Eccentric Chuck
Next in order of the compound chucks stands the eccentric, the use of which is not entirely confined to mere ornamentation, as it is often very convenient to the turner to have the power of shifting the centre of his work. Thus, a solitaire board may be drilled with the necessary cup-shaped holes, or any work of a similar character completed by the help of this chuck without the necessity for constant re-centering. The general work of the chuck in question is nevertheless ornamentation, for which it is peculiarly adapted either alone or in combination with other compound chucks, or overhead apparatus. The sliding plate of this chuck works between chamfered steel bars, the same as in the oval chuck. There is, however, no guide ring on the lathe head to regulate the movement of the slide, and therefore also no necessity for the projecting arms at the back. The slide, in fact, is moved by a screw with a graduated head, similar to those already described. Fig. 239 represents the common form of this chuck, in which the wheel which forms a dividing plate is moved by a tangent screw. The sliding plate is shown slightly drawn out by its screw, the degree to which it is moved being that of its required eccentricity. When the plate is drawn back to correspond with the base plate, the centre will be in a line with that of the mandrel, and any work turned upon the chuck in this position of the slide will be cylindrical. The central screw of all these compound chucks being alike and of the pitch of that on the mandrel, any of the ordinary cup chucks can be used with them to hold the work; or the eccentric chuck can be screwed to the elliptic, cycloidal, or any other in the set, by which means an endless variety of curves can be described. The effect produced by the simple eccentric chuck now described is as follows, the slide rest being used with it as a matter of course. Let a piece of box or other wood be fixed by means of a cup or other chuck upon the screw of the eccentric chuck, and the slide rest with a single point tool be brought in front of it. By means of this the work must be carefully faced, and made uniformly level. A ring A, Fig. 240, may now be cut, which will be concentric with the mandrel. The slide of the chuck being now drawn down by a few turns of the leading screw (the tool and rest being kept in its original position), the centre of the work will thereby be shifted, and the tool being advanced to touch the same, the circle B will be formed of the same size as the first, but necessarily cutting it at two points. Another turn of the screw will enable C, and similarly D, or any number of circles to be successively formed. The centres of these circles will be in a line across the face of the work. The ratchet wheel is added to enable the turner to arrange his circles round a common centre, instead of being thus obliged to keep them in a right line, and it will presently be seen what a beautiful variety of interlaced circles can thus be accomplished. The dividing wheel is, as previously explained, divided on its edge into an equal number of teeth, or racked for a tangent screw and divided on the face and edge. We shall suppose the number of divisions to be 120. Face the work afresh, and, drawing back the slide until the centre is concentric with the mandrel, as at first, cut a boundary circle, A, Fig. 241. Move the slide of the chuck a few turns, as before, and cut an eccentric circle. Now move the dividing wheel thirty teeth, and cut a second, and, advancing by thirty each time, cut a third and fourth, and Fig. 241 will be the result; the centres of the eccentric circles falling upon four points of the inner dotted circle, which is itself concentric with that first made.
If the same process is followed, but the number of the circles increased, a very neat snake-like ring will be formed, constituting a border, in the inside of which other combinations may be made. In Fig. 242, twelve interlacing circles are shown; in Fig. 243, twelve circles, described upon centres, which lie upon the circumference of a central circle of equal size. This last pattern, when more finely executed, by doubling or trebling the number of eccentric circles, forms the device generally cut upon watch cases, under the name of engine-turned. The best way to try patterns, is to cover the face of a piece of boxwood with paper, using a pencil in the tool-holder of a slide rest instead of a cutting tool. If a softer disc is used instead of box, round pieces of paper or thin card can be fixed upon it with ordinary drawing pins; and if the first pattern is unsatisfactory, a second, and any successive number of pieces, can be mounted, and fresh patterns traced by the same means. It would be mere waste of time to multiply specimens of the patterns that may be executed by the aid of the chuck just described; and, indeed, this could only be done by cutting in the lathe itself the blocks from which such specimens must be printed. For the present, at any rate, the principles only by which such devices may be executed will be given (as above,) and the designs will be left to exercise the ingenuity and taste of the reader.
It happens, moreover, that few as are the works devoted to the general principles and practice of plain turning, more than one has been published on ornamentation by the eccentric and other compound chucks, in which a variety of executed patterns appear, of more or less beauty; and in the English Mechanic has lately been printed a selection of exquisite designs by Mr. G. Plant, whose chuck, indeed (to be presently noticed), bids fair to supplant the most simple one now described. The chief recommendation, perhaps, in the latter, is its great simplicity, as it may be made by any amateur sufficiently practised in the use of tools; whereas the geometric chuck is too complicated to permit this. It will be observed, on inspecting the drawing, Fig. 239, that the divisions on the face of the wheel are continued on the side above the part that is racked; this permits them to be seen when the piece of work overlaps the circle of the wheel. The steel point shown at B, answers as an index, either to the surface marks, or to those on the side. The tangent screw is now generally fitted in a small frame, which is itself pinned at one end to the top plate, and kept up to the dividing wheel by an eccentric cam. This is not shown in the drawing; the plan is nevertheless good, as the screw is instantaneously released from gear at pleasure, when the wheel may be turned by hand to any desired position; after which a slight movement of the cam brings up the screw, and all is made ready for work. The eccentric chuck becomes available for such work as shown in Fig. 244, representing the bottom of a candlestick, ringstand, or similar article. In this case the centres of the eccentric work (now cut quite through) are on the circumference of a circle larger than, and outside, the work itself. Instead of cutting through the whole thickness of the stuff the outer circle may remain such, and the blackened part may represent an inner raised surface, when the contrast formed by the sharp edges round the pattern with the smooth circular part will be very agreeable to the eye. To improve still more this design, the outer part may be ebony nicely moulded and edged with ivory, and the raised part ivory; or the same may be alternations of ebony and holly, which will form a contrast almost equally agreeable. A small chisel-ended tool must be made for this work if the whole is in one block, as it will be necessary to leave a level surface upon the face of the lower part. There are an infinite number of designs of similar nature, which will occur to the reader when the principles of the chuck have been mastered, some of which would at first sight appear to have been worked by other means. Fig. 245, for instance, which is but a modification of the last, scarcely looks like lathe work, but can be cut more rapidly this way than any other—of course the fret saw will do similar work, but it would first have to be marked out, and afterwards the marks of the saw teeth removed, whereas the above is cut and polished at once. It may here be observed that the eccentric chuck itself is used to fix the position of the various circles to be cut, whereas the size of these circles is determined by the slide rest. Thus in Fig. 246, while the centre of the chuck is concentric with the mandrel, bring up the tool in the rest and cut the circle F, G, H, of which B is the centre; draw down the slide of the chuck until its centre is at C, leaving the slide rest as it is, and the circle F, E, D, will be formed of equal size with the first. Now move the screw of the slide rest so as to draw in the tool towards the centre of the lathe bed without altering the chuck, and the small circle will be the result, whose centre (being dependent on the chuck alone) is the same as that of the larger circle. Bearing in mind this principle, that the chuck determines the various centres only, and the slide rest the radii, little difficulty will be experienced in devising and executing designs. Such is the simple eccentric chuck, of which the use is tolerably extensive; but there are, nevertheless, certain positions in which the eccentric designs are required, which cannot readily be obtained by its means. Fig. 247 is one of these, in which a moment’s inspection will show the necessity of two distinct movements of the slide at right angles to each other. Hence a second slide is attached to the first at right angles, much the same in effect as a second chuck screwed upon the first but standing across it. This is the compound eccentric chuck to be subsequently described in detail. There is one drawback to the use of these chucks, namely—their excessive weight, which causes a great deal of vibration in the lathe itself, especially when the eccentricity of the slide or slides is great. An accidental blow moreover from the chuck under the above condition would be very severe. Hence the various cutters eccentric and others, worked by the overhead apparatus already in part described are infinitely more pleasant to use and even more effective and more easily managed. The eccentric chuck can be used in combination with these, and the capabilities of the two will thus be vastly extended, but in this case the chuck is kept stationary while motion is given to the tool, and the defect just alluded to no longer exists. In cutting patterns upon hard wood and ivory a common defect is shallowness of work, the cuts should not be so light as to give merely an effect of a design scratched upon the surface. The cut should be deep and clean, and the tool not only sharpened but polished so as to leave the device boldly executed, the small triangular and other shaped pieces left between the cuts standing up clear and solid. Some patterns, as the shell, which will be presently spoken of, require to be deep at one part and shallow at another. Some devices look best when cut with a point tool with double and others with single bevel to the edge, and the same design worked with different tools will appear almost like two distinct patterns.
The double eccentric is represented in Fig. 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 the division 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.
In Fig. 249, we give a simple specimen of work to be executed by the compound eccentric chuck.
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 to Fig. 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. 251 is 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 cutting small intersecting 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 like Fig. 254 will 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 be polished if 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. 255 is 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, the upper 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 at least one complete set of circles or other patterns have been cut.
The instrument just described is evidently unsuited for the drills and bead tools which present a concave edge like 246 A, B, C, enlarged sketches 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 in Fig. 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 at Fig. 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 mouldings can 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 round Fig. 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 was stated 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 as Fig. 251, the distance between a and b will 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. The position of the centres of 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 this must depend on the taste of the operator. The sole object in this place is to show the principles whereby 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 in Fig. 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 as Fig. 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 so thin as to bend under the fingers, although such extreme tenuity is not required in the present case.
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 to Fig. 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. 255 represents a tool similar to the last, but arranged 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 in Fig. 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 flutes round 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 in Fig. 256 consists of a plate with chamfered edges to fit the tool receptacle of the slide rest, having near each end small poppets 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 used only for vertical cuts (the holder, 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 in Fig. 259A, to take the place of the slide 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.
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 to Fig. 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.
Notes
20 A newer pattern appears on a later page.