The watchmakers' hand book

HAMMER HARDENING OF BRASS.

103. Plates. The selection of the metal will depend on the purpose for which it is intended, and the thickness must be such that, when hammered till of sufficient hardness, it will approximately equal one dimension of the required object; for it is advisable to remove as little of the surface metal as possible, a plate always hardening much more at the surface than in the interior.

There is considerable difficulty in indicating clearly in a book the exact mode of conducting the operation of hammer-hardening, and the assistance of a competent master is essential, at any rate for the first few trials. It must suffice to point out that the anvil, with a slightly convex surface, and the hammer, of sufficient weight, must be in very good condition and, if possible, polished on their faces; the head of the latter should be rather convex, and the pene or chisel end somewhat broad and gently rounded off in all directions, for it will be needed as a means of bending the metal upwards; the curvature being such that there is not a danger of starting a crack, etc., by its means. We have already spoken of these two tools (79, 80); it is only necessary to add that a thick straw pad should be placed under the anvil or block.

When one is compelled to use brass that is too thick, so that there is much work to be done with the hammer to reduce the thickness to what is required, it is a good plan to commence by elongating the metal in one direction, striking with the pene of the hammer a series of parallel blows in the direction of the required elongation; when the thickness is two or three times that ultimately needed, the surface is smoothed with the hammer-head and annealed; then it is brought to the right thickness by another hammering in the manner explained below, but it should be again pointed out that, when possible, metal of a suitable thickness ought to be taken in the first instance, since too much hammering has a detrimental effect.

Before hammer-hardening a plate, it must be dressed, an operation which consists in rounding off the edges very carefully in order to prevent their cracking, and in rounding the bottom and sides of internal angles which, without such a precaution would occasion a rupture. After this is completed, proceed to the hardening, using a rather heavy hammer, and giving sharp blows along lines parallel to the sides of the plate; commence from one of the corners in the case of a square plate; and with a round plate let the blows be in circles. In the latter case, work from the circumference towards the center, at the same time gradually increasing the force of the blows, since the metal opposes a greater resistance towards the center. If the work is done evenly and without hurrying, the surface will remain fairly flat, a fact which should be verified from time to time by the aid of a metal rule.

Round plates are sometimes hardened by commencing to hammer in the center and working towards the circumference along two radii in opposite directions; that is along a diameter. This first diameter is then crossed by another at right angles; the intervals are filled in with other diameters that must not touch until the entire surface is covered, always taking care to work from the center towards the circumference.

When the metal is thin only the hammer-head is used, but beyond a certain thickness the pene of the hammer must be employed until about half the required thickness is reached; the surface is planished and the hardening finished with the face.

Blows that are irregular, too hard or roughly given, will cause the metal to crack. Hurried working will disturb the molecular grouping of the alloy; it will at the same time be heated and therefore softened, thus losing all the good qualities that are anticipated from hammer-hardening, namely increased body and elasticity. It was in order to avoid this heating that the old watchmakers used to hammer the brass in cold water, an excellent precaution which is too much neglected at the present day.

Brass that is badly hammered, the blows being violent or irregular, will spring out of shape on being cut and occasionally crack when gilding.

If during the process of hammering, a crack is observed to be commencing at the edge, it must be removed with a rat-tail file, all sharp angles being rounded off; and when cracks immediately reappear on continuing the operation, it is an indication that the metal cannot support any further hammering cold.

If brass is compact or well forged it may be relied upon to preserve the oil at pivots, etc., better, as oil is decomposed more rapidly in presence of a finely divided metal.

104. Brass rods. Rods having a square section must only be hammered on two opposite faces.

A rod of square section can be hammered on all four faces but it must be first filed perfectly square; the hammering must not be pushed too far, and the four angles must be maintained right angles. If some are made obtuse and others acute, a flaw will be produced in the direction of a diagonal.

The three following methods are employed in the case of round rods:

The first consists in hammering over the entire surface, the rod being at the same time rotated on the anvil by hand; but this operation must not be much prolonged, as the metal is liable to crack lengthwise.

The second method consists in reducing the diameter of an annealed brass rod to about one-half or two-thirds its initial amount by causing it to pass in succession through a number of holes of the draw-plate.

When the third method, which is due to Brocot, is adopted, one extremity of the brass rod is gripped in the bench vise and the other end in a hand vise, which is then caused to rotate round the rod as an axis. If the torsion be continued until the metal is on the point of breaking, it will be found to be very effectually hardened. This method is resorted to with advantage for hardening pin-wire and the metal for making pillars.

TO ANNEAL BRASS.

105. When it is necessary to considerably reduce the dimensions of a piece of brass, either with the hammer, rolls or draw-plate, it must be annealed from time to time.

The metal should not be heated to redness; it is supposed, rightly or wrongly, that such a proceedings especially if repeated, separates a portion of the zinc, or at least changes the mode in which it is associated with the copper. Brass should be heated slowly and uniformly, in a moderate fire, until the temperature is such that drops of water thrown onto the surface are rapidly converted into vapour, or paper turns yellow and begins to smoke. It is then withdrawn from the fire and allowed to cool.

Brass is brittle when hot, so that it can only be worked cold.

When brass is annealed, just as when steel is tempered, the metal should not be allowed to rest on a bad conductor of heat, such as wood or stone, because there will be a tendency to uneven distribution of the heat throughout the metal.

CAST BRASS.

106. This is usually brittle, owing to the fact that the copper employed in its manufacture consists, as a rule, of all sorts of scrap, from good or bad metal; moreover, from motives of economy, the proportion of zinc is generally increased and, in pouring, the precautions essential to avoid the effects of liquation (102), etc., are frequently neglected. Such an alloy must never be used for small objects, it must be entirely excluded from a watch, and in a clock only such pivots as are called upon to perform an insignificant amount of work should be allowed to run in it.

In order to avoid injuring the file, or embedding in the metal any particles of the hard coating of oxide that always covers rough castings, it is usual to dip the object in dilute nitric or sulphuric acid (155), by which the oxide is dissolved.

TIN.

107. This is an elementary body, almost as white as silver and having a breaking strain of only 8 kilo. per sq. mm. of section (or 11,300 lbs. per sq. inch.)

Watchmakers use it in making solder. It is also sometimes used in the form of plates or rods for polishing with rouge, and it is said to be much more efficient when very pure.

If a strip of pure tin is bent, a crackling noise, termed the “crying” of tin, is heard. After frequent bending, the metal loses this property.

The degree of purity may be judged:

(1) By the loudness of the “cry,” which is found to be greater as the tin is purer;

(2) By the relative lightness of two balls of equal size, one of which is formed of very pure tin and used as a standard;

(3) By pouring the metal, when just melted, in a mould 1 or 2 centimetres (about ¾ inch) in diameter. If tin is pure, when cast into plates or ingots, the surface will be perfectly smooth, without exhibiting any sign of crystallization at the moment of solidification, whereas the presence of small quantities of foreign metals causes it to be covered with a network of needle-formed crystals, which are the more numerous according as the metal is less pure.

The Banca tin is almost chemically pure; English tin is also very pure; but others contain a small percentage of copper, lead, iron, or arsenic.

BRONZE.

108. Bronze is an alloy, in very variable proportions, of copper and tin, to which may be added, according to circumstances, a small percentage of lead or zinc, or even iron, when it is desired to increase the hardness or tenacity.

As a rule, this alloy is tough and hard to work; it is especially used for parts of large machines that are subjected to considerable pressure.

The fusion and casting of bronze require special precautions, for the proportion between the metals is liable to vary through oxidation of the tin, which then goes to form a dross, and the composition may vary throughout the mass. It sometimes results from this that the bronze bearings for the pivots in large clocks are not even as good as ordinary brass, and wear away more rapidly than the pivots.

Bronze is also used by watchmakers for making plates or small rods for polishers, and for the bells of clocks. Bell-metal contains about 78 per cent. of copper and 22 per cent. of tin; it has a beautiful fracture, and is very fusible and sonorous. The addition of any other metal is rather prejudicial than otherwise; this explains why so many clock bells are wanting in sonorousness.

An impediment to the use of bronze is its want of malleability; but Dronier has recently pointed out that such alloys may be rendered perfectly ductile and malleable by adding from ½ to 2 per cent. of mercury. These alloys are said to be less oxidizable than ordinary bronzes, and at the same time more hard, elastic, resisting and sonorous.

STERRO.

109. This is an alloy containing 56 per cent copper, 41 zinc, 2 tin and 1 iron. It resembles a reddish-colored brass, and has been much used in Vienna, where it is considered superior to brass from the point of view of ductility, tenacity and malleability.

An experienced horologist, M. Grossmann, made satisfactory lever escape-wheels of it, and he considers it to be superior to the best brass in regard to both density and elasticity. At the same time he points out that it clogs the cutter, and the color is inferior to that of good hard brass.

LEAD.

110. A metal with a brilliant bluish grey lustre, which rapidly becomes dull when exposed to the air. It is very malleable and ductile. It breaks with a strain of 2.9 kilo. per sq. mm. section (4,000 lbs. per sq. inch), but possesses extreme flexibility.

Lead is not used in horology, except as a constituent of solders; in these, however, it plays a very important part. It is occasionally used in the pure state as a lap for applying polishing materials, but more frequently alloyed with tin, by which hardness is imparted to the metal, the alloy being known as “pewter.”

NICKEL.

111. An elementary metallic body of a greyish-white color, resembling that of platinum. With care it can be forged when hot and formed into plates; its structure in that case is fibrous. Its hardness is the same as that of iron, and nickel will take a high polish. Next to iron, it is the most powerfully magnetic of all metals.

It can be caused to alloy with many other metals—notably iron, cobalt, copper, zinc, tin, and antimony. According to Stodart and Faraday, an alloy of 33 parts iron and 1 part nickel is as malleable as the former metal, but less liable to rust. Fleitmann has recently shown that by the addition of about 1-10th per cent of magnesium, nickel is rendered perfectly malleable and ductile, capable of being drawn into wires or rolled into sheets, and Garnier finds that 3-10ths per cent of phosphorus has a similar effect.

Nickel is useful as a coating for objects that are not subjected to friction, for preserving them from the action of the air. It takes a beautiful polish, and is not tarnished by being touched.

GERMAN SILVER.

112. Although the proportion of copper in this alloy is considerably greater than that of nickel, watchmakers frequently apply the latter name to it, doubtless on account of the beautiful polish of which the metal is capable and the comparative inoxidizability which it derives from the presence of nickel.

German silver is an alloy of copper, nickel and zinc, with the occasional admixture of a small proportion of iron or tin. When used in the construction of objects that require soldering, 2 per cent. of lead is added.

The alloy usually employed in horology is very malleable; it has a mean composition: copper, 60 per cent; nickel, 20 per cent; and zinc, 20 per cent. That containing 58 per cent copper, 14 nickel, 25 zinc, and 3 iron, is said to be highly elastic.

The following useful details with regard to the employment of German silver for watchwork are due to M. C. E. Jacot.

Watch movements have been made of this alloy for the past thirty years; it was long thought that the taste would die out, but, on the other hand, the demand for “nickel” movements increases each year.

The alloy is better prepared at the present day; it has a beautiful grayish-white colour, it is more malleable, and better to work than formerly, but still not so easy as brass. The latter alloy is less detrimental to the file, and can be turned and drilled more rapidly.

German silver is only used for the plates, cocks and bars. The barrels and wheels are of brass, and surfaces exposed to friction, such as the center pivot-hole (all other holes being jewelled) are bushed with the same metal, for it is observed that in presence of nickel oil is rapidly blackened and the pivots wear sooner than when working in good brass.

The color remains unaltered for a long time if the surface has been carefully smoothed in the first instance; and if cleansed with soap and water, its original freshness can be to a great extent restored. Some watchmakers prefer to employ chemical preparations for cleaning the metal.

The following is recommended as very effective for this purpose: Mix 50 parts alcohol, 1 part sulphuric, and one part nitric acid. Allow the pieces to remain in this liquid for 10 or 15 seconds, wash with cold water, and subsequently with alcohol, dry with a soft rag or in boxwood saw dust.

GOLD.

113. An elementary body, the most beautiful and the most valuable of all the ordinary metals. In the unalloyed state it has a pure yellow color, and when reduced to extremely thin leaves, appears green by transmitted light. It is the most malleable and ductile of all the metals, but its tenacity is low.

Gold resembles platinum, silver, iron, etc., in being capable of welding, that is to say, two pieces of the metal can be united without previous fusion. Indeed, by the application of great pressure it can be made to weld when cold.

It is insoluble except in aqua regia (a mixture of 1 part nitric acid and 4 parts hydrochloric acid), alkaline persulphides and selenic acid. Chlorine, phosphorus, and a few other substances can be made to combine with it by the acid of heat.

It is as a preservative, that is applied in layers termed “gilding,” that gold is principally used in watchwork, and some details will be found on this subject under “Gilding,” (articles 142-153). Owing to its softness the metal is not used in a pure state, but usually alloyed with copper. The principal alloys in use in this country are:

22 parts (carats) gold, 2 parts (carats) copper, for coin and wedding rings.

18 parts gold, 6 parts copper, for high-class jewelry and watch-cases.

15 parts gold, 9 parts copper, for ordinary jewelry.

12 parts gold, 12 parts copper; and 9 parts gold, 15 parts copper, for common jewelry.

The alloys used for soldering gold will be described under “Solders” (126).

Alloys of gold with silver and copper have been employed for making watch wheels; they wear well, and will take a beautiful polish, which is maintained for a longer time than in the case of brass wheels.

Chronometer balance-springs and the suspension-springs for astronomical clocks have also been made of gold-copper or gold-silver alloys rolled and hardened (591.) If carefully prepared, they maintain their elasticity unimpaired for a long period, and there is no liability to rust.

The dilatation for a given change of temperature is, however, greater than that of steel, so that a greater compensating effect becomes necessary, but this inconvenience is partially compensated for by its inoxidizability and the fact that it is not liable to become magnetic.

SILVER.

114. This metal in an unalloyed state is too soft for use in horology; its principal use is for cases, and as a constituent of solders.

Houriet made watch wheels of an alloy containing 2 parts silver to 1 part 18-carat gold, and he affirmed that this alloy became polished at the acting surfaces of the teeth. Jurgensen states that chronometer escape-wheels made of this alloy, carefully hammered, do not require oil at the points of their teeth.

Dumesnil proposed an alloy of 2 parts copper, 1 part silver, and 1 part zinc, all perfectly pure. Lecocq made chronometer balances in which the brass was replaced by pure silver deposited on the surface of the steel by electrolysis, thus avoiding the use of a fire. The compensation is said to have been very efficient.

ALUMINIUM AND ALUMINIUM BRONZE.

115. Aluminium is an extremely light elementary body, having a density of only 2.56; with equal bulks, therefore, it will weigh only about as quarter as much as silver. As its capacity for heat is very great, this metal is observed to heat or cool more slowly than other metals.

Pure, or in a slightly alloyed state, it has not been used in horology, except for pendulum rods and large hands in regulator clocks; in short, it can be employed where lightness is the principal quality in view.

It is extremely ductile. The presence of 1-100th part of bismuth, however, renders the metal somewhat brittle, and it develops cracks under the hammer. Traces of iron also decrease its malleability.

An alloy of 5 parts silver and 95 aluminium can be as easily worked as the pure metal, but is harder and takes a better polish.

We would add a curious observation of M. Redier: After passing a piece of aluminium several times through the draw-plate, he observed that the elongation had only occurred at the surface; for on cutting the wire at different points, he noticed that, throughout a portion of the length, the metal was hollow, a very fine capillary tube being thus formed.

116. Aluminium Bronze is an alloy of aluminium with copper. A alloy of 5 parts of the former to 95 of the latter has a beautiful golden color, but if the proportion is changed to 10 and 90 parts respectively, we obtain the most serviceable and the most easily worked alloy.

This bronze can be forged at a cherry-red heat, and even near its melting point; and its thickness can be reduced to a very small amount under the hammer. It is easily filed and turned, but does not possess any special advantage over brass, which is less detrimental to the file; the density is 7.7, very little below that of brass, 8.4.

It appears from a considerable number of experiments that it might be used with advantage for the bearings of axes that rotate with high velocities. It resists wear better than any other metal. In the experiments made by Foucault to demonstrate the rotation of the earth by means of the pendulum, he found that an aluminum bronze wire lasted for the longest period. Its tenacity is equal to that of iron. It has been shown that slide-bars of locomotives made of this bronze resist wear twice as long as those formed of the ordinary bronze. There would then be an advantage in using it for the bearings of foot-lathes, etc.

Grossman asserts that lever escape-wheels of this metal have proved satisfactory, and he makes the following observation on the subject. If aluminium bronze be reduced to three-fourths of its original thickness by hammering, it will begin to crack. This can be prevented by heating to a red heat and plunging into water; it can then be again reduced by one-fourth of its thickness, and again annealed, and so on. He reduced the thickness from 2.5 millimeter to 0.2 millimeter, and the metal resisted for a long period repeated flexures backwards and forwards; and he observes that no other metal, after being so much compressed, would possess the same marvellous degree of tenacity.

In order to obtain aluminium bronze of the best quality, the copper should be absolutely pure, and, in the manufacture, the alloy must be melted and forged two or three times in succession, as by this means the strength and tenacity are increased, and the metal can be more easily worked.

The beautiful golden color possessed by certain of these bronzes when polished, has caused them to be used for cheap watch-cases, but they always tarnish at those parts that are not subject to daily wear.

MERCURY.

117. This is the only metal liquid at the ordinary temperature; it solidifies at -40° C. (-40° F.). It possesses a high metallic lustre, resembling silver, but with a slightly bluish tint, and does not oxidize at ordinary temperatures.

Mercury alloys with many other metals, forming amalgams, and as small a quantity as 1-40th per cent of lead suffices to entirely alter its character. The presence of such traces can be easily detected by the liquid wetting glass or china, and therefore forming a tail when a vessel containing it is tilted.

The commercial metal is rarely pure, but the greater portion of the lead, tin, bismuth or copper, by which it is contaminated, can be removed by distillation. The most convenient method consists, however, in agitating the metal with either dilute nitric acid, a solution of mercurous nitrate, strong sulphuric acid, a solution of corrosive sublimate or of perchloride of iron, and subsequent washing with distilled water. When mercury is only contaminated with mechanical impurities, they can be very effectually removed by agitating with powdered loaf sugar.

This metal has many uses in the arts, for the construction of thermometers, barometers; for plating, etc.; in horology it is used for compensation pendulums, and has also been occasionally used for compensation balances.

PLATINUM.

118. This elementary body is almost as white as silver, takes a brilliant polish, and is highly ductile and malleable. It is the heaviest of the ordinary metals, the least expansive when heated, and has a breaking strain of 40 kilo. per sq. mm. section (56,500 lbs. per sq. inch.).

Platinum is infusible, except at the high temperatures attainable with the oxy-hydrogen blow-pipe. At a white heat, however, it softens, and can be forged and welded. It is unacted upon by the air at any temperature, and is insoluble in acids, except aqua regia (155), although acted on by certain alkalies.

This metal is used in the construction of scientific instruments, and for objects that are exposed to the air, as, for example, sun dials. Alloyed with irridium, (a rare metal of the same group) it possesses an excellent and unalterable surface for fine engraving, as the scales of astronomical instruments, etc. This alloy has also been adopted for the construction of international standards of length and weight.

Platinum is much employed for chemical apparatus, in consequence of its being unacted on by acids, and its non-liability to melt in ordinary furnaces. Both the pure metal and its alloys with silver have been employed in the form of wire for bushing the pivot-holes of watches, and in sheets for cutting out cocks and wheels, but the results obtained were not as good as with good brass. As a rule, such wheels are found to occasion a rapid wear of pinion leaves.

Attempts have also been made to construct balance-springs of this metal, but we are informed that they were not found to possess any sufficient advantages.

It is advisable to heat platinum in a spirit lamp or Bunsen burner; the naked flame is objectionable, because, being charged with a certain amount of carbon, it deteriorates the metal.

PALLADIUM.

119. This metal resembles silver rather than platinum, and is almost as infusible as the latter metal. It has a density of 12.5. When heated in contact with air it becomes blue, owing to the formation of an oxide. It possesses the remarkable power of absorbing (or occluding) about 900 times its own volume of hydrogen, if attached to the negative pole of a battery in acidulated water; its bulk is increased slightly by this charge, and, on expelling the gas by the aid of heat, the metal shrinks to less than its initial dimensions. Palladium is useful for the graduated scales of scientific instruments, since it is not discolored by sulphurous acid. It forms alloys with most of the metals and some of these can be hardened like steel. If 100 parts of steel be alloyed with 1 part of this metal, the resulting alloy is said to be excellent for making scientific instruments, and an alloy of 24 parts palladium, 44 silver, 72 gold, and 92 copper has been recommended for use in horology.

M. Paillard, of Geneva, has introduced balance-springs made of an alloy, whose composition is not given, possessing the following advantages: they are non-magnetic, their tenacity is considerable, are not tarnished by the air, sulphurous acid, or sea water; nor are they distorted by heating, and, on cooling, they recover their original elasticity, which is equal to that of steel hardened and tempered to a blue color. The co-efficient of expansion of this alloy is rather less than that of steel.

CHARACTERISTIC PROPERTIES OF ALLOYS.

120. Density. This is sometimes rather greater and sometimes less than that deduced from the densities of the constituent metals,[4] but no exact law has been discovered in regard to this question.

Hardness, Ductility, Tenacity. Alloys are usually harder, more brittle, and less ductile and tenacious than the most ductile and tenacious constituent metal.

Elasticity. The co-efficient of elasticity of an alloy generally approximates closely to the mean of the co-efficients of its constituent metals.

Expansion. The co-efficient of linear expansion of an alloy, that is to say, the number representing the proportional part of its length by which it increases for each degree rise of temperature, may be approximately estimated as follows: multiply the linear co-efficient of each constituent metal by the percentage of it present in the alloy, and divide by its density. Add together the several numbers thus obtained. Multiply this sum by the density of the alloy (which must be experimentally determined) and divide by 100. The resulting figure is the required linear co-efficient (122).

Fusibility. Alloys are always more fusible than the least fusible of their component metals, and often more so than any one of them.

Oxidation. As a rule, the air acts with less energy on alloys than on their constituent metals. There are, however, cases in which the converse is the case.

Action of acids. This is generally similar to the action on the predominating metal.

Observations. Alloys formed of metals that differ materially in density are rarely homogeneous, especially if they have been allowed to cool slowly. It is, then, essential that they be thoroughly stirred and cooled rapidly. It is for this reason that alloys are frequently poured out on to a flagstone to cool, or that they are compressed after pouring, whereby the formation of crystals is prevented.

121. Metals and alloys. The following table gives the more important physical properties of the metals and alloys generally met with, and will be found useful for reference. The precise meaning of each number may be gathered from the notes in paragraph 122.

122. Notes on the foregoing table. For a complete explanation of the several properties of metals and alloys that are enumerated in the above table, the reader must be referred to works on mechanics and physics, but the following explanatory notes are necessary.

The number in brackets after the name of each metal, etc., refers to the article in which it is considered.

The specific gravity of a substance is the ratio of the weight of a given bulk of that substance to the weight of the same bulk of water at a definite temperature. The numbers here given can only be regarded as approximations, as the specific gravity varies greatly with the state in which a body exists, the hammering it may have been subjected to, etc.

Degree of hardness is ascertained by means of the following standard series, observing which of them scratches the body under examination and which it is capable of scratching.

1, Talc; 2, Gypsum; 3, Calc-spar; 4, Fluor-spar; 5, Apatite; 6, Felspar; 7, Quartz; 8, Topaz; 9, Sapphire; 10, Diamond.

Linear expansion. These co-efficients represent the extension in length that the several substances undergo when heated: the first column for each degree Fahrenheit and the second for each degree Centigrade. The extension is given per unit of length; thus, 1 inch of copper at 32° F. will become 1 + 0.0000102, or 1.0000102 inch at 33° F.; and 1 + 30 × .0000102, or 1.000306 at 32 + 30 or 62° F.

Superficial expansion may be obtained by multiplying the linear co-efficient by 2, and cubical expansion by multiplying the same number by 3.

As in the case of specific gravity, these data, as well as those in succeeding columns, can only be regarded as approximations, depending on the condition of the metal etc.

Specific heat is the amount of heat required to raise the temperature of a substance one degree (the Centigrade scale being here adopted), that required for the same weight of water being taken as unity. The corresponding numbers on the Fahrenheit scale can be deduced from those here given by multiplying by 5 and dividing by 9.

The melting points are given on Fahrenheit’s scale and can only be regarded as approximate on account of the difficulty experienced in determining these high temperatures. Different observers often vary by two or three hundred degrees in their estimates.

Conductivity for heat and electricity are given in reference to that of silver, which is called 100. It surpasses all other known metals in both these properties when chemically pure, but a trace of impurity has a very prejudicial influence on them.

It will be observed that in many cases the conductivities have not been determined, a remark that applies to other columns of the table.

SOLDERING.

123. It is well known that a solder is an alloy employed to unite, by the aid of heat, two metallic bodies that are placed in contact. A solder, then, must be much more fusible than the metals it unites, otherwise these latter would be damaged by the degree of heat applied. Solder is all the less tenacious, and melts the more easily according as the proportion of the most fusible metal present is increased.

This fact is taken advantage of when several solderings have to be performed on the same object. The alloy last employed will require to be considerably more fusible than the first, as otherwise the heat would be so great that the earlier joints would melt. In an ordinary lead-tin solder, the fusibility is increased by increasing the proportion of the latter metal till the lead is to tin, as 6 is to 1. This alloy melts at 194° C. (380° F.), and the melting point may be still further reduced by adding a gradually increasing proportion of bismuth.

As the melting point of the solder approximates to that of the metals to be united, the risk of damaging these latter is of course increased, but, at the same time, the joint will be all the stronger, as the metal will be almost as strong there as at any other point, and it can be forged, etc.

Solders are distinguished as hard or soft; the former requires the application of a red heat, and can therefore only be used for such metals as gold, silver, brass; whereas the latter melt at very low temperature, and can be employed for metals that have low melting points, or when it is important not to exceed a moderate degree of heat. The joint is, however, the more solid according as the heat employed approximates to that at which the metal will melt.

124. Composition of solders. The solders ordinarily employed can be obtained from material dealers, but it is advisable to give here the composition of some of the more important, specifying the metal to which they are applicable.

125. Aluminium solders. I. Zinc, 70 parts; copper, 15; aluminium, 15.

II. M. Mourey employes a series of aluminium-zinc alloys, commencing with two per cent aluminium to 98 per cent zinc, and progressing to 20 per cent of the former to 80 per cent of the latter metal.

126. Gold solders. I. Gold, 6 parts; copper, 1 part; silver, 2 parts.

II. Gold, 15 parts; silver, 2 parts; copper, 1 part.

III. Gold, 11.94 parts; silver, 54.74 parts; copper, 28.17 parts; zinc, 5.81 parts. The three first metals are melted together in a crucible, and when they have somewhat cooled, a rather greater proportion of zinc than is here indicated (to allow for loss by volatilization) is added, and the alloy constantly stirred.

127. Silver solders. I. Silver, 2 parts; brass (for pin-wire), 1 part.

II. Silver, 5 parts; pin-wire brass, 1 part.

III. Silver, 10 parts; pin-wire brass, 5 parts; pure zinc, 1 part.

128. Tin solders. I. (ordinary soft solder.) Tin, 2 parts; lead, 1 part.

II. (Harder, and known as “Plumbers’ Sealed” solder.) Tin, 1 part; lead, 2 parts.

III. Many other proportions of tin and lead are occasionally used, ranging from tin, 1 part; lead, 25 parts, to tin, 6 parts; lead, 1 part.

IV. (Very fusible solder, melting in boiling water.) Lead, 3 parts; tin, 5 parts; bismuth, 8 parts. The fusibility is still further increased by adding mercury or cadmium.

129. Spelter solders. (Used for brazing.) Copper and zinc in varying proportions. It becomes more fusible as the amount of zinc present is increased.

METHODS OF SOLDERING.

130. A thorough cleansing of the surfaces to be united is always needful, but more especially so in the case of soft soldering. It may be effected by means of acids, or with a graver or scraper, etc.; the cleansed surfaces must not be touched with the fingers, and the soldering should be done at once. If acids are employed, the objects should be thoroughly washed after soldering, in order to avoid rust; and, after drying, they should be rinsed with alcohol.

The parts to be soldered are held in position with clamps, tweezers, pins, or iron wire. This latter, known as binding wire, is used for delicate objects and should be very pliable. When a high degree of heat is to be applied, all risk of the iron uniting with gold may be avoided by mixing a little sandiver with the borax employed. (See article 153).

Before heating, if there are already parts united with solder, they should be covered with borax to prevent softening.

Only a moderate heat should at first be applied, so as to melt the borax, or sal-ammoniac without displacing it. The violent frothing up, which is very liable to displace the parts or the fragments of solder, can thus in a great part be avoided. If a naked lamp-flame is used, or if it is directed on to the object with a blow-pipe, it should be, so to speak, large and soft, and the jet should not be directed to the point of juncture until the solder is observed to have fused. In soldering brass to steel, it is sometimes necessary to direct the flame against the brass only, in order, as far as possible, to avoid softening the steel. The hard solders for gold, silver, etc., require a considerable degree of heat, so that the objects must be heated to redness.

131. To solder gold and platinum to each other or to themselves. On a hard wetted surface, marble, for example, rub a piece of borax until a white liquid paste is obtained (or the powdered borax sold by chemists can be made into paste direct). Having prepared the borax, the surfaces to be united are cleansed either by scraping or with dilute nitric acid (155); the acid may be previously heated to boiling, as it will then act more rapidly; and the surfaces are subsequently scraped. They are now covered with the borax with a paint brush, set in position, and small pieces of solder placed on the junction. As already observed, the heating must at first be gentle to avoid displacing the solder by the frothing of the borax.

132. To solder silver. Also for uniting gold to silver, or silver, brass, steel to each other or to themselves. Proceed in the manner already explained for gold and platinum, except that the borax paste must be sensibly thicker.

133. To solder tin. Also for uniting gold, silver, brass to each other, or to other metals, such as steel, iron, etc. Clean the surface with a graver or scraper; sulphuric or hydrochloric acid may be used, but in this case the cleansing afterwards must not be forgotten.

The heating is effected as in soldering gold, unless a soldering iron is used, when the directions subsequently given should be followed.

134. To solder aluminium. M. Mourey recommends the following method.

One of the series of aluminium solders, No. II. (art. 125), is employed and, as a flux, two-thirds of balsam of copaiba, one-third very pure Venice turpentine, and a few drops of the juice of a citron; these constituents are pounded together in order to secure a perfect admixture.

The surfaces to be united are covered with solder (employing a soldering iron of aluminium) just as in the case of tinning (137), the flux just mentioned being used. The two surfaces, thus prepared, are placed in contact and maintained in the required position, and, after laying on the joint particles of solder that are richer in aluminium than the one used for preparing the surfaces, the whole is placed over a charcoal fire or heated before the blow-pipe, pressing gently on the pieces of solder, which will soon melt and should be distributed by means of a little tool of aluminium.

During this second stage of the process, it is necessary to be very cautious in the application of the flux; the pieces of solder should only be dipped in it before being placed in position, for the flux is mainly for use in preparing the surfaces; as soon as the solder has run well, the temperature should be lowered in order not to dry up and burn the solder, which would be apt to become brittle.

In preparing the solders, the aluminium is first fused and stirred with a small iron rod; then add the zinc and stir again; add a little tallow and cast the solder into rods.

The zinc must not be too much heated, as it will volatilize, leaving the alloy rich in aluminium and therefore brittle.

135. Fluxes for soldering. Various substances can be employed as fluxes for cleansing the surfaces to be united:

Sal-ammoniac reduced to powder and made into a paste with sweet oil, or merely dissolved in water. A paste formed of sal-ammoniac and resin, reduced to powder, with water or oil. Resin alone will suffice for the soft soldering of copper or brass. Venice turpentine, which has the advantage of not causing steel to rust, although it makes the objects sticky so that they require to be afterwards rinsed in alcohol or turpentine.

Various acid solutions are sold for the purpose and experience will enable the watchmaker to select that which is best adapted to his requirements.

Lastly, saturated chloride of zinc can be recommended. It is prepared as follows:

Some dilute hydrochloric acid (which also goes by the name of spirits of salts, or muriatic acid) is placed in a glass flask and strips of zinc are added one by one; the flask must be left uncorked and the zinc added a little at a time, lest the effervescence that occurs should break the vessel. When the zinc added is not acted on by the fluid it may be concluded that the acid is saturated or “killed,” and the fluid may then be transferred to a stoppered or corked bottle for use. In using it, a small quantity is spread over the surfaces that are to be united and the solder will be found to run with great freedom. Some authorities recommend the addition of sal-ammoniac to the extent of one-fourth the weight of acid taken. It is well again to warn the reader that the pieces must be thoroughly washed after employing these liquids, for, otherwise, they will cause tools with which they are brought in contact to rust and will rust themselves if they consist wholly or in part of iron or steel. The vessel containing the fluid must be kept well away from the work-bench.

The liquid can be used immediately after being prepared as above explained; but all acid reaction may be prevented by evaporating at a moderate temperature until of the consistency of oil; it is then allowed to cool and kept in a bottle.

136. The soldering iron with a head of copper, such as is used by tin-plate workers, is well known; if made on a small scale it may occasionally be of service to the watchmaker. The tool may be T-shaped, one end of the horizontal portion, the copper head, terminating in a rather thin blade, and the other enlarged, so that, when held in the flame of a lamp, it will store up a sufficient amount of heat. The upright part of the T corresponds, of course, to the handle. After the iron has been heated just short of redness in the dark, the end of the blade is moistened with soldering fluid and a small piece of solder attached to it. The object to be united is gently heated and also moistened with the fluid; the iron charged with solder is presented to it, often with the enlarged extremity of the head maintained in the flame of a lamp, and the solder will, as a rule, run without again heating the object, although this might be done while the iron is still in contact. It may be found convenient to fix the iron in a suitable position with the lamp below the large end of the head; the object will then be brought against the iron after being moistened with the fluid.

137. It is often advisable to tin the surfaces to be united previous to soldering them; in order to do this they are moistened with soldering fluid, small pieces of solder are then spread over, and these are fused by passing the hot iron over the surface; or the solder can be spread after fusion by means of a metallic rod charged with the liquid.

138. Brazing. This operation consists in soldering iron, steel, brass, or copper, with an easily fusible brass, which is specially prepared in the form of coarse dust, termed spelter solder, or cut in thin strips of convenient shape (129). The method resembles, in all essential particulars, the application of hard solders previously referred to (131, etc.)

Heat is usually applied direct by the blow-pipe, borax being used as a flux, and the precautions taken that are mentioned in article 130: it is necessary to avoid a greater degree of heat than would melt the brass, since the object might in that case be fused. For fine work, it is better to employ silver solder.

On an emergency, two pieces of steel can be united by brazing and subsequently hardened, and we have successfully practiced this method in such a case as the following: A small portion having been broken off from the quarter-piece of a repeater, we dovetailed into it another piece of steel of the required form, but a trifle too large at the upper side. When the brass had run well into the joint, and the piece was still at a full cherry-red heat, it was hardened, and afterwards cleaned and tempered to a blue color. The upper surface was then brought to shape with a good file, resting it on a wooden block against a projection, and, after making sure that it would act correctly, the whole was smoothed and polished. It has since worked well and does not show signs of wear.

BRONZING.

139. To bronze copper. The following are two methods recommended for bronzing objects of this metal, for example, a medal.

Dissolve two parts of verdigris (acetate of copper) and one part of sal-ammoniac in vinegar. Boil the solution, skim it, and dilute with water until it no longer possesses a feebly metallic smell, nor produces a whitish precipitate on the addition of water. Then let it boil again in an earthenware or porcelain vessel and transfer it, while boiling, into another vessel containing the perfectly clean medals, etc., and place the whole on the fire. As soon as the medals assume the required color, remove them, and wash carefully in clean water.

The objects must not be left too long in the acid bath over the fire, because the layer of oxide would become too thick, and would easily scale off the surface; whereas, if the operation is properly conducted, the coating adheres so firmly that it cannot be separated even by scraping. Of course, it is only after a certain number of trials, and with experience, that the exact moment can be ascertained for removing the objects from the bath. It is very necessary that the bath be not too concentrated, as the superficial oxide becomes proportionately less adherent: moreover, a whitish powder is deposited on the medal, which turns green on exposure to the air and spoils the appearance of the bronzing.

140. Chinese bronzing. The Chinese employ the following mixture for bronzing copper, the several constituents being powdered before being incorporated together: 2 parts of verdigris, 2 parts of cinnabar, 5 of sal-ammoniac, 5 of alum, and 2 parts of the beak and of the liver of a duck. A paste having been made, with vinegar, it is spread over the perfectly clean surface of the copper, and the whole exposed for an instant to the fire, then allowed to cool, washed, and the operation repeated as often as may be needed in order to obtain the desired tint.

By adding sulphate of copper to the mixture a browner shade will be obtained, and it may be made yellower by adding borax. Copper thus treated is said to present a beautiful appearance, and to be so permanent that neither air nor water has any influence against it.

141. To bronze brass. Dissolve copper turnings in nitric acid until it is completely saturated. Immerse the brass objects to be bronzed in this solution after they have been cleaned, smoothed with water of Ayr stone, and heated to such a temperature as the hand can just support; on being placed over a charcoal fire they will assume a green color; rub them over with rags, repeat the immersion and heating over charcoal until the required tint is obtained. The shade may be improved by oiling the finished surfaces.

It is asserted that by immersing copper articles in molten sulphur containing lampblack in suspension, they assume the appearance of bronze; and that they may even be polished without losing their color.

GILDING.

142. Gold gilding without the aid of mercury. Prepare the gold in fine powder, as explained in the following paragraph, or procure it from the dealers in chemical products, who manufacture it of various tints. Make a mixture of this powder with pure rock salt and cream of tartar (bitartrate of potash), pulverized in the same manner as described in speaking of silver-plating and take the same precautions in its application.

The gold surface will present a dull appearance; acid cannot be used to improve its color when operating, for example, on a wheel with attached pinion, but the same result may be attained by a very simple method. Rub the object after plating with cream of tartar, mixed with a large proportion of water; then immediately wash in an abundance of warm water at not less than 40° C. (104° F.); soap it thoroughly, so as to neutralize any acid that may remain, and finally pass through alcohol to dissolve any remaining soap.

The surface will be still further improved by rubbing with a very hard piece of pith, such as is occasionally met with.

M. Robert, in describing the above method, adds: “In this manner I have gilded cocks, domes, compensation balance weights, and even their brass rims. When, skilfully and expeditiously performed, the pinion need not be discolored; but, if it is at any time slightly marked, it may be restored by at once rubbing the surface with a soft stick and fine rouge.”

143. Preparation of the gold powder. As already observed this can be obtained of any desired color from the dealers in chemical products, but the following method is given for the benefit of any one who desires to prepare it for himself:

Place some gold in thin leaves in a dish, and add a little honey, thoroughly intermixing the two by the aid of a glass rod flattened at one end; then place the paste so obtained in a glass of water containing a little alcohol, washing it and allowing the powder to settle. Decant the liquid and again wash the residue, repeating the operation until a fine brilliant powder is obtained. This powder is mixed as required with rock salt and powdered cream of tartar in the manner already described.

144. Second method. Dissolve one part by weight (say about ten grains) of pure gold, rolled very thin, in aqua regia (155) contained in a porcelain dish, which may be gently heated on a sand-bath, and evaporate the acid until it assumes a blood-red color. Add about 30 parts, by weight, of warm distilled water, in which 4 parts of crystallized cyanide of potassium have been previously dissolved; thoroughly stir the mixture with a glass rod, and filter it through a glass funnel.

145. Third Method. Roseleur recommends the following solution for gilding by simple immersion. Distilled water, 17 pints; pyrophosphate of soda (in crystals) 28 ounces; hydrocyanic acid, 1-3 ounce; crystallized perchloride of gold, 2-3 ounce. The pyrophosphate is added, in small quantities at a time, to 16 pints of water, in a porcelain vessel, stirring with a glass rod and applying gentle heat; then filter and cool. The gold salt is dissolved in a small amount of water; filter and add to the cold solution of pyrophosphate; lastly, add the hydrocyanic acid and the solution, heated to the boiling point, is ready for use.

The articles to be dipped must be thoroughly cleansed and passed through a very dilute solution of nitrate of binoxide of mercury; they must be constantly agitated while in the bath and the best coating is obtained by dipping the articles in a nearly exhausted solution of the same kind immediately after the mercury solution.

146. Electro Gilding. But the method most usually adopted is that in which a battery is employed. It is, however, impossible, within the limits of this work, to explain the precautions that are necessary in conducting the process, managing the battery, etc., and the reader must be referred to works on electro-metallurgy for these details.

147. To prepare the pieces to be plated. After the surface has been stoned, boil the object a few minutes in a solution of soda or potash, and rinse in clean water.

Roseleur, in the articles already referred to, gives very full instructions, of which the following is an outline. The reader who desires to obtain more complete information can consult his works.

Attach the pieces to a cork and brush with a clean brush charged with water and pumice-stone powder and thoroughly rinse. Place them in a solution consisting of: water, 2¼ gal.; nitrate of binoxide of mercury, 1-14 oz.; sulphuric acid 1-7 oz. Then rinse again.

148. Graining. Mix thoroughly with the application of moderate heat, silver powder, 1 ounce; pure common salt, finely powdered, 13 ounces; cream of tartar 4 to 5 ounces. Make a thin paste of this mixture with water and spread with a spatula on the pieces; having mounted them on a cork to which a rotary motion is given, rub them in all directions with a brush with close bristles, adding fresh paste from time to time. When the desired grain is obtained, wash and scratch-brush with revolving wire brushes. Three of these are often used of varying degrees of hardness and a decoction of liqorice, weak size or stale beer is liberally applied to the surface.

149. Resist. This is a composition for covering steel parts in order to protect them from the action of the acids, etc., in the various processes of cleaning, graining and gilding. It consists of yellow wax, 2 ounces; clear resin, 3⅓ ounces; very fine red sealing-wax, 1½ ounces; finest rouge, 1 ounce; Melt the resin and sealing-wax in a porcelain dish, then add the yellow wax, and when the whole is thoroughly liquid, gradually add the rouge, stirring with a glass rod. The parts to be coated are slightly heated and covered with the mixture.

To remove the resist after the gilding process is completed, place the pieces in warm oil or turpentine, then in a very hot soapy or alkaline solution and lastly in fresh water.

150. When prepared as above explained, the object may be gilt by one of the preceding methods; of course a hot solution cannot be resorted to when the resist has been applied.

151. To clean objects that are of gold or gilt. The following method is equally applicable to pieces that are gilt, such as cocks, domes, etc., the frames and parts of timepieces and to either gold or gilt jewelry.

To about a tumbler of water add 20 drops of strong ammonia. Immerse the object several times in this mixture and brush it with a soft brush; as soon as the operation appears to be completed (which experience will soon enable the workman to ascertain), wash in pure water, then in alcohol, and dry with a fine linen rag. The original brilliancy of the gilding will then be restored.

When the coating is thin and has been galvanically deposited, only very soft brushes must be used.

Gilders, instead of dipping in alcohol and drying with a linen rag, usually immerse the pieces in boxwood sawdust, leaving them long enough to become thoroughly dry; after this treatment they merely require to be shaken and lightly rubbed with a fine brush.

The sawdust must be perfectly dry; indeed it is a good plan to slightly warm it by placing the wooden box containing it for a few minutes on a hot oven or stove in the winter and exposing it to a hot sun in summer.

Instead of ammonia, alum (156) is sometimes boiled in water and the objects dipped two or three times in this solution, subsequently brushing as in the previous case.

152. To restore the dead surface of gold or gilt objects. Place them for two or three minutes in chlorine water, rinse them in clean water, soap them and finally dry in sawdust. It is advisable that parts that are polished be prevented from actual contact with the liquid as it would produce a somewhat deadened surface.

153. To clean gold jewelry after soldering. Particles of binding wire are often left adhering to the surface of jewelry after soldering, and, on dipping the object into the dipping liquid, a layer of oxide may be formed. This can be removed without detriment to the polished surface by plunging the object for a few seconds in nitric acid (155).