1^ Ex Lib r is K. OGDEN 1 /^ A.^'^'^ /? X 'D m '^^ r^ ''^Pii' i^ f/^'^-^ ym ^^i^. FN. z o o H »-H '^ ^ S 5 (n ffi 'f^ o -n J -r pq O ^ PQ i •./" • xL 1 innm roinTurttii '^^ , i-i-i-q ffiimpiMililij S 'v^- o/.yc/!k<^^ .Mjf i^^/. j^^ /^ /jL ^<^^ c 3 IP IB ^ a SI 12 sr ^ss liCr<3^ixKC3XI^/-•« .a^mtiy M<^ /„/mia/ '■^'i.'l^u^l- o/^if -rtlcK, T^^ V«!l!^^^y» ^/-■'''}iX ■9 m\f^- ^1 e •9 ^V/.- .^.,///,A ,,.,^ ../.-iJ /< .^-ij /^/^ ^ — ?i=i THE SLIDE REST. At the bottom of Plate 1, Fig. 2, a per- spective view is given of the Slide Rest I have always used, never having posses- sed any other: it is very simple and com- pact in its construction; and, as far as regards Eccentric Turning, is a complete and effective instrument. It is of the construction of Messrs. Holtzapffel, of whom I purchased it many years ago, and by their permission I have introduced the engraving and give a description of it. In the course, however, of the long period I have possessed it, they have made many improvements and additions to their Slide Rests, as might reasonably be expected, and have greatly aniplified their power of action. The stand of the Slide Rest (shewn at A. A.) fastens to the Lathe Bed by a screw, in the usual manner. B. B. is attached to this stand by a stern passing into the projecting boss, and by the screw a. in the side of the boss, the stem is clamped fast, so that B. B. shall stand at the required height from the Lathe Bed and at any angular position with respect to the Mandril. C. C. slides from end to end on B. B. and is moved and held fast in its required place by the Slide Rest screw (not seen in the engraving), which is moved by its handle h. D. D. slides, backwards and forwards, in the piece C. C. at right angles with B. B. The tool to be worked with, fits into the socket e. e. and the square-headed screw at the top of e. e. clamps and holds the tool fast. At the end of the slide D. D. there are two adjusting screws d. d which regulate the depth and limit the cut of the tool. The cutting edges of the tools are ground up to various shapes — angular, square, and rounding, &c. according to the taste and fancy of the workman. In turning down the surface of tlie ivory or wood that is to be ornamented, I gene- rally make use of a tool with a rounding edge, which I sharpen on a stone by hand; but to grind and sharpen the angular and square, or flat cutting tools, I use a tool made by Messrs. Holtzapffel, by which any desired angle is obtained to a cer- tainty. This contrivance for setting the angular tools is highly convenient, if not absolutely necessary, as it enables the workman to sharpen the tool as often as he pleases, during the progress of a piece of Turning, which, without it, or some contrivance of the sort, it would not be prudent in hiin to attempt, for fear of altering the angle of the tool, and there- by spoil the work. 8 THE CHUCK. X DO not wish it to be supposed that I take to myself the credit of being the in- ventor of Compound Eccentric Chucks. Instruments, constructed on various plans, have appeared before the Public under that name — there is a description of one in the Manuel du Tourneur — and Messrs. HoLTZAPFFEL, and other manufacturers, have constructed them for a length of period. The one which I describe in the present Edition, happens however to differ essentially, in its construction, from those which have hitherto become known; and I offer it to attention as possessing far greater powers. It is the result of the perseverance and labour of a self-taught Amateur Mechanic and Turner, having been contrived and con- structed by myself many years ago, from the raw materials of brass and steel, with my own hands ; and I present it as an instrument to which I have never given publicity, excepting having shewn it and explained it to two or three friends. Had I not proved able to make it myself, my plan of its construction would never have been realized; and I, certainly, should not have had the means of producing the Compound Eccentric work which is exhibited in this Edition. Six-and-thirty years ago T purchased a Lathe and commenced Turning as an amusement; and I very soon saw that the Art of Turning might be greatly ex- tended by various little contrivances to be appended to the Lathe and Slide Rest, and by the construction of Chucks : but I found, at the same time, that one of the greatest difficulties that opposed the pur- suits of the Amateur Mechanic, was his not knowing how or where to ^ei his 10 projects carried into practical effect. I invariably found that the professional Mechanic, in the habit of constructing Machinery, considered it too great an in- terference with his own business to trou- ble himself with the projects of an Ama- teur: in fact, I saw plainly, that, to car- ry my plan of an Eccentric Chuck into practice, without being cramped or foiled in my views, it was absolutely necessary for me to become my own workman ; and I, therefore, took resolution and resorted to my own exertions and actual manual labour. I had, moreover, a strong mo- tive for going into the labour of making the Chuck myself, in a wish to keep the mechanism of it secret; and this I full well knew I should have no chance of doing, if the Chuck were manufactured by any other hands than my own: I, in fact, constructed the Chuck in aid of a plan I had conceived for rendering Bank Notes more difficult of imitation. I most cordially wish that everv Ama- 11 teur Turner would make known, where there is no object for secrecy, in some way or other, whatever miglit occur to him as being a novelty in the Art; it would prove a source of amusement to himself and of information to others. If he only gave specimens of the result of his labours, without communicating the particulars of his machinery, he would give a great stimulus to exertion in the Art of Ornamental Turning. Besides, there are facilities now open to the Ama- teur, for carrying his projects into prac- tical efi'ect, which did not formerly exist. There is no longer any occasion for him to be his own workman (unless secrecy be desired) — he can readily get any thing executed for him, let it be ever so extend- ed in its mechanism, or of ever so trifling a nature. If he wants a casting in brass or metal, or a piece of steel forged, or a mere screw made, he is able, without any sort of difficulty, to get it done at Messrs. IIoltzapffel's maiiufactoiy. This is, uu- 12 questionably, a very great practical con- venience. — I find it sOj andj now, conti- nually avail myself of it. My Compound Eccentric Chuck, as I now use it, and as it is represented by the Copper Plate Engravings inserted against the title page, has been altered to its present state since I executed the Specimens which were exhibited in the First Edition. The alterations I have introduced, considerably simplify its con- struction, and, at the same time, give it a power of adjustment and of produc- ing some patterns which it did not be- fore possess, and which I had never con- templated as coming within the range of the capabilities of any Eccentric Chuck, however extended its mechanism might be. I, however, profess to give a full de- scription of my Chuck, as I used it in ex- ecuting all the Specimens; and therefore, before I enter into a general description of it, in its present state, I will explain the particulars of the alterations I allude to. 13 On referring to Plate Fig. 1, the two circular moving pieces are seen with their appertaining circles divided into 96, and toothed wheels attached, each cut into 96 teeth, to be acted upon hy a click. When the Specimens which appeared in the First Edition were executed, these two circu- lar moving pieces were divided different- ly — the edge of the one next the Lathe head (marked L. Plate 1.) was racked on its edge, so as to be worked by a tangent screw, into 288 divisions, — whilst the edge of the other circular moving piece which is attached to the second Bed Plate was cut into 96 teeth and acted upon by a click. The tangent screw which acted on the racked edge, then in the place of L, was fixed in a frame, in the same manner as the screw d. d. in Fig. 1. The frame was moveable at one end as a centre, and at the other end there was a catch which kept the tangent screw fast to the racked edge of the cir- cle, or detached from that edge, at plea- 14 sure. The tangent screw was, therefore, susceptible of being employed as a click; at the same time, hy turning the screw round, the circle could be stopped at every possible point ; and a ring of brass, fixed on the head of the tangent screw, was decimally divided into a hundred parts, so that the power of division was very great. The tangent screw acting on a racked edge is by far the most com- plete of the two methods adverted to; but there are practical difficulties and mechanical labour attending its execu- tion, which induced me to adopt the click and toothed wheel system — and I also found that the number 288, into which the circle was racked, did not ac- cord, in point of angular adjustment, with the number 96, which was the num- ber of teeth in the toothed wheel. The al- teration I mentioned consisted, therefore, in making the two circular moving pieces alike in all respects, with a division of the edge into 96 teeth, to be worked by a 15 click. With the machinery I possess, I find, however, no difficulty in racking the edge of a circle into any number that is divisible by some other number : I lately racked one into Two hundred and seventy-two divisions, which is rather a curious number, being divisible by 136, 68, 34, and 17. I will now enter into some preliminary explanation of a few of the results which flow from the combined adjustments of the two circular moving pieces I have just adverted to, and of which the addi- tional Specimens will furnish some prac- tical examples. I consider them ex- tremely curious; and I think I may ven- ture to pronounce them, without fear of contradiction, as being completely novel in the Art of Eccentric Circular Turning. The engraving. Fig. 5, gives a plan of the BeJ Plate and Slide Plate of the Chuck; and the circular moving pieces, just mentioned, are affixed to the Slide Plates G. G. in the centre, as represented 16 at G. G, where there are two circular lines described. By means of the Slide Plates, therefore, the two circular mov- ing pieces may be placed eccentric to each other, and to the Mandril's motion. Now, suppose it be required to place 96 circles or dots,* consecutively, in the curve of an Ellipsis, the transverse dia- meter of which shall be three inches, and the conjugate diameter two inches. The method by which it is to be accom- plished with the Compound Eccentric Chuck is as follows: — Adjust and fix the describing point, or cutting tool, so as to cause its point to coincide with the cen- tre of the Mandril's motion, if it be in- * The diameter of the circles is determined by the position of the describing point, or cutting tool which is fixed in the Slide Rest. If the point or tool be adjusted to coincide with the centre of the Mandril's motion it will describe a dot, if it be ad- justed to the left of the centre of the Mandril it will describe a circle, the radius of which will be equal to the distance between the point of the tool and centre of the Mandril. 17 tended to describe a dot, or at a distauce from the centre of the Mandril equal ^to the radius of the required circle. Then % move the Slide Plate next the Lathe head (G. G. Fig. 5.) by turning* the screw {d. d. Fig. J,) \ of an inch from its central position, and the other Slide Plate \\ inch. Set the circular moving pieces so that the index points to divi- sion 96 on both. — Turn the Lathe round, and cause the fixed tool to describe the dot or circle. The circular moving piece, next the Lathe head, is then to be moved two divisions, making the index point to division 2; and the other circular moving piece is to be moved one divi- sion, in the contrary direction, making its index point to division 95. Another circle or dot is then to be described. The first circular movement is again to be moved two divisions, which will place the index at division 4. The other circular movement is to be moved one division, in the contrary direction, which will c IS bring its index to point to division 94, and describe a dot or point as before. The circular movements are to be moved and adjusted, in this vray, until the figure be completed : the circular movement next the Lathe head is to be moved two divisions at a time, in its direction, whilst the other circular movement is to be moved one division each time, in the contrary direction. The number of beautiful designs which may be obtained by combining, on this principle, two circular adjusting move- ments, is inconceivable. Consecutive cir- cles, &c. may be arranged, not only in elliptical curves, but in the shape of hearts — in straight lines — in triangles — in squares — in polygons, and in both inward and outward looped figures. In Ellipti- cal figures the ratio of adjustment, be- tween the two circular movements, is as two to one, in contrary directions; that is, if the one be moved two divisions each time, the other must be moved one divi- 19 sion each time, in the contrary direction. If one circular movement be moved four divisions each time, and the other two divisions in the contrary direction, the Elliptical pattern will consist of 48 con- secutive circles; if one of them be moved eight divisions and the other four, the number of consecutive circles, in the pat- tern, will be 24; and thus the number of the consecutive circles can be always re- gulated. With this same ratio of adjust- ment of the Slide Plates and of the cir- cular movements, the latter being in the same direction, instead of being in con- trary directions, the pattern formed will consist of two loops inwards. If the ratio of adjustment, between the two cir- cular movements, be equal (that is, if they each be moved the same number of divi- sions at every adjustment) and the move- ments are made in the same direction, the pattern will be heart-shaped. In all figures where the number of an- gles or loops are more than two, the loops 20 will invariably turn outwards when the circular movements are moved in contrary directions, and inwards when they are moved in the same direction. Triangles are obtained when the ratio of the circular adjustment is as three to one : and, Squares are obtained by ad- justing the circular movements in the ratio of four to one. Figures of six loops are obtained when the ratio of the adjustment of the circular movements is as six to one; and so on for all others. In fact, the adjustment of two circles, in the manner I have described, arranges the circles or dots which compose the pattern, in the curve of an Epicycloid ; and, in conformity with the properties of that curve, the number of loops in- evitably depends on the ratio of velocity belween the two circular motions. The circles or dots so arranged in the curve of an Epicycloid, will gradually ap- proach each other in one or more parts of the pattern, and recede from each 21 other in other parts; but this inequality of arrangement must not be looked upon as a defect in the Machinery, as, in reality, it results from natural causes in- herent in Epicycloidal motion. A com- pensating movement might be introduced into the Chuck that would correct this varying principle— I have applied it to other apparatus, and, at one time, in- tended to add it to the Compound Ec- centric Chuck, but I have never done so. 22 THE ENGRAVINGS. Jl will now give a description of the mechanical contrivance of the Chuck which I have denominated " Ibbetson's Improved Compound Eccentric Chuck/' and in the course of explaining the cop- per-plate Engravings of it, inserted in front of the title-page^ I shall particu- larly take notice of those parts which I consider to be new, and that give results which have not hitherto been looked up- on as coming within the range of Eccen- tric Turning. I M^ould not have it supposed to be my intention to offer instruction to the professional Mechanic, on matters which he may, probably, be already fully ac- quainted with. I consider that I am 23 addressing the Amateur who niaj know little or nothing about the mechanism of an Eccentric Chuck; and, therefore, if I am more diffuse in my description than by some may be thought necessary, and enumerate things that have been, over and over again, employed in the con- struction of Machinery, I will still hope to stand excused ; and I beg to be per- fectly understood as not taking credit for invention, in any instance, beyond what I shall specially lay claim to. Figure 1 gives a side view of the Chuck in its real dimensions, and as it appears when screwed on the Lathe. Figure 5 gives a Plan of the Bed Plates and Slide Plates of the Chuck; and. Figure 3 gives a Section shewing the internal construction of the circular movements of the Chuck. In figure 1 the piece A. B. B. is the Bed Plate of the Chuck next the Lathe- head, and, with the projecting piece D, 24 is formed out of one casting' of brass or metal. This Bed Plate screws on the nose of the mandril at its projecting part A. and carries the whole of the remain- ing parts of the Chuck. The projecting piece f. at the end of the Bed Plate op- posite to D. is kept to its place by steady pins, and is attached to the Bed Plate by two screws, one of which is seen just un- der/.* The Cut hereunder inserted is a section of the piece y. as it would appear across the Bed Plate. This piece 1. 1. 1. is made out of brass, separate from the Bed Plate, but attach- ed to it by the two screws 2. 2. and kept * It is to be understood that wluat is said with regard to this Bed Plate and its appendages, next the Lathe-head, applies also to the other Bed Plate and its appendages. 25 firm to its place by the steady pins 3 3. These steady pins can only enter into the Bed Plate a very little way, as shewn in the cut, on account of the screw d. d, one end of which passes through the hole at 4. This piece/, (shewn at/, in fig. 1.) must be fixed in its place on the Bed Plate be- fore the hole at 4. is drilled ; which hole, and also the screw hole through the piece D, must be both drilled at the same time, in the manner hereinafter explained. In figure 5, B. B. gives the outline of the Bed Plate, at one end of which is seen a portion of the screw d. d. fig. 1. G. G. figure I. gives the outline of the Slide Plate, which it will be perceived is not so long as the Bed Plate, thereby giv- ing more scope for eccentric adjustment. In fig. 5, E. E. is one steel arm and F. F. the other, between which the Slide Plate traverses. The two circular lines, in the centre, shew the hole through which the screw N. (fig. 3) passes ; and the large circle represents the outline of the screw 26 nut k. k. fig. 3 L. fig. 5^, is a portion of the toothed wheel which forms part of the circular movement, and 5. 4, is the click which stops the toothed wheel at any required division of the circle. In the Bed Plate B. B. (see figures 1 and 5, and Boss A. fig. 1.) there is a long open- ing, c. c. fig. b, represented by dots, and by dots at Boss A. fig. 1, which gives pas- sage to the plug and screw ring through which the screw d. d. acts, see fig. 4. E. E. and F. F. fig. 5, are steel arms with angular edges, which take into the dove- tailed edges of the Slide Plate G. G. The steel arm E. E. is retained in its position by two steady pins, represented by dots, and screwed fast to the Bed Plate by two screws. The steel arm F. F. is kept fast to the Bed Plate by two screws, and the holes in it, through which the screws pass, are elongated (as seen by dots), in order to meet the action of the clamp screws i. i. The Slide Plate G. G. tra- verses, parallel to the Bed Plate, between 9n the two steel arms E. E. F. F. ; and the screws i. i. which screw into the edge of the Bed Plate, are adjusting screws to press the steel arm into the grooved edge of the Slide Plate, so as to cause the Slide Plate to traverse with the pro- per degree of tightness. The screw d. d. (seen in fig. 1.) is the Slide Plate screw, and by the action of it the circular movements, which the Slide Plates carry, (hereafter described) become fixed at any required position eccentric to the man- dril. This screw is retained in its place in a different manner to any I have usually seen employed in similar cases, and is so secured that nothing like what is called loss of time can possibly occur ; and in every application of a screw, fitted as this is, I have found its action most efficient. One end of this screw has a countersunk conical hole drilled in it, to receive the point of the screw which screws tightly through the piece D. The other end passes through, and correctly fits, a round 28 hole in the piece /. (see 4. in the cut in page 24,) and the screw at D. presses the shoulder of the screw d. d. into close contact with the side face of the piece f. The part of the end of the screw which passes beyond the piece f. is left with a small shoulder flush with the face of the piece. A ring of brass (the ring seen at/, with division lines) fits up to this shoulder, and is kept firm to it by a milled-head screw ; and the end of the screw, beyond the screw nut, is squared, in order to its being moved round by a key. I divide this brass ring into one hun- dred, of which, four grand divisions are distinguished by 0, 1, 2, 3; and this ring is made to move round against the said shoulder, in order that 0. may, under any circumstance that may arise, be ad- justed to the line serving as an index on the top of/. The piece /. is also neces- sarily detachable from the Bed Plate, to make way for the screw d. d. being placed in its proper situation for action. 29 The Click seen at 4. 5. figure 5. is, I consider, an entirely new contrivance of my own invention, and I call it A double acting Micrometer Click. This double acting micrometer Click, has never been, however, actually applied to my Com- pound Eccentric Chuck; but having used it in other machinery, and found it to be very efiicient in its action, 1 resolved to give the present edition the advantage of its publication. The drawing of it in fig. 5 was taken, for the engraver, from a rough sketch I had made, wherein a little inaccuracy occurred which I now correct. It will be perceived that for want of room to place the spring (6, fig. 5), the screws which affix it to the Slide Plate enter into the grooved edge. This must not be, and I, jt C ± ^"llUUIIIIIIIIIIilliniln,; thereto re, suggest the substitution of a spring of a differ- ent shape, as here against shewn. The 30 Clicks which take into and stop the cen- tre wheel, are portions of small wheels, saj of wheels of twentj-four teeth. Through the centre of these a screw passes, and attaches them to a plate of brass about an eighth of an inch thick, of any shape, such as is represented bj the outline which encloses 4 and 5. This Click piece moves on a centre constructed as follows ; 1. 1. is a piece of steel, with a hole drilled through it, to receive the screw 3. (the head is seen at 4. in plate fig. 5.) which attaches it to the Slide Plate. The Click piece is fitted nicely on the shoulder 2. 2. and the screw 3. con- fines it so as to let it move round on that shoulder without shake. This steel piece is of such thickness as will place the Clicks in the same plane with the centre toothed wheel, and allow space 31 between the Click piece and Slide Plates, for the spring seen at 6, and roller seen at 7. The roller is hardened steel, and the spring, which should be rather a strong one, has a projecting ridge at its end, which acts against the roller. By pressing the end (5.) of the Click piece to either side, the spring will throw the Click, on the same side, into contact with the centre toothed wheel. Each Click has a screw through its centre, which attaches it to the Click piece; and one of them has, also, a screw which passes through an eccentric long opening in it, and clamps it fast to the Click piece in any required angular position. It is expedient that this Click, with the elongated eccentric opening, should be adjusted and clamped in its proper place in the progress of constructing the Chuck, before the circular movement is divided and figured ; and I recommend the fol- lowing method of proceeding. The Chuck being screwed to the mandril. 32 the two Slide Plates must be adjusted so that they will traverse on their respective Bed Plates, in a parallel line with each other as near as maj be, and the Click with the long opening is then to be placed in contact with the centre toothed wheel. The clamp screw of the Click must be loosened so as to allow the Click to move on its centre screw, it must also be ascertained that the Slide Plates now traverse perfectly in parallel lines to each other : and this point having been proved by two or three trials, the clamp screw in the long opening in the Click must be screwed quite tight, not again to he moved unless by any chance the Click should get out of this — its proper posi- tion. The place on the circle to which the index points, should be marked for the place of the prime division, which I shall further notice when I come to the description of the circular movements. I will here mention the method I employ to ascertain that the two Slide Plates tra- 33 verse in perfect lineal parallelism. The Chuck being screwed on the Mandril, a piece of hard wood is fixed on it, and the surface of the wood is turned down to a plane. A pointed tool is fixed in the Slide Rest, the point touching the wood, and the screw of the Slide Plate, next the Lathe head, being turned, and the Slide Plate being thereby caused to traverse both ways on the Bed Plate, the point of the tool will describe a right line on the piece of wood. This Slide Plate is then to be brought to its central position, and the screw of the other Slide Plate is to cause the wood to move, backwards and forwards, in a right line against the point of the tool. If the point of the tool traces, in the second instance, the same line it delineated in the first, the Slide Plates, as a matter of course, must have traversed in perfect lineal parallel- ism. If two lines any where appear, the error must be got rid of by adjusting the circular movement, next the Lathe head, D 34 whilst the clamp screw of the Click is loose, as before mentioned. The Click, at the other side of the Click piece, which has only a screw through its centre, is to be resorted to whenever an adjustment of the circular movement is required that cannot be ob- tained by the other Click alone. Sup- pose, for instance, a division of 192 be required, it cannot be obtained by one of the Clicks alone, but by the action of the two Clicks, conjointly, it can. The screw in the centre of the Click must be loosened, so that the Click will move on its centre, and the Click is to be brought into contact with the toothed wheel of the centre movement. The toothed cen- tre wheel must now be moved, so as to cause the index to point exactly half way between any two of the divisions of 96, and then the screw in the centre of the Click is to be screwed fast. In this state of the Clicks, if they be brought, alternately, into contact with the toothed 35 wheel, the centre movement will be moved only half a tooth at each adjust- ment, and thus a division of 192 will be obtained; and it is evident, that, by altering the angular position of this Click, the centre circular movement may be stopped at every possible point ; and this Click is, therefore, most truly speak- ing, A Micrometer adjusting Click. I have before mentioned that I had judged it expedient to remove the tangent screw and racked edge circle from my Chuck, and to substitute a click and toothed wheel. When, however, I de- cided upon doing this, I found that the common kind of click would not answer my purpose — that it was necessary to em- ploy one that would adjust to any minute portion of a tooth of the wheel; and it was, therefore, on this occasion that I first contrived the click which I here give a plan of, and which I have denominated The Single micrometer adjusting Click ; and this Click I now employ, in the Chuck 36 I work with;, on the circular movement which is between the two Slide Plates^ instead of the Double acting Click des- cribed at page 29. The adjustment of it is the same as that of the Click with the long opening (4, 5, fig. 5,) which has been already explained, and the necessity of using such a Click will be obvious when it is considered how very difficult it would be with the common Click to set the Slide Plates in perfect lineal parallelism. Without the power of parallel adjust- ment of the Slide Plates, and of retaining them in that position by means of the action of the Click on the toothed wheel, the Chuck would be very defective in its work : if they cannot be set parallel, they cannot be set at right angles, or at any other angle required; and thus squares, and triangles, and polygons, could not be correctly accomplished — indeed, there are so many figures and beautiful patterns that depend upon the correct angular ad- justment of the Slide Plates, that a micro- 37 meter adjusting Click, or something that will answer the same purpose, is actually indispensable. The division, on the divided circle of the circular movement, to which the index points when the Slide Plates are in lineal parallel position, and which division I have, in another place, called the prime division, is to have the num- ber 12 engraved over it. I have now, in the course of long practice, adopted and used, on various occasions, the simple and plain notation of the divisions of a circle which is shewn in fig. 1. The toothed wheel consists of 96 teeth, and every eighth tooth is distinguished, consecu- tively, by the numerals 1, 2, 3, 4, 5, 6, 7, a 9, 10, 1 1, 12. In the Plate there is only a divisional line to every two teeth, but, with reference to the Micrometer Click, before spoken of, I recommend that a divisional line be placed for every tooth in the wheel, and that the space of one tooth, say, the one next to division 38 12, shall be divided in half — that the space next to that be divided into three parts — and the next space into four parts, and I give a cut hereunder to explain exactly vt^hat I mean ; and this engraving I executed by means of mj Compound Chuck. Practice has taught me that the fewer the figures, the less frequently will mis- takes arise, and the less puzzling will be the adjustment of the circular move- ments. The scale on the edge of the Bed Plates (see Plate I, fig. 1, at B. B.) should be so divided that everi/ turn of the Slide Plate screw shall cause the index to point to a divisional line; the grand divisions are to be distinguished by a numeral, and each of them is to contain ten of the smaller divisions ; and, when the circular movements (see K. K.) are in the middle 39 of their respective Bed Plates and con- centric with the Mandril, the index is to point to the divisional line on the scale which has engraved over it. It has been already suggested that the Slide Plates are to act in perfect lineal parallelism when the index, to that cir- cular movement which is between them, points to the division marked 12, and from thence it follows, that they will also act in lineal parallelism, when the index points to division 6. When the index points to division 3 or 9, they will act at right angles to each other. When the index points to division 2, 4, 8, or 10, their action will be at an angle of 60; and so on for their acting at any other angle. The Manuel duTourneur was the first book that gave any account of an Ec- centric Chuck ; and I do not now know of any other book that does so. That book gives, also, a description of a Com- pound Eccentric Chuck; but according 40 to the construction of it therein set forth, it is an instrument very limited in its action and powers. The Slide Plates have no circular movement between them, but are fixed to act at right angles to each other ; and they, moreover, can only be thrown out of centre at one end of the Bed Plate; but the discrepances which arise from this construction of the Chuck will, however, more fully appear from the Specimens that will be herein given of the action and powers of a Compound Eccentric Chuck constructed on a dif- ferent plan. It appears from the title page of the edition of the Manuel du Tourneur which I possess, that it was published by Ber- geron in 1792; and from that period the defects I have mentioned, in the construc- tion of the Compound Eccentric Chuck, have continued unheeded by the manu- facturer of Turning Apparatus. A new Compound Eccentric Chuck, just finished by one of our first-rate London manufac- 41 turers, has been shewn to me, which, as heretofore, partakes of these and other most glaring defects. Figure 3, is a Section — supposed to be through the centre of the Chuck, and coincident with the centre of the Man- dril, — showing the internal construction of the circular movements ; and, in des- cribing this Section, I will detail the progress pursued by myself in the manu- facture and putting together of the seve- ral parts of the Chuck. The Boss of the Bed Plate, A. fig. 1, being screwed and fitted on the screw of the Mandril, a hole was turned out in the centre of it equal in diameter to the width of the long opening c. c. to be made in the Bed Plate. The face of the Bed Plate was then turned down, with the Slide Rest, and cleaned off with fine emery paper to a true plane; and the ends of the Bed Plate were also turned off with the Slide Rest. The Bed Plate was now unscrewed from the Mandril to 42 be chucked again in the following man- ner, in order to the back part of it being turned and polished off. I have brass flanch Chucks, with holes through the flanch part, for screws to pass, to attach circular pieces of mahogany to them about an inch in thickness. One of these Chucks was screwed on the Man- dril, and the face of the mahogany countersunk with the Slide Rest, to re- ceive, tightly, the face and ends of the Bed Plate ; and the Bed Plate was held fast in this countersink by placing a circular piece of plate brass (with a hole at the centre to pass a screw) on the Boss A. and screwing it to the wood. The Boss A. and back of the Bed Plate was now turned off and polished. The Bed Plate was then unchucked, and the holes drilled and screwed for the steady pins and screws which attach the steel arms to the Bed Plate, also the screw holes, in the edge of the Bed Plate, were drilled and screwed to receive the screws 43 i. i. ; and the long opening c. c. in the Bed Plate was worked out by drilling and filing. The steel arms with their angular edges, having been got up with the greatest care, so, as far as possible, to secure the Slide Plate to traverse be- tween them in perfect parallelism with the surface of the Bed Plate, are to be screwed in their places to the Bed Plate. The Slide Plate having been prepared, and its faces made parallel, and its edges grooved and nicely fitted to slide be- tween the steel arms, is to be placed be- tween them on the Bed Plate, and, by the adjusting screws i, i, made to move rather tightly. Oil-stone dust and oil was now, from time to time, applied to the grooves, and the Slide Plate moved backwards and forwards on the Bed Plate until the an- gular edges of the steel arms and the grooves of the Slide Plate became a per- fect Jit by grinding. During this grind- ing process the screws i, i. were used, from time to time, to keep the Slide Plate 44 in rather tight contact with the steel arms. Let it now be supposed that every thing exhibited in figure 5 is finished and at- tached to the Slide Plate and Bed Plate by their respective screws; and that the next thing to be done is to drill the holes through the pieces D. and/, fig. 1, pre- paratory to fixing the Slide Plate screw d. d. in its place. It is, evidently, most essential to the good and correct working of the Chuck, that this screw should lie, when in its place on the Bed Plate, in a perfectly parallel line with the grooved edges of the Slide Plate and midway be- tween them; and that to accomplish this the greatest care must be taken in drilling these holes. The Slide Plates of the Chuck I work with happen to act with great accuracy; and, therefore, under the idea of its being acceptable to the Ama- teur, I will detail the method I pursued in adjusting the Slide Plate screws. — I first ascertained the distance that the 45 screw d. d. should range from the surface of the Bed Plate, (see figure 1) and I filed up a bit of brass plate to the exact thick- ness, that, when it was laid on the face of the Bed Plate, the edge of its upper sur- face extended exactly to where the centre of the screw d. d. should be. This bit of brass served then as a gauge, and by the aid of it I drew a fine line across the out- side faces of the two pieces D. and/, which marked, exactly, the distance from the face of the Bed Plate where the holes were to be drilled. The next thing was to ascer- tain and make a mark in each of these lines exactly equidistant from the grooved edges of the Slide Plate, and midway between them ; and I did not succeed in doing this to my mind, until I had contrived and made a tool, or gauge, expressly for the purpose. I give a description of this gauge, as it enabled me to accomplish a thing which I had previously despaired of doing. 46 I Ill I The piece A. B. C. D. is of brass plate, rather more than the eighth of an inch thick. The angle at A. fits the angular edges of the steel arms E. E. F. F. fig. 5, and when it is applied to one of these edges, the edge from A. to B. rests on the face of the Bed Plate B. figure 5, and the space d. d. passes over the other steel arm and brings the part D. H. to the opposite face of the Bed Plate. A pin of steel b. b. fits into and passes through a hole dril- led through the part of the gauge as seen at D. H. and is held fast in its required position by the clamp screw C. The ex- treme end of the pin at H. b. intersects the line which had been previously drawn 47 across the pro joe tine; pieces D. andy. on the Bed Plate Ciu; 1, and by repeated trials — first applying the angle A. to one steel arm and then to the other, and marking with a pencil the point at which the end of the pin crossed the line — I, at length, adjusted the end of the pin so that its ex- treme edge pointed exactly midway be- tween the two steel arms, and then with a fine point I marked the place on the pieces D. andy. At the points where the cross lines intersected, which had been as- certained in the manner I have just ex- plained, and marked on the pieces D. and f, dots were now made with a centre point, and holes were drilled through these pieces from those dots, in the fol- lowing manner: — The drill stock was screwed on the Mandril, with a drill in it of the proper size for the screw hole to be drilled through D, and a pointed cen- tre was placed in the cylinder of the front centre head. The dot in the piece D. at the intersection of the cross lines, was E 48 placed to the point of the drills and the dot in the piece f. to the point of the front centre head; and the hole was dril- led through D. bj turning the Lathe rounds and gradually screwing forward the cylinder with the pointed centre. The hole through the piece/, was then drilled with a proper size drill ; the centre point in the front centre head beings in this case^ pressed into the hole that had been drilled through the piece D. By placing the screw d. d. in the situa- tion and manner here represented, the Slide Plates may be thrown out to either end of the Bed Plate, thereby giving to the Chuck the power of forming Squares^ and of executing a great deal of beautiful work, which no Chuck could do that is constructed on the ordinary plan of throw- ing out at only one end. These screws, moreover, should be of the same velocity as the screw of the Slide Rest ; that is, they should have the same number of threads to an inch ; and, in makins; them. 49 every possible care must be taken to secure them against ])eing, in the least, what is called drunken. I worked out these screws in the following manner, in the Lathe with the screw stock and dies, which I have found to be a very effectual way of making a good and correct screw. Having procured two pieces of round bar steel, sufficient in diameter to form the shoulder seen at/", above the letter B, I filed them up to the exact length required for the screw ; and, having centre-pointed them at each end, a conical hole was drilled at one of their ends to receive the point of the screw, as seen at D. These pieces were then chucked between two centres, and turned down, in the Lathe, in the usual way, to the proper size to form the screw, finishing off the shoulder and end beyond it, to the dimensions as seen at /. The screw dies of the proper thread for the screw d. d. being placed in the screw stock, one of the pieces of steel prepared for the screw, as just mentioned, was put 50 between the dies, and again chucked in the Lathe between two centres. The Lathe being turned round, the die stock and dies were caused to traverse and form a, screw-thread from one end of the steel piece to the other ; and bj continually working the dies, backwards and forwards, in this way, — using plenty of oil, — and screwing up the dies by little and little, as occasion served, the screw was completed. These screws cannot, however, be finished off until after the gun-metal rings (here- after described) are screw-tapped and finished, as they must be made to fit, or screw through those rings in the most perfect manner. Throughout the pro- cess of making these screws, the die stock must be kept firm and steady in the two hands, and be caused to traverse at right angles with the screw that is being made. If the die stock be allowed, in any part of its progress, to incline to one side or other of the screw-piece, the screw will, in that part, be imperfect — 51 will partake of the defect called drunken- ness. The Slide Plate is now to be adjusted on the Bed Plate, exactly in the middle, between its two ends ; and, whilst in this situation, a hole is to be drilled through them both, at one corner, about half an inch from the end of the Slide Plate and the grooved edge. This hole is to receive a steady pin, to afford the means of ad- justing and securing the Slide Plate in the same central position wlienever required. The Bed Plate being now screwed on the Mandril, and the Slide Plate being se- cured in its central position by the steady pin, a hole is to be turned through the Slide Plate of the size required to receive the plug piece N. N. fig. 3, and a coun- tersink is to be turned out round this hole to receive the shoulder of the piece P. P, as seen in the engraving fig. 3. The Slide Plate may now be removed from the Bed Plate, and the holes drilled in it, screwed, and finished off for the screws 52 which belong to^ and fix the index 1. 1, fig. 1, and the index S, the click 4, and the spring 6^ fig. 5. The piece P. P^ the plug piece N. N^ and the screw-nut k. k, fig. S, are made of steel; and the cylindrical piece or ring q. q. fig. 3 and 4, is made of gun-metal. The piece P. P. must be correctly turned out to fit;, tightly, into the countersink in the Slide Plate. The cylindrical part of the plug piece N. N. next its screwed end, must fit tightly into the hole in the centre of the piece P. P, and must pass, loosely, throuo:h the hole in the centre of the Slide Plate; thus, by the action of the screw-nut k. k, the piece P. P, the Slide Plate G. G, and the plug piece N. N. will be attached as firmly together as though they were formed out of one piece of metal. The part of the plug piece N. N. seen at 4, must be finished off to a true cylinder, and the gun-metal ring q. q. must be made to fit it, rather tightly, in the most correct manner ; and the ring 53 being then removed from the plug, the holes are made in them to receive the screws?, d. To make these holes correctly, I had two drills, which run true in the Lathe, of sufficient length to pass through the pieces D. and/, fig. 1, and reach to the plug ; the shank, between the stock and the point of one of these drills, exactly fitted the screw-hole in the piece D. and the shank of the other, the hole in the piece f. When the drill was passed through the screw-hole D. the front centre point was pressed into the hole in the piece f. and the Lathe turned round until the plug became drilled half through. The drill which fitted the hole in the piecey. was then placed in the stock, and the front centre being pressed into the screw-hole in the piece D. and the Lathe turned round, the plug became drilled through its other half, and as this was the largest of the two drills, it was passed quite through the plug. This hole in the plug was afterwards broached out, so as 54 to leave plenty of room for the screw d. d. to pass through it without touching ; and any burr that was found on the edges of the hole was carefully removed. The gun- metal ring was now placed on the plug, and the places marked on it where it was to be drilled and screw-tapped to receive the screw d. d. This was done, by means of the two drills, in the same way as the ^ole was drilled in the plug ; but the drills were not worked into the ring more than about two-thirds of the ring's thickness ; because, if the drill were passed quite through the ring, a burr would be thrown up on the inside next the plug, which would render it impossible to remove the ring from the plug. The ring, therefore, is to be taken off the plug (a mark being first made on the ring to record its proper position on the plug), and the holes are to be completed through its two sides, with a drill, of the proper size for the screw d. d. fixed in the drill stock screwed on the mandril, the ring being pressed 55 against the drill by means of the front centre point, which is to be adjusted in the hole on the opposite side. The screw- taps_, corresponding with the screw d. d, are to be passed through these holes in the ring, from side to side ; and the screw- holes being completed with the finishing tap, the screw d. d. can be now finished off ({IS before mentioned), so that the ring may work freely, but tightly, from one end of it to the other. The screw d. d. having been worked through the screw of the ring from end to end^ two or three times, with plenty of oil, the ring was taken off the screw, and any burr the screwing had thrown up inside the ring, was thoroughly- filed away with a riffier file,* as the least burr would of course be an impediment to the ring being placed on the plug. The Bed Plate being screwed on the * Riffler Files are variously shaped. The one I used was bent, so that the burr could be removed without defacing, in the least, the inside surface of the ring. 56 Mandril^ and the Slide Plate secured in its place by the steady pinSj the piece P. P. is to be turned truly over and shaped as seen in fig. 3, and the holes drilled in it and screw-tapped to receive the screws s. s. The piece K. K. (made out of well hammered brass) is to be fitted most cor- rectly^ by turning and a little grinding with oil-stone dust and oil, to move round the piece P. P. The piece which the screws s. s. clamp to the piece P. P. is turned out of a ring of steel, and by caus- ing the flanch rim of it to protrude beyond the top edge of P. P. and extend over part of the top surface of K. K, the latter is confined and kept firm to circulate, with- out the least shake, on and round the piece P. P. The outside surface of the brass ring piece K. K. is divided into 96 divi- sions^ and figured as already explained. The piece L. L. is made out of well ham- mered brass, and the edge of it is cut into 96 teeth as seen in figure 1, and it is shouldered into the piece K. K. in the 57 manner seen in figure 3, to which it is screwed by four screws o. o. The part 3. 3. and other space not sliaded with lines, holds oil, none of which can possibly es- cape, excepting between the bevelled sur- faces of K. K. and P. P. being those which require it. For lubricating the surfaces that are in moving contact, such as the surface in question, I use neat's-foot oil, which I thicken by grinding with it a small portion of black-lead. In figure 3. the toothed wheel piece L. L. has a projecting part, which constitutes the nose screw of the Chuck, as seen in figure 1, and the whole, from the surface of the Slide Plate to the top of the nose screw, I designate as '^ the Circular Move- ment of the Second Bed Plate." In figure 1, the toothed wheel piece L. L. forms part of the " Circular Movement of the First Bed Plate;" and, as there seen, it is screwed to the projecting part at the back of the second Bed Plate. This projection at the back of the second 58 Bed Plate forms one casting with the Plate, and is turned off, under the same plan of chucking, &c. as has been sug- gested regarding the Boss A. at the back of the first Bed Plate. A shallow counter- sink is turned out in the toothed piece L. L. into which the projection of the second Bed Plate, just mentioned, must correctly fit, and the Bed Plate and the piece L. L. are then to be firmly screwed together by four screws passing through the Bed Plate at its projecting part, and screwing into the toothed piece L. L. the heads of these screws being, of course, countersunk in the Bed Plate. After I had constructed my Chuck on the plan I have now detailed, and accord- ing to the representation of it in the en- graving fig. 1, and had done a great deal of work with it, and had proved it to be a very efficient instrument, I yet thought that greater steadiness might be obtained by enlarging the diameter of the circular movement of the first Bed Plate. I, ac- zt p^^ ^ o 59 cordingly, made the alteration ; and as my object is to relate all I know on the sub- ject of the Chuck, T give a diagram, of this alteration, in the real dimensions of the pieces which compose it. The annexed wood-cut is a section through the centre, shewing a modifica- tion of the construction of the circular movement and its appendages^ whicli I have recently introduced into my Chuck on the Bed Plate next the Lathe head^ in substitution of the one represented by the engraving, figure 3. By doubling the dia- meter of the moving circular plate, additi- onal steadiness is obtained ; and the power of angular adjustment is greatly increased by having a stop wheel of 192 teeth instead of one of 96 ; and, besides, the construc- tion is more simple and easy. G. G. is the Slide Plate, made of brass, attached to the Bed Plate that screws on the Mandril. A piece of steel P. P. P. P. is shouldered into this Slide Plate and kept firm to it by four screws (see two of them marked 4). N. re- 60 presents the eireular hole passing throus^h the Slide Plate and steel piece^ to receive the plug N, described before and shewn in the engraving figure 3. A circular brass plate K. K. the edge cut into 192 teeth, is fitted to move round, without the least shake, on the steel piece P. P. P. P. A steel plate L. L. is screwed by six screws (see those marked 6) to the steel piece P. and the brass circle with teeth is kept firmly in its place by it. The centre part of the plate L. L. is turned out to make room for the plug screw nut, figure 3. N. Into the brass plate K. K. there are four pillars S. S. screw quite tight, at an equal distance from the centre of the plate and from each other. O. O. is a plate of brass screwed firmly to these pillars, in the man- ner seen. When this plate is screwed to the pillars the edge is turned truly round, and divided and figured into twelve grand divisions, and each of those divisions, again, into eight parts. A slender piece of brass plate is screwed to the back of the steel 61 piece P, on one of tlie sides that project bejond the Slide Phite, to carry the index to the circular division. A piece of brass plate is also attached, by screws, to the back of the piece P. to carry the micro- meter click (before described) that is to act on the toothed edge of the plate K. The space which is obtained by means of the pillars, between L. L. and O. O. is for the Slide Plate screw, which, in the en- graving fig. 1, is seen next to the toothed wheel L. L. The second, or upprr Bed Plate, shewn in fig. 1, and represented in fig. 5 by B. B. is, under this modificaiioii of the Chuck, substituted by O. O. The steel arms E. E. F. F. seen in figure 5, are attached to O. O. in like manner, as they therein appear; but, as O. O. is a circular plate, the adjusting screws i. i. cannot be used ; and, therefore, two snail -headed screws may be substituted, or a bar of brass, of the thickness of the adjust ible steel arm, may be screwed to the plate pa- rallel to the arm, and two screws passed F 62 through it, in a plane with the plate, which when screwed will press against the steel arm as occasion may require. In my Chuck I have adopted the latter. Having now gone into an explanation of every thing that particularly occurs to me, with regard to the Compound Eccen- tric Chuck, the next thing will be to give the Specimens of simple Eccentric Turn- ing which have appeared in the first and second editions. INTRODUCTION TO THE FORMER EDITIONS. J- URNiNG is now so generally resorted to as an amusement^ that the communication of any thing, which may tend to produce novelty in the art, cannot fail of being interesting to the Amateur ; besides, there can be no better means employed to pro- mote improvement than circulating the result of experience. Turning has been the favourite amuse- ment of the Author for many years, and from the time he first took to it, he has 64 sensibly felt the advantage he would have derived^ could he have informed himself of the progress which had been made by others^ and he regrets the information that has daily escaped him, for want of a reci- procity of communication among his co- temporary Turners. With regard to him- self, he has long had it in contemplation to make known the result of some of his labours; but the very great expense of get- ting the necessary engravings executed — indeed the almost impossibility of getting them done at all — has hitherto prevented him from carrying his intention into ef- fect. He has, however, in pursuing his object, constructed, himself, a piece of Machinery which enables him to engrave his own copper-plates. Having so far overcome his difficulties, he ventures to offer to the attention of the 65 Turner, a Series of Specimens in Eccen- tric Circular Turning; and should this be the means of inducing others to com- municate the result of their labours to the Public, in the same or any other branch of Turning, he will be much gratified. The copper-plate Engravings represent the pieces of Eccentric Circular Turning to be executed on ivory, wood, or any other material ; and each plate is accom- panied by such Practical Instructions, as will enable any one, who has acquired the least practical knowledge in the art to produce the desired effect. SPECIMENS IN eccentric Circular Ctirning* SPECIMEN I. — ^"^^ — Xhe pattern in Eccentric Turning which is described in this Specimen, and repre- sented in the accompanying plate, is peculiarly adapted for the lid of a snuff- box; or three or four of the centre figures may be selected, and applied to decorate a set of backgammon-men. This Specimen is composed of seven sets of circles, of different radii, arranged, at different eccentricities, round the com- mon centre. The number of circles which compose the interior, or centre set, is 68 twelve ; the number in the exterior set^ is two hundred and eighty-eight : the latter number may^ however^ be greater than can be obtained with the common eccentric chuck, and another set, there- fore, is described, which may be substi- tuted by those who have not the means of adopting the one exhibited in the plate. The following is a practical description of the method to be pursued to produce a piece of Eccentric Turning similar to Plate I. The tools with which the work is to be executed are double angular, Nos. 25, 32, and 36, according to Messrs. Holtzap- FFEL and Deyerlein's construction of this sort of tool ; ^ and the slide rest is to be ' It has been often suggested to me, that it would have been better to have given a particular descrip- tion of these tools. My answer to which has always been, that, it formed no part of my plan, when I published these Specimens, to give any ac- count of the construction of the machinery. I con- sidered that the amateur who was disposed to engage in the execution of any of these Specimens, must 69 set at right angles witli the mandril of the lathe. Fix an angular tool. No. 25, in the slide rest, and adjust the eeeentric chuck, slide rest, and the point of the an- gular tool, with the nicest correctness, to the common centre, and proceed to exe- cute the interior, or centre set of circles. necessarily be acquainted with the tools, usually employed in this branch of Turning, and that it was, therefore, sufficient to refer him to the manu- factory where I knew they could be obtained, and where I always procured them myself. 70 FIRST SET OF CIRCLES. ^ Eccentricity equal to 3. Radius equal to 2. To produce the eccentricity, turn the slide screw of the eccentric chuck back- wards three turns ; to produce the radius, turn the slide rest screw backwards two ^ The Eccentricity and Radius are noted, in this manner, throughout. My object in doing this has not, I find, been exactly understood. It is this : All such figures depend solely on the ratio which the Eccentricity bears to the Radius. In this case the ratio is as 3 to 2 ; and this being known, the same figure may be produced of any size ; and the same rule applies to all other cases. By attending to this the patterns may be varied, in size, at pleasure j and thereby the different figures, forming these specimens, may be combined in various ways, and infinite variety of new patterns may be produced. For instance : If it were required to place this figure in lieu of the centre figure, in Plate II. — As it is, it would be too large j but if the eccentricity be pro- duced by I \ turns of the screw, and the radius by I 71 turns ;3 then describe twelve circles, equi- distant from each other, round the com- mon centre. These circles must be cut sufficiently deep to give a sharp edge to the figures, which the angular tool will produce ; and this effect must be obtain- ed, although it may be attended with the labour of going over the circles, and cut- ting them deeper, a second or third time : but to whatever depth this set of circles be cut, the same depth must be preserved throughout all the other parts of this pat- tern, excepting the exterior set of circles, regarding the depth of which, mention will be hereafter made. turn, the figure will be the same, though of only half the size, and would then be small enough to be introduced as the centre figure in Plate II. It might also, on the same principle, be enlarged. The eccentricity may be produced by turning the screw 3| turns ; and the radius, by turning the screw 2| turns. The ratio, in this case, is still as 3 to 2 3 but the figure becomes increased in size. * It is to be understood that the slide screw of the eccentric chuck, and the screw of the slide rest, are equal in velocity. 72 SECOND SET OF CIRCLES. qOq^ o o o . o O JD OqO Eccentricity equal to 6. Radius equal to 1. To produce the eccentricity, turn the slide screw of the eccentric chuck back- wards three turns ; which, in addition to the former, makes the eccentricity equal to six.* To make the radius equal to one, * I have adopted the expressions of " turning the screw backwards," and '' turning the screw for- wards," as being the matter of fact, and the precise things that must be done to produce the eccentricity and radius. And as every one must know what is meant by turning a screw backwards or forwards, I adopted those expressions, as being 7nore intelligible than any other I could make use of. I am induced to offer this explanation, in conse- quence of the following paragraph, which appeared in a little amateur production, published two years after mine. The paragraph alluded to runs thus : The expression " advancing the point," though not 73 turn the slide rest screw forwards one turn, which is a decrease of the former radius equal to one turn. Then with the angu- lar tool as before, describe twelve equi- distant circles. THIRD SET OF CIRCLES. Ecceutricity equal to 10. Radius equal to 3. Change the angular tool to No. 36, hut, before it is fixed in the slide rest, adjust it to the radius and depth of the circle which was last turned. Then, to produce the eccentricity, turn the slide screw of strictly correct, has been adopted in preference to " moving the small wheel backicards," as more intel- ligible. 74 the eccentric chuck backwards four turns; and, to produce the radius, turn the slide rest screw backwards two turns. Describe forty-eight equidistant circles. FOURTH SET OF CIRCLES. Eccentricity equal to 3. Radius equal to 16. Proceed with the same angular tool, and, to produce the eccentricity for this set, turn the slide screw of the eccentric chuck forwards seven turns. To produce the radius, encrease the former radius by turning the slide rest screw backwards thirteen turns. Then describe twenty- four equidistant circles. 75 FIFTH SET OF CIRCLES. Eccentricity equal to 23. Radius equal to A\. Continue with the same angular tool. The eccentricity is to be encreased by turning the slide screw of the eccentric chuck backwards twenty turns ; and the radius is to be decreased by turning the slide rest screw forwards eleven turns and a half. Then (supposing the eccentric circle to be divided into ninety-six,,) be- gin at eccentric division No. 96^ and describe sixteen circles : miss eight divi- sions, set the eccentric circle to division No. 24, and describe sixteen more circles: miss eight divisions, set the eccentric circle to No. 48, and describe sixteen more circles : miss eight divisions, set the 76 eccentric circle to No. 12, and describe sixteen more circles. SIXTH SET OF CIRCLES. Eccentricity equal to 29y. Radius equal to 2. Change the angular tool to No. 25 ; which, before it is fixed in the slide rest, must be adjusted to the radius and depth of the circle last turned. The eccentricity is then to be encreased by turning the slide screw of the eccentric chuck back- wards six turns and a half, and the radius is to be decreased by turning the slide rest screw forwards two turns and a half. Describe ninety-six equidistant circles. 77 SEVENTH SET OF CIRCLES. Eccentricity equal to 33. Radius equal to |. Change the angular tool to [No. 32; and, before it is fixed in the slide rest, adjust it to the radius of the circles last turned. The eccentricity is then to be increased by turning the slide screw of the eccentric chuck backwards three turns and a half; and the radius is to be de- creased by turning the slide rest screw forwards one and three-eighths of a turn. Describe two hundred and eighty-eight equidistant circles, not^ however, of the depth of the circles previously turned^ but of such a depth only as will just make the figures which the tool leaves, sharp at top. Or, for common eccentric chucks, the following may be adopted. 78 SEVENTH SET OF CIRCLES. ADAPTKD TO AN ECCENTRIC DIVISION OF NINETY-SIX. Eccentricity equal to 33. Radius equal to 1. Proceed exactly in the same manner as described for the set of two hundred and eighty-eight circles : the only difference is^ thatj in this set, the radius is to be made equal to one turn of the slide rest screw, and the number of equidistant cir- cles must be limited to ninety-six. ri..te 9 79 SPF.CIMEN II This Specimen consists of seventeen sets of circles^ of different eccentricities and radii, arranged round the common centre, in the manner represented in Plate II. The exterior sets are produced bj an eccentric circular division of two hundred and eighty-eight, and are formed into the figure of an Etruscan Border ; but, as this high number of divisions cannot be obtained with the common eccentric chuck, a method is hereafter described, by which a Border, similar in figure, may be produced with an eccentric circular division of only ninety-six. To produce a piece of Eccentric Circu- lar Turning, similar to the pattern r('j)re- 80 sented in Plate II, the following arrange- ment must be minutely attended to. The work, in the first instance, is to be brought to a plane and polished surface ; and the eccentric circles are to be execu- ted, with double angular tools, Nos. 28 and 36. Set the slide rest at right angles with the mandril of the lathe, and let it remain in that position until the work be completed. Fix an angular tool. No. 28, in the slide rest, and adjust its point, the eccentric chuck, and the slide rest, to the common centre, with the greatest possible correctness ; then proceed to execute the interior, or centre set of circles : these circles are not to be cut deep into the surface of the work ; but must be cut suf- ficiently so to leave the figures sharp at top. 81 FIRST SET OF CIRCLES. Eccentricity equal to 1 Radius equal to |. To produce the eccentricity, turn the slide screw of the eccentric chuck back- wards one turn. To produce the radius, turn the slide rest screw backwards half a turn. Describe twelve equidistant circles. SECOND SET OF CIRCLES. Eccentricity equal to 4. Radius equal to 1-|. To produce this eccentricity, increase tlie former eccentricity by turning the 82 slide screw of the eccentric chuck back- wards three turns ; and to produce this radius^ increase the former radius by turn- ing the slide rest screw backwards one turn ; then, with the same tool as be- fore, describe twelve equidistant circles. These circles must be cut considerably deeper than the first set of circles; rather more so than will be sufficient to leave the figure, which is formed by the inter- section of the circles, sharp at top : but to whatever depth these circles are cut^ the same depth must be preserved in all the sets of circles remaining to be exe- cuted; excepting those composing the border, regarding which mention will be hereafter made. 83 THIRD SET OF CIRCLES. Eccentricity equal to 7|. Radius equal to 2. Change the angular tool, and fix No. S6 in the slide rest; but, before it is fixed, adjust its point to the radius and depth of the circle last turned. Then produce the eccentricity by turning the slide screw of the eccentric chuck backwarks three turns and a half; and produce the radius, by turning the slide rest screw backwards half a turn. Describe thirty-two circles at the following distances: viz. (sup- posing the circle of the eccentric chuck to be divided into ninety-six,) begin at division 96, and describe eight circles, one circle at every alternate succeeding division : miss eight succeeding divisions^ set the eccentric circle at division 24, 84 and describe eight more circles, one circle at each alternate , division : miss eight succeeding divisions^ set the eccentric circle at division 48, and describe eight more circles, one circle at each alternate division : miss eight succeeding divisions, set the circle of the eccentric chuck at division 72, and describe eight circles as before. FOURTH SET OF CIRCLES. Eccentricity equal to 13. Radius equal to 3y. Change the angular tool, and fix No. 28 in the slide rest; but, before it is fixed, adjust its point to the radius and depth of the circle last turned. Produce the ccoentricity by turning the slide screw of 85 the eccentric chuck backwards five turns and a half. Produce the radius by turn- ing the slide rest screw backwards one turn and a half. Then describe forty- eight equidistant circles. FIFTH SET OF CIRCLES. Eccentricity equal to 19|. Radius equal to Z\. Change the angular tool, and fix No. S& in the slide rest ; but, before it is fixed, adjust its point to the radius and depth of the circle last turned. The eccentri- city is to be produced by turning the slide screw of the eccentric chuck backwards six turns and three-fourths : the radius remains as before. Describe sixtv-four 86 circles^ and arrange them in the following manner: vh. Set the eccentric circle at division 96^ and describe sixteen circles, one circle at each following division : miss eight divisions^, set the eccentric cir- cle at division 24, and describe sixteen more circles : miss eight divisions, set the eccentric circle at division 48, and describe sixteen more circles : miss eight divisions, set the eccentric circle at divi- sion 72, and describe sixteen circles as before. SIXTH SET OF CIRCLES. Eccentricity equal to 1 9| Radius equal to ^ Proceed with the same angular tool. No. 36, and with the same eccentricity. 87 Decrease the radius by turning the slide rest screw forwards three turns. Then (supposing the eccentric circle to be di- vided into ninety-six) describe four cir- cles, one circle at each of the divisions undernamed : viz. at division 20, 44, 68, 92. SEFENTH SET OF CIRCLES. Eccentricity equal to 2I|. Radius equal to 1. Proceed with the same angular tool. No. S(S. Increase the eccentricity by turning the slide screw of the eccentric chuck backwards two turns : and in- crease the radius by turning the slide rest screw backwards half a turn. Then 88 describe four circles^ one circle at each of the following divisions, viz. at 20, 44, 68, 92. EIGHTH SET OF CIRCLES. Eccentricity equal to 17|. Radius equal to 1 , Proceed with the same angular tool. No. 36. Decrease the eccentricity by turning the eccentric slide screw forwards four turns; and, with the same radius as before, describe four circles, one at each of the following divisions, viz. 20, 44, 68, 92. 89 NINTH SET OF CIRCLES. Eccentricity equal to 30. Radius equal to \. Change the angular tool, and fix No. 28 in the slide rest ; but, before it is fixed, adjust its point to tlie radius of the circle last turned. The circles in this and the succeeding sets, which compose the Etrus- can Border, are to be cut no deeper than will make the figures perfect at top. Produce the eccentricity by turning the slide screw of the eccentric chuck back- wards twelve turns and a quarter; and reduce the radius by turning the slide rest screw forwards half a turn. The set of circles now to be produced, is the exterior of the nine sets which form the Etruscan Border. The circles in this set are two hundred and forty, which are to be described in the following manner : Set the circle of the eccentric chuck 90 (which is supposed to be divided into two liundred and eighty-eight) at division 5, and describe twenty circles, one circle at that and at each succeeding division : miss four divisions, set the circle of the eccentric chuck at division 29, and de- scribe twenty circles as before : miss four divisions, set the circle of the eccentric chuck at division 53, and describe twenty more circles ; and so on for the rest of this set, which, if correctly executed, will be completed by describing the last circle, in the last series of twenty, at division 288. 91 TENTH SET OF CIRCLES.' Eccentricity equal to 29|. Radius equal to \. Proceed with the same angular tool and radius as before ; and decrease the ec- centricity by turning the eccentric slide screw forwards five-eighths of a turn. The circles in this set are twenty-four^ and are to be described at the following distances. Set the circle of the eccentric chuck at division b, and describe one circle : miss eighteen divisions, set the circle of the ec- centric chuck at division 24, and describe one circle : miss four divisions, and de- scribe one circle at the succeeding divi- sion ; and so on, missing eighteen and four divisions alternately, and describing one circle at each division between those * This and the following Illustrations exhibit the progress of the Etruscan Border ; the lowermost circles being those vvhitli are to be produced. 92 two scries, till the last circle being descri- bed at division 288, completes the set. ELEVENTH SET OF CIRCLES. Eccentricity equal to 28|:. Radius equal to f. Decrease the eccentricity by turning the slide screw of the eccentric chuck forwards five-eighths of a turn; and then proceed, with the same angular tool and radius as before, to describe twenty-four circles in the same manner as directed for the tenth set. 93 TfFELFTH SET OF CIRCLES. Eccentricity equal to 28^ Radius equal to \ Decrease the eccentricity by turning the slide screw of the eccentric chuck forwards five-eighths of a turn; and pro- ceed to describe twenty-four circles in the same manner as directed for the tenth set. THIRTEENTH SET OF CIRCLES. Eccentricity equal to 27\. Radius equal to \. Proceed with the same angular tool and radius as before ; and decrease the eccen- tricity by turning the slide screw of the 94 eccentric chuck forwards five-eighths of a turn. This set consists of one hundred and eighty circles^ which are to be de- scribed in the following manner : Set the circle of the eccentric chuck at divi- sion 5_, and describe fifteen circles^ one circle at that and at each succeeding di- vision : miss four divisions^ set the circle of the eccentric chuck at division 24^ and describe one circle : miss four divisions^ set the circle of the eccentric chuck at division 29^ and describe fifteen circles : and so on for the remaining divisions of this set. 95 FOURTEENTH SET OF CIRCLES. Eccentricity equal to 26|. Radius equal to \. Proceed with the same ang;ii!ar tool and radius as before ; and decrease the eccentricity by turning the slide screw of the eccentric chuck forwards five-eighths of a turn. This set consists of twenty-four circles, which are to be described at the following distances : Set the circle of the eccentric chuck at division 288, and describe one circle : miss eighteen divisions, set the cir- cle of the eccentric chuck at division 19, and describe one circle : miss four divi- sions, and describe one circle at the suc- ceeding division : and so on, missing eigh- teen and four divisions alternately, and describing one circle at each division be- tween those two series, till the last circle 96 beins: described at division 283, com- plates the set. FIFTEENTH SET OF CIRCLES. Eccentricity equal to 26|. Radius equal to \. Decrease the eccentricity by turning the slide screw of the eccentric chuck forwards five-eighths of a turn : and then proceed^ with the same angular tool and radius as before^ to describe twenty-four circles, in the same manner as directed for the fourteenth set. 97 SIXTEENTH SET OF CIRCLES. Eccentricity equal to 25 i. Radius equal to \. Decrease the eccentricity by turning the slide screw of the eccentric chuck forwards five-eighths of a turn ; and then^ with the same radius and angular tool as before^ describe twenty-four circles at si- milar distances to those of the fourteenth set. SEVENTEENTH SET CIRCLES. Eccentricity equal to 25. Radius equal to \. Decrease the eccentricity by turning the slide screw of the eccentric chuck for- 98 wards five-eighths of a turn^ and proceed with the same angular tool and radius as before. This set of circles completes the Etruscan Border^ being the interior of the nine sets of which that Border is com- posed. There is the same number of cir- cles in this as in the exterior or ninth set^ viz. two hundred and forty, which are to be described in the following manner : Set the circle of the eccentric chuck at division 288, and describe twenty circles, one circle at that and at each succeeding division : miss four divisions, set the circle of the eccentric chuck at division 24, and describe twenty circles as before : miss four divisions, set the circle of the eccen- tric chuck at division 48, and describe twenty more circles : and so on for the rest of this set, which will be completed, if correctly executed, by the last circle, in the last series of twenty, being described at 283. The labour attending the execution of borders of this sort is very considerable. 99 particularly when they are composed of so minute a circular division as that just described. This alone will probably be sufficient to induce attention to correct- ness in placing the circles at their assigned distances ; for it must be recollected that the omission of a circle would considera- bly injure the general effect;, and a circle misplaced would totally spoil it.^ By the following method an Etruscan Border, similar in figure to that which is represented in Plate II, may be pro- duced with an eccentric circular division of only ninety-six. This Border consists of five sets of circles, which are to be cut sufficiently deep to make the figure per- fect at top. * At the time I wrote this I was unconscious I had afforded an opportunity of applying these re- marks. In the copper-plate Engraving (No. 2.) I had omitted every alternate circle in the second set of circles in the Etruscan Border. This circle was, however, properly inserted in the wood-cut illustration (see l7th set of circles). The omission of it in the copper-plate is not only very apparent. 100 NINTH SET OF CIRCLES. ADAPTED TO AN ECCENTRIC CIRCULAR DIVISION OF NINETV-SIX. .••••••••••, Eccentricity equal to 33. Radius equal to |. Change the angular tool^ and fix No. 28 in the slide rest; hut, before it is fixed, adjust its point to the radius of the circle last turned. Produce the eccentricity and radius, and make them greater than required for the ninth set, adapted io an eccentric division of two hundred and eighty-eight, by three turns backwards of the slide screw of the eccentric chuck, and three -eighths of a turn backwards of the slide rest screw. but may, certainly, be said to " injure the general effect." It was not, however, discovered until after it was before the Public, and it will now serve as a beacon to those who may be desirous of perfecting such kind of work. 101 This set of circles is the exterior of the five sets which are, now, to form the Etruscan Border : the number of circles in this set is eighty-four, which are to be described in the following manner. Set the circle of the eccentric chuck (which is supposed to be divided into ninety-six) at division 2, and describe seven circles, one circle at that and at each succeeding division: miss one divi- sion, set the circle of the eccentric chuck at division 11, and describe seven circles as before : miss one division, set the cir- cle of the eccentric chuck at division 19, and describe seven more circles: and so on for the rest of this set, which, if cor- rectly executed, will be completed by describing the last circle, in the last series of seven, at division 96. 103 TENTH SET OF CIRCLES. Eccentricity equal to Sl-j'g. Radius equal to \^. Proceed with the same angular tool as before. Decrease the eccentricity by turning the slide screw of the eccentric chuck forwards one turn and fifteen- sixteenths of a turn. Decrease the radius by turning the slide rest screw forwards one-sixteenth of a turn. The circles in this set are twenty-four^ which are to be described at the following distances : Set the circle of the eccentric chuck at divi- sion 2^ and describe one circle : miss five divisions^ set the circle of the eccentric chuck at division 8^, and describe one cir- cle : miss one division, set the circle of the eccentric chuck at division 10, and describe one circle : and so on, missing five divisions and one division alternately. 103 and describing one circle at each inter- mediate division, till the last circle, being described at division 96, completes the set. ELEVENTH SET OF CIRCLES. Eccentricity equal to 29-^'g^. Radius equal to |. Proceed v^^ith the same angular tool as before. Decrease the eccentricity by turn- ing the slide screw of the eccentric chuck forwards one turn and fourteen-sixteenths of a turn. Decrease the radius by turn- ing the slide rest screw forwards one-six- teenth of a turn. There are seventy-two circles in this set, which are to be de- scribed in the following manner : Set the circle of the eccentric chuck at division 2, and describe five circles, one circle at 104 that and at each succeeding division : miss one division, set the circle of the eccentric chuck at division 8, and describe one circle : miss one division, set the cir- cle of the eccentric chuck at division 10, and describe five circles : and so on, till this set be completed. TfFELFTH SET OF CIRCLES. Eccentricity equal to 27-x^. Radius equal to \^. The same angular tool as before. De- crease the eccentricity by turning the slide screw^ of the eccentric chuck for- wards one turn and thirteen-sixteenths of a turn. Decrease the radius by turning the slide rest screw forwards one-sixteenth of a turn. This set consists of twenty- four circles, which are to be described at 105 the following distances: Set the circle of the eccentric chuck at division 96, and describe one circle: miss five divi- sions, set the circle of the eccentric chuck at division 6, and describe one circle : miss one division, and describe one circle at the succeeding division : and so on, missinff five divisions and one division alternately, and describing one circle at the intermediate divisions, till the set be completed. THIRTEENTH SET OF CIRCLES. • ••••• • •., • Eccentricity equal to 25|. Radius equal to |. Decrease the eccentricity by turning the slide screw of the eccentric chuck forwards one turn and ten-sixteenths of a turn Decrease the radius by turning the 106 slide rest screw forwards one-sixteenth of a turn ; then proceed with the same an- gular tool as before. This set of circles completes the Etruscan Border^ adapted to an eccentric circular division of ninety- six. It consists of as many circles as the exterior set, viz. eighty-four, which are to be described in the following manner : Set the circle of the eccentric chuck at division 96, and describe seven circles, one circle at that and at each succeeding division : miss one division, set the circle of the eccentric chuck at division 8, and describe seven circles as before : miss one division, set the circle of the eccentric chuck at division 16, and describe seven circles : and so on, till the set be com- pleted at division 94. 107 SPECIMEN in. — • » ♦ — This Specimen is composed of five sets of circles, of various radii, which are ar- ranged round the common centre, at dif- ferent eccentricities, in the manner repre- sented in the accompanying Plate (III) : by reference to this Plate, aided by the following data, the Turner will be ena- bled to produce a corresponding piece of Turning. The tools to be used are double angu- lar, Nos. 28 and 36; and the slide rest is to be set at right angles with the mandril of the lathe. The work to be turned (be- ing first properly fixed in the eccentric chuck) must be brought to a plane and polished surface : then fix the angular tool No. 36, in the slide rest ; and, after 108 adjusting its pointy, the eccentric chuck, and the slide rest, to the common centre, with the greatest possible correctness, proceed to execute the centre, or interior set of circles. FIRST SET OF CIRCLES. Eccentricity equal to 1 ^ . Radios equal to 1|^. Produce the eccentricity by turning the slide screw of the eccentric chuck back- wards one turn and a quarter. Produce the radius by turning the slide rest screw backwards one turn and an eighth of a turn. Then describe eight equidistant circles : these circles are to be cut suffi- ciently deep to make the figure, which is 109 left by the intersection of the circles, sharp at top ; and the same depth must be preserved throughout all the other sets. SECOND SET OF CIRCLES. Eccentricity equal to A\. Radius equal to 2\. To obtain the eccentricity turn the slide screw of the eccentric chuck backwards three turns and a quarter. To obtain the radius turn the slide rest screw backwards one turn. Then, with the same angular tool as before, describe twenty-four equi- distant circles. no THIRD SET OF CIRCLES. Eccentricity equal to 5^ Radius equal to 1 1|. Produce the eccentricity by turning the slide screw of the eccentric chuck backwards five-eighths of a turn. Pro- duce the radius by turning the slide rest screw backwards nine turns and five eighths of a turn. Then^ with the same tool. No. 36, as before, describe twenty- four equidistant circles. Ill FOURTH SET OF CIRCLES. Eccentricity equal to 2\\, Radius equal to 4|. Change the angular tool, and fix No. 28 in the slide rest ; but, before it is fixed, adjust its point to the radius and depth of the circle last turned. To produce the eccentricity add to that required for the preceding set, by turning the slide screw of the eccentric chuck backwards sixteen turns and three-eighths of a turn. To produce the radius decrease that which was required for the preceding set, by turning the slide rest screw forwards seven turns. Describe ninety-six equidistant circles. 112 FIFTH SET OF CIRCLES. Eccentricity equal to 27\. Radius equal to \\. Increase the eccentricity required for the set last described^ by turning the slide screw of the eccentric chuck backwards six turns and a quarter; and decrease the radius by turning the slide rest screw for- wards three turns and a quarter. Then describe ninety-six equidistant circles. 113 SPECIMEN IV. — ■» ♦ * — This Specimen consists of five sets of circles^ which form the outermost figures, and of five sets of arcs of circles, or curved lines, which form the centre figure. The circles are of different radii, and are ar- ranged, at different eccentricities, round the common centre. The arcs of circles, or curved lines, are all of the same radius and eccentricity, and are produced from the point of the common centre, but vary in their measure. Plate IV represents the arrangement of these circles and arcs ; which, together with the following prac- tical directions, will enable the workman to execute a corresponding piece of Ec- centric Turning. In order to understand the description, hereafter given, of the method by which 114 the arcs of circles, or curved lines, are to be produced, the following observations must be attended to. It must be recollected, that, in Eccen- tric Turning, all circles and arcs of cir- cles, are produced by the rotation of the lathe ; that the radius of all circles, and of all arcs of circles, depend on the ad- justment of the slide rest ; and that the locality, or what is called eccentricity in this kind of Turning, of all circles, and of all arcs of circles, is assigned to them by the operation of the eccentric chuck. If a tool, therefore, be applied to the surface of the work, at any point with- out the centre of the lathe's motion, and the pulley wheel, which gives motion to the mandril of the lathe, be moved com- pletely round, a circle will be described: if the pulley wheel be moved but half round, the tool will describe a semicircle, or an arc of 180 degrees : and if the pul- ley wheel be moved but a quarter round, the tool will describe a quadrant, or arc 115 of 90 degrees. The pulley wheel which gives motion to the mandril of the lathe, aflfords, consequently, the practical means of measuring all arcs or curved lines ; and it will give their measure both minutely and correctly^ if a circle on the face of it be divided into some convenient num- ber of parts. For instance, suppose such circle were divided into forty-eight parts, and that to produce an arc, or curved line, the said pulley wheel be moved forwards twelve of those parts, the mea- sure of the arc, or curved line, thereby produced, would be equal to -Hj i^ *^^ pulley wheel be moved twenty-four divi- sions, the measure of the curve would be equal to ^^, &c. &c. It is on this prin- ciple that the curved lines in question are produced, and that the measure of them is defined. The work to be turned must be fixed in the eccentric chuck, and brought to a plane and polished surface ; a double an- gular tool, No. 32, may be used through- 116 out this piece of Eccentric Turning ; and the slide rest is to be set at right angles with the mandril of the lathe. Fix the angular tool in the slide rest, and adjust its pointy the eccentric chuck, and the slide rest, to the common centre, with every possible degree of correctness. In this state of things, move the lathe round, and pressing the point of the angular tool gently against the surface of the work, describe a very minute dot ; from which dot all the curved lines, which form the centre figure, are to be pro- duced, in the following manner. 117 FIRST SET OF ARCS, Eccentricity equal to 5. Radius equal to /). Measure of the arcs ^. Produce the eccentricity and radius by turning the slide screw of the eccentric chuck and the slide rest screw backwards five turns each. Set the circle of the ec- centric chuck at division 96, turn round the mandril pulley wheel until the dot, at the common centre, comes under the point of the tool ; and then, setting the point of the tool in this dot, describe a curved line by moving the pulley wheel forwards (supposing it to be divided into 48) twelve divisions.^ Then describe five other arcs, or curved lines, one at each ' It would tend very greatly to the correct execu- tion of this centre figure, if stops were to be applied 118 of the following divisions of the circle of the eccentric chuck, 16, 32, 48, 64, 80. to the pulley wheel, so as to secure it from moving, either way, beyond the intended limits of the curve. Since the first edition was published I have seen various methods of stopping the pulley wheel, dif- ferent to that I had, myself, adopted. Most of the lathe makers have now some contrivance they affix to their lathes, which they call the " segment stop." These contrivances are available for executing the arcs of circles in question, and all others ; but why the lathe makers call it the segment stop I cannot say. It would have been better if it had been called otherwise, as there is no possible motion of the lathe that can describe the segment of a circle. Every curved line that is produced by the motion of the mandril of the lathe, must be either a circle, or an arc of a circle ; whilst a segment of a circle is a superfices comprehended between two lines, viz. by a straight line denominated a chord, and by a curved line, denominated an arc. 119 SECOND SET OF ARCS.'' Eccentricity equal to 5 Radius equal to 5. Measure of the arcs ^-^. These arcs^ or curved lines^ are to be produced from the centre dot^ in the same manner as those of the former set^ but the pulley wheel is to be moved only eleven divisions. There are twelve curved lines of this measure to be described, one at each of the under-named divisions of the circle of the eccentric ckuck, vi%. 2, 14, 18, 30, 34, 46, 50, 62, 66, 78, 82, 94. •* In this and the following illustrations of the arcs, the lines which meet at the centre are those which are to be produced. 120 THIRD SET OF ARCS. Eccentricity equal to 5. Radius equal to 5. Measure of the arcs |§, Produce six arcs^, one at each of the following divisions of the circle of the eccentric chuck, viz. 4, 20, SQ, 52, 68, 84. FOURTH SET OF ARCS. Eccentricity equal to 5. Radius equal to 5. Measure of the arcs -j^g. Produce six arcs, one at each of the following divisions of the circle of the ec- centric chuck, vi%. 6, 22, 38, 54, 70, 86. 121 FIFTH SET OF ARCS. Eccentricity equal to 5. Radius equal to 5. Measure of the arcs -^g. Produce twelve arcs, one at each of the following divisions of the circle of the eccentric chuck, vi%. 8, 12, 24, 28, 40, 44, 56, 60, 72, 76, 88, 92. FIRST SET OF CIRCLES. Eccentricity equal to \A\. Radius equal to 5. Proceed with the same ano-ular tool and radius as before. Increase the eccentri- 122 city by turning the slide screw of the eccentric chuck backwards nine turns and one-eighth of a turn ; and then (sup- posing the circle of the eccentric chuck to be divided into 96) produce forty- eight circles in the following manner : viz. Describe one circle at division 96 : set the circle of the eccentric chuck at divi- sion 1^ and describe another circle: miss two divisions^ set the circle of the eccen- tric chuck at division 4, and describe a circle : set the circle of the eccentric chuck at division 5;, and describe another circle; and so on^ missing every alternate two divisions, till the forty-eight circles be completed. 123 SECOND SET CIRCLES. lOOOOOOOOo, ^ooo— ^Oo^ Eccentricity equal to 19|. Radius equal to \. The same angular tool as before. Pro- duce the eccentricity by turning the slide screw of the eccentric chuck backwards five turns and five-eighths of a turn. Produce the radius by turning the slide rest screw forwards four turns and a half Describe ninety-six equidistant circles. 124 THIRD SET OF CIRCLES. Eccentricity equal to 24f . Radius equal to 4. The same angular tool as before. Pro- duce the eccentricity by turning the slide screw of the eccentric chuck backwards four turns and three-fourths of a turn. Produce the radius by turning the slide rest screw forwards three turns and a half. Describe thirty-two equidistant circles. 125 FOURTH SET OF CIRCLES. Eccentricity equal to 29y. Radius equal to 2\. The same angular tool as before. In- crease the eccentricity by turning the slide screw of the eccentric chuck back- wards five turns. Decrease the radius by turning the slide rest screw forwards one turn and a half Describe thirty-two equidistant circles. \26 FIFTH SET CIRCLES. Eccentricity equal to 30^ Radius equal to 2. The same angular tool as before. In- crease the eccentricity by turning the slide screw of the eccentric chuck back- wards one turn. Decrease the radius by turning the slide rest screw forwards half a turn. Describe thirty-two equidistant circles : these circles are not to be pro- duced at the divisions of the circle of the eccentric chuck adopted in the third and fourth sets, but midway between those divisions. 127 SPECIMEN V. ^ ♦ «» This Specimen is composed of a num- ber of concentric circles, and of arcs of circles, which cross each other in the manner represented in the accompanying Plate (V). The concentric circles in- crease in radius, in a uniform ratio from the common centre : the arcs of circles are all of the same measure, and are pro- duced, not from the point of the com- mon centre, but from points equidistant from it. The tool to be used, to produce a piece of Eccentric Turning corresponding with this Specimen, is double angular No. 28, and the slide rest is to be set at right angles with the mandril of the lathe. The work to be turned, being properly fixed in the eccentric chuck, is to be 128 brought to a plane and polished surface. Then place an angular tool. No. 28, in the slide rest, adjust its point, the slide rest, and the eccentric chuck, to the com- mon centre, and proceed to execute the concentric circles. 77//; CONCENTRIC CIRCLES. Radius of the first circle equal to 1. Radius of the second circle equal to 1-^. Radius of the third circle equal to 2, &c. To produce the radius for the first, or internal circle, turn the slide rest screw backwards one turn. Describe one cir- cle. To produce the radius for the second circle, increase the radius of the former 129 by turning the slide rest screw backwards half a turn. Describe another circle ; and so oUj increasing the radius of each suc- ceeding circle, bj turning the slide rest screw backwards half a turn, until eighty circles are produced. THE ARCS OF CIRCLES, OR CURBED LINES. Eccentricity equal to 30. Radius equal to 30. Measure of the arcs' equal to \^, These arcs of circles, or curved lines, are to be cut with a similar angular tool, ' The method of producing ai)d measuring the arcs, already described for Specimen IV, must be attended to in this Specimen. Vide p. 1 11. 130 No. 28, and to the same depth as the con- centric circles. Supposing the radius of the exterior of the concentric circles to have been equal to 40^^ produce the radius for the arcs^ or curved lines^ and make it equal to 30^ by turning the slide rest screw forwards ten turns and a half Produce the eccentricity by turning the slide screw of the eccentric chuck back- wards thirty turns. Turn the mandril pulley wheels until the centre of the inte- rior concentric circle coincides with the point of the tool. Move the pulley wheel forward^ without letting the tool touch the work^ equal to an arc of ~% and put on a stop to prevent its moving beyond that point. Move the pulley wheel back again equal to an arc of ^, and put on a stop to prevent its moving, any further that way. The tool being now applied to the sur- face of the workj and the mandril pulley wheel moved through the space thus li- mited by the stops, an arc will be described 131 equal to if; viz. an arc, which will begin at a distance from the common centre equal to ~, and end at a distance from the common centre equal to ^'. There are twelve sets of these arcs to be produced and arranged in the following manner; each set to consist of five arcs. Set the circle of the eccentric chuck (supposing it to be divided into 96,) at division 96, and describe one arc at that and at the four succeeding divisions : miss three divisions, set the circle of the eccen- tric chuck at division 8, and describe five other arcs; and so on for the rest. The divisions of the circle of the eccentric chuck, at which the arcs in each set are to be described, are as under. 1st set of arcs, at Nos. 96, J, 2, 3, 4. 2nd do 8, 9, 10, 11, 12. 3rd do 16, 17, 18, 19, 20. 4th do 24, 25, 26, 27, 28. 5th do 32, 33, 34, 35, 36. 6th do 40, 41, 42, 43, 44. 132 7th set of arcs, at 48, 49, 50, 51, 52. i 8th do 56, 57, 58, 59, 60. ^ 9th do 64, 65, 66, 67, 68. 10th do 72, 73, 74, 75, 76. 11th do 80, 81, 82, 83, 84. 12th do 88, 89, 90, 91, 92. i c§S° i 08° 080 opo 133 SPECIMEN VI. — » ♦ » — The accompanying Plate (VI) repre- sents the manner in which the sets of eccentric circles^ and the sets of arcs, or curved lines, are to be arranged in this Specimen. The sets of circles are of dif- ferent eccentricities and radii; and the arcs^ or curved lines, are all of the same measure, and are produced from points without, and equidistant from, the com- mon centre. To form a piece of Eccentric Circular Turning, corresponding with this Speci- men, use a double angular tool. No. 28, and set the slide rest at right angles with the mandril of the lathe. The work to be turned is to be first properly fixed in the eccentric chuck, and brought to a plane and polished surface. 134 Then place the angular tool. No. 28, in the slide rest; adjust its point, the slide rest, and the eccentric chuck, to the com- mon centre; and proceed to execute the arcs of circles, or curved lines. THE ARCS, OR CURVED LINES. Eccentricity equal to 12. Radius equal to 12. Measure of the arcs ^g. Produce the eccentricity by turning the slide screw of the eccentric chuck back- wards twelve turns. Produce the radius by turning the slide rest screw backwards twelve turns. Then adjust the mandril pulley wheel to the measure of the arcs of circles, or curved lines, in the same man- ner as directed for those in Specimen V. These arcs of circles are, in all respects, similar to those described in Specimen V, 135 except in their dimensions^ and are to be described exactly in the same manner, at the same divisions of the circle of the eccentric chuck, at the same distance from the common centre, and should be cut sufficiently deep to bring the surface left between them to an angle at top. CENTRE FIGURE, OR FIRST SET OF CIRCLES. Eccentricity equal to li. Radius equal to 1 . Remove the stops from the mandril pulley wheel, and continue with the an- gular tool. No. 28. Produce the eccen- tricity by turning the slide screw of the eccentric chuck forwards ten turns and three-quarters of a turn. Produce the 136 radius by turning the slide rest screw forwards eleven turns. Describe eight equidistant circles^ of the same depth as the curved lines. SECOND SET OF CIRCLES. Eccentricity equal to 4|. Radius equal to 17. The same angular tool;, No. 28, as be- fore, and the circles are to be cut to a suf- ficient depth to make the spaces, which their intersection leaves, sharp at top. Produce the eccentricity by turning the slide screw of the eccentric chuck back- wards three turns and one-eighth of a turn. Produce the radius by turning the slide rest screw backwards sixteen turns. Describe twenty-four equidistant circles. 137 THIRD SET OF CIRCLES. Eccentricity equal to 30. Radius equal to \. The circles in this and in the following seven sets, are to be produced by the an- gular tool. No. 28, and all cut to the same depth as the second set. Produce the eccentricity by turning the slide screw of the eccentric chuck backwards twenty- five turns and five-eighths of a turn. Pro- duce the radius by turning the slide rest screw forwards sixteen turns and a half. Describe twelve equidistant circles. 138 FOURTH SET OF CIRCLES. Eccentricity equal to 29|. Radius equal to 1 . The eccentricity is to be obtained by turning the slide screw of the eccentric chuck forwards half a turn. Obtain the radius by turning the slide rest screw backwards half a turn. Then describe twelve equidistant circles, which are to circumscribe those of the third set. 139 FIFTH SET OF CIRCLES. Eccentricity equal to 29. Radius equal to \\. Produce the eccentricity by iiirning the slide screw of - 5... -:..,. 3o + . c.,.u.^3^^- ^■-^'^^.■^'^1^'; ^^--^'-^ ■ :,,^j *Miv (»"•-'/ ouv>.c^ ^■»^. •• •'-•'— ^•'fP-^^^y^P' -^A V^' ^^^'' /^■: ■f w^maSaSm '^ H, An: m -^^ ■/ r -' ^■^' ' r - V'N \ ^i r ^^ ■'[■ii% MU/^^' \:^^m K^-^lr^ '^'/^ ,v^\V^^^^.^ ^.:\y,,'-'^^' J'C\' ';:,•''.«= T^ ■ ry^ 'm!c ^ ^y^ Ill lil IN il I I ill I II i ill III llilllll A 000 093 556 9 ''^W I /^ I /^ r^m ^^i-^m ; ^T "x. -I