect security with compactness and portability. Tool merchants’ catalogues show a number of styles. In the lamp shown by [Fig. 34], benzoline is burnt. When the lamp is in use and the body of it is very hot, the inside pressure does not exceed three-fifths of an atmosphere, whether the regulator R is open or almost closed. Thus the danger of explosion, which is such a drawback to some of the lamps that use ordinary paraffin, is avoided. The upper parts of the lamp are subjected to great heat and therefore are packed with asbestos, which serves as a filter and stops any impurity in the benzoline from getting to the burner. The flame can be lowered to a glimmer when not actually in use, thus saving the trouble of relighting. When the lamp is to be used, the regulator R is screwed up tight; and care must be taken to ascertain, from time to time, that the burner or nipple C is open and perfectly clean. If this becomes obstructed, it can be cleaned by unscrewing the tube T and passing a fine steel wire through the hole. The lamp should be completely filled with benzoline every time it is to be used. A little methylated spirits is poured into the basin A, and set alight. When the apparatus has become slightly warm, the regulator is opened gradually. To extinguish the flame, the regulator must be screwed up tight. If any escape is observed round the screw of the regulator, the square P should be screwed up with the key supplied by the makers, so as to tighten the asbestos packing. The lamp above described is only one of a great number of such appliances, but it is fairly typical of them all. The difference between a solderer’s and a brazer’s blowlamp is merely one of size and power.

Fig. 35.—Soldering Lading-can handle

Fig. 36.—Soldering Lug to Lamp Bottom

How to Operate a Mouth Blowpipe.

—The operation of using the mouth blowpipe does not consist in blowing intermittent and strong blasts with the lungs, as this would soon exhaust the wind power. For very light jobs, however, this method is sometimes adopted; but once the proper way is discovered, the user naturally falls into the use of this method.

The proper way to keep a continuous blast is to breathe naturally through the nose, and at the same time keep the cheeks distended by forcing the air at sufficient pressure from the lungs. The cheeks naturally resist the pressure, and force the air through the blowpipe. The operation requires some practice and a clear nose passage. There is practically no limit to the time a continuous blast can be kept up.

The blowpipe flame is produced by holding the blast end of the blowpipe just above the wick of the taper and touching the flame; the blast then causes a long blue flame to project. This flame is hottest at the tip, which is slightly brown.

Typical Blowpipe Jobs.

—Some of the photographic reproductions in this chapter show the methods of soldering comparatively light and heavy articles. [Fig. 35] shows a lading-can handle being resoldered. As it had broken away, the old solder remained, and the joint did not need cleaning. It is dabbed with the killed-spirit brush, and a small piece of solder put near the joint. The flame is first played on the parts away from the solder to get them to the requisite heat, and as the heat reaches the solder it melts, and flows where required. Where the solder should be the thickest, that part of the joint is inclined downwards.

A job needing very much heat, and therefore a continuous blast for some time, is shown by [Fig. 36]. A lug is shown being soldered to a heavy brass lamp bottom. Before putting the lug in position the parts of the joints have to be tinned. This consists of applying a film of solder. In this case the heat is applied to the lamp bottom for several minutes, and without loss of time the part where the lug fits is cleaned with a fine file, the spirit brush dabbed on a piece of solder, put in position, and the flame again applied. The solder almost immediately flows over the cleaned portion; if it does not flow as required, the flame is played on the solder and lamp bottom, a dab with the spirit brush helping matters. The lug, which should have been previously tinned, is placed in position on the lamp bottom, and with a slight application of the flame, the solder flows and unites the parts firmly together. It should be particularly noted that, when uniting light articles to heavy ones, the light ones should be tinned first, and secured to the heavier article whilst the latter is still hot.

Fig. 37.—Soldering Wires of Vegetable Masher

Fig. 38.—Holder for Applying and Adjusting Solder

[Fig. 37] shows the wires of a vegetable masher being soldered. There is nothing special about the job, except that the solder cannot be placed on the joint. To effect this a piece of tin ([Fig. 38]) is indented at one end, and a small hole made in the centre of the depression. The bead of solder is placed in this depression, and held over the joint to be soldered; the flame is then played on the joint and on the solder which flows through the hole.

Fig. 39.—Brushing Solder around Dial Ring

Fig. 40.—Tinning Dial Ring

[Figs. 39] and [40] show the method of tinning a brass dial ring. The ring is filed clean and placed on a piece of asbestos board, the flame being applied until the ring is sufficiently hot all round. A bead or two of solder is placed on, and, as they melt, the solder is brushed round as shown in [Fig. 39] with the spirit brush, the flame being applied at intervals to aid the flow.

Fig. 41.—Re-soldering Kettle Spout

Re-soldering Kettle Spout.

—Refixing a spout in a “tinned” wrought-iron or copper kettle. The spout and that part of the kettle which comes in contact with it should first of all be filed bright and clean. Next place the spout in position, apply killed spirits, and hold it over a bunsen flame, as in [Fig. 41], until sufficient of the strip solder is melted to flow around and sweat through to make a strong sound joint. Should any difficulty be experienced in getting the solder to flow readily, apply a little more flux.

Soldering Corroded Metal.

—When the surface of metal to be soldered is badly corroded, and it is difficult to obtain a clean, bright surface preparatory to soldering, it should be treated to a liberal application of raw spirits of salts (hydrochloric acid), which will soon remove the cause of the trouble, but all traces of the acid should be washed away with clean water before attempting the soldering. It is also a good plan in these cases to tin the surface by repeatedly rubbing it with a hot bit and solder, together with plenty of killed spirits, before proceeding with the actual soldering process.

Soldering Small Work.

—When soldering two small awkward-shaped pieces together, they can be held in position by pressing slightly into a piece of damp clay. When the work has several soldered joints it can be buried in sand or covered with clay to confine the heat to the part being operated on.

Although care should be taken to limit the solder to the area of the joint, there are circumstances in many cases where it is difficult to prevent some of it from straying. To clean this off, resort may be had to the blowpipe, applying the blast and quickly wiping the surface while the solder is in a molten state. Or it may be filed off while cold and finished with a scraper or a knife and emery-cloth. Or if there is only a thin film the knife or emery-cloth alone will suffice.

Soldering Pipe Joints.

—Most joints in lead, tin and compo. pipe are now preferably made by means of a blowlamp, or with a mouth blowpipe, strip-solder being used. When making the joint, heat the pipe in the immediate vicinity, and, dipping the solder in the flux, stroke it around the pipe to form the joint.

In soldering block tin or compo. pipe with a bit, if this is too hot it will promptly melt the pipe. This is also liable to happen with very thin zinc. The only way to prevent this is to have the bit just hot enough to melt the solder, and not to let it rest any length of time on the soft metal.

Figs. 42 and 43.—Soldered Branch Joint on Tin or Compo. Pipe

In making connections with soft pipe it is better to make use of brass couplings, and these can be soldered more easily and safely by means of the blowpipe than with a bit. First clean and tin both ends of the coupling, and with the bit put a little ring of solder round about ¹⁄₈ in. from the end, as shown at D in [Fig. 42]. Next with a penknife cut a hole in the pipe B where the connection is wanted, a neat fit for the end of the coupling tail A, scraping the surface of the pipe all round the hole. Insert the coupling in the hole in a vertical position. Sprinkle a little powdered resin round the joint, or smear it with fluxite. Using the flame of a spirit lamp or a candle and a mouth blowpipe, heat the upper part of the coupling, being careful not to allow the flame to come too near the soft pipe. The solder will soon melt, and run down into the joint (see D in [Fig. 43]), when the flame must be instantly withdrawn. The same proceeding can be adopted in soldering the other portion of the coupling into the connecting pipe. If a vertical position is inconvenient for the coupling it can still be soldered in that position, and afterwards twisted carefully into the desired position. In [Figs. 42] and [43], C represents a wood plug for steadying the coupling tail.

Fig. 44.—Soldering Birdcage Wires

Soldering Birdcage Wires.

—For this job, it is better to flatten out the solder to the thinness of brown paper and with a pair of scissors or shears to cut it into very narrow strips. Take little pieces about ¹⁄₄ in. long, and with the fingers pinch them round the wires just above the joints to be soldered. Touch each joint with a small quantity of killed spirit, and apply the flame of a small blowlamp just underneath the joint; this will cause the solder to run in the joint in an instant (see [Fig. 44]). The flame is quite free from smoke, and does not discolour the wire in the least, as the solder will run long before the wire is red hot. Every joint may thus be neatly made. With a thin piece of copper wire secured in a handle as illustrated, the solder may be drawn any way desired to make special joints in awkward places, where the point of an ordinary soldering bit could not be used.

Sweating.

—In the preceding [chapter] it was shown how useful [sweating] is, when accomplished with the help of the bit. In blowpipe work, also, this method is of much utility, particularly in delicate work where portions have to be joined up in very precise relations. After tinning the joint faces the pieces are secured in accurate relationship with binding wire, or by bolts or screws or other means, or a soldering clamp is employed, having jaws which clamp the pieces and enable them to be adjusted to the exact locations desired, and the flame then brought to bear until the work is hot enough to cause the solder to run.

An example of the usefulness of sweating occurs in the making or repairing of metal name plates having superimposed brass, copper, or other metallic letters. The plate having been flattened and polished and the letters cut out, filed and finished, the backs of the letters must be rendered chemically clean by careful scraping, and are next “tinned” with soft solder. The tinning may be done in several ways, but the easiest is by the blowpipe, using resin oil as flux.

Each letter may be placed in succession on a lump of charcoal, using plenty of the resin oil, and applying the flame of the blowpipe to the surface while one hand holds the charcoal and the other the strip of solder. To prepare the solder, which is sold in sheets by the pound, cut some strips ¹⁄₃ in. wide. Take hold of one end 1 in. from the end, and with a sharp knife scrape the surface, drawing the knife edge downwards. Do not use the last 2 in. of the strip, as the handling of this part makes it chemically unclean. The greater part of the solder should be about the edges of the letters. The next operation is to solder the letters to the brass plate. As the brass plate also must be chemically clean, the parts where the letters are to go should be lightly scraped. Having ruled parallel lines in order to get the letters in line, lay each down in its proper place, and draw a pencil line round it; then with a scraper just remove the surface of the brass where the letters are to be soldered. A thin piece of solder is now placed underneath each letter, and each in turn is fixed in its place and secured with a loop of binding wire screwed up tight. Nothing now remains to be done but to apply the blowpipe flame and resin oil, when the solder will run underneath the letters. It is better to set the plate on some small lumps of charcoal. When the letters appear to be set fast, remove the plate and boil it in a solution of potash, about ¹⁄₂ lb. to 1¹⁄₂ gal. of water, and clean in dry sawdust. The resin oil may be made by dissolving resin in sweet oil by gentle heat, until the oil will cause the solder to run.

CHAPTER VI
Soldering Aluminium

It is well known to those accustomed to the art of soldering that there is no solder which operates with aluminium in the same way that ordinary solders operate with tinplate, copper, brass, etc. Aluminium soldering presents so many difficulties that it has been thought desirable to devote a separate chapter to the subject.

There is more than one reason for the difficulty encountered. Aluminium does not alloy readily with solders at temperatures as low as other metals require; and, secondly, aluminium alloys with lead solders only with great difficulty, and with but a small proportion of lead at that. Consequently, lead solders are not suitable for aluminium. Another and even more serious reason is in respect to the refractory oxide which forms at soldering temperatures, and which is undoubtedly responsible for most of the trouble.

The soldering of aluminium is one of the most debated subjects in metal working. Almost as soon as aluminium was prepared on a large scale, it was discovered that the ordinary solders and fluxes did not answer with it. Either pure tin or pure zinc will wet aluminium, and can, therefore, be used as solder for it; experience shows that the tin soon falls apart, while zinc by itself is brittle and discolours badly. The failure of tin is due to the fact that it forms with the aluminium an alloy that is decomposed by the action of the oxygen present in the air.

Although aluminium is popularly supposed to be non-oxidisable, really the surface is covered with a very thin film of oxide, which prevents solder from alloying with the metal. Aluminium when heated rapidly oxidises. It is customary to scrape the metal before and during the soldering; and although some workers say that it is useless to scrape before soldering because oxidation immediately starts again, it is obvious that a thin film is more easily penetrated than a thick one. Often it answers to scrape with the copper bit during the soldering, previously rubbing off the oxide with emery cloth. The work should, if possible, be backed with asbestos, to keep up heat in the metal. To discover whether the surface is thoroughly tinned, wipe off lightly, and the untinned parts will then soon become apparent. If the oxide is not scraped off beforehand, it will probably mix with the solder and form a scum, which will make a neat flow difficult. Scum should be lightly removed with an old knife blade. It is essential to “tin” every part to be joined, as the solder will not take on any spot that has not been rubbed in some way, unless previously coated.

Solders for Aluminium.

—Hundreds of aluminium solders have been invented, naturally all claimed to be strong and durable, the alloys containing various metals, such as aluminium, antimony, bismuth, cadmium, chromium, copper, lead, manganese, silver, phosphor tin, tin, and zinc. A [table] of the most approved aluminium solders is here given.

Many of the best solders for aluminium contain a small proportion of phosphor tin. A molten alloy containing phosphorus placed on aluminium tends to absorb oxygen from the impure film as well as the surrounding air.

Compositions of Aluminium Solders

In making the solders here given, it is advisable to avoid loss of the more easily volatile of the metals by adopting the following precautions: The aluminium is melted first, the zinc is added in small pieces, then tin in small pieces, and lastly the phosphor tin.

Inasmuch as zinc alloys with aluminium more readily than does any of the common metals, solders that will readily “tin” aluminium generally contain zinc in varying proportions. The solders found most satisfactory contain zinc, tin, aluminium, and a very small proportion of phosphor tin; but they do not run very freely or fuse so readily as the ordinary tin and lead solders, and it is necessary to use a higher temperature, so high, in fact, that difficulty is found in using these solders with a soldering bit, and it is generally necessary to use a blowlamp.

While there is no solder that allows aluminium to be soldered with the facility and success experienced with other metals, that of Richard’s is extensively used, and seems to have given as good results as any. It consists of the following ingredients: Tin 29 parts zinc 11 parts, aluminium 1 part, and 5 per cent. phosphor tin 1 part—practically the same as that given in the last line of the table. This solder has withstood the test of time better than many of the patented solders, and can be used in jointing aluminium to aluminium, also aluminium to copper or brass, and without the use of a flux. In making the solder it is advisable to avoid loss of the more easily volatile of the metals. The aluminium should be melted first, then the zinc, tin, and phosphor tin in the order named.

When using phosphorus instead of phosphor tin in the making of aluminium solder, it will first be necessary to incorporate it with the tin, for which purpose take a length of 1-in. gas barrel, attach a screwed cap at one end, and close the opposite end with a tin (not tin-plate) plug. Remove the screwed cap, and, having carefully dried between blotting paper the proper proportion of phosphorus, insert the latter in the tube and replace the cap. Now put the plugged end of the tube into the molten tin; this will melt the plug of tin and so allow the phosphorus to come in contact with the molten metal. The ingot of phosphor tin formed is afterwards alloyed with the other ingredients, as already explained.

Fluxes for Aluminium.

—A large variety of fluxes have been tried with more or less success, namely, borax, copper chloride, lithium chloride, paraffin resin, sal-ammoniac, stearin, silver chloride, tin chloride, venetian turpentine, tallow, vaseline, and zinc chloride. Stearin is undoubtedly the most reliable of them all, but no flux is needed for solders containing phosphorus, which is itself a flux.

The Soldering Bit.

—The average temperature required to make a satisfactory and thoroughly sweated joint in aluminium is from 650° F. to 680° F., according to the size of the article. A blowpipe or blowlamp will be of great value, and is frequently preferable to a bit. Should a bit be used, see that it is of aluminium or nickel instead of copper, the point and the soldered joint being kept much cleaner whilst removing the film of oxide during the soldering operation. Another advantage is that the point or “face” of the bit can be “tinned” with the same flux as that which is used for the joint. More care must be taken in the manipulation of the aluminium soldering bit owing to its lower melting temperature than the copper and nickel bits.

The Process of Soldering Aluminium.

—The soldering of aluminium must be performed quickly to be satisfactory, as the metal, if not coated at the first attempt, may be injuriously affected. “Tinning” the parts required to be soldered first is another important factor; also the distance of the overlap of the joints should not exceed more than ¹⁄₈ in., so as to allow the solder to flow thoroughly through; it does not flow so readily as when soldering other metals.

In soldering large pieces, where the ordinary overlap is not allowable, and where a butt joint would be weak, fit the pieces together as at A ([Fig. 45]).

Fig. 45.—Aluminium Fitted Together for Soldering

Solder always flows towards the hottest point. This tendency enables one to direct its course under the blowpipe or blowlamp flame. A large flame should only be employed in “heating” up the part to be soldered on large and heavy work. With a small pointed flame directly on the solder and the parts on which it rests, the solder will flow quickly, and leave a smooth, even surface at completion.

Some aluminium solders now on the market are so hard that it is necessary to heat them and the work to redness before they melt. Sheet aluminium is easily warped by heat, and also contracts badly. If the solder is too high in melting point, the metal must also be brought to that point to cause proper union. If a hole is being filled in, the body of the metal on heating expands all round and partly closes the hole; also both the solder and the patch whilst hot are slightly expanded. In cooling, the hole enlarges, the patch contracts, and the solder also contracts; cracks result. The body of the work, if not exactly evenly made, will warp, which is fatal to engine and similar work. By using a low-heat solder (melting point, about 700° F.) these troubles should be avoided.

Soldering Aluminium to Copper or Brass.

—Aluminium can be readily soldered to copper or brass with fine solder (2 parts of tin and 1 part of lead): tin the metals, using stearin as flux previous to making the required joint. It is essential that both the “tinning” and soldering should be thoroughly done. Do not expect the solder to pull the joint together, but see that the joint is kept under slight pressure until the solder is hard, otherwise the joint will not be perfect. Many workmen refuse to place any reliance in such joints.

Finally, it seems very likely that, at any rate as regards factory work, the use of solder on aluminium objects will be wholly discarded in the future in favour of fusion welding or autogenous soldering, in which process no alloy is interposed between the surfaces to be joined. Information on the subject is given towards the end of this book.

CHAPTER VII
Wiping Joints on Lead Pipes

Plumbers make joints in lead pipes with soft solder which, by means of cloths, they “wipe” to the shape shown by [Fig. 47].

[Figs. 46] and [47] show the difference between a copper-bit or blowpipe joint and a wiped joint.

Fig. 46.—Copper-bit Joint on Lead Pipe

Fig. 47.—Wiped Joint on Lead Pipe

Plumbers’ Solder.

—As already stated, coarse, or plumbers’ wiping solder, is made in the proportion of 2 of lead to 1 of block tin. Care must be taken that the lead is quite pure and free from any other metal, as zinc-adulterated solder will be difficult to use, and joints made with it on service pipes will not be sound. In melting up scrap lead for making solder, only sheet lead should be used, as the lead used in the manufacture of sheets is much purer and contains a greater proportion of pure pig lead. The scraps must be quite dry; a damp piece dropped into a pot of molten metal may cause a serious accident, as the contents of the pot may be blown out.

To test the quality of solder when made, heat it as for wiping a joint; the correct temperature is determined by dropping a small piece of newspaper into the pot, and if it quickly burns and catches alight the solder is right for using. Next pour a small quantity on to a cold but dry stone or cement floor. This, on cooling, should have a few spots on the surface about the size of a threepenny-piece, and on the under side should be bright nearly all over. Solder of this quality would, if properly used, stand any pressure without sweating. If the solder on the stone or cement floor looks white on both sides, or has a few small bright spots on the under side only, it is too coarse and requires more tin. On no account should the solder be heated to redness, as the tin rises to the top and quickly turns to dross (see [p. 11]). If this should happen to solder that is being used for service pipes, it should be rectified by adding more tin.

To purify a pot of “poisoned” solder (solder that contains zinc), melt, stir in a handful of common sulphur or powdered brimstone until the mass is of the constituency of wet sand, heat to the ordinary working temperature, and carefully remove the crust that forms on the top, and the solder will then be fit for use, except that a little tin must be added to it. The presence of zinc in solder can be detected by the difficulty of forming joints, the metal falling apart and working very lumpy, and the joints when finished having a dirty grey appearance.