ae would inform me if I can obtain the cupric oxide for ANSWERS TO CORRESPONDENTS. e negative plate, or how can I prepare and compress it, c. I am following Mr. Gillett's instructions on the honograph construction, I should think it would make excellent battery for the motor.-EXPERIMENTER [74098.]-Gas-Engine.-Would any reader give me 1. Write on one side of the paper only, and put drawings rrect size of gas-engine required to give out enough dose HINTS TO CORRESPONDENTS wer to drive a lathe 4in. centre screw-cutting, also the to queries, and when answering queries, put the numbers nount of gas it would require to keep it running for six for illustrations on separate pieces of paper. 2. Put titles purs per day!-AN AMATEUR.ne Can any kind friend as well as the titles of the queries to which the replies [74099.]-Lathe Making. lease help me out of a difficulty? I have a set of cast-refer. 3. No charge is made for inserting letters, queries, Egs for the headstock and tailstock of a 33in. centre or replies. 4. Letters or queries asking for addresses of ck-geared screw-cutting foot lathe, which I purchased, manufacturers or correspondents, or where tools or other d am in a difficulty as to fitting them up. I will supply articles can be purchased, or replies giving such informaquestion asking for educational or scientific information eleton drawings, if any reader will kindly take the tion, cannot be inserted except as advertisements. 5. No ouble.-FITTER. and the names of correspondents are not given to inis answered through the post. 6. Letters sent to correquirers. spondents, under cover to the Editor, are not forwarded, [74107]-Standard Candle.-How is the standard Age (74101.]-Vulcanite.-Will any kind reader inform [74102.]-Asbestos Paint.-Can any reader give me [74104.]-Furnace.-Will any brother-reader kindly Ra[74106.1-Area of Steam-Piping. Could you ndly inform me how to calculate the necessary sectional eas of 90ft. of steam-piping? There are to be four ght-angle bends in this run with about 18in. centres. here are to be five compound engines taking steam only he way, but with double cranks-I mean there are two fligh-pressure and two low-pressure cylinders. The areas each piston are 758q.in. The speed to be 400 revoluons per minute. They cut steam off at 75 per cent. of L. P. Process.e stroke. The stroke is 6in. Steam-pressure 150lb.(74107.] The New Diazotype erhaps J. T. N." would be good enough to add as a applement to his excellent article on the new diazotype rocess an explanation of the composition of the various developers" he mentions therein. To me-not having Kudied chemistry-they are so much Hebrew, and I am are very many of our readers are in the same sorry light. Articles so translated are of little use.-F. M. [74108.]-Making Gelatine Insoluble.-Can any eader tell me of some substance which, added to gelatine, ill make it insoluble in water? I want it for decorative urposes.-F. M. [74109.]-Stamping Photo. Mounts with Gold etters. Can anyone kindly tell me how to stamp hoto. mounts with gold letters? I want to stamp the ames of photos. on cardboard mounts in gold. I have ome printers' type and a bookbinder's type-holder. W.P.G. Lacquer for Telescope. Can any [74110.] eader tell me how to lacquer or polish the brass tube if my telescope? It is 32in. in diameter and about ain. long, and has become very much tarnished and amount of polishing that I have tried joiled, and appears to have the desired effect.-DIRTY TELESCOPE. (74111.1-Small Arc-Lamp-How can I make a w small arc-lamp, suitable for a small shunt dynamo giving about 5 or 6 ampéres at from 48 to 50 volts pressure) R. W. J. [74112.1-Stencil Ink.-I have occasion to use a good deal of stencil ink. I buy it in cakes, but it is too expensive. I tried lamp-black and glue, but it is not Could anyone recommend any recipe!so good. CRAIGROYSTON.O (74118.1 Dynamo-Designing.-To MR. BOTTONE AND OTHERS In designing and proportioning F.M.'s., should not the cubical contents of armature core, F.M.'s, wokes, and magnet-cores be equal !-L. L. L. practice, plate, and then the answer to questions 1, 2, and 3 No; to 4, The ordinary commercial acid; to 5 and 6, Depends on what is required to be done; and 7, On what New Form of Pianoforte Keyboard. A new sort of a coating is required.)-F. W. G. (It depends floating it on water will soon loosen the silhouette, and on what has been used to fasten it on, but, probably, Ww. A. (The address of the Institute of Patent Agents is 19, Southampton-buildings, London, E.C.)-Paul von Jankó, has been exhibited recently in that can then be remounted with simple starch paste.) form of pianoforte keyboard, the invention of Herr HOME-WORK (It is, then, an examination question, Manchester. There are what appear to be six rows (in.), while the questions. The object of such questions is to compel than the ordinary keyboard. This is really the Bethe student to think, and so gain a full knowledge of case, for an octave on the Von Jankó system extends to the fact (Not arrived at 74086 yet, and for obvious reasons, we cannot spare space for such of keys occupying a space considerably less in width his subject.)-J. JONES. Only by analysis can you detect the difference, unless only to about 12 centimètres are only six keys in the octave in any one you have had experience in examining samples of such ordinary piano demands 16 (6in.) for the same needs two rows of for his salts, when a goed guess may be formed)-TURNER range. The economy of space is due to do not know of a society; but the Secre- that tary of the Amalgamated Society of Engineers. Query is to our to the Secretary of the Institution of Electpply complete obtave, and these two are in form exactly Engineers, 4, The Sanctuary, Westminster, S. W. We alike. None are raised above the others, but all believe we answered you before.)-B. T. C. (Please see occupy the same plane. Each note is separated indices. No honest man wants an ink that dis- from the nearest by an interval of two semitones. (You will find all Thus the lowest row of the six manuals gives this appears completely.)-J. G. T. about the use of petroleum and its derivatives as gas succession of sounds-C, D, E, F sharp, G sharp, in back volumes.)-V. lower manuals. know affection of the eyes, and the cataract is a well A sharp. The row immediately above would gire upon it in a general way some years ago. As a rule, it sharp, D sharp, F, G, A, B. The whole of the is removed by operation; but only a surgeon-oculist can chromatic scale can therefore be played by striking is, re the best advice on any special case after examina- alternately the keys on the twed that it may be tion of the patient.)-J. W. (Why not follow the Each key, however, is directions? We presume you know why iron and brass are used in juxtaposition.) - G. H. (See indices. For struck at three different points-it rises by stages, most purposes it is a copper bit held in an iron shank. as it were, and may be used, at the convenience of "Clean the work" is the secret, but flux must be the performer, either as belonging to the first, third, applied. 2. Do you mean find the throw of one in and fifth rows, or to the second, fourth, and sixth. existence, or what the throw should be! Either way it In other words, though there appear to be six sets is explained in the textbooks.)-EDWARD SCADDAN. of keys, there are in reality only two, because the (We cannot say that we like the shape, but other people same key may be struck, according to the conmay find that an attraction. Thoroughly well adver tised it may take.)-VINDEX. (Better communicate venience of the player, upon any one of three with the police at Scotland-yard if the man does not different rows. [74114.]-Accumulators-Acid for.-In actual how often does the dilute sulphuric acid vant replacing? Is water only merely added from time o time, or are they charged once for all, and continuusly worked till the cells are used up altogether (acid nd lead plates)? Full information will much obligeAN OLD M.8.E. [74115.)-Fuel for Steam Boiler.-I have a Lancashire boiler, and am desirous of burning ordinary coke from the gas-works, mixed with small steam coal in equal Will the coke be injurious to the boiler!quantities. JOHN THOMAS. [74116.]-Horse-Power for Sewing-Machine. -I am sorry I did not put my last query clearly enough, I should have said, What fraction of one horse-power is required to drive an ordinary domestic sewing-machine? One continually sees engines and motors quoted as having H-P. to 1-50H.P., &c.-WAUTON. TERMS OF SUBSCRIPTION. PAYABLE IN ADVANCE. 60. 6d. for Six Months and 11s. for Twelve Months, post free to any part of the United Kingdom. For the United States, 13., or 3dol. 25c. gold; to France or Belgium, 13., or 16f. 50c.; to India (via Brindisi), 15s. 2d. to New Zealand, the Cape, the West Indies, Canada. Nova Scotia, Natal, or any of the Australian Colonies, 138. The remittance should be made by Post Office Order. Back numbers cannot be sent out of the United Kingdom by the ordinary newspaper post, but must be remitted for at the rate of 4d. each to cover extra postage. Messrs. JAMES W. QUEEN and Co., of 934, Chestnut-street, Phila delphia, are authorised to receive subscriptions for the United States for the ENGLISH MECHANIC, at the rate of 3 dols. 25c. gold, or Thirteen Shillings per annum, post free. The copies will be forwarded direct by mail from the publishing office in London. All subscrip tions will commence with the number first issued after the receipt of the subscription. If back numbers are required to complete volumes, they must be paid for at the rate of 3d. each copy, to cover extra postage. Vols. XXIV., XXX., XXXII., XXXVI., XXXIX., XL., XLII, Indexes for Vol. VII., 2d. each. Post free 24d. each. Indexes to Vol. XL., and to subsequent vols., 3d. each, or post free 34d. Cases or binding, ls. 6d. each. • It must be borne in mind that no Displayed Advertisements can appear in the "Sixpenny Sale Column." All Advertisements must be prepaid; no reduction is made on repeated insertions, and in cases where the amount sent exceeds One Shilling, the Publisher would be grateful if a P.O.O. could be sent, and not stamps. Stamps, however (preferably halfpenny stamps), may be sent where it is inconvenient to obtain P.Ö.O.'. The address is included as part of the Advertisement, and charged for. Advertisements must reach the Office by 1 p.m. on Wednesday k insure insertion in the following Friday's number Postage Stamps for exchange. Anything bric-àbrac preferred. Selections seat on approval.-Address, COLLECTOR, 125, Coltman-street, Hull. Wanted, small Loco. or return-tube Boiler in exchange for vertical Field-tube BOILER (18 tubes, works at 80lb.) and cash.A., 36, Park, Lincoln. Wanted, rare Postage Stamps. Exchange rare Roman and other Ancient Coins, Silver Watch, Fishing Rod, Revolver, Gun, &c.-COLLECTOR, 125, Coltman-street, Hull. Wanted, about 4H.P. Steam-Engine and Boiler, complete, with all fittings. Exchange about 3H.P. Give difference in eash.-T., 6, South End, Croydon. Exchange Safety Bicycle, in perfect order, cost 214, for Drilling Machine, geared, and to drill, in., or other tools, with part cash-such as forge, anvil, &c.-BROOKS, Kingston-road, Wimbledon. Bin. Slide-Rest, good maker, nearly new, cost £5; also pair 5in. Lathe-Heads, top-geared. What offers?-Txos. HoY, Southgate, Sunderland. Twelve 28. parts "Cyclopædia of Tools." 210 ENGLISH MECHANIC. Wanted, Carbon and Zinc Plates, brass parts of Wimshurst Machine.-ALCOCK, Sporle, Norfolk. 18ct. gold (24oz. case) keyless Lever Watch, jewelled in 10 holes, rubies, independent centre seconds, with minute recorder, quite new, scarcely scratched, a most accurate time-keeper, cost £25. Exchange Price's Universal Lathe, 3in. centre, 3ft. bed, screw-cutting, milling vice and dividing appliance complete; must be in condition equal to new.-W. H. RILEY, 38, Queen-street, Ulverston. 4 centre Bench Lathe, chucks, 20in. arm fretsaw combined, for 52 or 54in. Bicycle, ball bearings, or value.-E. P., 21, The Avenue, Field-street, Kettering. Powerful Medical Coil, with all the latest improvements, bichromate battery, handles, &c., quite new; also two large size Bichromate Bottle Batteries, quite new. Offers.-Below. Horizontal Steam Engine. 1in. stroke, fitted on polished walnut stand, a very handsome little affair, equal new. Offers requested.-W. WHITE, 17, York-street, Nottingham. Army Service Snider Rifle, in good condition as new, has won several prizes; will accept Jewelry in exchange to value £3.-Leeds-terrace, 279, St. Philip's-road, Sheffield. Grand Bright Beam Model Engine, 2in. bore Valuable double 12-bore Breechloading Double Gun. Offers wanted for 2H.P. Vertical Engine, new; Electric Gaslighter, two ebonite Bell Telephones. Exchange Waterbury. £17 Cushion Safety, new Exchange for solid-tire Safety and offers.-WALTON, London-road, Gloucester. What offers in exchange for Pyrometer, by Casella, reading to 1,400; small launch engine. Photo. sent.-Psacr HUDDLESTON, 21, Upham Park-road, Chiswick. Siemens Dynamo, compound wound, 32 100 vol Edison lamps; focussing are lamp and some cable. Exchange offers wanted.-HUDDLESTON, Upham Park-road, Chiswick. What offers in exchange for job lot of Batteries, 21 Indicators, various sizes; 2 Sounders, Relay, and SwitchesHUDDLESTON, 21, Upham Park-road, Chiswick. Half-plate, with several dark slides wanted. Will exchange electrical goods for good one.-HUDDLESTON, 21, Upham Parkroad, Chiswick. Bench Drilling Machine. 4ft. S lathe bed; Planing Machine, 3ft.; Launch Patterns, 2 by 3. Exchange offers -FREDE. COOKE, King-street, Southsea. Wanted, a Double Crank Axle with wheel, for common lathe.-MITCHELL, Chalk Hill, Bushey, Herts. -horse Gas-Engine, new. Exchange anything useful. Particulars, can be seen working.-A. KING, 78, Jamesstreet, Sheerness, Kent. 3 bellows, in exchange for 8-slide ditto, speaking front, bellows.-F Organ Soundboard wanted, with four or five slides and. CARTER, Newfields, Billingshurst. Wanted, -plate Instantograph or Meritoire Camera set (1890). Exchange Vertical Engine, nearly finished; suit small boat or lathe.-MARTIN, East-road, West Ham, E. dia. Astronomical Telescope, Refractor, o.g. 4in. Exchange for anything in photography.-W. FREEMAN, 52, Frederick-street, Throston, Hartlepool. Good Magic-Lantern wanted, biunial or pair dissolvers preferred. Good exchange.-WM. TAYLOR, Market-place, Driffield Lathe, 6in. back-geared, gap bed, compound sliderest, &c., in exchange for good Safety Bicycle or offers to value £10. -Apply, letter only, B. L., Fenchurch House, Fenchurch-street, E.C. Microscopic Slides, wanted. Exchange "Whitaker's ALMANAC," from the commencement in 1870 to 1885 inclusive, sixteen years, paper covers, in good order. Address-A. D. MORAT, 13, York-street, Liverpool. "English Mechanic." Vols. XXXII., XXXIV., XXXVI., XXXIX. to XLVI., XLIX. to LII.; Iron Camera Stand, all adjustments; Model Vertical Engine; Brass Model Locomotive. What offers?-MOODY, 28, Elsden-road, Bruce-grove, Tottenham. Gentleman's Watch, value £1. Exchange good Bull Wanted, 3in centre Bench Lathe. Good exchange.- Wanted, Safety or Folding Tricycle in good order. "Saunier's Treatise on Horology," with coloured folding plates, bound half-calf; "Saunier's Watchmaker's Handbook," Swiss Mandrel, 5in. face-plate, with slide-rest, uprighting tool, extra set of dogs and cutters, is new condition. Exchange offers invited.-MCELROY, Derby-road, Heaton Chapel. Wanted, Flywheel, about 18in., with four or five speeds, and handles, cost 25s. Will exchange for 4-volt Pocket Accumulator Diamond Oil Filter. new, will clean three quarts New Vertical Engine, 1 bore, weighs cwt., New Horizontal Boiler, in. plate, 30 by 16 in- Wanted, Safety Bicycle. Exchange ordinary Launch and HORIZONTAL PATTERNS, two-horse, and cash.-J. P. COCKBURN, 23, West-street, Berwick-on-Tweed. Small Treadle Lathe, in good condition. Exchange furniture offers. Also hen Canary and breeding cage, and small cage. Offers.-Below. "History of England," by Murdock. London, cost £5. Exchange Grandfather's Clock, Air Gun, or offers.-Below Lady's Workbox, inlaid brass and pearl, cost 40s. Exchange pet Monkey, small Rifle, or offers.-P. MUCKLE, 2, Bowles place, Whetstone, N. Wanted, Lathe or Heads, &c. Exchange OrchesTRIONETTE, 17 tunes, cost £3. Wanted, Lathe Wheel, 80lb. Exchange handsome Cockatiel, in cage.-BERNHARD, Colborne Ho, Dartmouth. Wanted, "Amateur Work,' Vols. I. and II., old series. Exchange Books, &c. What offers for handsome male Cockatiel and cage ?-BERNHARD, Colborne Ho, Dartmouth. Kangaroo Bicycle, double balls all over, splendid Handsome Vertical Boiler, 6in. by 10in., and Splendid and 1-plate mahogany Bellow Camera, nearly new, coat 52s. 6d. Will exchange for small Lathe, value 408.-3, ALLAN SANDERSON, Rosedale, Pickering. Dynamo wanted (Plating) in exchange for complete LIGHTING OUTFIT, Dynamo, &c., and eight lamps, value about £10.— WOOLIDGE, Brockley, S.E. Safety, Ivel pattern, hollow throughout, plated parts, tangent spokes, cradle-spring saddle, Bown's bearings, ball rat-trap pedals, all accessories. Exchange Screw-cutting Lathe, about 4in. -NIPHLOG, 6, Station-terrace, Plumstead. Boiler wanted, suitable for small launch, about 1H.P. Would exchange good 54in. BICYCLE or cash -Full particulars to W. BAMES, 16, Caroline-buildings, Bath. The Universal Amateur Exchange offers largest assortment of Electric, Optical, Mechanical, Photographic, and Miscellaneous Appliances. Best value, cash or goods, given.CAPLATZI, Chenies-street, W.C. Large Binocular Microscope, value £20. Wanted, first-class Photo and Mechanical Magic Lantern Slides.-Address, M. R. H. D., 11, Butcher-row, Shrewsbury. Electro-Plating Plant. Exchange for anything useful, or part cash, to the value £4 108.-9TONEHAN, 6, Liverpoolroad, Canning Town, E. One-man Gas-Engine, seen working. Wanted, Screw Cutter, Shaper, or offers in machinery.-R. W., 17, Pitlakebridge, Croydon. Wanted, Safety Bicycle. Exchange splendid Model A 5in. Lathe, with 50 chucks, one amateur chuck, A £20 Mineral Water Machine for £5, a £10 &c., complete. Offers. Street Coil for £4, a £40 Steamer for £8 value.-CAPLATZI. Complete Stand, Wires and Fittings for a powerful Coil, 10.; the Lenses for a 20s. telescope, 88.; for Magic Lantern, 58. value.-CAPLATZI. 4in. Spark Wimshurst Machine, parts complete, for 10s: 10 candle-power Dynamo Castings and Wires, for 10s. value. A library of 1,000 Educational and Scientific WORKS, quantity of Musical Instruments, to be exchanged immediately for any Scientific Apparatus-CAPLATZI, Chenies-street. Exchange Brass Locomotive for Vertical Brass Boiler, about Sin. by 4in, with fittings.-A. BERAT, 17, Blagrave Villa, Friar-street, Reading. Wanted, a 2-cylinder semi-portable Engine and Boiler combined, 4 or 6H.P., under type. Can give in exchange 2H.P. Otto GAS ENGINE, Atmospheric, 12in. Brake, Lathe, and Saw Bench, with sawa, &c.-F. BAMFORD, Lister-place, Wardleworth, Rochdale. I have a good Tricycle to exchange, with ball bearWhat offers in Lathe from 4in. to 5in. centre, with backgear?-Below. ings to all parts except pedals, front steering and double driving. I have a miniature Bellows Camera, 2 by 3, with three double dark slides, in case complete, with dry plates, wax dishes, chemicals, and a lot of other things, together with tripod stand. What offers in sets of small Twist Drills up to jin, &c.?-ELI Drsox, Thomas street, Lindley, Huddersfield. COLUMN. Advertisements are inserted in this column at the rate of 6d. for the first 16 words, and 6d. for every succeeding 8 words. New Illustrated Price List of Screws, Bolts and NUTS for Model Work, drawn to actual sise, sent on receipt of stamp. -MORRIS COHEN, 132, Kirkgate, Leeds. Millar's Electric Depot, 14, Deansgate, ManCatalogues 3d. chester.-Best of everything electrical. Large steck. Low prices. meter, in brass only.-CLEGG, Belinda-street, Hunslet, Leeds. Wheel-cutting and Dividing to 12 inches dis Tam o' Shanter Hones.-Fine, medium, sharp size, post free. Try these famous hones.-TAM O' SHANTER HONE CO. qualities-razor, knife, joiner's-ls. 3d., la. 6d., and 2., according to Dalmore, Stair, Ayrshire. square. sight and Spectacles." Patent lock-joint Copper Bit, several soldering irons in one, 38.-Below. By-pass Economic Gas-Tap for workshops, &c, saves cost in one week; 1s. 3d., free.-Below. Spindles on Anti-Friction Bearings, for grind stones, emery wheels, &c., 46. 6d.-BAUGHAN and Co., Charlbury Oxfordshire. Cure for Baldness. Pure spirits of petroleum, 18. pint san, free.-JONES and Co., Viaduct-street, E. Seltzogenes, Gasogenes, and Siphons Repaired.8. B. PEARSON, Siphon and Gasogene Manufacturer, Lawrencestreet, Sunderland. Piles!-Agonising cases cured.-Palmer's "Indian Ointment," 18jd.; three, 2s. 6d. (internal remedies included).-Chapelterrace, West Auckland, Durham. ness. Grateful Testimonial.-"Was dying from weak- to amateurs. ham, gives theory of aetion and many experiments. Post free, 134.— "The Wimshurst Machine," by W. P. MendKING, MENDHAM, and Co. Lucas and Davies have Removed, owing to ncrease of business, to larger premises.-67, Farringdon-road, E.C. Model Engines.-Lucas and Davies' Enlarged and Illustrated Catalogue, castings, Anished parts, &c., post free, id. The Above contains all information, and is illustrated from photographs of the finished engines. Two New Features introduced.-Triple-expansion Engines and Bent Steel Crankshafts are entirely original novelties. Photos. of these Triple Expansion Engines can de had, price 6d., post free 7 stamps. The Designs are all new, and are not copies of the stereotyped models of other arms. of engines, and quality of castings. Models of every description repaired and put in working order. Lucas and Davies, Mechanical and Scientifle Model Makers, 67, Farringdon-road. Edward Hines, Griffia Works, Norwich. Amateurs' Lathes and Tools of every description. Catalogues, post free, 6d. Mackies, Limited, Sole Manufacturers of Mackie's Patent Spring Pulleys, 70,000 in use, Berks Iron Works, Reading. 3 The English Mechanic Fig. 16, a float for horn, &c.; Fig. 17, a grindstone driven by foot; Fig. 18, the spindle of a grindstone; Fig. 19, the crank AND WORLD OF SCIENCE AND ART. of grindstone and the crank-pin; Fig. 20, a bearing of lignum vitæ for grindstone spindle; Fig. 21, piece of grindstone treadle, showing method of pivoting it to stand; Fig: 22, an arrangement of oilstone slips having variously-shaped edges. FRIDAY, APRIL 10, 1891. LATHEWORK FOR AMATEURS.-II. THE Further descriptions of these different tools will not be added. They are not solely confined to use with the lathe; they belong to other mechanical arts, principally to joinery, The illustrations show their forms, and their and are thus beyond the scope of this treatise. uses will be described later on. The float, Fig. 15, perhaps needs a few words of description. It is a kind of file, the same length as a wood rasp, cut on its breadth with teeth very close together. This tool is used by workers in lead and other soft metals to round off fins and solder seams; and also by workers in horn for roughing out this material. The Grindstone. HE choice of locality for a workshop is not such an easy or unimportant matter as at first sight one would be led to suppose. The preservation of tools and machinerymatters of the first consideration-require certain conditions not always found. The turner's workshop should be thoroughly well lighted, and should have several windows. Its best position is on the ground level, with a northern aspect. Excesses of heat and of cold are both injurious; tools and work should be sheltered from the sun's rays, and in cold and damp weather a small fire should be lighted. The northern aspect insures a more equally constant daylight: the direct After acquiring such tools as enumerated rays of the sunlight falling but for a short above, the turner should consider as to the time, and then obliquely, the woods and means of keeping them always ready for the work are not exposed to so much risk of use-that is, properly ground and sharp. He splitting or warping-mishaps which are should then set up the necessary appliances. very necessary to guard against. A work-First, a grindstone, which must be neither shop situated in too hard nor too soft, of a fine and even grain, an upper story has many inconveniences. It is about 2 in. thick, and 18in. to 2ft. in diameter. difficult to set up a forge there, and further, the noise of the anvil, the vibrations of the lathes and grindstones, the strokes of the hatchet, the mallet, and the hammer, the screeching of the saw and the file, are all likely to give great annoyance to people inhabiting the lower stories. very When the bearings are quite round, a square part is made to take the crank, and beyond this square part a shank is left which may be turned with the hook-tool, though it need not be perfectly true and straight. This shank, shown on the extreme right of Fig. 18, is to be threaded, to receive a nut which fixes the crank. Sometimes a projecting ridge is left about the middle of one of the collars, see Fig. 18, which is buried in the bearing, and so stops longitudinal motion. Formlerly the projecting ridge was left halfround; but this is an erroneous form, and defectiveness of this shape without further contemplation of the work will show the explanation. When the spindle has been turned, the crank, illustrated at Fig. 19, is to be forged. This is ordinarily made C shaped, but for elegance only. It has been proved that this shape adds nothing to the power of the lever, which acts only according to the length of its radius. Thus a straight crank, though less graceful, would be equally effective. This crank has holes at its two ends, and one of these is squared to fit on the square part of the spindle. The crank-pin, made in the form of a screw, is fitted in the other hole, and it may be riveted either with or without screwing. To facilitate the comprehension of this description, consult the illustrations in Figs. 18 and 19. When the spindle has been made, the grindstone is to be mounted upon it. With this object the stone is placed upon the joiner's bench, so that its central hole is over one of the holdfast holes. Then the spindle is put in the hole and jammed with wooden wedges and tested for uprightness on its four faces with a square. This done, the spindle is fixed with the wedges, which are carefully driven so as not to disturb the uprightness of the spindle. Some lead is next melted in an iron ladle; this must not be In giving these dimensions they are not insisted upon absolutely, but indicate approximate sizes, which may be increased or diminished according to individual judgment or particular requirements. Next should be procured a frame, and a trough to contain water, so that the grindstone may be imThe running mandrel lathe is, as a rule, mersed in it. Some people use a grindstone placed as near as possible to a window, and dry, but this proceeding has two drawbacks: in such a manner that daylight may come the first is that the fine dust of the stone from the right of the turner. The dead-floats about in the air, and gets into the centre lathe and the engine-turning lathe lungs through the nose and mouth. This made too hot, which may be tested by should be arranged so as to receive the light dangerous to health. The second drawback gritty dust is very annoying, and even plunging a piece of paper into the molten on the face. A workshop should always be in good order and tidy, and these two qualities contribute much towards the preservation of the tools and the perfection of the work. It is, however, certain that this precept is seldom practised, and too often tools are left about pell-mell. Through such carelessness, much time is lost, and tools are prematurely worn out. Amateurs and workmen, too, are earnestly recommended to adopt the habit of systematically rearranging their tools when they cease working. Tools for Preparing Materials for Turning. be placed upon the lathe, whether this be the stone, which ultimately destroys the metal, and if it is burned the lead is too hot merely scorched. Then the molten lead is it must be allowed to cool until the paper is poured into the hollow around the spindle; must be turned over and the lead poured into when this is done on one side, the grindstone the hollow on the other side. This method of fixing the spindle is better than that of be taken to see that it is not split or scaled. of working, and finally falls out. When this When a grindstone is bought, care should using plaster, which cracks under the shocks These defects are sometimes concealed with happens the spindle must be replaced true plaster covered with grit. The stone should for a second time, and the operation is not be sounded or rung by striking on its edges an easy one; the stone will most surely run with an iron tool. Then see that the axle-out of true. hole is really in the centre; this may be With the grindstone properly mounted on measured by a piece of string. When this hole is large and round it is an indication that the stone has been used before, and has been re-dressed. Largeness of the hole is a serious defect, because it is the cause of much difficulty which will be experienced later on when mounting the stone on its axle. A its spindle, the next step is to place this spindle to run on its bearings. The frame to receive the stone having been made, either after the style illustrated by Fig. 17, or according to any other, the positions are marked for the lignum-vitae bearings, one of which is illustrated at Fig. 20, shallow When the grindstone has been procured, mortices are made to receive the lignum-vita attention must be given to the spindle or blocks which are bedded into them. axle, illustrated at Fig. 18, which is to sup- couple of wood screws passing through the The principal of these are illustrated on port it. Select a piece of iron bar about in. block, one on each side of the V-notch, and the accompanying plate, and are as follows: square, more or less, according to the weight screwing into the frame, will secure each Fig. 1, a joiner's bench fitted with a stop; of the stone. File off the angles where the bearing. Though with a heavy stone these Fig. 2, a plain holdfast; Fig. 3, a holdfast bearings will come; then centre the ends as screws are not necessary, or with the screws, with clamping screw; Fig. 4, an ordinary and turn with a round-nosed hooked tool; shown in Fig. 20, the upper parts of the truly as possible, mount the bar on the lathe, the mortised recesses are superfluous. As frame saw for wood; Fig. 5, a ripping saw then smooth with a flat tool. In giving lignum vitae blocks have V-shaped notches in frame; Fig. 6, a turning saw; Fig. 7, a these details, the beginner is not counselled cut in them, and it is in this V that the frame saw for metal, called a hack saw; Fig. 8, a double-bevel hatchet for roughing iron as a commencement; but they are given will have been previously adjusted so that to take a hook-tool and set to work turning spindle will rest. The width of these bearings woods; Fig. 9, a turner's hatchet, or side hatchet with single bevel; Fig. 10, a drawing so that he may know how to make his own their thickness shall be neither more nor knife; Fig. 11, a paring knife, used on a grindstone-axle when his hand has become less than the length of the collars turned block by placing the hooked end through the practised. Also so that when he is having on the spindle. Exact fitting here will ring of an eye-bolt; Fig. 12, a joiner's trying having the bearings of the spindle turned, which motion should not exist. his grindstone mounted he may insist on prevent any lateral motion of the grindstone, plane; Fig. 13, a smoothing plane; Fig. 14, and not permit them to be filed. A careless projecting ridge has been made on one of the a rebate plane; Fig. 15, a rasp for wood; workman might make a defective spindle, spindle collars, exactness in the fit of the "Lathework for Amateurs" is mainly adapted from and it is useful for the amateur to know the bearings lengthways is not necessary. "L'Art du Tourneur," by Desormeaux; but deletions and additions are numerous and extensive. The illustrations proper method, so that he may guard against are new, and the treatise entirely remodelled. being deceived. VOL. LIII.-No. 1859. When a When the spindle is placed in position, the bearings should be covered by strips of make a hole through the leg of the grindstone-frame near the foot, to allow a bolt to pass through. Then fix a wedge-shaped piece of wood under the treadle-board, as shown at Fig. 21, and bore a hole through it as illustrated. An iron coach-bolt passed through both these holes will hold the treadle nicely when the nut is firmly screwed on. a matter of fancy-6in or 7in. diameter is It is made of flat steel wire of the section Fig 91. When all this has been done the bearings are oiled, and before putting water into the trough, the grindstone is set revolving, to be assured that it is perfectly round and has no untrue parts. If either of these defects exists, they are to be corrected. The grindstone is set turning towards the person working it, and taking an old file, having its end broken off, and using the crosspiece turns, then hardened, tempered, and blued. of the frame as a rest for the file, this is used It is brazed into a small brass block lin. by after the manner of a turning-tool, and grooves are made in the stone near its two in., and the width of the gong wire. These grooves are made deep Nothing will do except brazing in this case, enough to show all round the circumfer- and the operation must, of course, perence, and thus determine the quantity of superabundant material which is to be cut off, and the positions of it. corners. If much material is to be removed, the grindstone is taken out of its bearings, and by means of an old chisel and a hammer the material is chipped away in small pieces. This is called hacking, and it may be done by means of a hatchet or an adze. The stone is then replaced in its frame, and, always turning it towards the operator, the truing is finished by means of an old plane-iron. Some workmen maintain that iron is best for this truing process; others assert that steel is preferable. A plane-iron, which is made of iron and steel, should suit both parties. If there is but little to be taken off, the stone may be at once turned true with the old plane-iron last spoken of. In any case, this operation should be done with the stone dry. When the grindstone is quite true and straight upon its edge, pour some water in the trough and arrange a kind of shield made of wood or of cloth to prevent the water splashing over the operator when grinding tools. These may then be sharpened in the manner to be described later on. formed before it is hardened. be To make a gong successfully requires a Fig. 92 is a general view of the gong and B A Fig 92. Such is the most usual method of mounting a grindstone of medium size. Stones to be turned by hand do not entail so much work, but these are not so useful. This treatise need not be extended by describing the thousand and one ways of mounting grindstones. The most perfect and the most generally used has been explained. Later on will be described how to mount a grindstone of medium size, using as a driver the lathe fly-wheel. The cabinets of amateurs sometimes contain small grindstones, mounted horizontally on a table, making twenty, and sometimes even thirty, turns for each stroke of the foot. These increased speeds are obtained by the aid of toothed standard, together with the hammer. The wheels and pinions hidden beneath the brass block already referred to is screwed, table. These grindstones are not recom- by means of two good screws, to the standard mended for use for grinding tools, but they A. This standard is a massive support fixed are treated upon in the article on the polishing at the lower end to the sounding-board, which forms the bottom of the clock-case. Its exact height will be governed somewhat by the build of the case, but should be about 15in. to 16in. over all. The top is formed of brass, and measures 4in. high, 24in. wide, and full ĝin. thick. Into this the stem (of steel wire, in. diameter) is tightly screwed. The lower end of the stem is provided with a brass shoulder-piece, B, which can be adjusted to any height within certain limits, and a nut and washer-these latter secure it to the sounding-board. The sounding-board machine. The drawing, Fig. 22, gives an idea of a grinding arrangement consisting of slips of oilstone. It is very useful, and does not cost much; a piece of board has grooves made in one of its sides, and a slip of stone is fixed in groove by means of a wooden wedge; all of this is made clear by inspecting the illustration. (To be continued.) a and dimensions. In the bottom edge a dovetail slot is cut, into which is fitted a piece of hard leather. The head is made to slide along the stem, and is set by means of a screw at the top. The object of this sliding is to adjust it so as to strike the gong at the particular point which brings out the full tone. This point, as far as I am aware, can only be determined by trial. There may be some way of calculating it; but I leave that to soundtheorists, and perhaps one of them will 3/4 in Frg. 93 enlighten us on the point. The hammer falls The gong must be fixed far enough from the back plate to give the pendulum perfect freedom, and the hammer stem must be bent outwards accordingly. 45.-The Pendulum. The length of our pendulum is 12.3in. nearly, or a trifle over 124in. The length is measured from the point of suspension to the "centre of oscillation,' ," which is a rather difficult matter to determine accurately, but may be roughly taken as a point a little lower than the centre of the "bob." The length is calculated as follows:-Multiply together the numbers of the centre, third, and 'scape wheels. Divide the product by the numbers of third and 'scape pinions, and by the number 30. This will give the number of vibrations required per minute. Thus84 × 78 x 24 = 26,208 (7 x 7 x 30): = 107. 26,208 We therefore want 107 vibrations per minute. 375.4 107 = 3.508 3.508 12.257 = the length required. In all these calculations 375'4 is a constant, whatever the number of vibrations may be. The rule is: Divide 3754 by the number of vibrations per minute, and square the result, which gives the required length in inches. Now to make the pendulum: The usual way is to have a brass rod and lead bob, which is usually covered with thin brass. The bob slides easily over the rod, and is raised or lowered by means of a thumbscrew underneath. The rod can be in. wide by in. The lower end is tapered to form a screw. The thumbscrew itself should have plenty of depth, to bite well, and be not less than in. diam. The "bob" must weigh at least 1lb., and may with advantage be 14lb., if the workmanship throughout the clock is good. Lead bobs, brass-covered, can be bought, but readers can have them cast in solid brass if they prefer to do so. A compensation pendulum of this length would be very little good. The top of the rod has a fine sawcut, into which is inserted a flat steel suspension spring; a piece of wide watch-spring lin. long answers very well. It is secured in passed through the whole. To this spring a small block of The suspension-spring slot in the back of bridge and the brass block rests ut in the bridge. Fig. 94 The square formed on hammer arbor. The head shows top of ted up'um-rod, and method of exact size of the gong, as with the bells, is is of brass, ĝin. thick-Fig. 93 shows shape suspensiizontal stra HOW TO CONSTRUCT A QUARTER must be of pine, without any flaws, and sup CHIMING CLOCK.-XI. 44.-The Hour Gong, &c. FTER the bells, we naturally come to the gong and hammer, though, as a AF ported only at the edges. It must not be by a The hammer consists of a brass wir matter of fact, the fixing of the gong must screwed into a boss which fits tightly on be left till the clock is fitted in its case. |