STACK 
 ANNfcX 
 
 5 
 
 027 
 
 642 
 
 >;.t: 
 
 
 ^
 
 DESCRIPTION 
 
 O F A N 
 
 ENGINE 
 
 FOR 
 
 DIVIDING MATHEMATICAL INSTRUMENTS, 
 
 By Mr. J. R A M S D E N, 
 
 MATHEMATICAL INSTRUMENT-MAKER, 
 
 Publiflied by Order of the 
 COMMISSIONERS of LONGITUDE. 
 
 LONDON: 
 
 Printed by William RichardsoWj 
 
 AND 
 
 Sold by John Nourse, in the Strand; and MefT. Mount and 
 
 Page, Tower-Hill. 
 
 MDCCLXXVII. 
 
 [TRICE FIVE SHILLINGS,!
 
 PREFACE,. 
 
 MR. Ramfden^ Mathematical Inftrumcnt-maker,; 
 in Piccadilly i was paid the Sum of 615 /. by- 
 certificate from the Commiffioncrs of Longitude,, 
 upon delivering to them, upon oath, a full and 
 complete written Explanation and Defcription of his 
 Engine for Dividing Mathematical Inftruments (ac- 
 companied with proper Drawings) and of the Manner 
 of Ufing the fame, and alfo of the Engine by which 
 the Endlefs Screw, being a principal Part of the faid- 
 Dividing Engine, was made; and upon agreeing and- 
 entering; into articles with them for affigning; over the 
 Right and Property of the faid Engine to them, for 
 the Ufe of the Public; and engaging himfelf to give 
 to the faid Commiflioners, and fuch other Perfons,, 
 being Mathematical Inftrument-makers, not exceed- 
 ing Ten, as fhall be appointed by them, during the 
 fpace of Two years, from the 28 th of OBohcr 1775, 
 to the 28th of OElober 1777, fuch Inftrudlion and 
 Information with regard to the making and ufing of 
 the faid Engine, as may be fully fufficient to enable 
 any intelligent workman to confl:ru6l and ufe other 
 Engines of the fime kind ; and alfo binding himfelf 
 to divide all Odants and Sextants, by the faid Engine, . 
 
 which J 
 
 1 ryf^a*".
 
 P Pv E F A C E. 
 
 which fliail be brought to him by any Mathematical 
 Inftrument-makcrs for tliat purpofe, at the rate of 
 Three ShilUngs for each Octant, and at the rate of 
 Six Shilhngs for each brafs Sextant, with Nonius Di- 
 vifions to Half Minutes, for fo long a time as the 
 faid Commiffioners fhall think proper to permit the 
 faid Engine to remain in his pofleffion : of which 
 Sum of 615/. ,paid to the faid Mr. Ram/deny 300/. 
 was given him as a Reward for the Improvement 
 made by him in the Art of Dividing Inflruments by 
 means of the faid Dividing Engine, and for Difcovcr- 
 ing the fame ; and the remaining 315/. in confider- 
 ation of his making over the Property in the faid 
 Engine to the Commiffioners of Longitude, for the 
 Ufe of the Public, and for the other Confiderations 
 .before-mentioned. 
 
 In order to render this Infirument more extensively 
 ufeful, the Commiffioners of Longitude ordered the 
 written Explanation, with Drawings, of the Dividing 
 Engine, to be prepared for Publication : and it is now 
 
 publifhed accordingly. 
 
 ■ Greenwich, NEVIL MASKELYNE, 
 
 _Nov.2^, 1776. Astronomer-Royal.
 
 DESCRIPTION OF the ENGINE 
 
 FOR DIVIDING 
 
 MATHEMATICAL INSTRUMENTS. 
 
 THIS Engine confifts of a large Wheel of Bell-metal, 
 fupported on a mahogany ftand, having three legs, 
 Avhich areilrongly connected together by braces, fo as 
 to make it perfeftly fteady. On each leg of the lland is placed 
 a conical friftion-pully, whereon the Dividing-wheel refts : to 
 prevent the Wheel from iliding off the friftion-puUies, the 
 bell- metal center under it turns in a focket on the top of the 
 ftand. 
 
 The Circumference of the Wheel Is ratched or cut (by a 
 method which will be defcribed hereafter) into 2160 Teeth, 
 in which an endlefs Screw a6ts. Six revolutions of the Screw 
 will move the Wheel a fpace equal to one degree. 
 
 Now a Circle of Erafs being fixed on the Screw Arbor, 
 having its Circumference divided into Sixty Parts, each Divi- 
 ficn will confequently anfwer to a Motion of the Wheel of 
 Ten Seconds, Six of them will be equal to a Minute, &c. 
 
 A Several
 
 % DESCRIPTION OF the ENGINE for 
 
 Several clifFerent Arbors of tempered fteel are truly groiuid 
 into the Socket in the center of the Wheel. The upper parts 
 of the arbors that ftand above the plane are turned of various 
 fizes, to fuit the centers of different pieces of work to be 
 divided. 
 
 When any Inftrument is to be divided, the Center of it is 
 very exa£i:ly fitted on one of thefe Arbors, and the Inflrument 
 is fixed down to the plane of the Dividing-wheel by means of 
 fcrews, which fit into holes made in the Radii of the Wheel 
 for that purpofe. 
 
 The Inftrument being thus fitted on the plane of the Wheel, 
 the Frame which carries the Dividing-point is conne6ted at 
 one end by finger fcrews with the frame which carries the 
 cndlefs fcrew ; while the other end embraces that part of the 
 fleel arbor, which ftands above the Inftrument to be divided, 
 by an angular notch in a piece of hardened fteel : by this means 
 both ends oi the frame are kept perfeftly fteady and free from 
 any fhake. 
 
 The frame carrying the Dividing-point or Tracer is made 
 to flide on the frame which carries th« endlefs Screw to any 
 diftance from the center of the Wheel, as the Radius of the 
 Inftrument to be divided may require, and may be there faf- 
 tened by tightening two clamps ; and the Dividing-point or 
 Tracer being connected with the clamps by the double-jointed 
 frame admits a free and eafy motion towards or from the cen- 
 ter for cutting the divifions, without any lateral fliake^ 
 
 From
 
 Dividing MATHEMATICAL INSTRUMENTS. 3 
 
 From what has been faid it appears, that an Inftrument 
 ■thus fitted on the Dividing-wheel may be moved to any angle 
 by the fcrew and divided circle on its arbor, and that this 
 angle may be marked on the Limb of the Inftrument with the 
 greateft exaftnefs by the Dividing-point or Tracer, which can 
 •'Only move in a dired line tending to the center, and is alto- 
 gether freed from thofe inconveniences that attend cuttino- by 
 means of a ftraight edge. This method of drawing lines will 
 alfo prevent any error that might arife from an expanfion or 
 ^contradion of the metal during the time of dividing. 
 
 The Screw-frame is fixed on the top of a conical Pillar, 
 which turns freely round its axis, and alfo moves freely towards 
 ■or from the center of the Wheel, fo that the Screw-frame may 
 be intirely guided by the frame which connefts it with the 
 center : by this means any excentricity of the Wheel and the 
 Arbor would not produce any error in the dividing; and, by a 
 particular contrivance, which will be defcribed hereafter, the 
 fcrew when prefled againft the Teeth of the Wheel always 
 moves parallel to itfeif ; fo that a Line joining the center of 
 the Arbor and the Tracer continued, will always make equal 
 angles with the Icrew, 
 
 Figure i . reprefents a perfpe6tive view of the Engine. 
 
 Fig. 2. is a plan of half dimenfions; of which Fig. 3. repre- 
 fents a fe£lion on the line IIA. 
 
 The large wheel A is 45 inches in diameter, and has ten 
 radii, each being fupported by edge-bars, as reprefented ia 
 Fig. 3. Thefe bars and radii are connefted by the circular 
 ring B. 24 inches in diameter, and 3 deep : and, for greater 
 ftrength, the whole is call in one piece in bell- metal. 
 
 A 2 As
 
 4 DESCRIPTION of the ENGINE for 
 
 As the whole weight of the wheel A refts on its rhig B, 
 the edge-bars are deepeft where they join it ; and from thence 
 their depth diminiflies, both towards the center and the cir- 
 cumference, as reprefented in Fig. 3. 
 
 The furface of the wheel A was worked very even and fiat, 
 and its circumference turned true. The ring C *, ot fine brafs, 
 was fitted very exactly on the circumference of the wheel, and 
 was faftened thereon with fcrews, which, after being fcrewed 
 as tight as pollible, were well riveted. The face of a large 
 chuck being turned very true and flat in the lath, the flat- 
 Fig. 3. tened furfiice A of the wheel was faftened againft it with hold- 
 fafts : and the two furfaces and circumference of the ring C, 
 a hole through the center and the plane part (b) round it, and 
 the lower edcre of the rinjr B were turned at the fame time. 
 
 D is a piece of hard bell-metal, having the hole, which 
 receives the fteel arbor (d), made very ftraight and true. This 
 bell-metal was turned very true on an arbor, and the fiice, 
 which refts againft the wheel at (b), was turned very flat, fo 
 that the fleel arbor (d) might ftand perpendicular to the plane 
 of the wheel : this bell-metal was faftened to the wheel by fix 
 fteel fcrews (1). 
 
 A brafs focket Z is faftened on the center of the mahogany 
 ■ ftand, and receives the lower part of the bell-metal piece D, 
 being made to touch the bell-metal in a narrow part near the 
 mouth, to prevent any obliquity of the wheel from bending 
 the arbor : good fitting is by no means neceffary here ; fince 
 any fliake in this focket will produce no bad effe>5l, as will 
 appear hereafter when I defcribc the cutting frame. 
 
 The 
 
 * See a feftion of the ring at C, Fig. 3.
 
 DivioiNo MATHEMATICAL INSTRUMENTS. 5 
 
 The wheel was then put on its ftaiid, the lower edge of the 
 rhig B, reiling on the circumference of three conical friction- Fi^;. i,2,<t 3. 
 pullies VV, to facilitate its motion round its center. The axis 
 of one of thefe pullies is in a line joining the center of the 
 wheel and the middle of the endlefs fcrew, and the other two 
 placed fo as to he at equal diilances from each other. 
 
 F is a block of wood flrongly faflenedto one of the legs of fig. «. 
 the {land; the piece (g) is fcrewed to the upjx^r fide of the block, 
 and has half holes, in which the tranfverfe axis (h) turns : the Fig. 4.^ 
 half holes are kept together by the fcrews (i). 
 
 The lower extremity of the conical pillar P terminates in a Fig. 1&4,, 
 cylindric fteel pin (k), which paflcs through and turns In the Fig. 4. 
 tranfverfe axis (h), and is confined by a cheek and fcrew. 
 
 To the upper end- of the conical pillar is faflened the frame pitr. . 
 G, in which the endlefs fcrew turns: the pivots of the fcrew 
 are formed in the manner of two fruflrums of cones joined 
 by a cylinder, as reprefented at X-. Thefe pivots are confined Fig. 5, . 
 between half holes, which prefs only on the conical parts, and 
 do not touch the cylindric parts : the half holes are kept toge- 
 ther by fcrews (a), which may be tightened at any time, to- 
 prevent the fcrew from Ihaking In the frame. 
 
 On the fcrew arbor Is a fmall wheel of brafs K, having Its Fig. i, 2, 
 outfide edge divided Into 60 parts, and numbered at every ' '' 
 6th divifion with i, 2, &c. to 10. The motion of this wheel 
 is fhewn by the Index (y) on the fcrew frame G. ^k-i^si 
 
 H repr^fents part of the ftand, having a parallel flit In the Fig. i, 
 dlredllon towards the center of the wheel, large enough to re- 
 ceive
 
 o 
 
 DESCRIPTION OF the ENGINE ran 
 
 ceive the upper part of the conical brafs pillar P, which carries iht 
 fcrew and its frame: and as the refiflance, whenthe wheel is 
 moved by the endlefs fcrew, is againft that fide of the flit H 
 which is towards the left hand, that fide of the flit is faced with 
 brafs, and the pillar is prefTed againft it by a fteel fpring on the 
 oppofite fide : by this means the pillar is fbrongly fupported la- 
 terally, and yet the fcrew may be eafily preffed from or againft 
 the circumference of the wheel, and the pillar will turn freely 
 on its axis to take any diredlion given It by the frame L. 
 
 Fig. 4. At each corner of the piece I are fcrews (n) of tem.pered fteel, 
 
 having polifhed conical points : two of them turn in conical 
 holes in the fcrew-frame near (o), and the points of the other 
 two fcrews turn In holes in the piece Q^; the fcrews (p) are of 
 fteel, which being tightened prevent the conical pointed fcrews 
 from unturning when the frame is moved, 
 
 ;Pig.i.2.6. L is a brafs frame which ferves to conneft the endlefs fcrew, 
 its frame, &c. with the center of the wheel : each arm of this 
 frame is terminated by a fteel fcrew, that may be paffed through 
 
 Fig. 4. any of the holes (q) in the piece Q^, as the thicknefs of work 
 to be divided on the wheel may require, and are faftened by 
 
 Fig. 1 &2. the finger-nuts (r). 
 
 At the other end of this frame is a fiat piece of tempered 
 
 Fig. 6. fteel (b), wherein is an angular notch : when the endlefs fcrew 
 
 is prefl'ed againft the teeth on the circumference of the wheel 
 
 ■Pig. I & J. which may be done by turning the finger- fcrew S, to preis 
 
 againft the fpring (t), this notch embraces and preftes againft 
 
 Fjg. 2. the fteel arbor (d). This end of the frame may be raifed or 
 
 .4 deprefled
 
 Dividing MATHEMATICAL INSTRUMENTS. 7 
 
 prefled by moving the prifmatic Aide (u), which may be fixed Fig. 1.2.6. 
 at any height by the four fteei fcrews (v). 
 
 The bottom of this Aide has a notch (k), whofe plane is Fig. i & 6. 
 parallel to the endlefs-fcrew, and by the point of the arbor (d) Fig. 3. 
 refting in this notch, this end of the frame is prevented from 
 tilting : the fcrew S is prevented from unturning by tightening Fig. 1..2. 
 the finger-nut (w). 
 
 The teeth on the circumference of the wheel were cut by 
 the followino; method. 
 
 'to 
 
 Having confidered what number of teeth on the circum- 
 ference would be moft convenient, which in this Engine is 
 2 1 60, or 360 multiplied by 6, I made two fcrews of the 
 fame dlmenfions, of tempered fteel, in the manner here- 
 after defcribed, the interval between the threads being fuch 
 as I knew by calculation would come within the limits of what 
 might be turned off the circumference of the wheel : one of 
 thefe fcrews, which was intended for ratching or cutting the 
 teeth, was notched acrofs the threads, fo that the fcrew, when . 
 preffcd againfi: the edge of the wheel and turned round, cut in 
 the manner of a faw. Then having a fegment of a circle a 
 a little greater than 60 degrees, of about the fame radius with 
 the wiiecl, and the circumference made true, from a very fine 
 center, I defcribed an arch near the edge, and fet off the chord 
 of 60 degrees on this arch. This fegment was put in the 
 place of the wheel, the edge of it was ratched, and the num- 
 ber of revolutions and parts of the fcrew contained between 
 the interval of the 60 degrees were counted. The radius was ; 
 corrected in the proportion of 360 revolutions, which ought
 
 8 DESCRIPTION of the ENGINE for 
 
 to have been in 60 degrees, to the number adually found : and 
 the radius, fo corrected, was taken in a pair of beam-com- 
 paffes : while the wheel was on the lath, one foot of the com- 
 ■ ■ paffes was put in the center, and with the other a circle was 
 
 defcribed on the ring; tiien half the depth of the threads of 
 the fcrew being taken in dividers was fet from this circle out- 
 twards, and another circle was defcribed cutting this point; 
 a hollow was then turned on the edge of the wheel of the fame 
 curvature as that of the fcrew at the bottom of the threads : 
 the bottom of this hollow was turned to the fame radius or 
 diflance from the center of the wheel as the outward of the two 
 circles before-mentioned. 
 
 The wheel was now taken off the lath, the bell-metal 
 .Tig. 3; piece D was fcrewed on as before direfted, which after this 
 ought not to be removed. 
 
 :Fia.i,z,i. From a very exa£l: center, a circle was defcribed on the ring 
 C, about -1- of an inch within where the bottom of the teeth 
 would come j this circle was divided with the greateft exaftnefs 
 I was capable of, firfl into 5 parts, and each of thefe into 3 ; thefe 
 parts were then bifefted 4 times (that is to fay) fuppofing the 
 whole circumference of the wheel to contain 2160 teeth, this 
 being divided into 5 parts, each would contain 432 teeth, which 
 being divided into 3 parts, each of them would contain 1 44, and 
 thisfpace bifected 4 times would give 72, 36, 18, and 9; there- 
 fore each of the lafl: divifions would contain 9 teeth : but, as I 
 was apprehenfive fome error might arifc from quinquefedlioa 
 and trifeftion, in order to examine the accuracy of the divifions, 
 
 .Fig. 7. I defcribed another circle on the ring C, -j-V inch within the 
 .former, and divided it by continual bifcftions, as 2160, 1080, 
 
 5405
 
 Dividing MATHEMATICAL INSTRUMENTS. 9 
 
 540, 270, 135, 674-', and 23I-I and, as the fixed wire (to be 
 defcribed prefently) croffed both the circles, I could examine 
 their agreement at every 135 revolutions (after ratching could 
 examine it at every 33^) ; but, not finding any fenfible difference 
 between the two fetts of divifions, I, for ratching, made choice 
 of the former; and, as the coincidence of the fixed wire with 
 an Interfe6tion could be more exactly determined than with a 
 dot or divifion, I therefore made ufe of interfeftions in both 
 circles before defcribed. 
 
 The arms of the frame L were conneifled by a thin piece of ^'S 7' 
 brafs of i of an inch broad, having a hole in the middle of vV 
 of an inch in diameter; acrofs this hole a filver wire was fixed' 
 exactly in a line to the center of the wheel ; the coincidence of* 
 this wire with the interfe6lions was" examined by a lensi^'-g. inch 
 focus, fixed in a tube which was attached^to one of the armsL,*, 
 Now, a handle or winch being fixed on the end of tlie fcrew, the 
 divifion marked 10 on the circle K was fet to its index, and, by 
 iTieans of a clamp and adjufting fcrew for that purpofe, the in- 
 terfeftion marked i on the circle C was fet exaftly to coincide 
 with the fixed wire ; the fcrew was then carefully prefied againft 
 the circumference of the wheel, by turning the finger-fcrew S ;, 
 then, removing the clamp, I turned the fcrew by its handle 9 
 revolutions, till the interfe£lion marked 240 came nearly to the 
 wire ; then, unturning the finger-fcrew S, I releafed the fcrew 
 from the wheel, and turned the wheel back till the interfedion 
 marked 2 exaftly coincided with the wire, and, by means of 
 the clamp before-mentioned, the divifion 10 on the circle be- 
 ing fet to its index, the fcrew was prcfTcd againfl the edge of 
 
 * The Interfedions are marked for the fake of illuftration, though properly, 
 iavifiblc, they lying under the brafs plate. 
 
 K tlia
 
 10 DESCRIPTION OF the ENGINE for 
 
 the wheel by the finger-fcrew S; the clamps were removed, 
 and the fcrew turned 9 revolutions till thelnter fedion marked 
 I nearly coincided with the fixed wire ; the fcrew was releafed 
 from the wheel by unturning the finger-fcrew S, as before, 
 the wheel was turned back till the interfedioii 3 coincided 
 with the fixed wire ; the divifion 10 on the circle being let to 
 its index', the fcrew was preffed againft the wheel as before, 
 and the fcrew was turned 9 revolutions, till the interfeClion 2 
 nearly coincided with the fixed wire, and the fcrew was releafed; 
 and I proceeded in this manner till the teeth were marked 
 round the whole circumference of the wheel. This was re- 
 peated three times round, to make the impreflion of the fcrew 
 deeper. I then ratched the wheel round continually in the fame 
 direftion without ever difengaging the fcrew, and in ratching 
 the wheel about 300 times round the teeth were finifhed. 
 
 Now it is evident, if the circumference of the wheel was 
 even one tooth or ten minutes greater than the fcrew would re- 
 quire, this error would in the firft inftance be reduced to ^-^--„- 
 part of a revolution or two feconds and a half; and thefe errors 
 or inequalities of the teeth were equally diftributed round the 
 wheel at the diftance of 9 teeth from each other. Now, as 
 the fcrew in ratching had continually hold of feveral teeth at 
 the fame time, and thefe conftantly changing, the above- 
 mentioned inequalities foon correfted themfelves, and the teeth 
 were reduced to a perfedl equality. The piece of brafs which 
 carries the wire was now taken away, and the cutting fcrew 
 was alfo removed, and a plain one (hereafter defciibed) put in 
 its place : on one end of the fcrew is a fmall brafs circle, having 
 its edge divided into 60 equal parts, and numbered at every 
 
 fix til
 
 Dividing MATHEMATICAL INSTRUMENTS, ii 
 
 fixth dlvifion, as before-mentioned. On the other end of the 
 fcrew is a ratchet-wheel C, having 60 teeth, covered by the 
 hollowed circle (d), which carries two clicks that catch upon Fig- >'• 
 the oppolite fides of the ratchet, when the fcrew is to be moved 
 forwards. The cylinder S turns on a ftrong fteel arbor F, which 
 paffes through and is firmly fcrewed to the piece Y : this piece, 
 for greater firmnefs, is attached to the fcrew-frame G by the 
 braces (v): a fpiral groove or thread is cut on the outfide of Fig. 4- 
 the cylinder Sj which ferves both for holding the firing and 
 alio giving motion to the lever J on its center by means of a 
 {leel tooth (n), that works between the threads of the fpiral. 
 To the lever is attached a ftrong fleel pin (m), on which a 
 brafs focket (r) turns : this fockct pafles through a flit in the 
 piece (p"*, and may be tightened in any part of the flit by the 
 finger-nut (f) :■ this piece ferves to regulate the number of re- 
 vohitioiis of the fcrev/ for each tread of the treadle R. Fig. i. 
 
 T is a brafs box containing a fpiral fpring ; a flrong gut is Fig. i, 
 faflened and turned 3 or 4 times round the circumference of 
 this box ; the gut then pafTes feveral times round the cylinder 
 S,. and from thence down to the treadle R, Now, when the 
 treadle is preflTed down, the firing pulls the cylinder S round 
 its axis, and the clicks catching hold of the teeth on the ratchet 
 carry the fcrew round with It, till, by the tooth (n) working Fig. 4.' 
 in the fpiral groove, the lever J is brought near the wheel (d), 
 and the cylinder flopped by the fcrew head (x) ftriklng on the 
 top of the lever J; at the fame time the fpring is wound up 
 by the other end of the gut paffing round the box T. Now, Fig. i,. 
 when the foot is taken off the treadle, the fpring unbending 
 itfelf pulls back the cylinder, the clicks leaving the ratchet and 
 
 B 2 fcrew.
 
 12 DESCRIPTION OF the ENGINE, &c. 
 
 Tig. 4. fcrcw at reft till the piece (t) ftrikes on the end of the piece (p) : 
 the number of revolutions of the fcrew at each tread is limited 
 by the number of revolutions the cylinder is allowed to turn 
 back before the llop ifrikes on the piece (p). 
 
 When the endlefs fcrew was moved round its axis with a 
 confiderable velocity, it would continue that motion a little 
 Fig. I &: 4. after the cylinder S was {lopped ; to prevent this the angular 
 lever ■» was made ; that when the lever J comes near to flop the 
 fcrew (x), it, by a fmall chamfor, prefles down the piece y. of 
 the angular lever ; this brings the other end » of the fame lever 
 forwards, and Hops the endlefs fcrew, by the fteel pin y, ftriking 
 upon the top of it : the foot of the lever is raifed again by a 
 fmall fpring preffing on the brace (v). 
 
 Ti^.i.i.f^. D, two clamps, connected by the piece «, Aide one on each 
 arm of the frame L, and may be fixed at pleafure by the four 
 finger-fcrews g, which prefs againft fleel fprings to avoid fpoil- 
 ing the arms : the piece (q) is made to turn without Ihake be- 
 tween the two conical pointed fcrews (f), which are prevented 
 from unturning by tightening the finger-nuts N. 
 
 Fig. 6. The piece M is made to turn on the piece (q), by the conical 
 
 pointed fcrews (f) refting in the hollow centers (e). 
 
 As there is frequent occafion to cut divlfions on inclined 
 planes, for that purpofe the piece y, in which the tracer is 
 fixed, has a conical axis at each cud, which turn in half holes: 
 when the tracer is fet to any inclination, it may be fixed there 
 by tightening the fleel fcrews /8. 
 
 jS Defcription
 
 [ ^3 ] 
 
 Defcription of the Engine by which the endlefs Screw 
 of the Dividing-engine was cut. 
 
 F 
 
 I G. 9. reprefents this Engine of its full dimenfions feeii 
 from one fide. 
 
 Fig. 8. the upper fide of the fame as feen from above. 
 
 A reprefents a triangular bar of fteel, to which the trian- 
 gular holes in the pieces B and C are accurately fitted, and 
 may be fixed on any part of the bar by the fcrews D. 
 
 E is a piece of fteel whereon the fcrew is intended to be 
 cut; which, after being hardened and tempered, has its pivots 
 turned in the form of two fruflums of cones, as reprefented 
 in the drawings of the Dividing-engine *. Thefe pivots were 
 very exacSlly fitted to the half holes F and T, which were kept 
 together by the fcrews Z, 
 
 H reprefents a fcrew of untempered fteel, having a pivot I, 
 which turns in the hole K. At the other end of the fcrew is 
 a hollow center, which receives the hardened conical point of 
 thefteel pin M. When this point is fufficiently preffed againft 
 the fcrew, to prevent its fliaking, the fteel pin may be fixed by 
 tightening the fcrews Y. 
 
 N is a cylindric nut, moveable on the fcrew H ; which, to 
 prevent any fhake, may be tightened by the fcrews O. This nut 
 is conne£ted with the faddle-piece P by means of the interme- 
 diate univerfal joint W, through which the arbor of the fcrew 
 H pafles. A front view of this piece, with a fedion acrofs the 
 
 fcrew- 
 
 • Fig- 5.
 
 [ H ] 
 
 fcrew-arbor is reprefented at X. This joint is conne(Sled with 
 the laut by means of two fteel flips S, which turn on pins 
 between the cheeks T on the .nut N. The other ends of 
 thefe flips S turn in like manner on pins (a). One axis of this 
 joint turns in a hole in the cock (b), which is fixed to the 
 faddle-piece, and the other turns in a hole (d), made for that 
 purpofe in the fame piece on which the cock (b) is fixed. By 
 this means, when the fcrew is turned round, the faddle-piece 
 will Aide uniformly along the triangular bar A. 
 
 K is a fmall triangular bar of w^ell-tempered fteel, which 
 Hides in a groove of the fame form on the faddle-piece P; The 
 point of this bar or cutter is formed to the (hape of the thread 
 intended to be cut on the endlefs fcrew. When the cutter is 
 fet to take proper hold of the intended fcrew, it may be fixed 
 by tightening the fcrews(e), which prefs the two pieces of brafs 
 G upon it. 
 
 Having meafured the circumference of the Dividing-whed, 
 I found it would require a fcrew about one thread in a hun- 
 dred coarfer than the guide-fcrew H. The wheels on the 
 guide-fcrew arbor H, and that on the fteel E, on which the 
 fcrew was to be cut, were proportioned to each other to pro- 
 duce that effedl, by giving the wheel L 198 teeth and the 
 wheel () 200. Thefe wheels communicated with each other 
 by means of the intermediate wheel R, which alio ferved to 
 give the threads on the two fcrews the fam.e direilion. 
 
 The faddle-piece P is confined on the bar A by means of 
 the pieces (g), and may be made to Aide with a proper degrqe 
 of tightnefs by the fcrews (n). 
 
 THE END.
 
 \ 
 
 -Til T
 
 u^l^aam^m
 
 c
 
 ■-'. /''a. 
 
 '-"/'
 
 l-lau- K 
 
 J
 
 f- RN REGIONAL LIBRARY FACiLlT> 
 
 D 000 011 452
 
 \i-.