ECCENTRIC TURNING.
Plate 5.
Plate 5.
This name includes all the various, beautiful, and intricate work for which the powers of a lathe are so justly celebrated, and which, once seen, must be admired by all who love the fine arts and examine the powers of machinery. The eccentric cutter, the drill, the eccentric chuck, and the universal, or vertical cutter, are all indispensable for those who wish to perform ornamental turning, and with them the most delicate and intricate patterns can be worked with a precision and accuracy that are truly wonderful. A sliding, or parallel, rest is absolutely necessary for turning patterns, as upon it, in some degree, depends their exactness. Fig. 1,plate 5, is the drawing of one. The foot, A, screws firmly to the bed of the lathe, like the common rest, and the upper part fits into the socket, B, and, by means of the nut, C, is turned in any direction you wish. D D is a bed of steel, five or six inches long; through the groove down the middle is a screw which passes from one end to the other, and, by turning the squarehead, E, the tool slider, J, is pushedbackwards or forwards, while the rest itself remains stationary. The steel bed is graduated. Between the bed and the screw, E, is a small brass wheel, divided into numbers, G; this regulates the position of the tool. The tool slider, J, fits into the bed, H, and slides in and out; J is the part where the tool slips in, and it is kept firm by a screw, K. The handle draws it to and from the work, and the nutsll, regulate the depths of the cuts. The tools belonging to this rest, 1, 2, 3, 4, 5, are of steel, about two inches long, and are ground to different angles: there are various sizes of each. When you intend to ornament a piece of wood or ivory, first turn it quite round, and smooth it with the common tools; you must then make the surfaceperfectly flat, and to accomplish this, adjust the sliding rest at a proper distance, put in one of the round-ended tools, No. 5, let it justtouchthe wood by setting the screws,ll; put the lathe in motion, and gently approach the tool to the work; if it cuts too deep, tighten the screws a little more; if too little, push the screw forward. Keep the tool steadily up to the work by pressing on the lever, S, which impels the tool to slide forward, then, withthe right hand, turn the head, E, by means of a handle, P, which will thus enable the tool slide to run from one end of the brass bed to the other, at the same time that the lathe is turning rapidly round, and thus the surface of the wood is rendered perfectly smooth, level, and polished. Sometimes, however, it will require to be worked over in this manner three or four times before it becomes quite flat; and frequently, even when it appears level, there will still be a hollow in the middle, which will quite destroy the accuracy of the patterns: to discover whether this is the case or not, take the T square, seeplate 1, fig. R; place it with its edge against the wood: if you can see light between it and the work, the surface cannot be even, and requires smoothing over again. The next process is to cut very delicate circles all over the work, at regular distances: this is done to take off the bright look of the wood, that the patterns may appear to greater advantage. Put into the tool slide a double angular tool, No. 4; adjust it so as to make a distinct, but still delicate, cut into the wood. Make one cut in the middle of the work; move the brass wheel, G, one number, or from 1 to 2; make a secondcut; move to 3, then to 4, and so on: each circle you will find enlarges gradually, till you arrive at the end of the wood. Pattern 1,plate 6, is a specimen of this work; but remember, it is merely a preparation for other patterns. In doingside work, as the side of a box, or a knitting-case, unscrew the screw C, and turn the brass bed of the rest round till in a line with it, then proceed as directed for face work. The wood being ready, we will now go on to give a description of the eccentric cutter,plate 5, fig. 2. Like the tool slider, it fits into the sliding rest, but now it is no longer the work which moves round and the tool stationary, but the wood remains firmly fixed while the tool rapidly revolves and cuts the patterns. For this purpose, it is obviously necessary that the fly wheel should turn the cutter, while the small wheel remains immovable. Several methods are used to perform this: the one givenplate 4, fig. K, is the easiest. The frame here represented should be of iron, firmly screwed to the bench of the lathe, and of sufficient height to be about a foot above the head of the workman. In front is a spindle, which works in two nuts, No. 1 1, exactly in a line with the mandrel. Twowooden wheels, No. 2 2, are fastened to this spindle; the one on the left hand remains stationary over the fly wheel of the lathe, by which it is turned, the other slips backwards and forwards, according to the work it is required to do. Take off the usual catgut from the fly-wheel, and pass a long one over it, and over the small wheel on the over-head frame, No. 2. When the cutter, 2,plate 5, is fixed in the slide rest, draw the other small wheel on the spindle, No. 2, forward, till just above the rest, then pass a catgut over it, and round the small brass wheel, B, of the cutter, and the whole will turn together. The brass wheel of the lathe must then be fixed at one particular number. It is usually divided into three hundred and sixty divisions, each marked by a small hole in the brass wheel, as in fig. A,plate 4, and it is by properly dividing the numbers on this plate that the accuracy of the patterns depends; to keep the wheel steady, a small steel key,h,plate 4, is slipped into the brass knob, O,plate 4, and the other end, being pointed, enters into one of the small holes, say the one marked 360; the work is then immovable until you remove the key into another hole. The cutter itself is of brass,with a spindle, C, which works in two brass collars. At one end is the wheel, B, by which it is turned, at the other a steel frame, T D, which is marked on the upper edge in small lines, E, to regulate the quantity of eccentricity. The steel tool-box, F, holds the tool, which is kept firm by a small screw underneath. By means of a screw through the frame, D D, similar to that of the sliding rest, the tool is pushed backwards and forwards, and cuts a large or a small circle. G is the nut that moves it, and it also is divided into numbers. This cutter, for many patterns, is quite as useful as the eccentric chuck, but, in conjunction with the former, is invaluable, and the patterns performed by them may be multiplied according to the taste and genius of the turner. The two screws, H H, fix the depth of the cut; the wheel of the sliding rest determines the necessary distance, that of the cutter the eccentricity, while the brass wheel keeps the pattern accurate. The tools, Nos. 1, 2, 3, 4, 5,plate 5, are of various forms and sizes: care must be taken not to break them, and the cutter must be constantly well oiled with olive oil; the holes, K K, are made to receive it. In using this tool, make the wheelof the lathe go very quick, but approach the tool very gently and slowly to the work. The better to do this, the lever, S, is used; it enters into one of the holes in the side of the cutter, and into a similar one in the sliding rest, so that by a slight pressure the tool is impelled gently forward. There are generally about two dozen tools shaped like those in the plate, but of various sizes.
To imitate the second pattern,plate 6, which, it will be perceived, is a number of circles, slide the cutter towards the edge of the work by turning the screw of the slide rest, then, to make the outer circle of the border, turn the small nut, G, of the cutter six times round; put a double angular tool into the tool box, screw it firmly, adjust your cutter by the screws, H H, to the proper distance, and stop your wheel with the steel key at 360. Cut one circle, alter your wheel thirty numbers, cut another circle, then thirty numbers more, till the twelve circles are all cut. This done, alter the wheel fifteen numbers, which will make the circle cut half through two of the former ones, then move 30, as before, till the twelve are done. For the small inner circles turn the nut, G, of the cuttertwo turns back, to reduce the size, and move 30 as before. The pattern in the middle is still circles, though differently arranged. Draw back the cutter till a little past the middle of the work, then unscrew the nut, G, fifteen turns, cut one circle, move the brass wheel 15, cut another; move 15, cut another; then move 45, cut another; move 15, then 15, and so on till all are finished.
Third pattern.—Set the cutter at five turns, and move five numbers on the brass wheel for every circle. For the middle pattern, turn the nut of the cutter eight times, move ninety numbers on the wheel, till four circles are cut; then move 45, cut another; then 90 again. To make the small circles, turn the nut, G, backward two turns, and move 90 as before, for the four first circles; then move 45; then 90 to the end.
Plate 6.
Plate 6.
Fourth.—The border of this pattern is the same as the one in No. 3, only you place a piece of wood about a quarter of an inch in depthacrossthe bed of the lathe, letting it pass half under the slide rest; screw the rest down firmly, and proceed as above. By thus raising the rest in a slanting position, half the circle only is cut, which has a verypleasing effect. For the centre pattern, set the cutter at a small circle, cut one in the middle, having the wheel fixed at 360. Then move the brass wheel of the slide rest,plate 5, three numbers for each circle; these done, return to the middle circle and continue the same to the other end. Then move the brass wheel of the lathe to 45, and repeat as above, three numbers for each circle, till the next row is finished; then again move forty-five numbers on the large wheel; and so on to the end.
Fifth pattern.—Set the cutter at a large circle, the brass wheel at 360. Move 5 for four circles, then move 15, then 4 four times more, then 15 again, and so on to the end. For the middle, set the cutter to a small circle, and move the brass wheel of the lathe 90 four times.
Sixth pattern.—Set the cutter to the largest circle it will make, begin in the middle of the work, set the wheel at 360, and move ten every time.
To assist the beginner, a drawing is given of the wheel, supposing the largest number to be 360, A,plate 4. By this the numbers are all arranged; a table of the divisions is also given; for on the proper and accurate calculation of the numbers dependsthe exactness of the patterns. The plate on the wheel divided at 144 is the plate for marking half-circles and arcs, as inplate 12, fig. 3, which shall be described hereafter. These patterns are very beautiful, and, from the arcs being gradually reduced in size, they have a curious and elegant appearance, but they cannot be workedwithoutan eccentric chuck.
The drill is a most useful auxiliary to the eccentric cutter, not only for drilling holes, which it does with great nicety and speed, but also for making mouldings and patterns of various kinds. Unlike the cutter, which moves either in a large or small circle, the drill can only work upon its own centre, and therefore the size of the pattern depends upon the tool placed in it, its position being regulated by the screw in the sliding rest, into which it slips like the cutter. It is turned by a rope exactly the same as in the directions already given for the eccentric cutter, and greatly resembles it in shape, except at the end, A,plate 7, which is made just to receivethe tool, and a small screw keeps it firm. Suppose you wish to ornament anything—say, the pen-holder,plate 9—with concave mouldings, as in A. Having set the rest, by the aid of the T square, exactly in the same slanting direction, put a round-ended tool, No. 3, into the drill, set it to the proper distance, fix the brass wheel at 360, cut a round hole; move the wheel to 72, cut another, and so on till five are drilled; then, without altering the rest, put in a smaller round-ended drill, hold it by means of the lever well up to the work, make the large wheel go very quick, and slowly turn the screw of the slide rest, so as to impel the drill which ever way you wish. Do not cut too deep at first, or you will break the tool; if a great depth is required, go over in the same line three or four times. This done, count 72, as before, and proceed the same; the pattern will have the appearance of the pen-holder in the drawing. The end, B, after being turned to the shape, is ornamented in small holes, that resemble a honeycomb, in the same manner, with a round-ended drill; counting so as to make them fit nicely between each other. To do this, you must be able to subdivide your first numbers. Thus, suppose you drill a round hole at 1, 40, 80, and so ontill you come to 360, these numbers can be divided by beginning the next row (which must be begun the breadth of the tool from the former one, by turning the slide-rest screw half, or a whole turn, according to the breadth of the tool) at 20, then count forty numbers as before; but if you had taken forty-five instead of forty for your number, you could not have divided it evenly in the second row, so as to make the holes intersect each other. Be very careful to remember how many times you turn the slide-rest wheel, that each cut may be of equal length. There are generally about four dozen tools belonging to the drill, of various sizes, but of the shapes given inplate 7.Nos. 1 and 2 drill large or small holes, as for instance, round the sides of a turned pincushion, or needle-book, for the stitches to go through; 3 is used to make concave mouldings, or to cut quite through the work in straight lines, as in the lighter case, E,plate 9. This pattern looks very pretty, and is quite easy, if your work is turned sufficiently thin; it should be lined with coloured velvet. No. 4 makes concave mouldings flat at the bottom; these tools arealso used to cut round dots: 5, cuts small or large beadings, which give great lightness and finish to the work. Having made a moulding with the hollow tool No. 2 of the slide rest, choose a beading tool that just fits the moulding, put it in your drill, set it to cut sufficiently deep to be quite round at the top; having cut one, count by the brass wheel the proper distance, to make them fit close, but without one spoiling the shape of the other; the round dots on the bottom of the lighter case are intended to represent these beads. Tool No. 6 cuts mouldings of the same shape as the drawing. In using this and the tools Nos. 7 and 8, be careful, after the first cut, where you place them for the second, to make them fit; and in using all the drill tools, make the lathe go as quick as you can, but move yourtoolveryslowly, and keep the drill slide well oiled.