48 [73949.]-Dynamo.-There is not any harm in the spindle being of steel, and in one piece with the web of the armature. This is the form I adopt with all my smaller machines, and they work extremely well; but the bearings must be of brass, otherwise the magnetic field is too much dispersed. [73952.]-Galvanometer.-Cannot understand S. BOTTONE. your galvanometer at all: it must be a freak of nature, or rather science; anyhow, I will explain as far as I can. Your needle must be soft metal and not magnetised. If this is the case, it can be deflected either side at will. On making contact the needle not being, strictly speaking, truly balanced, deflected to the side which had lost its centre of gravity, then again on returning to its original position, and making contact same time, the same state of affairs would happen, and needle deflected to opposite side, and so on. [73953.]-Porous Pots.-These require no preparation before use; but red ones are better than white ones for this form of battery. You must not expect much current from these cells: their precluded any hope of friction by tension keeping many questions under one head. The number of somewhat less. But why insert resistance to waste find four storage cells too many, it is likely that [73963.]-Induction Coils, &c.-Rather too four Bunsens will be enough, as the voltage is various types of cells, and not enough acquaintance cells depends entirely on the construction. If you have had to do with always give off gas and deteriorate in various ways. energy?-why not try what three cells would do? I have not at hand the figures of resistance of the with their actual working to give advice. Those I MR. BOTTONE.-Unless you give me the dimensions question first, the battery would not light one such in series will give 50 volts (2 volts each cell), and steam-pipes the following is a good rule :- Let = number of revs. per minute. Make the area of exhaust pipes equal to the area of quantity in flow and return pipes (supposing supply be fixed in a room used as an airing closet. 4. The leposit in cistern is generally of a sandy or muddy ature, very different from rocky deposit frequently lavound in cylinders. 5. Greater facility for cleaning ut. 6. The escape pipe may be taken direct out of top of cistern. Unless) in cylinder arrangement he flow pipe is on a level with water in supply istern, the escape pipe will stand full of water, and vhen driven hard the steam will blow this water iolently out, sometimes, if fixed into guttter or long roof, on to a passer-by, or under the slates, and thus through a ceiling. DENNY. [73969.]-Winding for Armature: Current. -To MR. BOTTONE.-Put 1lb. No. 18 d.c.c. on your rmature, connect up in series with the F.M. coils, Irive at 2,500 rev. per minute; you will then get bout 50 volts. As the total internal resistance of he machine is, when thus wound, about 1 ohm, you would get on the short circuit about 50 mpères, or enough to burn up your machine; but with an arc lamp presenting about 12 ohms reistance, you would get 4 ampères of current, and his would work well. This machine would also bight well 4 or 5 incandescent lamps of 48v. to 50v., f run in parallel. S. BOTTONE. [73971.] Coil Boilers.-When shutting off team with a fire under above, I open the fire-door I have no damper fitted), blow the steam off, and work the hand-pump. The pump is of ample size, 30 that I can cool the coil pretty quickly, and then leave it for a short time, but would not care to let the coil remain dry whilst hot. I have found no difficulty yet as regards incrustation; nor do I ex#pect any, as the circulation is so rapid. Even if any were to form, I think it would be very soon loosened by the varying expansion of the pipe under heat, and at once blown through. LONDON RIVER. [73973.]-Motion of Waves.-A body floating Awith the tide has a slight recoil. It is said that rotary motion was obtained from the tide at an sarly date. F. ASKEW. A BELT now being made for a Louisiana electriclight company will be the largest in the world. It is to be 6ft. wide, 167ft. long, and will take the skins of 175 animals to complete it. When finished it will weigh two tons, and cost 10,000dols., or about 10dols. per square foot. Variations of the E.M.F. of Primary Cells. At a recent meeting of the Royal Society, a paper by Messrs. G. J. Burch and V. H. Veley was read on "The Variations of Electromotive Force of Cells consisting of Certain Metals, Platinum, and Nitric Acid." The following conclusions were drawn from the results of the experiments:-(1) When the metal, copper, silver, bismuth, and mercury are introduced into purified nitric acid of different degrees of concentration, and a couple made of platinum, the electromotive force of such a cell increases considerably from an initial value until it reaches a constant and-in most cases-a maximum value. The rise of electromotive force is attributed to the production of nitrous acid by the decomposition of the nitric acid, and the final value is considered to be due to the former acid only, while the initial value is due for the most part to the latter acid, though it is affected to a remarkable degree by the amount of impurity of nitrous acid, either initially present or produced by minute and unavoidable uncleanliness of the metallic strip and the containing vessel. (2) If nitrous acid has been previously added to the nitric acid, then the maximum electromotive force is reached at once. (3) If the con- namely, increase of temperature, of ditions impurity, and of concentration of acid-are such as would favour a more rapid solution of the metal, and consequently a more rapid production of nitrous acid, then the rise of electromotive force is concomitantly more rapid. (4) Conversely, if the conditions are unfavourable to the production of nitrous acid, the rise of electromotive force is less rapid. (5) If any substance, such as urea, be added, which would tend to destroy the nitrous acid as fast as it may be formed, then the rise of electromotive force is extremely slow, being dependent upon the number of molecular impacts of the nitrous acid upon the surface of the metal. kindly enlighten me as to the potentials of the two poles of this instrument? Is there a constant difference between them, and does one always remain positive and the other negative? If the coil were connected to a am able to understand the coil without a condenser.STULTUS. charged quadrant-electrometer, what would happen? I [73976.]-Testing Paint.-Will any of your correspondents give a quick way of testing quality of oxide paint on ironwork ?-A. F. [73977.1-To Mr. Bottone.-I want to have a set of batteries for experimental work, and lighting a 4-volt Would four lamp at three to five minutes at a time. No. 2 Lechanché porous-pot form do? If not, what is best! Also, I want to construct a dynamo like the one in your book, "The Dynamo: How Made and Used"; but instead of having the magnets rectangle shape, I want them to be round. What length and diam. ought they to be (not including pole pieces)? Is much magnetism lost at the joints of a dynamo? Can you also tell me how to melt vulcanised indiarubber, and how to make a good composition for bicycle tires?-X. Y. Z. [73978.]-Laboratory Floor.-The laboratory occupies the top floor of our warehouse (wholesale druggists). Will anyone kindly tell me the best method of treating the floor to make it water-tight, and so protect the floor of pitch and sand might do; but would not the heat below? Zinc or tin sheeting is inconvenient. A coating (steam-pans, &c.) render this disagreeable? Shall be thankful for advice.-NESCIENS. H. S. [73985.] Castor-Oil.-Kindly inform me of the simplest methods for extracting castor-oil from the seed, the cold-drawn process, or any other approved method? Also, if there is any book published on the extraction of oils from the seeds ?—D. M. [73996.]-Boat.-During the winter months I have been altering my boat; but now I find it very difficult to get a compound to fill up the nicks that will resist the action of sea-water, and will not melt with the heat of the sun. Would any one tell me of a compound that would do what I want?-W. M. S. [73987.]-Indiarubber.-Will some fellow reader kindly say whether sulphuric acid is at all used abroad in the preparation of the above, or of guttapercha? Any information will oblige.-TOJIN. [73988.J-Steam-Engine.-I wish to make a steamengine, 1in. bore, 3in. stroke, with automatic expansiongear, breadth of steam-ports. 3-16in.; lap of valve, in.; throw of eccentric, 5-16in. Would some of your readers kindly tell me the dimensions of expansion-valve and throw of eccentrics? Also, dimensions of governor-balls and drag-link to suit this engine?-RIVET. [73989.]-To Mr. Bottone.-I have six stoneware cells, the size is 4in. high, 1in, wide, and 1fin. broad. I should like to turn these into accumulators. Will ordinary sheet-lead do cut up into plates for the same? runs in each cell. I should like to try the red-lead paste to about 71b. to square foot. I think of having five plates fill the cells up. What is the red-lead wet up with, or does it require to be put into the cells dry with the plates? [73979.]-Carbon Filaments for Incandescent Will Mr. Bottone please to tell me what quantity of redLamps. In my house, which I have recently had fitted lead in each cell? Will it matter whether the plates are with the electric light, eight of these filaments have perforated or not? I should like the tops to be sealed broken in less than two months. They have been fairly down, as I should like it for pit use, put into a small box, used, and the suppliers assure me that the current is the lamp on the top of ditto. Will three of the above regular and accurate. Can I obtain the filaments cells light a 2 candle-lamp, and if so, what will be the wholesale and fit them myself? Also, what is the time it will burn after being fully charged? Will it take probable cause of the constantly recurring breakage?-long to charge the same with a dynamo going at 150 volts, and how shall I know when these cells are fully charged for lighting when filled up with red-lead paste? Will Would Mr. Bottone kindly oblige by giving me a bit of a sketch in which way they are coupled up in series, and in which way are the wires from the dynamo to these cells to charge when they are in a box all sealed down. Could these six cells be also charged with one of Mr. Bottone's small dynamos running 3,00) per minute?-IMPROVER. NESCIENS. [73980.)-Resistance for Arc-Lamp. SWITCH A WAY Mr. Bottone or Mr. Allsop give me the size and quantity of wire for resistance with sketch-LINESMAN. 73981.]-Gas Engine.-Many thanks to "Jock" for his reply re gas engine. Would he further help me by saying how to make water jacket? also, how to fix cylinder to bed (horizontal engine)? Also, are the exhaust and igniting valves worked from a second shaft and gear 2 to 1. If so, how? What is the greatest pressure per sizes of bolts and metal would be a very great help to square inch in cylinder? A rough sketch with a few others beside-NAN. [73990.]-Book-edge_Marbling.-Will "Practical Bookbinder" help me? I am a printer, and am required to fill up time at bookbinding, principally stationery. My greatest difficulty is the marbling of book-edges, and I have for some time been making experiments, but the result so far has been a dismal failure. My colours get mixed and blurred on the gum solution, notwithstanding that they are mixed with different proportions of gall, and I cannot get them to run into veins any how. If the gum is thick, a large quantity is lifted with the paper; and if thin, the colours sink into it. What shall I do? Are the veins produced by the manner in which the colour is splashed on, or should they run into fine streaks of themselves? If by throwing on, will the quantity of bristles in the brushes make any difference? Should the colours be moderately thick, or thin?-DOLERS. [73991.]-Sectional Area of Steam-Pipe.-How can I find the sectional area of a steam-pipe ?-E. L. P. [73992.]-Dynamo Calculations.-To MR. BOTTONE. Since the maximum effect of a dynamo is obtained when the magnets are wound to the point of saturation, how is this accomplished for magnets of all sizes? I have a magnet-core whose extreme dimensions are 6in. by 44in. by 4in., giving an area at each end of 19sq.in. Now, if 25 lines of force per square inch of this surface are required to magnetise the iron core to the point of saturation, how many ampère turns of wire will be required? Twenty-five lines per square inch is said to be absolute saturation; but what about the cubic contents of iron that may be beneath that square inch? The simple statement as above is surely incomplete without reference to the quantity of iron, as well as the area through which the lines pass. How do you calculate the number of lines passing through the armature core?— COLONIAL. [73993.]-Dynamo Reckonings.-To "J. W. W. B."-Will you kindly explain the following? Take 5,000 ampère turns, how are the various quantities allotted1st, for air resistance; 2nd, for magnets; 3rd, for armature? Also, how you reckon the density of lines on the square inch of armature? Given the following quantities-viz., revolutions of dynamo, number of volts, and number of armature turns; from this, how do you reckon I shall feel extremely obliged for the above information. the number of lines passing through the armature core? -MARCH. [73994.]-Bookbinding.-What height ought the top of the "tub," or frame, the laying-press lies on to be? Having never seen inside a bookbinder's workshop, do not know. Some one told me "proportioned to my height"; if so, I stand 5ft. 8in., and have long arms.-W. H. B. [73982.]-Electro-Motor.-To MR. BOTTONE.-In your book on Electro-Motors," p. 43, you give dimen-heat steadily. sions for an electro-motor with ring armature 3ĝin. outside diameter. Will it drive a small tricycle? and what size, and how much wire shall I put on to give the best Also, what would be the cheapest and best result? battery to drive it with? and how long could I drive it before it would want a rest!-R. BLOXAM. [73983.]-Dyeing Hair.-I wish to dye human hair, of a nice light brown colour, and can get the desired effect from catechu, but the colour does not stand. Can any of our readers kindly tell me what to add to the above to make the dye a fast and permanent colour, and [73995.]-Brick Ovens.-Could any correspondent give advice or information on the subject of brick ovens ? I wish to construct a good one with flues and furnace; one which will heat easily, be economical, and keep the The primitive oven heated by hot wood ashes placed within the oven does not meet these requirements. I wish my oven to be large enough to bake bread for a household of 20, or thereabouts. I do not know the class of workman to whom to apply; and I do not understand the principles of the working of an oven sufficiently to direct an inexperienced bricklayer myself. I wish to secure a good, strong bottom-heat without a scorching top-heat. What kind of chimney is necessary! must the vent be necessarily long? Full information will greatly oblige. Any information will be welcome.BRICK OVEN. ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 1356. [74001.]-Dies Clogging.-Why, in cutting brass screws with die-stock, do one or two threads of the dies sometimes get clogged with the brass? I have found the same thing happen to taps in cutting female threads in brass. The metal seems to stick in the threads as tightly as if brazed there. difference. Oiling seems to make no appreciable I don't think it is from any fault in the tackle, as they are by the Morse Company, and almost new. The only remedy I know of is to use them on wrought iron; this cuts the brass out, but I should like to prevent the clogging. Can anyone help ?-A YOKEL. [74002.]-Cutting Square Threads. I wish to cut several square-threaded screws, gin. and in. diam. Can anybody tell me if this can be done with stocks and dies? I have a serew-cutting lathe, but think it would he easier to make taps and dies than to cut all in the the. The internal thread is in an awkward position in heavy casting, so that it could not be cut in the lathe. a recipe for a good steel bronze for brass-work?-APPRENTICE. [74012.]-Steel Bronze.-Will any reader give me -The front of the Market Coffee Tavern in Lancaster is composed of a hard material in imitation of serpentine [74013.]-What is Titancrete Composed of! MARCH 20, 1891. marble, which has withstood the action of the atmo- [74014.]-Waxing Photos.-When a photo. is [74015.]-Gun Action, Hardening.-Would some [74016.]-Tools.-Will any readers of this paper kindly give me illustration of a few hand-turning tools for brass and iron, for, being a young amateur at the job, I am at a loss to know what shape to make them? and also, what would a compound slide-rest cost for a threeand-a-half centre-lathe.-SLOW COACH. [74017.]-Bulge.-To what extent will a thin sheet of metal, fitted like a drum to the end of a pipe, bulge, on pressure being applied to the pipe? The diam. of drum to be 1in., would thin sheet brass bulge more readily than iron?-E. A. C. [74018.]-Moulds for Electrotypes. -Can any reader inform me the best plan of taking moulds from very small set-up type for the purpose of making electrotypes therefrom? The electrotypers seem to use some composition on a cardboard base. I have tried wax, plaster of Paris, sulphur, sulphur and iron, but they do not answer so well as the mould usually adopted in the trade.-C. W. S. [74019.]-Ink-There is a purple ink sold in France that turns black on exposure. I have been told that it is logwood solution with a trace of yellow chromate; but I do not thind this is the case, for when greatly diluted it still turns black. Can any reader inform me about this! -C. W. S. [74 20.]-Coil.-Will some reader kindly tell me the quantity and size of wire, size of core, &c., for a small pocket medical coil, 3in. by 1in., to be worked by a pint bichromate battery? I want to get as strong shocks from it as possible.-W. A. J. Can you inform me the dimension of the different parts last year? I am desirous of making one or two of these transmitters for use in a small house. frames be procured anywhere ?-MICROPHONE. [74021.]-Blake Transmitter-To MR. ALLSOP.of a Blake transmitter? have a damper, as shown in the article you contributed Also, why it is necessary to Clark, W. Gleave, A. Fellows, and H. Fellows, G. W. Editor, 10, Victoria-terrace, Clontarf, Dublin. It con- The English Mechanic AND WORLD OF SCIENCE AND ART. LATHE APPLIANCES.-VIII. Die Chucks for Wire and Rods. THE also serves to straighten the wire projecting proper tools: it is too long to be minutely The drawings marked 17 to 19 show a two-die chuck which has independent dies. The screws which press the dies together, and thereby grip the work between them, are tapped through an iron ring. With dies shaped as those shown, the motion of one is much greater than that of the other when changing from one size of work to another. For this reason the pinching-screws shown in the drawing are not alike in length. If a pair of dies are used, both of which are notched alike, they will of course each travel an equal distance when changing from one size to another. The drawings marked 20 to 26, show a die chuck, elaborated from the one marked 14 and 15, in which the work is not injured by the end of the pinching-screw. In this chuck there is a jaw interposed between the work and the pinching-screw, and this is a great improvement. The long bearing surface afforded by the jaw also causes this chuck to hold the work much more firmly, though it does not get bruised so much as by the end of the pinching-screw as previously mentioned. The sheet of illustrations is marked with numbers from 1 to 29 inclusive, and these will make reference to the drawings easy. The body part of the chuck, which screws The letter W appears within a circle in on to the lathe-nose, is the first piece to make several drawings. In every case the circle when constructing either of the die chucks so marked is intended to represent an end illustrated. Side views of these several body view of some work gripped in the chuck. parts are marked 1, 14, 17, and 20 on the Most of the drawings give side or end views drawing. Considerable deviation from any of the various parts, and the few (three) of the forms given is allowable; but some which show sectional views are distinguished one of these will generally suit. The main by the usual section lines drawn through point for consideration is the length of the them. These are marked 2, 6, and 23. Four body part-that is, the amount of projection distinct forms of die chuck are illustrated on from the nose. the sheet of drawings; but as there are When the lathe-mandrel is tubular, and shown different methods of construction in so allows space for the work to project behind the details of each, as well as the different the chuck, the chuck should be made snug; designs, the method of making a much but when the mandrel is not hollow, it is greater variety is made clear, and several important modifications are suggested in the text. chucks. The plan of turning a groove in the mandrel thread, close to the shoulder, does not entirely supersede the necessity of clearing away the thread from the mouth of the chuck, though the groove certainly weakens the mandrel at its admittedly weakest place. It is not now demanded by the exigencies of manufacture, as it was when the thread on the nose had to be chased by hand with a comb-chaser. Methods have changed since then, and there is now no valid reason for grooving the thread on the mandrel-nose. When the thread has been cut, and the first turn or so cleared away, as above stated, the casting should screw on the mandrel right up to the shoulder, and touch all round. When it does so in a satisfactory manner, the embryo chuck is loosened and removed from the progenerate chuck in which it has been held. The casting, now screwed to fit the nose, is put on its place and turned true and smooth all over. The diametrical groove may give some trouble in turning that portion of the casting through which it passes-namely, the face and a short distance back. Care must be taken not to get the edge of the groove broken off where the tool drops out of cut, and this is sure to happen with cast iron if not provided against. The edge will not break away raggedly if it is filed off somewhat chamfering towards the cut, as often done on work when planing up to a sharp corner. The tool will then cut to the last, up to the moment of dropping out of cut, instead of breaking off just the extreme end of the shaving, and with it the corner of the work. This refers to cast iron; but there will be no trouble with any of the brassy metals, which have greater tenacity. often very convenient to have space within the body of the chuck to admit some surplus material projecting behind the die. For example, the end views of the sliding The sectional view marked 2 shows about an die or dies shown in connection with each inch of space provided with this object, and chuck, and marked 9, the lower part of 16, the the amount may be increased even threefold, lower part of 19 and 25, each differs from in some cases with advantage. Excessive the others. Thus are shown four different overhang is, however, always detrimental in Shaping the groove to receive the slider forms suited for the diametrical groove any chuck, and it is hard to conceive a case next calls for attention. Its form and across the face of the body of the chuck in where any good reason can be assigned for position should be determined and marked which the dies are fitted, three of which are not making the lathe-mandrel tubular. on the body, and precautions taken to get quite unlike, though all are adaptable to Most mandrels, including those originally it truly central. If the form of the groove any of the chucks. Another example is designed to remain solid, will bear boring is carefully turned in the middle of its length furnished by the pinching-screws marked out to a fairly useful diameter, though some by the aid of a tool fixed in the sliding-rest, 13, 27, 28, and 29. These all differ as to will not allow a hole to be made entirely it will give the best gauge lines for working the methods of actuating them; but either through. Still, a hole bored several inches to, For accuracy and speed in cutting out method may be adapted to any of the deep into the mandrel from the nose-end will the groove to shape, a cutter mounted on a be an improvement on the solid mandrel. geared drilling spindle, such as that which The drawings marked 1 to 13 represent a The operation of boring up a mandrel, formed the subject of the last piper, may be die chuck which has the peculiarity of pinch-running in its own bearings, is not a very chosen. The body of the chuck, screwed ing the work and fixing the die simultane- serious undertaking, and few people who tightly on the mandrel, is fixed by any ously by means of one screw. This chuck is have ever worked with a tubular mandrel, dividing appliance, so that the groove lies perhaps not suited for common use in a and the appliances incidental to it, would horizontally. A suitable cutter is introgeneral jobbing workshop, as careless usage hesitate to convert any solid mandrel that duced, and the spindle packed up, to give does not agree with its construction. With happened to come under their dominion. the necessary width to the groove. A trip is moderately careful treatment it is a very A casting is suited for the body of the then taken through the roughly cast groove. enduring and useful appliance. Probably chuck, and a pattern for the foundry is The body is then rotated exactly half-way the reason why it is not more often seen first prepared. Iron is a perfectly suitable round, and refixed by the dividing appliance, amongst the usual assortment of lathe- material, but some bronze or brass alloy is and a second trip is taken through, which chucks is owing to its merits being but little often employed. When there was some will make the two sides of the groove correknown, and even the principles of its con- difficulty in getting small iron castings that spond. By packing up the spindle a small struction do not appear to be understood could be easily worked with the tools, or, to amount, and taking another cut along commonly. say the least, when every iron casting could each side of the groove, it will be The drawings marked 14 to 16 show a not be depended upon, there was good reason still further straightened and smoothed. The chuck which has the end of its pinching- for using gunmetal, &c.; but now, iron that number of cuts necessary or desirable to screw impinging directly on the work. This will work almost equally well can be got make the groove the required size, and also end being generally made small, badly without much trouble, and it makes excellent sufficiently smooth, will naturally be marks the work held by it. The small material for the purpose in question. governed by the peculiarities of each casting amount of surface contact does not afford The casting is chucked, so as to run fairly operated upon, and cannot be stated a very enduring hold, and consequently true, in a four-jaw chuck such as was definitely here, though two cuts often the work often becomes loosened whilst described on p. 500, Vol. LI., or in any other suffice. When spindle and cutter are not it is being acted upon by the turn- chuck that will hold it firmly with the end available, other and less satisfactory means ing tool. This chuck seems to stand rough that is to be screwed on to the mandrel out-may be employed. usage, The hole for the thread is bored, Planing and slotting are both applicable and the end is turned true and flat. Cutting processes for this purpose. If the necessary the thread by which to screw the chuck on machine of either kind is available, the the mandrel, is a process that needs care and groove can be quickly got out parallel. The and it may be mentioned that wards. it generally gets plenty. All these diechucks are commonly set for the work to run true by the aid of a hammer, which tool VOL. LIII.- No. 1357. 84 ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 1357. tools used either in planing or slotting will not, however, give a symmetrical sectional form, unless great care is taken to set each tool very nicely to correspond with the fellow one which operated on the other side of the groove. A certain amount of filing will generally be requisite to finish the work of the planer or shaper. MARCH 27, 1891. good cast steel of suitable temper, and they groove in the body, holds the die by friction in should be hardened and tempered all over. the V-grooves when the wedging force of Each end of a screw that is employed to nip the pinching - screw is inoperative. A the work or the slider must be hardened and small hole, shown also in 5 at the lower part tempered, and the entire screw is all the near the angle of the V, is drilled through better for being so treated. Sharp angles the die whilst the two halves are together. should be avoided at any part where the When these are afterwards separated, the The groove may be made true and smooth head and the screwed part join; and with inner face of each half by means of a pinby filing only, and small sheet metal tem- this precaution there is little fear of breakage drill, which bores the enlarged holes condiameter changes-for example, where the larger hole is bored some distance into the plates to gauge the form and dimensions of in hardening the screws. the grooves will be a great help to accuracy. annealed during the process of manufacture, spiral spring is made of round steel wire, Such templates are easily made from any the screws are very likely to go out of shape, coiled to the correct diameter waste scraps Unless properly centric with the original small one. A stiff of sheet metal. A cutting- and perhaps the thread-rate will alter in and so long that the coils come near together, punch or drift may be used, and will produce hardening. The tempering of the screws is but do not touch when the two halves of the a good result; but this tool is too costly to easily done by flaring off with oil. The threads sliding die are together. This spring will make or to buy for it to be suited for use of these screws may be those commonly used hold the slider in the body by pressing the when making only one chuck. A drift may and known as Whitworth's, or the orna- halves outwards against the V-grooves in the fit the hole, be made, at no great cost of time or trouble, mental lathe threads as preferred. perfectly suited for regulating the form of the groove after it has been filed nearly to as follows:-1 is a side view of the body of of the pinching-screw. The central square size and shape. Such a drift can be filed up Bennett's chuck, the sliding die-piece being is a hole through the screw, as shown at 13, The drawings shown in the illustration are marked 8 and 9; the former shows the end from a bar of steel, and the teeth made on it removed. 2 is a sectional view of the same, intended to receive a square-ended key, body. The two ends of this sliding-die are by filing notches, which need not be deep, cut through horizontally, to show the shape which is shown at 10 and 11. It is someand the drift need not be hardened if in- of the V-grooves, in which the die-pieces thing after the style of the keys used tended to be used only once. is wanted for the body of the chuck to rest lathe-nose is shown; also at the right-hand powerful key, such as the one illustrated, Good support slide. The thread for attaching it to the for opening railway carriage doors. A against, so as not to damage it when driving corner a section of the steel ring fixed to the is the drift; but it is better to force the drift front of the chuck by four small countersunk pinching-screw of this chuck, and also of through by screw pressure, if this can be headed screws (shown at 3). The steel ring others. The end of the square key should managed. Drifting and filing are alter- strengthens the chuck by holding the two be chamfered, and likewise the square hole nating processes in making the groove. wanted to efficiently tighten the The dies for these chucks may be made of of the die. The outer edge of this ring inserted in the latter. The squares themsteel, or of iron, or of brass, &c. If steel is extends to the full diameter of the most selves, both internal and external, should sides of the body against the side pressure in the screw, so that the former is readily used, the question of hardening becomes an projecting portion of the chuck, so as to not, however, be made to taper but to a very important one. These dies are awkwardly- form a guard against anything catching an trifling amount. shaped pieces for hardening easily, except by eccentric projection, and the edge is well experienced hands. When left soft, steel rounded to make it harmless if the hand of should be curved to the same radius as the dies are not so satisfactory to use as case- the user happens to come against it when diameter of the body of the chuck, and not hardened iron ones. suitable material, and when the jaws are is very Good iron is a very rotating. The circular ends of the die shown at 4 made of it, they can be case-hardened, general diameter In this particular design there to the smaller circle given by the length of either all over, or only at those parts where under every condition of various dia- the body, whilst it will not in the least add little projecting beyond the the die itself. actually required to withstand wear and tear. meters of work. The simple process of case-hardening by 12, and shown in position at 4, is used for reflection will explain. For the same reasons, the chuck, even larger bearing surface in the V-grooves of This will give the die a means of yellow prussiate of potash is suffi- small diameters, as shown at 4; the die is the same method will be applicable to the cient for this purpose, and the dies are easily inverted for medium diameters, and removed, sliders of the other chucks illustrated. The loose die marked to the working diameter, as hardened all over, and are better done so as at 3, for large diameters. By this arrangethan only partially. The more elaborate ment the motion of the sliding-die across the mentioned; the drawing above the figure is process of case-hardening by soaking the iron face of the chuck is not great, and the pinch-a side view. On the left is shown the end for hours in a mass of leather parings or ing-screw, marked 13, itself projects but very view of the die, and this also indicates the similar material, all being kept heated, is little, even when gripping work of the way to get the die shaped from a piece of The extra die marked 12 has been not necessary for the purpose now under largest diameter the chuck will admit. consideration. near the middle of the square. of the figure 13 the end form of the finished it in the position shown by the dotted circle die is shown, as it is also at 4. square bar steel by drilling a hole through grooove in the upper corner is intended for wire from the smallest diam., say in., that the chuck will hold, to in. On the right in. to gin. diam. Rods larger than this, up to about 1in. diam., are held by the groove in the lower part is for rods from The larger Dies made of brass and similar materials are for most purposes almost useless unless the working parts are properly lined with steel; and it is more troublesome to do this than to make the dies from the solid metal. Case-hardened iron may be selected as best when all things are considered. of than the diameter of the body, so that it never projects beyond the body when shifted The sliding-die is made somewhat shorter diameterways to suit any size of work. The steel ring, as shown in 1, 2, and 3, is, therefore, large enough to circumscribe the greatest projecting; but if the ring were to in the illustration, it would require to be much larger in diameter to extend at least as be used on either of the other chucks shown far as the projecting screws. main die as shown at 3. a moment's The small across the The hole in the die through which the work is to be passed, and there held by the pinching screw, is generally made somewhat heart-shaped. When a pair of dies grip the work between them, parts which bite are the steel ring fastened to the body of the 16, show another chuck. generally tangential to the work, and the chuck by four small screws. The face of the chuck drawn at 3 shows biting is at three or four places around the over the two segmental side portions forming diametrical dove-tailed groove work. Several of the illustrations show this. the face of the body, and is screwed against face as shown by 15, in which the slider The next illustrations, marked 14, 15, and When making the heart-shaped hole, the a flat shoulder behind. The ring fits one is shaped as shown by 14, and it has a largest diameter the chuck will admit is the most effective adjunct to prevent the sides tailed groove are shown by the end view of The body of this gauge for the large end of the heart. The from spreading apart under the influence of the slider beneath 16, which is the front apex is made by drilling a small hole, just the jamming action of the die. Thus the ring is a 16 fits. The shape and size of this dovebeyond the circumference of the large one, opening, in which the figure 3 is printed, 16 marks work pinched, in the angular part the size of the smallest work the die is in- shows the full capacity of the chuck for re- of the heart-shaped hole, by the pinchingtended for. Straight lines tangent to these ceiving work. The pinching-screw has its screw shown at 28. The central view. The letter W in the centre of 15 and two circles give the angular sides, and by inner end showing above the 3, and this is shorter than the diameter of the body of the these angular sides the work is held. The also shown in the next drawing, 4. The chuck, and its ends are square; but in both angle formed here is usually about 60°. In sliding-die, removed from the body, is shown these respects it may be made otherwise, and some cases, however, it is 90°, as shown in at 4, front view, and at 5, edge view. One the remark made relative to the curvature of The slider as shown, is the chuck first described at 3. The large half of this die is shown at 6, a vertical the ends of the slider marked 4 should not be hole and the small hole are both bored section, and at 7 a view of the inner side. forgotten in this connection. when the chuck is on the lathe-nose and The threaded portions of these two illustrathe slider is in place; the slider being tions show the matrix for the pinching-body at right angles to the dovetailed groove, shifted along its groove the necessary amount, screw, 13. Just below the figures, in both and a pinching-screw, the shorter of the two after boring the large hole, to bring it into illustrations, is shown the plane against which marked 28, is inserted for the purpose of correct position for the small one to run truly the work is pinched. Lower still, the circle fixing the slider. The point of this screw A hole is tapped through the side of the the material between the two holes and make bored to contain a stiff spiral spring tightly ing side of the slider, which affords but a very A triangular file will soon remove in 7, and the blank in 6, show the hole should not itself impinge direct on the slantthe sides straight. two halves of the die outwards against the V-from the inside by means of a coiled when in its place. This, pressing the slight hold. The hole should be enlarged central. The pinching-screws must be made from rose cutter |