nets, were turned on the lathe. Turning is performed by the lathe, of which there are various kinds, and several instruments, as gouges, chisels, drills, formers, screw tales, used for cutting what is to be turned into its proper form as the lathe turns round. The operation differs very essentially from most others, in the circumstance that the matter to be operated upon is put in motion by the machine, and is wrought by means of edged tools presented to it, and held fast; whilst, in most others, the work is fixed, and the tool put in motion by the workman. In turning, the work is caused to revolve upon a stationary straight line, as an axis, while an edge tool, set steady to the outside of the substance in a circumvolution thereof, cuts off all the parts which lie farther off the axis, and makes the outside of that substance concentric to the axis. In this case any section of the work, made perpendicularly to the axis, will be of a circular figure; but there are methods of turning ellipses, and various other curves, which are known by the name of engine turning. When compared with many other mechanical operations, the art of turning may be considered as perfect in the accuracy and expedition of the work, which is produced, and that independently of any extraordinary skill or dexterity of the workman: the lathe is therefore resorted to by mechanics to perform every work it is capable of, and these are so numerous as to demand, in preference to other mechanic operations, a minute detail. Lathes are made in a great variety of forms, and put in motion by different means; they are called centre lathes where the work is supported at both ends; mandrel, spindle, or chuck lathes when the work is fixed at the projecting extremity of a spindle. From different methods of putting them in motion, they are called pole lathes, and hand wheel-lathes, or foot wheellathes; for very powerful works they are turned by horses, steam engines, or water mills. The lathes used by wood turners are generally made of wood, in a simple form, and are called bedlathes, the same kind will serve for turning iron, or steel, but the best work in metal is always done in iron lathes, which are usually made with a triangular bar, and are called bar-lathes. Small ones, for the use of watch-makers, are called turnbenches, and turns, but there is in fact no proper distinction between these and the centre-lathes, except in regard to size, and that they are made of iron instead of wood. The pole-lathe is now so little used as to make a particular description unnecessary, we may, therefore, proceed at once to that arrangement in which a bar forms the connecting link between the centres. The triangle bar lathe is shown at fig. 1, plate TURNING. Fig. 2 is an end view of that part which is above the bench or frame. A A represents the upper surface of a very thick and solid mahogany bench, upon which the whole is fixed, and the foot-wheel is situated beneath it, if convenient, to apply it in this manner; the puppets, and other parts of the lathe, are all fitted upon a strong triangular bar G, made of cast iron, planed and ground perfectly straight and true; it is supported by standard a b and c, fixed to the bench by screws, as shown in the figure. Upon this bar the puppets H, I, and K, are fitted with the most perfect accuracy, and H, which is called the back puppet, can be fastened upon any part of the bar, by a screw e beneath it; the other two puppets are likewise furnished with screws beneath, to fasten the bar to them; but these two are supported independently of the bar, being connected together by a thick plate of metal D, screwed to their lower surfaces, and this is fixed on the standards a and b, so as to form an insulated frame, a K bI and D, containing the mandril or spindle L. The puppet K has a steel pivot with a hole in the end to receive the pointed end of the mandril L, a screw f is placed behind to force it up, and another at the top, to fasten it when adjusted, so that the neck of the mandril will exactly fit, without shake, into the steel collar which is fixed in the upper end of the puppet I. The back puppet H has a hole bored through it, exactly in the line of the spindle, to receive a cylindrical steel pin n, which has a sharp conical point to support the end of a long piece of work: a screw m is placed behind to force it up and keep the work always tight, and a screw z fastens the pin in its place. The rest of the lathe is thus made:-A brass piece o o, called the saddle, is fitted upon the sides of the bar; upon this a steel slider P is fixed, having a tube Ÿ to receive the shank of the rest T, with a screw to fasten it at any height; the slider p has a dove-tailed groove in its lower surface for the reception of dove-tails, formed at the upper ends of two steel bars; the two bars are united by a horizontal piece beneath the bar, the whole being made of one piece, bent like a staple or fork, and its two arms, 1 and 2, fitted in mortises cut through the saddle; by this means, a single screw, 4, tapped through the horizontal piece, and the point pressing on the under side of the bar, will fasten the rest, drawing the slider p down upon the saddle, by the two dovetails, and, at the same time, drawing the saddle down fast upon the bar. The mandril L is made hollow nearly through, and, at the open end, is cut with a female screw, for the reception of male screws upon the various chucks, which fit to the lathe. This is a better method than the common way of a male screw on the mandril, because of the care with which the male screws for the chucks can be cut in brass, and the convenience of putting long work up the hollow mandril. This lathe has all the parts of the wooden lathe, but is far more convenient, because of the ease with which the puppet and rest can be shifted and fixed by only the finger and thumb, and yet the whole is much stronger, the puppets being so low from the bar; and another advantage is the accuracy with which the back centre-point n always keeps in a line with the mandril, which is indispensable for good turning; also the puppets being so slender, the operator has better access to the work than between clumsy wooden puppets, and which are not so strong as the small metal ones. The process of turning may now be briefly examined. A piece of wood being chosen is by means of the saw, axe, and chisel, reduced to a cylindrical form, and by the rasp or draw knife it is made tolerably correct; a chuck is then selected which has a hole in it nearly the size of the piece of wood. The diameter of this being taken in the outside end of the callipers, the chuck is screwed into the mandril, the rest fixed in a convenient position, and the hole in the chuck turned out by the right side tool, to the size measured by the inside end of the callipers. The hole should be rather conical, and the wood, being rasped to the same figure, is driven in fast by a hammer. By turning the mandril slowly round, it will be seen if the wood is fixed straight in a line with it, and if not a blow or two of the hammer properly directed will rectify it. The rest is set with its edge parallel to the outside of the piece of wood, and it is roughly turned by the gouge to a cylinder. To do this the gouge is held very firmly down upon the rest, taking its handle in the right hand and placing the fingers of the left in the hollow part near the work; the edge is presented to the work in such a direction that the tool is nearly a tangent to the surface of the cylinder. In this state it cuts best, and must be held very firmly to prevent the edge being depressed by the motion of the work; for, if it does, it will take hold too deep and tear the work. This tool is applied first to one end of the work and gradually advanced to the other, turning the work true all the way, and reducing it till the callipers determine it to be near the intended diameter. The chisel is now employed to smooth the cylinder; its handle is held in the right hand, whilst the left grasps the blade and keeps it steady upon the rest, holding the edge a little inclined over the work, so that one side of the flat part of the blade lays on the rest, and the other side is elevated that the plane of the blade, and consequently the edge, is not horizontal but inclined thereto; so that one corner of the edge of the chisel is elevated upon the work, then the bottom or near the bottom of the edge of the chisel cu's away a shaving off the work, and this is the only way in which it will cut; for, if the edge of the chisel is held parallel to the axis of the cylinder, it acts across the length of the grain of the wood, scraping away the fibres one by one without cutting, and leaves the surface very rough. Some chisels have their edges inclined, for the convenience of holding them properly before the work. The work, being thus reduced to a rough cylinder, must have its end made exactly flat; to do this the thin side of the chisel is laid upon the rest, so that the plane of the edge may stand exactly upright; the hand is depressed that the lower corner of the edge will rise against the work and cut a deep circle into it near the end, and being steadily advanced cuts to the centre, separating a thin round chip and leaving the end quite flat. The cutting corner of the chisel must be directed exactly perpendicular to the length of the work in advancing it, otherwise the end will be either concave or convex, and care must be taken to keep the plane of the edge truly upright, and hold it very fine, for there is danger of the work drawing the chisel into the end of it with a deep spiral cut like a screw, and tearing it out of the chuck. The gouge and chisel are only used for turning soft wood, such as alder, sallow, beech, &c.; but if the material to be turned be hard wood, as ebony, lignum vitæ, or ivory, bone, &c., the same mode of chucking is employed, but the tools and the manner of holding them is different. The hard wood tools are made with a stronger and more obtuse edge, for a fine keen edge would be carried away by the work when hard. In turning soft wood, as before mentioned, the edge of the chisel is at a considerable distance from the rest, and inclined upwards at such an angle as would cut off the greatest chip. But in hard wood the rest is raised nearly to a level with the axis, so that the upper flat surface of the tool points to the centre of the work to be turned; it is to be held down as firmly as possible to the rest, and advanced to the work at intervals whenever it ceases to cut, by having removed all the projections of the work without the circle it describes by its revolution. The tools used for turning brass, or cast iron, are made from bars of steel; for, as those who turn metal are usually general mechanics, they make the tools themselves, and adapted for any particular occasion they require; the principal tools are gravers, square tools, pointed tools, round tools, and hooks. The graver is made like those used by engravers, from a square steel bar, cut off by an oblique plane at the end, which makes a lozenge or diamond face, and produces two inclined edges at two of the flat sides of the bar; these two are inclined opposite ways, so that the graver serves either for left or right-hand work by only turning it one quarter round to bring up another side. The point formed by the acute angle in which the two inclined edges meet is best adapted for cutting of any other form, and is exceedingly strong; the flat sides give it an excellent bearing upon the rest; another convenience of the graver is the ease with which it is sharpened, which is an object in turning hard metal, when it is so frequently necessary; it only requires to be held on the grind-stone in the proper angle, to grind the diamond face away, and thus make sharp edges with the two flat sides. Gravers, and all tools for metal, are hardened and tempered to a light straw color, so as to leave them very hard; cast steel is the best material. The graver is used to rough the work, its point being used to cut grooves all over the surface till it is true, and then the welved edge of the graver, or else a square or round tool, makes it smooth and a proper figure. It is necessary in beginning to turn with a small sharp point; for the resistance to any kind of edge would, in beginning, be so great as to tear every thing in pieces. Square tools are made like a narrow chisel, except that they are very thick, and the angle of the edge very obtuse; the upper surface, which is flat, is, in turning, made to point to the centre of the work. Round tools are like the former, except that the edges are made round for forming hollow mouldings, &c. The pointed tool has two inclined edges forming a point which cut grooves in any piece of work; or its edges may be used to turn shoulders either right or left. Drills of various sizes to bore holes in chuck work; they are fixed in handles. Right and left side tools, such as before described. Heel tools are used for turning wrought iron, steel, or copper; they are made with edges of all the shapes above-mentioned, but the end where the edge is formed is bent, so that when it is presented to the work, in its proper direction, the handle is inclined upwards, in such a position, that the end of it will lay on the turner's shoulder, and he holds it down firm with both his hands, the heel of the tool being supported on the rest. The metals above-mentioned are of a fibrous texture, and turn away in a connected shaving, the tools are therefore presented in the direction of a tangent to the work, the same as for soft wood; but as the drift of the work would force the tool endways, if held in the same manner as the chisel, it is necessary to have a heel, or angle, which is placed immediately upon the rest, then the long handle serves to guide and fix it, and by elevating the end the edge cuts deeper. Cast iron is turned by hook tools; their edges are formed in various ways, but very obtuse, being nearly a right angle: "in turning they are held in such a position that a line bisecting the angle of the edge is made to point nearly to the centre; but as the work is usually large, and the metal very hard, some contrivance is requisite to keep the tool up to the work, they are therefore made with a hook which has the edge at the end of it; the hook part is laid over the rest, in the same manner as a crow bar is used to draw out a spike or nail, and then, by raising or depressing the end of the handle, the edge is caused to approach or recede from the work with any required force, by only a moderate power applied at the end of the long handle; cannons, and other heavy cast iron work, are turned in this manner. The eccentric chuck and slide-rest are very essential parts of a good turning lathe, and, as both these instruments have been materially improved by Mr. Ibbertson, we cannot do better than furnish our readers with an account of that gentleman's apparatus as constructed by Messrs. Holtzapfel and Deyerlein. Fig. 3, plate TURNING, represents the chuck in its most simple form, but which is abundantly sufficient to show its nature and construction, and by means of which we may produce any of the eccentric figures in this work. Fig. 1 is a front view, and fig. 4 is a side view: the letters in each figure refer to the same parts in each view, we shall, therefore, rather more minutely describe fig. 3. AAA is a plate of brass, or metal, of sufficient substance to be firm and solid, on which plate two slides of steel are affixed by the screws B, B, B, B ; the holes which admit the screws are made a little oval, to enable the slides to move Dearer or further apart if necessary. C, C, C, C, are four pieces of metal firmly fixed to plate A, and having a screw in each which presses on the sides B, B. DD is a plate of metal or brass, sliding between B, B, B, B, in a dove-tail, and must be made to fit very accurately when the slides are parallel to each other, and is moved between the slides by means of a screw I, working in a slit made in the plate A; and which screw regulates the eccentricity, as it moves the plate D either nearer or further from the centre of the chuck. E is a circular plate of metal, whose edge is cut into teeth, and which is capable of being turned round its centre, and is held in any position by the catch G which falls in between the teeth, and is held in its place by a spring K. On the centre of the wheel E, is affixed a screw F, as shown more plainly in fig. 4, whose threads correspond with the screw of the mandril of the lathe, for the purpose of fixing any chuck, on which is fastened the substance on which we are working. O, fig. 4, is a solid piece of metal, whicr screws on the lathe, and on which the plate A is fastened (A, fig. 4), by a rim enclosing the plate A, fig. 1, and fixed by screws, or, as sometimes is the case, A and O are in one solid piece. Fig. 5 is a view of the slide rest, looking down on it, and fig. 6 is an elevation; the letters in both figures refer to the same parts in each. Thus, AA represents the bed of the lathe; B, B, are two pieces of brass, or metal, affixed by the screws, as shown in the figure, to a bed of cast iron; C is a plate of iron, sliding between the two pieces B, B, in a dove-tail, having a nut and screw, moved by a handle, as shown at H, by which it is drawn nearer or farther out; D is another piece of metal affixed to C, and at right angles to it, having a groove or channel through it to admit the screw K, which has a nut, to which the piece of metal E is fixed; I, I, are two pieces to fix the tool F, by means of the two screws I,I; on the axis of the handle G is a graduated circular plate, which turns with it, and, being affixed to the screw K, moves the plate E and tool F according to the diameter of the circle required. In fig. 6, L is the stand to which the plate B is affixed, and, by means of the nut N, is raised or depressed at pleasure, between the standard MM in a dove-tail. The whole is kept firm in its place by means of the nut and screw O, underneath the bed of the lathe. We may now illustrate the use and application of the eccentric chuck and slide-rest. Screw the chuck C in the mandril of the lathe, and bring the centre F of the slide DD to correspond to the centre of the plate A; then on the screw F fix whatever you wish to turn, and make the face perfectly level in the common way: then fix your slide-rest firm on the bench of your lathe, by means of the screw O, and elevate A, by means of the nut N, till the point of your tool F shall be of the same height as the centre of the chuck: by means of the handle G, make the centre of your tool correspond to the centre of your work very accurately, and let the plate C be at the end of the plate B, close to the screw H; then, by means of the screws at I, I, fix your tool so that its point shall just touch your work. Your instrument being thus accurately adjusted, you may proceed to the operation of describing any eccentric circle. And here it may be noted that the several screws I, fig. 3, in the eccentric chuck, and those at K and H, are best made with the same tool, and of a determined number of threads to the |