If the cork or pith is hard and only a little metal has to be removed, the operation is successful; but it is apt to result in more metal being removed from the edges than from the center. When much has to be removed, the spring must be cemented to the polishing plate (shown at G, Fig. 269, and described in article 345) with fine wax, thoroughly liquid, so that on pressing the spring all its coils may come in contact with the plate; it must be held thus until cold. Now adjust the leveling screws, so that the whole surface bears flat on the glass; rub it as long as is considered necessary, and detach the spring as soon as the plate is sufficiently heated; boil in alcohol to clean its surface.
591. To Harden Gold Springs. Gold detent, thermometer, suspension and balance-springs can be obtained of a high degree of elasticity. Rolling hardens them, but renders them very brittle. They can be made supple and elastic, not by hardening, as in the case of steel, but by annealing, care being taken not to exceed a certain degree of heat. The spring may be coiled on a block and placed in a tube that has a smooth steel lid, then heat the tube in the flame of a spirit lamp, and as soon as the steel is of a blue temper, remove the flame and allow the whole to cool.
Others anneal by keeping the spring in boiling oil for a definite period.
The hardness of a gold spring increases with the proportions of alloy it contains, and, if well annealed, it will be very elastic and will break when bent too far, as in the case of steel.
592. To Ease an Index on Its Endstone Cap. It is a common but bad practice among watchmakers to scrape the inside of the ring of the index or to cut it through. A better method is as follows: Resting the index on a cork, cover the inside of its ring with oil stone dust and make the cap rotate in its seat by means of a pinion calliper, the two points of which are inserted in the screw-holes. The operation is repeated as often as may be required.
DIAL PLATE.
593. To Cut the Large Hole in the Timepiece Dial Plate. Some workmen cut the hole in the dial-plate of a timepiece by means of a strong pair of compasses, one leg of which terminates in a bullet-nose that is supported in a central hole, while the other is provided with a hardened cutting point that serves to scrape out a groove.
Others use a rule that revolves on a conical point and carries a slide with a tracing point which can be replaced by a sharp-pointed cutter. Proceed in exactly the same manner as when using the compass, but a greater force can be applied, because, while one hand steadies the center, the full force of the other is applied to the cutter.
A third and still simpler plan is adopted by some clockmakers. A rod of the diameter of the central hole, and a cutter of which only the cutting point projects, are gripped in a vise at a distance apart equal to the radius of the hole to be made. Then passing the rod through the central hole and holding the plate in both hands, rotate it, at the same time applying pressure so as to cause the cutter to form a groove. When a moderate depth has been attained, invert the plate and cut one on the opposite side. Care is necessary when the grooves are on the point of uniting; on the removal of the center, smooth the edge with a half round file. Some workmen consider it more convenient to set the cutter and rod in a thick piece of wood that is rounded at the top and made flat on its two sides towards the bottom, so as to be firmly held in the vise.
594. To Drill an Enamel Dial. Take a hard, well-sharpened graver and moisten it with turpentine or turpentine that contains camphor in solution, or in the following mixture, which is still better:
| Turpentine | 62 | parts | by weight. |
| Oxalate of potassium | 4 | ” | ” |
| Camphor | 4 | ” | ” |
The two latter substances are reduced to powder and dissolved in the turpentine, and two parts by weight of sandal wood may be added.
The graver point is placed on the dial at the point at which a hole is required and the graver is rotated backwards and forwards between the fingers. Practice, acquired by drilling a few holes in broken dials, will soon indicate the degree of pressure that can be applied without fear of accident. Some workmen prefer only to apply the maximum pressure while the graver rotates in one direction, reducing it during the opposite movement; others hold the handle or tang in one hand and rotate the graver with the other, always in the same direction.
The operation is continued, frequently arresting it, however, in order to set the graver and moisten it, until the copper-plate and back enamel are perforated.
As soon as this point is reached, take an iron or steel spindle, pointed at one end. The point must be more obtuse than the hole already formed in the dial. Charge this end with emery or oilstone dust, and place in the chuck in your lathe; when the spindle is caused to revolve the enamel on the contour of the hole will be rapidly removed. When the copper disc is reached, a fine-pointed and sharp graver must be used to remove the metal that is exposed as well as that which is covered with only a thin layer of enamel; then renew the operation with the spindle, occasionally drawing a file along the surface of the acting cone. Or the cones of solid emery to be obtained at material stores can be used for this purpose. A workman must be very careless or unskilful to fail in rapidly drilling a hole in a dial by this method without accident, and he may carry on the process easily until the hole is large enough to permit the introduction of a rat-tail file.
595. To Enlarge a Dial-Hole With a Rat-Tail File. As an extra precaution the contour of the hole on either side may be coned with a spindle as explained above, so as to reduce the thickness of enamel to be acted upon by the file; but a watchmaker that has had any experience can dispense with such a preliminary, which we would at the same time recommend.
The file must enter the hole freely. If only the point can do this, the file must be held very short, so that the finger may come in contact with the dial before the larger diameter of the file locks in the hole, as this would almost certainly crack the enamel. Some workmen avoid such an accident by forcing on to the file a rather long cork of small diameter.
With a view to avoid scratching the face of the dial in case the file is drawn out of the hole in its backward movement, it is well to round off and polish its point.
During the forward movement a slight circular motion is given to the file, and in returning no pressure is to be applied; the file must merely slide over the surface. It is dipped from time to time in the liquid mentioned in the last article. When the hole is large enough, a conical spindle should be used to smooth its edges as in the earlier stages of the process.
596. To Remove Enamel from the Back. To remove portions of the enamel from the back when it touches part of the motion work, etc., various methods are adopted.
The little spindles of solid emery that may be obtained at material stores may be used for the purpose.
Some watchmakers use a flattened lead ball perforated at its center and carried on a taper arbor, forming a kind of small grindstone, rounded across its rim. The arbor is held in a chuck and the edge of the lead disc is moistened with water, and emery powder sprinkled over it; when set in rotation the surface to be removed is held against the lead, the necessary pressure being applied by the finger against the other face. Water must be frequently sprinkled on the surface so as to avoid heating, and to maintain the emery in its place, and the dial is washed occasionally to examine the progress of the work.
In place of lead, some use emery formed into a solid block with shellac or various kinds of cement; it is centered on a large taper arbor, and should be at least a quarter of an inch thick and rounded at its edge. Such a disc is very hard when cold; it is used in the manner explained in the last paragraph, but wears more rapidly than the lead disc, if the latter is well made and supplied with emery of the right degree of coarseness, in sufficient abundance and evenly distributed.
597. Dials Fixed by Screws through the Edges. The screw-holes at the edge are drilled in the manner already explained in article 594, and the center hole is enlarged as there described, if this is found to be necessary in order to permit the free passage of the hour wheel. The diameter of a dial may be reduced if it is too large in the manner explained in article 600. When it has been thus prepared, place it in position, the XII being exactly opposite the pendant, with the movement in the case, and close the bezel. If the dial is found to shake under the bezel it should be fixed with three or four small wedges of pegwood, care being taken that they do not subject the dial to much pressure. The accuracy of the position may be tested by holding a stretched piece of cord over the dial, and observing whether it passes at the same time through the middle of the pendant, the center hole, the XII and the VI. When the dial is thus found to be properly placed, mark one of screw-holes on the watch-plate through a dial-hole. Some care is necessary in doing this lest the hole is marked eccentrically or the dial is displaced by pressure against one side of the hole in it, which might result in the dial being cracked by the screw. Now remove the plate from its case and drill its screw hole in the drilling tool; tap it and fit the screw. Replace the plate in the case, and, after fixing the dial to it with the one screw thus fitted, carefully mark the second hole, etc.
Some workmen expedite the operation by marking and drilling the two holes at the same time; but if at first they do not succeed in making them in the required position they materially increase the time occupied, as one hole at least requires to be bushed, etc.
598. Dials Held in Position by Feet. If the dial has feet, and it is required to adapt them to the plate, they must be first carefully bent straight; then take a piece of stiff card board of moderate thickness, and laying it on a piece of lead, punch out with a sharp-edged punch, or other means, a round hole of the diameter of a foot. Having inserted one foot in this hole, and placed the card on a flat surface with the dial uppermost, apply a slight pressure to this latter so as to mark the position of the second foot. Then punch out a second similar hole at the point thus indicated. If the operation has been properly conducted the two feet will enter the holes easily, but at the same time without constraint or shake, and they should project on the opposite side.
It now only remains to cut out the cardboard to the size of the plate, and, after making a central hole and a mark to exactly correspond with noon, to place it in position in the frame and under the bezel, as though it were the actual dial. Then mark the two holes for the dial feet, using a sharp-pointed chamferer that just fits the hole, held vertical and rotated by one hand, while pressure is applied by a finger of the other hand.
Some workmen merely prick holes in the card with some sharp-pointed instrument, or even force the feet through it at all risks; hence it happens that feet are often bent out of the vertical, and, in order to be able to bend them into the required position, it becomes necessary to enlarge the holes in the plate and bend the dial feet.
599. To Cut a Large Hole in a Dial. To set a Seconds Dial. This operation is performed in the ordinary lathe. The hole is cut by a ring of thin iron or copper cut with saw-like teeth round its edge, as shown at V, Fig. 270, kept in rotation and charged with fine emery and oil or water or, what is better, turpentine. The mixture described in article 594 will secure a still more rapid action.
It is advisable that the thickness of the ring be made to gradually diminish from e towards i, as indicated by the section at S, so as to prevent it from choking and probably cracking the dial.
The following arrangement may be adopted: Prepare a strong ring with a projecting internal ridge, shown in section at A B C; cement the dial, g d, to this ridge, or fix it by any convenient means, and attach this supporting ring to a chuck that rotates in a direction opposite to that of the cutter, but much less rapidly. On reaching the copper disc, reverse A B C and repeat the above process on the back enamel. The copper is thus exposed on the two sides. On filling the deeper groove with dilute nitric acid the metal will gradually be eaten away, and the acid should be renewed as often as may be needed. It then only remains to smooth the edge, beveling it on the front side, and to cement the seconds dial in position.
The use of acid may be avoided and the cutter passed through the copper, but greater care must be exercised, because the work is more difficult when operating on metal. It will, however, not be difficult after a few trials.
Willis recommends that the dial be cut straight through, commencing at the back and using emery and oil, the dial being cemented on a brass block immediately below the cutter, and rather less in diameter than the hole produced. He mounts the cutter on a stock that is provided with a pump center, the point of which is maintained throughout the operation in the small hole or point that marks the center of the hole. The great advantage of this method is that the taper of the hole is in the required direction and no filing is necessary.
600. To Reduce the Diameter of a Dial. Resting the dial in an inclined position against a block, file its edge with a smooth or half-smooth file, which must only be allowed to act while advancing, and is at the same time displaced sideways and turned so as to follow the contour of the dial. The file should be dipped occasionally in turpentine, and when sufficient enamel has been removed, pass a new emery stick over it to remove the file marks.
601. To Remove a Figure or Name from a Dial. Oil of spike lavender may be employed for erasing a letter or number.
Enamel powder made into a paste with water, oil, or turpentine, is also used for this purpose. It should be previously decanted so as to obtain several degrees of fineness. The powder used for re-polishing the surface where an impression has been removed must be extremely fine. It is applied on a piece of pegwood, although some use ivory.
The last and best system is to use diamond powder. Take a little of the powder, made into a paste with fine oil, on the end of a copper polisher, the surface of which has been freshly filed and slightly rounded. On rubbing the marks they will be seen to rapidly disappear.
The surface is left a little dull; it may be rendered bright by rubbing with the same powder mixed with a greater quantity of oil and applied with a stick of pegwood.
Watchmakers will do well to try several degrees of fineness of the diamond powder on old dials.
METAL DIALS.
602. To Restore a Silver Dial. We proceed to describe several methods of doing this, but would at once observe that when the earlier ones are adopted, the hours, if they are painted, necessarily disappear; whereas they can be retained by resorting to the last method although great caution must in that case be taken; moreover, it is much more difficult to accomplish than the others.
603. First Method. This is the most expeditious system, and at the same time the most certain of success.
If the hours are in enamel, there need be no fear; if engraved and filled with black composition, this will disappear, but it can be replaced without difficulty. There remains the case of painted hours to be considered.
First make thin marks with a fine point along the lines of all the figures, taking care not to pass beyond their ends: and do the same for the dots and lines that indicate the seconds. By using a glass and following the instructions given in article 619, no difficulty will be experienced in doing this, and the fine lines and dots thus made will afford sufficient guide for re-marking the hours.
Begin by cleaning the dial with a brush and fine pumice-stone so as to remove spots and slight scratches.
604. To Frost the Surface. In order to frost the surface of the dial, take a spirit lamp with large wick, and direct a blow-pipe flame from it against the under side of the dial, which is held by one hand with a hooked support. If the flame is gently directed over the entire surface of the back, a good dead surface is obtained that resists a moderate degree of friction either in soaping with a fine sponge, or washing in a large quantity of water, or in applying soft bread and oil of spike lavender to erase irregularities or marks made in painting the figures.
The application of the flame is several times repeated, so as to obtain a decisive and even frosting; but it is necessary, with a view to avoid buckling the thin metal, to place an iron or copper washer behind the dial. The flame oxidizes the surface of the metal; that is to say, it causes the oxygen of the air to combine with the copper which is alloyed with silver.
605. Pickling or Bleaching the Dial. Introduce sufficient warm water into a suitable flat vessel to completely cover the dial, and gently pour into it a few drops of sulphuric acid (oil of vitriol), so that the two liquids are in the proportion of about 1 to 10; then lay the dial in this dilute acid for a period that varies from half to one or two minutes. The frosting will first become yellow and then of a beautiful white color. Wash it in a large quantity of water, wipe with a fine linen rag, and apply the flame momentarily to the back in order to prevent the formation of spots on the surface.
When several dials have to be operated upon, the acid is put in a porcelain dish and boiled by a lamp. Then place each dial for a moment in it, wash in an abundant suppl of water, and dry by tapping with a fine linen rag.
606. Second Method. For the benefit of such as care to experiment with it, we add the following method: Brush the dial with a coarse brush and pumice-stone reduced to an impalpable powder until no scratches are visible. Make it red-hot and allow to cool. Then dip for two or three seconds in a porcelain vessel containing dilute sulphuric acid; on removal it will be found to be white, but rather dull. In order to produce a clear frosted surface, place the dial in a mixture of
| 6 | parts | by weight of | nitric acid of 1.22 sp. gr.[8] |
| 21 | ” | ” | sulphuric acid. |
| 50 | ” | ” | water. |
Allow the metal to remain in this acid until no more globules are seen to form on its surface, then withdraw it and immediately place in cold water. The dial will be observed to be nearly black; it is then pickled as above explained (605), washed well, heated red-hot and, when cold, again pickled; the operation is concluded by thoroughly washing its surface.
607. Third Method.[9] Cover the surface of the dial with a thin layer of soap, and brush it over, taking care to avoid touching the hours if these are not enamelled. This can best be done with a fine brush and pumice stone reduced to an impalpable powder. When the dial has been made as clean as possible by this means, wash it carefully with water and tartrate of potash (cream of tartar), then plunge it immediately in the hot solution of nitrate of silver (608) attaching it to the silver wire which is fastened to the zinc and copper discs 609; in two or three minutes the surface of the metal will be perfectly frosted, and, if each operation has been cautiously performed, the hours will remain intact.
Each time the zinc and copper discs are used they should be cleaned with nitric acid, and rubbed over with pumice stone. As soon as the dial is clean, immerse it in the solution; the least delay is apt to cause the surface to become oxidized through contact with the air.
608. To Prepare the Silver Solution. Dissolve an ounce[10] of solid nitrate of silver (lunar caustic) in a small quantity of water; filter the solution and add twice its volume of liquid ammonia. In a separate vessel dissolve 6 ounces of yellow prussiate of potash and 4 ounces of crystallized carbonate of soda in 60 ounces of water, contained in a vessel of enamelled iron, which must be placed on the fire. When near the boiling point add the concentrated solution of nitrate of silver, and allow the mixture to boil for an hour, taking care to add hot water in sufficient quantity to make up for that lost by evaporation; then filter the resulting solution.
609. To Prepare the Discs and to Plate. In order to use this solution for restoring a dial or plating any other object, take two discs about the size of a half dollar, one made of zinc and the other of copper, and, after making a small hole in each, unite them with a copper wire, or, preferably, with one of silver. After having attached the dial or other object to this connecting wire, immerse the entire system in a glass or earthenware vessel, and pour over it a sufficient quantity of the solution, previously made hot.
If the object operated upon is perfectly clean, bright and free from all greasy or oily matter, its surface will be found in two or three minutes to be covered with a firmly adherent layer of silver. When only a small piece is treated it will suffice to immerse it in the hot liquor, and rub it with the finger; a bright silvered surface will thus be obtained.
610. To Clean Metal Dials of Clocks. When the hours are neither enamelled nor engraved, it is necessary to first trace out the several lines and dots in a manner similar to that explained in article 619.
611. Ordinary Mode of Cleaning the Dial. Very often it is possible to make a silver or plated dial of either watch or clock sufficiently clean by merely brushing with powdered cream of tartar worked into a paste with water, carefully rubbing around any painted figures with a fine stiff brush. Then wash with clean water, dry by gently tapping with a fine linen rag, and expose to a slight heat. (This is in part the same method as is described in article 607; the two may be combined). If the dial is tarnished, it must be silvered as explained below.
612. To Plate a Brass Dial. Preparing the Silver. Place in a glass flask from 100 to 150 grains of pure silver made into thin strips by means of a hammer or rolling mill. Add five or six times the weight of dilute nitric acid so as to completely cover the silver, and warm the vessel, taking care to avoid breathing the fumes or admitting them to the workshop. The metal will be dissolved, and, on continuing the application of heat until all the liquid is evaporated, crystals will be found at the bottom. When cool fill the flask with warm water and, as soon as all the crystals are dissolved, pour the solution into a porcelain dish, previously half filled with water. Place in it a sheet of clean copper of about the size of three fingers, and allow it to remain for the night.
On the following day all the silver will be found attached to the plate, and it can be collected by immersing this in water. Carefully pour off the water from the fine powder thus obtained, and wash it once or twice with an abundant supply of pure water; then dry thoroughly with the application of very moderate heat. If the silver thus obtained is not required for immediate use, it should be kept in a dark blue bottle to avoid the influence of light and moisture.
613. To Prepare the Surface of the Dial. It must be quite smooth, thoroughly washed and dried. M. Robert recommends that the smoothing be accomplished by using soft water of Ayr stone, rubbing in all directions, in order remove scratches. Or pegwood charcoal can be used, sloped at one end like a whistle, and applied with water. Others employ pumice-stone powder and very fine emery paper.
614. To Apply the Silver. Take equal parts of rock-salt and cream of tartar, pound them together, and when well mixed, take about 60 or 80 grains of the mixture, and add to it 15 or 20 grains of silver, prepared as above described, and add a few drops of water to form a thick paste, which must be well mixed and worked up on a ground glass plate by means of a horn spatula to remove all grits. A glass pestle may be used for this purpose.
The dial having been prepared, take up some of the paste with a perfectly clean and rather stiff brush, and spread it over the surface of the dial, rubbing quickly and somewhat harshly. The brush should be worked about in all directions, so as to avoid scratches, until the silver is found to adhere firmly to the dial. According to M. Robert, this rubbing is to be continued until the required grain is obtained; but M. Fournier states that it should be arrested when the surface possesses a lead-grey color; the dial is then well washed, dried, and the operation re-commenced exactly as before except that the brush used is softer. A good surface will thus be formed, and it will be whiter if the proportion of silver in the paste is increased.
The result attained in great part depends on the skill of the operator, and this can only be acquired by experience.
615. Observations. If the mixture contains too much of the salt or too little silver, the latter will adhere with difficulty, and will come off in lumps or scales; moreover, it will not have so white a color.
As the proportion of silver is increased, the white becomes gradually better; but, on the other hand, if it is in excess the surface will be coarse and uneven. Too much or too little water will have nearly the same effect. The color is worse if the dial has been imperfectly smoothed, and when several days or even hours are allowed to elapse between the cleaning and silvering.
It is essential that the rock-salt and the cream of tartar be perfectly pure; if they contain any earthy matter it will scratch the surface and impair its whiteness.
As soon as the operation is completed, the dial must be washed in an abundant supply of pure water; any neglect in this particular will cause it to blacken. This washing may be performed with an ordinary watch-brush, charged with cream of tartar. Then rinse the dial, and dry, tapping gently with a fine linen rag, and finish by slightly warming it.
616. Gold Dials. It will not be necessary to say much on this subject. In order to restore the color to a gold or gilt dial, it may be dipped for a few seconds in the following mixture: Half an ounce of cyanide of potassium is dissolved in a quart of hot water, and two ounces of strong ammonia mixed with half an ounce of spirits of wine and added to the solution. On removal from this bath, the dial is immediately immersed in warm water; then brush with soap, rinse, and dry in hot boxwood dust. Or it may be simply immersed in dilute nitric acid, but in that case any painted figures will be destroyed.
617. Another Receipt. The following is the method ordinarily adopted for coloring gold dials; but it is to be observed at the outset that, although apparently characterized by extreme simplicity, a good deal of skill is needed to ascertain when the mixture is of the right consistency, and when the dial has been sufficiently exposed to its action.
Make a mixture of 4 oz. saltpetre, 2 oz. alum and 2 oz. common salt (the purest attainable), with a very little water. On placing this in a blacklead crucible over the fire it will become limpid, and must be allowed to boil until somewhat pasty and of a pale yellow color, stirring all the while with a stick. Now take two dials, back to back, that have been cleaned and blackened by annealing, and pass a platinum wire through their centers so that they hang horizontally, resting on a loop at its end; immerse the dials in the hot color crucible, and, after holding it for a short time, withdraw them and immediately immerse in a vessel of nearly boiling water standing close by. The “color” will then be washed, and the progress of the work can be observed. The dials are again dipped in the crucible if necessary, and will probably require about three minutes’ immersion in all. It is advisable that the “color” be thick rather than thin, as in the latter case the dials are apt to be clouded.
618. To Re-Paint the Hours on a Dial. The following system has reference to metallic dials, but the reader will be able to select without difficulty the parts that are applicable to altering and retouching the figures on an enamel dial.
We can answer from experience for its being successful, but would at once observe that it cannot be practised hastily, because some skill is essential in addition to patience and care: with them, success is certain.
619. First Method. Before removing the hour figures and the divisions for minutes, mark them with a fine steel point, using a lens and proceeding with great caution. These marks will remain, so that after the dial has been colored or otherwise treated, it will only be necessary to trace over them with a fine brush charged with ink.
The short horizontal lines at the top and bottom of each figure, termed serifs, as well as the two circles that enclose the minute divisions, can be drawn with a sharpened point of the screw-bar compass.
620. Second Method. Lay on the dial to be treated, or on another of the same dimensions that has the hours well marked, a piece of tracing paper, so that neither it nor the dial can be displaced, and, using India ink and a fine drawing pen, accurately trace the hour figures and the minute divisions. When the ink is dry, invert the paper and trace the figures, etc., thus obtained on the other side of the paper, this time using a pencil instead of ink. Laying the paper on the dial so that neither can slip, pass with a rounded point of some soft metal over all the figures and divisions. Now remove the paper without permitting it to rub against the dial. If the pencil has been selected of a suitable degree of hardness, and the operation skilfully conducted, the marks showing the hours and minutes will be clearly visible, although faint, and, holding the glass to the eye, the several marks must be traced over with a fine brush or pencil. If this operation is performed carefully, the dial will present a very good appearance.
621. Third Method. Place the dial within a kind of large barrel that has at its center a thick pivot projecting. The three rules, D, F, J, Fig. 271, can be fitted on to this by their central holes so as to rotate on it. Being supported by the rim of the barrel, they will pass very near to the surface of the dial without rubbing against it. From an inspection of the figures it will be evident that D is used for forming the bars of an X, F for those of a V, and J for that of an I. Of course the serifs at either end of a numeral are made with the compass.
It is unnecessary to observe that if the edge of the rim be graduated, and the rules terminated by any convenient arrangement for arresting their motion at the graduations, the hours can be traced on a dial from which all marks have been erased. It then only remains to paint them in with ink.
622. Inks for Painting the Hours. Work up some clean lampblack in oil of spike lavender. Then add a small quantity of spirit varnish, and thoroughly mix the whole. This is applied with a fine brush, and the success of the operation depends very much on the selection of this latter.
623. Another Recipe. Mix together ivory black, pure wax, and turpentine; the more the turpentine is in excess, the more will the ink be colored. It is best adapted for filling in the figures engraved in dials, and a gentle heat should be applied to impart a smooth surface. Any irregularities in the painting may be erased by the aid of oil of spike lavender and soft bread.
HANDS.
624. To Set a Watch-Hand in Position. The most delicate part of this operation is the enlarging of the center hole of a minute hand and the closing of the hour hand socket when necessary.
Set the hand in cement on a brass plate that has a hole passing through at the point corresponding to the socket. The hole must then be enlarged with a semi-cylindrical drill to a diameter such that it will only be necessary to gently pass the broach through afterwards. The drill must not be worked too rapidly, and the plate may require to be immersed occasionally in water, so as to avoid heating the cement and thus loosening the hand.
When the hole in a watch-hand is too large, it may generally be sufficiently reduced by means of the staking tool.
625. To Redden Watch-Hands. Make into a paste (while holding over a lamp) a mixture of two parts carmine, two parts chloride of silver, and one part Japan varnish. Having spread some of this over the hands, lay them face upwards on a sheet of copper, applying heat until the desired tint is produced.
GLASSES.
626. To Drill Glass. A hole can be rapidly made in a piece of glass by using a steel spindle ground at the extremity to a point with three or four faces, and hardened in mercury. This spindle may be chucked in the lathe, or rotated between the finger and thumb, the point being moistened from time to time with turpentine or the mixture mentioned in article 594. The glass operated upon should be held against the blade with the thumb or a pad immediately behind it, and should receive a gentle rocking motion so as to prevent the drill from choking in the hole formed; and as soon as the point appears on the other side, the drilling should be re-commenced from that side. It is a good precaution to mark the point at which the hole is required with a diamond or the steel point before commencing, and the pressure applied while drilling must be but slight.
627. To Cut Glass. It is possible to cut a sheet of glass roughly to any required shape with an ordinary pair of scissors, if the operation is performed under water. Of course a smooth edge cannot be obtained by such means, but it will often be found sufficient.
A more exact method is to use a piece of ignited charcoal or the pastile mentioned below, first making a scratch as a starting-point and holding the heated substance a little in advance of the crack: this will follow the direction in which the hot body is moved. The method is available for dividing glass tubes or other objects in irregular shape.
What is known as the “Berzelius pastile” for cutting glass is formed of the following mixture: Gum arabic, 6 parts; gum tragacanth, 2³⁄₁₀ parts; benzoin, 2³⁄₁₀ parts; lampblack, 18 parts; and the requisite quantity of water. Mix the gum tragacanth with water and leave it to swell up for some hours; dissolve the gum arabic in a sufficiency of water, and powder the benzoin finely. Mix the three, forming a paste of such a consistency as to be moulded, the lampblack and a little water being also added. The pastiles are then formed by rolling between two plates.
The diameter of a watch-glass can be reduced by centering it in a lathe, chucking it between two pieces of cork or a pair of cork arbors, and applying a moistened piece of glass to the edge, or an emery stick. When the desired diameter is attained, polish the edge with pumice-stone followed by putty powder applied on a wet cork.
BROACHING.
628. To Broach a Hole Vertically. A hole in a plate, as for example, that in a barrel, is seldom maintained at right angles to the surface by young watchmakers when they have occasion to employ a broach. By adopting the following very simple method, success may be assured:
Take along cork of a diameter rather less than that of the barrel or other object operated upon, and make a hole in the length of the cork through which the broach can be passed. When the cork has been turned quite true on its end and edge, the broach is pushed through and used to enlarge the hole; by pressing against the back of the cork it is kept always against the barrel, and the vertically of the broach is thus maintained.
629. To Broach and Maintain the Hole Round. Many workmen either use bad broaches or work them in a jerky manner so as to make striæ within the hole. To avoid such distortion when uncertain of the hand, draw the broach somewhat out of the hole and insert in the space thus left one or two pieces of hard wood, forming a kind of jacket, so that at least two cutting edges of the broach may be prevented from acting; the broach forcing its way into the pieces of wood, will carry them round with it. A few trials will enable a workman to employ this method.
When operating on holes that are rather large it is a good practice to use broaches that are semi-cylindrical or triangular, their sections being as shown at C, A, or D, Fig. 272. C and D are excellent for smoothing a hole, but remove very little metal; A does more work in a given time and, if well handled, will maintain the hole very round. When operating on a large hole, these broaches can be rotated in a brace; but, in the case of small or medium size holes, it is much better to mount them in a drilling headstock like those used by case-makers for the joint holes, and the tools can be revolved by the aid of a hand or foot-wheel. Only one precaution need be noted, namely, the necessity of avoiding the application of too much pressure, so that the broach jams in the hole.
SOLID AND HOLLOW SQUARES.
630. To File an Arbor or Drift Square by Hand. The most expeditious mode of making a square, as, for example, that of a barrel-arbor, is by using the tool described in article 513, or one of analogous construction; but in their absence the square must be made by hand.
Soften the jaws of a hand-vise and make four flat faces on them, forming an exact square, either by filing or by attaching pieces by rivets. Having clamped the steel on which a square is to be formed in the vise, hold this in one hand and rest it in a recess in a wood block; with the other hand hold the file, determining its position by laying it on the upper face of the square before applying it to the arbor. After giving one or two strokes, test the truth of the face formed by again laying the file on the upper face of the vise. Then turn the vise through a quarter of a circle and proceed in the same manner; and so on for the other two faces. Before finishing the square and while there still remains a slight excess of metal on each face, ascertain, by examining the end and measuring the lengths of the faces, whether the square is accurately formed.
Put in the lathe and draw with flat file in the direction of the axis along each face. If the square is to be polished after hardening, proceed in the same manner, using an iron polisher in place of the file, to which longitudinal, transverse, and circular movements may be given.
After hardening, the square may be tempered to some shade between pale yellow and a deep blue, according to the purpose for which it is intended.
631. Another Method. Let it be required to fit a square to the hole in a keyless winding pinion, the diagonal of which is a′ b′, Fig. 273. Turn the end c d of the rod down until it exactly enters the square hole. Measure with a tapered strip of brass whose edges are filed sharp the diagonal a′ b′; this will give the diameter a b of the larger portion of the rod, as will be gathered from the figure a′ d b′ c.
Turn down the portions of the rod on which the square is to be made and file four faces, each time arresting the action of the file when it is on a level with the smaller cylindrical portion, maintaining the angles equal by observing that the four portions of the circumference retain their equality while gradually diminishing. By a little care and using the square-headed hand-vise described above, success may be assured.
632. To Drift a Square Hole in Steel of Moderate Thickness. The steel in which it is required to make a square hole must be very soft and thoroughly annealed, otherwise it is sure to crack under the action of the drift or when hammered.
To make the hole in the center of a stop-finger, for example, the hole must first be drilled of a diameter less than the side of the final square: the drift is then inserted, liberally supplied with oil. On removing the drift, the square is enlarged by means of a fine square file acting on each of its corners; then with slightly larger drifts the hole is gradually increased to the required size. They are driven with a rather heavy hammer, care being taken to maintain them vertical and with each change of drift a file should be passed over the surface to remove the metal that collects at the corners.
633. To Drift a Stem Winding Pinion. For this purpose the methods explained above are insufficient, on account of the great thickness of metal, which we repeat, must always be very soft.
Nevertheless, by using drifts that are very slightly conical, short, and roughed like a file in an inclined direction, and by using a number that succeed one another of gradually increasing diameter, steel of considerable thickness can be treated in the above manner; but it is far less expeditious than the method explained below.
The piece of steel with a hole drilled through it should be from a third to half as large again in diameter as it is finally required to be. After turning the surface true and the two ends flat, the tube is driven on to a long drift of suitable temper, well oiled and of nearly the diameter of the hole to be made. Clamping this drift in a hand-vise or sliding tongs, rest the steel tube on an anvil with its axis and one face of the drift parallel to the surface, and forge the tube with a medium size hammer. Turn the drift through a quarter of a circle, again forge the tube, and so on. Care should be taken that the drift is forced further into the tube from time to time, oil being at the same time applied.
A punching machine is also very serviceable for the purpose of drifting. Sometimes the attempt is made to forge the metal red-hot, but this is much more difficult on account of the rapidity that is needed in threading the hot steel, hammering and removing it. Moreover, the steel has to be heated several times and is apt to be burnt.
If the method above explained, in which the metal is kept cold, is carefully performed, it succeeds very well, but it must be observed that steel is often met with that is irregular in composition and cracks.
TO STRAIGHTEN A ROD, PLATE OR WHEEL.
634. A Steel Rod. When the rod is short use a large pair of sliding tongs or a hand-vise, the jaws of which have been softened in order to make a groove in each parallel to their edge. Placing the rod in the cylindrical recess thus formed between the jaws, fix one side of the hand-vise in a bench vise, holding a spirit lamp near the jaws and, as the steel changes its color, tighten the slide or screw of the former. When the metal assumes a blue color and the jaws are as tight as possible, remove the lamp, allowing the whole to cool slowly or by applying water.
The jaws should be formed so as to bend the rod rather more than is ultimately required, because steel on being released is apt to partially recover its initial curvature.
When the rod is long grip its two ends in the frame of a fret-saw, which should be somewhat strong. Then hold a lamp under the rod, at the same time stretching the rod more and more, and allow the steel to remain stretched until quite cold. If it has been sufficiently stretched the metal will be rendered perfectly straight.
635. A Plate, Escape-Wheel or Stem Wind Wheel. In the middle of a square plate that is moderately thick, fit a strong screw with a large and long head; this screw must pass freely through a disc that is perfectly flat and fits easily into the upper side of the escape-wheel. Now fix the plate between the jaws of a bench-vise, and, placing the wheel between this plate and the disc with a moderate pressure applied by the screw, hold a lamp to the under side, gradually tightening the screw as the steel changes color so as to obtain a maximum pressure when a blue temper is reached. Leave the whole to cool in position.
636. A Verge, Small Arbor or Pinion Staff. When steel is sufficiently tempered, it may be laid flat on a smooth piece of copper held in the vise and flattened by hammering as in the case of an ordinary rod; but if it is hard the blade of the hammer must be used. Every watchmaker knows, for example, that a verge is straightened by striking with the blade against its concave side, while the convex side rests flat on a smooth anvil. By the action of the hammer the side that is struck becomes a little longer, thus straightening the staff, It is not usually necessary to remove the marks left by the hammer, but if this has to be done the operation should be continued beyond what is necessary to straighten the metal, then temper it to a blue color and allow it to cool.
A small smooth taper arbor or pinion staff, can be straightened by resting it on a wood block, and rubbing the concave side lengthwise with a worn file of medium cut, applying considerable pressure, the arbor being firmly supported below to avoid breakage. The result is the same as with the blows of a hammer, but the marks left are barely visible.