" This machinery is intended to supersede the use of the eccentric chuck, by assuming a more natural and easy method of engraving, by the tool or cutter tracing the work, instead of the article doing it, that is to be ornamented. By this improvement, the action of the tool is more distinctly seen, than could be, by the movement of the chuck, especially after a few circles have been cut; for, by their rotation, the eye (particularly of an amateur) is soon fatigued, and yet to these inconveniences a turner must continue to submit, if no better method could be contrived.
"The principal advantages of the present invention, are the following. At a comparatively trifling expense, (to the costly machinery now in use,) a turner may be put in possession of an apparatus, which will answer all the purposes of eccentric and cycloidal turning, and which will, at the same time, form a complete drilling frame. As an apparatus intended to supersede the use of the eccentric chuck, it combines many advantages, amongst which, three may be mentioned that are of importance: - 1st, As all patterns are worked by the divisions of the plate on the small wheel of the lathe, a much more extensive variety of circles can be obtained, than could be by the divisions of the eccentric chuck. 2d, By slackening the screws ss, in the large slide of the compound sliding-rest, a change may be effected from the rectangular position of the cutter-frame, to an oblique position; and, after the proper angle is obtained, (the screws being tightened,) the segments of circles can be worked round a centre with greater accuracy, than could be by tracing over patterns which I believe is the common method; while the alteration of my machinery, for such purpose, would scarcely occupy a minute of time; an object which is of no small importance for the "dispatch of business. 3d, The loss of time in centring the work, ccasioned by the necessity of removing it from one chuck to another, to receive the different ornaments, (an evil severely felt by turners.) is obviated by my improvement; as also the great difficulty, so often experienced in getting the face of the work to run true again, after taking it from one chuck to another; from their liability to get out of truth by the wearing of the screws in fixing them to, and removing them from, the spindle of the lathe; in which case every effort at fine-finishing would he inevitably defeated.
"To apply my apparatus for cycloidal turning, the addition of a rod is required to connect the cutter-frame with the universal chuck, after it is screwed on the spindle of the lathe; bit which, on account of its connexion, (being a bad draughtsman,) I am unable to send. The following description will. I hope make its construction appear sufficiently intelligible.
"The edge of the plate of the universal chuck, (the machine on which the work to be turned and ornamented is fixed, and which is a common appendage to all lathes,) I have divided into 144 equal parts, which form a wheel: and upon the face of the left-hand head of the lathe is fixed a plate, and a corresponding one on the side of the rest, through which the axis of the rod connecting the chuck and cutter-frame revolves. Now if upon the rod is fixed a wheel of twelve teeth, working on the wheel formed by the edge of the universal chuck; and if upon the other end of the rod is fixed a wheel of the same size and number as those which work the cutter-frame, and to work in one of those wheels; then it must be obvious, that, by the chuck revolving once, the wheel of twelve would make twelve revolutions, which number would be given to the cutter-frame, thereby tracing an accurate circle of twelve cycloids. Again, by changing the wheel of twelve to another of proper proportions of 144, a number of cycloids would be described equal to that proportion.
Then, by sliding the connecting-rod out of gear, and moving the universal chuck any number of teeth forward or backward, the cycloids would beautifully intersect each other.
"It may, perhaps, be unnecessary to add, that this, and the eccentric apparatus, must be worked by the hand-motion of the cutter-frame." (In the opposite page are given two specimens of wood-blocks, cut by Mr. Wightman in less than four hours.)
"To change it into a drilling frame, all that is required, consists in throwing all the wheels out of gear, and passing a string over the groove in the cutter-frame, to work on a pulley P, which is fixed on the same arbor as the pulley used in double-stringing a lathe. Then pass a string, (which should be kept for the purpose,) over the last-mentioned pulley, and under the large or fly-wheel of the lathe; and after the drill has been fixed in the socket of the cutter-frame, and adjusted to run true, or central, the machine will be ready for work. Now it must be clear that, by working the treadle of the lathe, as in turning, a rotary motion would be given to the cutter-frame; and after the tool has been ad= vanced to the work, then, by moving. the large or right angle slide of the rest, a straight line would be drilled, of a length in proportion to the movement of the slide. Then change the division of the plate on the small wheel of the lathe, and if the first line was cut from the centre, then cut the next to the centre, and so on till the whole is completed, when a beautiful circle of straight lines would be cut from a centre."
A very ingenious expanding chuck was invented by Mr. Lewis Gompertz. Figs. 1 and 2 represent two perspective views of the chuck; the first, as employed to grasp a piece of wood of large dimensions; Fig. 2. is an opposite view shown by the dotted lines c c, Fig. 2. The three clamps, d ef, one of which i. shown entire by Fig. 2, are then fixed in these grooves by their jointed ends g with the jaws collapsed, to bite a smaller object. Fig. 3 shows one of the claws or jaws separately. The same letters in each figure refer to the same parts. The body of the chuck a, is cylindrical, and made of hard wood, with a screw-thread cut on its periphery. Three longitudinal rectangular grooves b b, (only two of which are seen,) are then made throughout its length, slantingly, as by means of a pin through their centres h, which pass through the solid back of the chuck i, and are rivetted to k, the metallic hoop of the same. The clamps thus fixed have a range of motion in the grooves, as represented more clearly by Fig. 2; the shaded part l shows the clamp in the position, when employed, as seen in Fig. 1; the same in dotted lines m, as when employed in Fig. 3; and the angular piece n represents that portion of a triangular pyramid which is formed in the centre of the cylinder a, by the slanting cuts before-mentioned. The clamps d e f are made strong, steeled, and hardened at the jaws; their external edges (curved as represented) are filed into grooves or notches, to correspond with the screw-thread on the hard wood cylinder a; the metallic ring, or circular nut o, which is, of course, cut with a screw to fit both the former, an therefore be wound over any part of the cylinder, and by that means hold down the clamps firmly to the object they grasp.