Soldering, Brazing and Welding :: CHAPTER IV Soft-soldering with the Copper Bit

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.

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