Curiosities.

Figs. 244, 245.

Fig. 246.

Fig. 247.

Fig. 248.

The double eccentric is represented inFig. 248. The part A is the foundation plate, with a projection at the back, tapped to fit the mandrel. B, B, the lower guide bars; K, K, the lower sliding plate. All the above parts are precisely similar to those of the simple eccentric chuck. Upon the face of this lower slide are attached two chamfered guides, C, C, at right angles to the first. They are kept in place by screws passing through oval holes on their faces, and tightened when required by screws, tapped into four little square blocks, D, D. Between these guides slides the upper plate, which carries the screw for chucks, and the dividing wheel as before worked by a tangent screw, G; to either end of which a key is fitted. The leading screws, E and F, which move the two slides, have squared ends projecting both ways, so that the plates can be made to work eccentrically in either direction, which is sometimes an advantage. The chucks do not screw down upon the face of thedivision plate, on account of their projecting parts at the back; and very commonly a round plate, O, somewhat smaller than the wheel and about ¼ in. thick is attached to the face of the latter to raise the work still higher, so that the dividing plate can be readily seen. The more compactly, however, the parts of this chuck are made, and the less the work projects from its face the better; as there will be the less strain upon the central pin, and upon the plates and their guide bars when the tools are applied to the work.

To be able thus to place in the centre of rotation any given point in a piece of work, whatever may be the form of its boundary lines, is of immeasurable advantage, even though the capabilities of this chuck are confined to objects of plane superficies, it being impossible to reach by its means the side of a cylinder, or the surface of a sphere or spheroid. It is evident that any line upon the face of a box, for instance, whether the latter be square, round, octagonal, or of any other form, may be followed with two movements of the slides, combined with the rotatory movement of the dividing wheel. Thus, a border of interlacing circles may be carried round the edge of such a box,Fig. 248; or, a series of such circles forming constantly diminishing octagons, hexagons, squares, &c., may be thus readily executed. Nevertheless, what was said of the simple eccentric chuck, applies with even greater force to the compound eccentric. It is a heavy piece of apparatus, requiring a lathe with substantial poppets and bed; the whole well braced to the floor and wall, to withstand the excessive vibration caused by the revolution of the apparatus. It was, indeed, in view of this and similar appliances that we insisted in our initiatory paper upon the great importance to the workman, of adequate strength and solidity in the various parts of the lathe itself.

InFig. 249, we give a simple specimen of work to be executed by the compound eccentric chuck.

Fig. 249.

Fig. 250.

The compound geometric chuck of Ibbetson, manufactured by Holtzapffel and Co., is a double eccentric considerably improved and of very extensive application. A full description of it is published in a book written by the inventor, in which an immense number of patterns executed by its means is given with detailed directions for their execution. As these patterns are almost essential to a description of the apparatus as exemplifying the working of its several parts, the reader is referred to the book in question, or to a translation of it into French in the supplement to Bergeron's work. To enable the turner to execute patterns on the side of cylindrical pieces a chuck is used called a dome chuck, similar toFig. 250. A rectangular frame of brass, A, carries a sliding plate C, at right angles to it, the latter having a tailpiece which fits accurately between the frame, and is tapped to receive the finely cut leading screw with divided head, B. A nut at the back of the frame clamps the slide in any desired position. Upon the upper face of the latter is a wheel racked on the edge so as to be moved by the tangent screw, E.This wheel, like that of the oval and eccentric chucks, turns on a strong conical central pin, and has a screw attached of the same pitch as that on the mandrel. The chuck is screwed to the mandrel by the projecting flange, F. The work is thus mounted at right angles to its ordinary position.

By this arrangement any point in the side of a cylinder can be brought in contact with a tool fixed in the slide rest, and by means of the graduated screw heads of the latter and of the chuck various devices can be accurately made. This chuck may be used alone or in combination with the eccentric, and the quick revolution of such cumbrous pieces that would be a great drawback to their use is less frequently required, now that the following apparatus has been added to the lathe, and eccentric revolving cutters, with drills and other tools, have taken the place of heavier and more inconvenient apparatus. It is indeed much more convenient in the majority of cases to keep the work itself fixed, and to operate upon it by tools put in rapid motion, because the latter, from their excessive velocity compared with that which can be conveniently given to the material, make better work, and at the same time from their lightness impart no tremor to the lathe while in motion. The cuts thus made are in consequence very clean and smooth, and free from those slight undulations apparent when any vibration takes place in the lathe itself. The different varieties of overhead apparatus have been already described and illustrated, and it only remains to describe more in detail the revolving cutter frame, drills, and other apparatus used therewith.

The following pieces fit into the top of the slide rest in what is called the tool receptacle, and are advanced to the work by means of a lever as already described.Fig. 251is the revolving cutter frame, the spindle of which is put in rapid motion by a cord from the flywheel passing to the small pulley through the medium of the overhead apparatus, as shown in a previous page. For the purpose of cuttingsmallintersecting circles, a forked drill,Fig. 252, or a crank formed drill,253, will suffice, and if these are made to cut deeply the result will be a succession of hemispherical knobs or beads (these must not intersect). A drill likeFig. 254will give a knob raised in steps, and it is plain that by cutting the end of the drill to a section of the required moulding the latter may be rapidly executed. The flat inch long cutters used with the geometrical chucks (when the work revolves instead of the tool) are, of course, made of a variety of forms upon the same principle. Cases of these drills and cutters beautifully finished are sold by all the leading dealers in turning lathes and apparatus. It is essential that these tools be kept very sharp, and that their cutting edges should bepolishedif first-class work is to be done. The difference in the appearance of execution is very evident when the cutter is thus perfect, as every cut bears a high polish, which cannot otherwise be imparted. Nothing can be applied to finish eccentric work except friction with a hard brush, and even this is much better avoided, as rubbing of any kind tends to round edges which should be kept sharp and to obliterate the finer and more delicate lines. It is likewise the best plan to finish with any particular tool all the work to be done by it without removing it from the tool holder for the purpose of sharpening. If, however, this is necessary the following contrivance must be used to insure the precise form which the cutter had at the commencement of the work. This being likewise necessary with respect to the fixed tools for ornamentation, the apparatus requisite in either case will be introduced here, the drawings and description being extracted from Holtzapffel's valuable work already alluded to.

Fig. 251.

Figs. 252, 253, 254.

Fig. 255is arranged for flat tools of various angles, or drills with single joints. A, is the stand of brass, with two turned and hardened steel legs. To this is hinged at G, by a screw joint, the part K, theupper part of which forms a semicircular arc, C. A second arc, B is fixed at one end to the stand A, and passes stiffly through a mortise at the top of K. The latter can be raised, therefore or lowered at pleasure upon this second graduated arc, and clamped at any angle by the screw H. To the lower part of K is pivotted the tool holder, D, the upper part of which is pointed, and screws as an index upon the arc C, showing the angle at which it is placed. This tool holder is clamped by a nut at the back, which fits the end of a screw seen near the point. The figure below shows a tool holder which fits into the projecting parts of D, and serves to hold the small flat tools. Below is a similar holder, used for round-shanked drills. F is one of three flat slabs upon which the tools are to be ground,there being one of iron, one of brass, and one of hard wood with a flat strip of oilstone imbedded in it, flush with its upper surface. The tool and its fittings are generally arranged in a box with three drawers; these contain the slabs of oilstone and metal, with the powders necessary for grinding and polishing. To use this instrument, the point of D is adjusted to the required angle for one side of the point of the tool. (It is shown at 40 deg. in the sketch.) The latter is then placed in the holder, and made to project until, when the angle of the chamfer is adjusted on the arc B, the part A is level, and therefore parallel to the surface of the grinding plate. The whole thus forms a tripod, the third leg of which is formed by the tool itself. The latter is first rubbed on the oilstone with a little oil. It is then finished more perfectly on the brass slab, dressed with oilstone powder and oil. Previous to this the tool is moved one or two degrees more upright by the arc B. A narrow facet is thus ground, having a dull grey polish. The tool is now carefully wiped clean, and polished with crocus and oil upon the slab of iron. If the point of the tool is central, with a chamfer both ways, the point of the tool holder is first adjusted on one limb of the arc and the tool ground, and then the same adjustment made on the opposite limb, so that the other side of the point can be operated upon. Thus tools of any angle and any bevel may be sharpened to a nicety without fear of altering the original form of the point, and this may be done, if necessary, during the process of eccentric turning, although, as before stated, it is better to fix the tools well sharpened at the commencement of the work, and not remove them until atleastone complete set of circles or other patterns have been cut.

Fig. 255.

Figs. 246, 247.

The instrument just described is evidently unsuited for the drills and bead tools which present a concave edge like246A, B, C, enlargedsketches of tools copied from Holtzapffel's work. For these the latter directs to use large or small cones (247) of iron and brass, to be dressed, the first (which is the polisher) with crocus, the second with fine emery and oil, the flat side of the tool being held towards the point of the cone, the bevel towards the thick end. Part of the edge of C must be delicately sharpened by hand, as no guide can be used for the step-like portion of the edge. The cones for sharpening are either mounted in the usual manner, by one or both ends in the mandrel of the lathe, or fitted into the spindle of a small drilling lathe-head, the pulley of which is connected by a catgut band with that of the mandrel of the small lathe-head, being fitted with a tailpiece to fit the rest socket, or otherwise mounted on the lathe-bed. The smaller cones especially require to be driven at a high speed. When larger circles or mouldings are to be cut, these small crank-form drills are no longer available, and are replaced by a very simple, but most effective contrivance called the eccentric cutter, by which any work that is within the scope of the eccentric chuck and fixed tool may be executed with great precision and rapidity. This is represented inFig. 248[20]—a small oblong frame of brass, about two or two-and-a-half inches in length, and half an inch or so in breadth is traversed by a fine screw, prevented from moving endwise by a collar, as in the slide rest (of which, indeed, this is a miniature). A slide, C, with a little tool holder at the top of it, is moved along the frame by the leading screw, the head of the latter being graduated, and also the upper surface of one or both sides of the frame. The projection A, fits into the end of the drill holder, and is secured by a screw. Circles of a diameter equal to B, B" may thus be cut, and their effect varied by placing tools of any form of edge in the tool holder. Such a tool as A, will thus no longer cut a minute circle forming a hemispherical raised knob, but will form a circular moulding, such as that shown in part atFig. 249, except when the tool holder is on the middle of the frame and the tool concentric with the mandrel. The single point tools, however, with single or double bevel, are more commonly used, in this cutter, as mouldingscan be turned as efficiently with hand beading tools, with or without the eccentric chuck, according to their required position. It may here be mentioned that eccentric work should always be cut on wood of one colour, or on ivory, as the veinings of the richer fancy woods, which are so beautiful in other cases, only serve to confuse the tracery made by the eccentric cutter. Of all woods for fancy work with the eccentric chuck or cutter, nothing equals African black wood. It is, however, costly, and only ranges to a diameter of five inches, as great part is unsound. The rind is hard, thick, and white, similar to boxwood. Next to this for such work stands, perhaps, cocus, or cocoa wood, which is not the tree bearing the cocoa nut, the latter being a palm, which is more like cane in texture. One of the most effective patterns to be formed by the eccentric cutter is the shell,Fig. 250, in which one side, or rather one portion of the circles composing it, is very deeply cut, while the opposite part is shallow. This can be simply effected by throwing the sole of the rest out of the level, by placing a thin piece of wood or metal across the lathe bed, so as to tilt up the rest and place it (with the cutter) in an inclined position. The tool will thus begin to cut at one part before it touches the surface elsewhere, and the desired effect will be readily produced. In using the eccentric cutter great rapidity of motion must be given to it, but the tool must be advanced very carefully, or it will be broken. The lever handle is the best to use for the purpose. Akin to the shell pattern are those in which part only of the circles are cut, leaving an effect shown by the border roundFig. 250. This is produced in the same way as the last, being, in fact, a ring of shells in their initiatory stages. This is a very effective snake-like pattern, when fairly and cleanly cut. When the eccentric cutter is used, it must be remembered that the principle of work is not quite the same as with the eccentric chuck. With the latter it wasstated that the size of the circles depends on the slide rest and the position of their centres on the chuck. In the present case the eccentric cutter regulates the sizes, and the screw of the slide rest itself the positions of the centres of the circles, since the part A of the cutter will always be in the centres of the same, and this part is attached to the rest. It will be understood that this remark respecting position of centres only relates to circles lying on the diameter of the work, such asFig. 251, the distance betweenaandbwill be taken from the division plate on the pulley of the lathe. The way to cut the above, for example, will be as follows:—Place the slide rest so that when the cutter tool is in the centre of the frame it shall be concentric with the mandrel. In this position it will only make a dot in the centre of the work. Turn the screw of the cutter frame until you have a radius sufficient for the centre circle. Set the mandrel pulley with the index in No. 360, put in motion the overhead apparatus and cut the circle, move the screw of the slide rest a few turns (thus fixing the centre of the second circle), until you find that the cutter will form the circle cutting the first, and passing through its centre. (Observe, this being the size of the first, the screw of the cutter frame is not turned.) Cut the circle in question, move the mandrel pulley a quarter round, so that the index is in No. 90, and cut another; repeat the process twice more, and 1, 2, 3, 4, will be cut. Theposition of the centresof Nos. 5, 6, 7, 8, will now have to be determined as before, by working the main screw of the slide rest; but, as their size is less than the preceding set, the screw of the cutter frame must likewise be turned to diminish them to the required degree. When by these combined movements their position and size have been determined, they must be cut by the aid of the division plate, in the same manner as the last, and so on, till the whole have been cut. With respect to the ratio in which the circles diminish, and the precise sizes of them, no rule can be given, as thismust depend on the taste of the operator. The sole object in this place is to show theprincipleswhereby these patterns are to be executed. A good deal of care is requisite in practice, and the memory has to be often rather severely tasked. The best plan is always to try a proposed pattern upon boxwood or paper, before risking it upon more valuable material; and, where it can be done, it is well to write down the numbers to be used on the various division plates. A single false cut, it must be remembered, will spoil the whole work, at a great waste of time, loss of material, and annoyance, only to be appreciated by those to whom such an untoward accident may have happened. The drilling apparatus, without the eccentric cutter, but fitted with a round-headed drill, is used for the production of fluted works, such as that shown inFig. 252, A and B. The drill being inserted in the end of the spindle, and its point or end (of any desired form, either round, flat, or pointed) being brought opposite one end of the flute, the lathe is to be put in motion as in ordinary ornamental drilling, the mandrel being, of course, held fast by the index and division plate. At the same time that the drill in rapid motion is brought against the work by the lever handle, the screw of the slide rest is slowly turned, and thus the groove or flute is drilled out by the combination of longitudinal and vertical action. The number of flutes in any given size of cylinder is determined, first by a horizontal sectional plan on paper, and regulated accordingly by help of the division plate and index. In making such an article asFig. 252, it will economise material, whether ivory or blackwood, or a combination of the two, to form it of at least three pieces, making the divisions at C, D. Care should be taken to leave below the bowl, which should be as thin as paper if of ivory, the part C on which the beads are to be drilled. The pedestal can then be screwed into this, and will not penetrate the bottom of the bowl. Ivory may be screwed in an ordinary set of stocks and dies if care is taken not to screw up the latter too quickly. Lard may be used as a lubricant in cutting this material, whether for sawing or drilling. The part with raised mouldings between A and D is ornamented with a vertical or universal cutter, and for greater ease and exactness a template may be used in the slide rest by means of which all the curves of the moulding may be accurately followed by drill or cutter. The minute beads round the edges of the small mouldings are made with two sizes of A,Fig. 246; a little knob is thus formed rising from a hollow. The small knobs used as feet may be rapidly formed by a hand beading tool of semicircular section, similar also to A,Fig. 246. A pin may be left on each, or they may be drilled and attached by small screws of brass wire made on purpose. The following cement will enable the turner to make an ivory bowl for the above ornament so thin as to be transparent; indeed it may be thus made sothin as to bend under the fingers, although such extreme tenuity is not required in the present case.

[20]A newer pattern appears on a later page.

Figs. 248, 249.

Fig. 250.

Fig. 251.

Fig. 252.

Take the finest sifted lampblack and make it into a paste with glue, about as thick in consistency as paint. After turning the ivory tolerably thin, paint this on the inside; let it dry, and repeat the process till sufficient is laid on to form a kind of hollow core, of strength sufficient to support the ivory against the action of the tool.The material may now be thinned and ornamented from the outside. When finished, soak a few minutes in warm water, and then agitate in cold; it will become quite clean as before.

By altering the direction of the motion of the revolving cutter, the several cuts made by it will assume a different character, and the work will present a series of hollows scooped out, so to speak. The cutter,253, being fixed in the tool holder of the top slide, will work vertically only, and produce patterns similar toFig. 254, of the nature of basket work. This is exceedingly effective, and, as it may be cut so deeply as to penetrate the material of hollowed works, the latter may be lined with red or other bright coloured silk or velvet, and a variety of designs thus worked out. It is very necessary in using the vertical cutters to move the tool holder forward very gently, giving it at the same time great rapidity of revolution. Without this it will at once stick fast in the work. The character of the designs may, of course, be infinitely varied by using cutters of different sections, as in the case of work done with fixed tools with the aid of the eccentric chuck. The same cutters will, in fact, serve both purposes.Fig. 255represents a tool similar to the last, butarranged to cut horizontally. With this, fluted work can be done: but it is evident that the cord from the overhead apparatus cannot here be directly applied, owing to the horizontal position of the driving pulley. Additional guide pulleys, therefore, become necessary, and, when these have to be arranged, the apparatus is generally modified, and the universal cutter is used, of which one form is shown inFig. 256, and though it is not so good a pattern as that which is described in a later page, it is nevertheless suited for use with the old pattern of slide rest already delineated. With this the direction of the cuts may be varied at pleasure—they may be perpendicular, horizontal, or radial, and, when the templates before mentioned are added to the slide rest, an infinite variety of devices may be cut upon spherical and curved surfaces, so that the cutter thus modified is fully entitled to its title of "universal." The design,Fig. 258, is entirely the work of revolving cutters and drills used with a template of the required section. It is intended for a lady's workbox, opening with a hinge on the line,a, b, and containing in separate compartments the various articles required. It may be made entirely of ivory, lined with red or blue satin, and the flutesround the body may be cut through to allow the lining to appear. In the latter case, however, if the box is of ivory, black velvet may be used to enhance the contrast, and, as the glossy pile would be outwards, a second lining of any desired colour should be added with the best side inwards. The rings for the handles, as for all similar purposes, can be quickly made with the tool,Fig. 259. A hollow piece of ivory being taken, and turned smooth inside and out, one side of the tool is applied, as in the figure, so as to cut half through the work. It is then removed, and the opposite edge applied to the inside until the ring falls off completely finished. It is then cut through with a thin saw or knife, and inserted in the tailed ring or other projection intended to receive it. Handsome works in ivory should always be kept under glass shades. The universal cutter shown inFig. 256consists of a plate with chamfered edges to fit the tool receptacle of the slide rest, having near each end smallpoppets which support the round rod connecting the pulley bearing piece, A, with the part, E, which carries the tool, F, the latter being attached by a small slot and set screw to a cylinder revolving in E, and having at its upper end the driving wheel, C. At G is a circular piece or wheel racked on the edge, and turned by the tangent screw, G. The hinder poppet is rectangular, and has divisions marked upon it on each side of the angle numbered from the apex. The racked wheel may with advantage be similarly graduated. When the part E is vertical the cutter will be in a position to work horizontally, and the pulley support will be vertical. By turning the tangent screw, both the parts move together; but if desired the pulleys can move independently by unscrewing D and L. The angular poppet may be made semicircular if preferred, the degrees being numbered either way from 0" in the centre. When the tool holder is horizontal, or approaching that position, the nut, D, must be loosened, and the pulleys placed so that the cord will not slip off. They may be dispensed with if the apparatus is to be usedonlyfor vertical cuts (theholder, E, will be horizontal); but if a radial pattern is to be cut, in which the angle is to be constantly varied, the pulley piece must be used and the pulleys re-arranged at D, as required from time to time. There is a somewhat neat and serviceable little apparatus represented inFig. 259A, to take the place of theslide rest and its revolving cutters, and although its powers are limited, much may be done with it. The spindle A, works through brasses in the poppets, B, B, and is put in motion by a cord from the overhead passing over the pulley in the centre. This spindle, which holds the crank-formed and other drills in a socket at one end, moves freely through the bearings endwise, and is kept back from the work by a spiral spring working against the end of the handle, C. This handle does not turn with the spindle, but is mounted like the handle of a carpenter's brace, or that of an Archimedean drill stock. The whole apparatus fits into the socket of the ordinary rest. A screw should have been shown in the drawing, passing through B towards the pulley, to regulate depth of cut.

Figs. 253, 254.

Fig. 255.

Fig. 256.

Fig. 258.

Fig. 259.

Figs. 259A, 260.

Once fixed by the screw of the latter in its intended position the tool is advanced to the work in a straight line by pressing the handle C, and is released from the cut as soon as this pressure is withdrawn. With different sizes of cranked, forked, or round ended drills, a good deal of ornamentation may be done with this simple tool, which is also useful for ordinary light drilling. By putting in the socket a round ended drill, and using the radial movement (turning the whole round in its socket in the arc of a circle), short flutes can be drilled out deep in the middle, forming basket work similar toFig. 260, which is exceedingly pretty when carefully executed. There is little difficulty in making drills and cutters, as steel of all sizes in round and square bars may be had at the chief tool shops, especially at Fenn's, in Newgate-street. In making the revolving cutters, however, it is necessary to observe the position of the axial line, which must pass through the cutting edge. After the drill is roughly finished, therefore, it should be mounted in the tool holder with which it is to be used, and carefully tested upon a piece of unimportant work. If in revolving against the latter it leaves a part of the material untouched, the edge is not truly in the centre of rotation. The flat side of the drills are to be diametrical, and hence, as Holtzapffel remarks, these drills can only be sharpened on the end. The latter authority also says most of the drills embrace (in contour of edge) only about one-fourth of the circle, as when the drills are sharpened with one bevel they can only cut on the one side of the centre, and if the drills were made to embrace the half circle the chamfer of the edge on the second side would be in the wrong direction for cutting, and consequently it could only rub against the work and impede the action of the drill. All ornamental cutters and drills should be kept in a box with small separate divisions to fit the shanks, which are all of one size. The points can then be seen and the selection made of any required pattern.

Many turners take special interest in the production of objects in the lathe, that at first sight appear impossible to be produced solely by its means. Inasmuch as such works manifest the skill and patience of the artificer, they will always meet with appreciation; and, although otherwise useless, they serve as elegant objects of vertu, and are well worthy a place among the rare ornaments of the drawing rooms. When first the Chinese balls, consisting of a set of hollow spheres one within the other, all exquisitely carved, were brought to England, it was believed they were made in hemispherical pieces, united round the equatorial line with some kind of cement, the joint being carefully concealed. I am not sure that they are made in a lathe in China; but, at all events, they are so made in England, and our home productions almost rival those of that strange yet clever nation. I say almost, because the carving in ivory done by the Chinese is in some respects unequalled, nor do I suppose that work requiring in many instances years of patient industry could be made to repay the cost of manufacture in England. No sooner were these curiosities in vogue here than all kinds of similar impossibilities were manufactured. Stars with from three to a dozen rays made their appearance, enclosed sometimes in similar sets of hollow spheres—the rays projecting beyond the limits of the outer shell—others were wondrously enclosed in cases with flat sides, cubes, pyramids, six, eight, twelve-sided hollow cases, all turned fairly in the lathe, were produced with similar contents, so that the apple in King George's dumpling became a very secondary wonder. The starry inmates were evidently too large for the houses; yet there they were—legs and arms, of course, sticking out through doors and windows, simply because there was no room for them inside. We will penetrate the mystery, commencing with a single hollow ball containing a star of six rays, the bases of the latter standing on a central cube.

In the first place a perfect sphere is required, and consequently the slide rest and template, or spherical rest, must come into requisition unless the turner can produce a ball by hand tools alone. Let this sphere, or rather its boundary line, be drawn on paper of full size with the compasses,Fig. 262, A, B, C, D. Draw the diameters A, D, C, B, at right angles to each other. This will give you five points, which on the sphere itself (on which these lines will have to be drawn, including also another, answering to A, B, C, D) are centres of six openings, here represented by the circles, through which the tools have to be introduced to hollow out the sphere and form the star. The points of the latter will be in the centres of these openings. Draw in addition the plan of the central cube, and one ray of theproposed star; next draw an inner circle, here dotted to mark the thickness of the outer envelope. The object of this drawing is to enable you to make a set of curved tools, one of which is shown black at E, and a set are marked on a plate of steel, from which they must be cut out. A close inspection of the figure will show that if ball,Fig. 262, were turning on the point A, A D being its axis of revolution, tools of the given section introduced at D would cut away the material round the point or ray, leaving the latter standing;[21]and this operation repeated at the five remaining openings would entirely free the central cube with its rays according to the proposed design. The tools have to be introduced in order, beginning with the smallest; and although the above remarks will make clear the principle, there are several points to be attended to in practice, and some few accessories are required which will now be explained. It is evident that for every different sized sphere fresh sets of tools will be requisite, which will also vary in pattern according to the intended form of the central base on which the rays stand; a cube or flat-sided solid requiring one tool at least, with a rectilineal edge; spherical or other solids demanding others whose ends are of different section. Hence, in all cases, full-sized plans of the proposed work must be drawn, and special tools designed therefrom.

[21]There is an error in the position of this tool, which, thus placed, would not leave the point of the star.Fig. 270will explain the method better.

Fig. 262.

Figs. 269, 269B, 270.

Fig. 269Ais introduced to show more clearly the result of the application of the first set of tools, or rather of the first application of the set, as the latter are used throughout.

The blackened part will be entirely cut away in this operation, the shaded part meeting it will be removed when the tools are transferred to the adjacent opening, the cuts meeting those first made. Hence the tools need only reach fromatob, and can be more easily introduced than if the curved part were longer. Gauges,Fig. 269B, A, must likewise be made of thin brass or tin, that the progress of the work may be examined, and each opening in the sphere should likewise be measured with a gauge, or with compasses fixed to one width by an adjusting screw.

The proper chuck for this work is the capped ball chuck already described, by loosening the cap of which any one of the six openings may be brought under the action of the tool, these openings being, in fact, bored out simultaneously with the formation of the star. After the first point or ray of the star has been completed, the ball may be reversed and the opposite ray formed. These are now to be secured by plugs, which are to be turned conical, to fit the opening of the ball at one end, and of a length to rest upon the central cube at the other, being also bored out to fit over the rays, which they should embrace closely at top and bottom, even if not at the other points of its length. (Fig. 269C, A and B.) This is to be repeated as each ray is formed, so that the central star may be held in place until the work is finished, when the plugs are removed, and the star will be entirely detached. The above-named tools being straight on the right hand side of the shank will not form a finishedconicalpoint or ray. Hence it is recommended to file away that side, so that when flat upon the rest, the back of the tool may be an exact counterpart of a ray,Fig. 270, A. There is, however, no absolute necessity for this, as the star point can be first made blunt, with perpendicular sides, which can then be neatly finished by a separate tool made for the purpose, and kept up to a very keen edge. The first and smallestof the set of tools here shown, is the one with which the flat sides of the cube are formed, and it must be bevelled from underneath, so as to present a cutting edge on the end. The curved tools should cut on the end and both sides of the crook.

Figs. 270A, 271.

It is quite possible to make the above in mahogany, but a closer grained wood is much to be preferred, as the tools used—which are held flat upon the rest—are rather scraping than cutting, and mahogany, and fibrous woods in general, cannot be thus worked neatly. Boxwood is, in every respect, the best material to begin upon, ivory and blackwood being reserved until the eye and hand have become accustomed to such work. The whole operation requires great care, and is rather tedious, but the result ought to be a sufficient reward. The external surface may, of course, be ornamented with the usual apparatus, but the star should be left clear and sharp. The edges of the openings should have a light beading, cut with a bead tool,Fig. 271, A and B.

Amongst the various purposes to which it is possible to apply the lathe, may be noticed the drilling out grooves and mortises, a method used in some of our Government arsenals, for cutting the recesses for the reception of the Venetian lath work in cabin doors. The same method is, of course, applicable to numberless similar cases, although designed for the special object named. The apparatus is shown complete in the drawing,Fig. 272, and the component parts in the succeeding diagrams. A is a kind of compound slide rest, or vertical straight line chuck, having a movement in a direction parallel with the lathe bed at F; while the circular plate being pinned through its centre to a slide, H, can be moved up and down by means of thehandle G. This circular plate can be set in any position, and has a projecting shelf or rest to carry the work, which is steadied by guide pins, as will presently be explained. The part F, has a bed similar to that of an ordinary slide rest, which is clamped to the lathe bed by a bolt and nut, as usual. This carries likewise chamfered bars, between which slides the horizontal plate to which the vertical part of the apparatus is attached. This is first a plate with chamfered edges,Fig. 273A, and a second similar but rather wider plate,Fig. 274B, with guide bars, likewise chamfered, to slide upon A. From the front of B rises a stout pin, on which the circular plate, C, turns, which can be clamped by a central nut, or otherwise, as in an ordinary compound slide rest. This nut should not project above the general level of the plate. On the face of the latter is, as previously stated, a rest, or narrow metal shelf, D, and pins,e,f. The plate may be variously arranged in this respect by substituting any kind of holdfast or guide, according to the work desired to be done by its aid. The upper slide is depressed by a hand lever acting on a pin fixed in the sliding plate,Fig. 275; or, if preferred, by a similar lever, with a quadrant and chain, or rack movement. The horizontal slide is worked by means of a stirrup for the foot, with cord attached, acting on a bell-cranked lever, seen in the first figure. To cut the grooves in a bar, for Venetian blinds—as described—the lath to bedrilled is attached to a flat strip of thin iron, drilled with holes,Fig. 276A, as wide apart as the required distance between the grooves. It is then laid against the shelf, and the guide pins are made to enter the holes in the iron. The clamping nut of the round plate is loosened, until the bar is set to such an angle that the grooves to be cut will form vertical lines,Fig. 276. It is then clamped securely.

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