TURNING. 



ment, it is faid, the ancients turned all forts and kinds of 

 vafes, many of wliicli they enriched with figures and orna- 

 ments in balfo relievo. Thus Virgil fays : 



" Lenta quibus torno facili fuperaddita vitis." 



The Greek and Latin authors make frequent mention of 

 the lathe, and Cicero calls the workmen who ufed it, vafcu- 

 larii. It was a proverb among the ancients, to fay a 

 thing was formed in the lathe, to exprefs its delicacy and 

 juftnefs. 



The art of turning is of confiderable importance, as it 

 contributes eilontially to the perfeftion of many other arts. 

 The architeft ufes it for many ornaments, both within and 

 witliout highly finifhed houfes. The mathematician, the 

 aflronomer, and the natural philofopher, have recourfe to 

 it, not only to embellifh their inftruments, but alfo to give 

 them the neceflary dimenfions and precifion : in (hort, it is an 

 art abfolutely neceffary to the mechaiiift, the goldfmith, the 

 watchmaker, the joiner, the fmith, and others. 



As the operation of turning is to be performed by 

 the aid of the lathe, the ftrufture of that machine is the 

 firft thing to be confidered. In our article Lathe, we have 

 given a defcription of the moft perfeft kind of lathe, made 

 in iron, with a triangular bar ; and m the article RosE- 

 Engine, we have defcribed a curious lathe for ornamental 

 turning ; but it is to be obferved, that a much more fimple 

 machine will anfwer all the common purpofcs of turning. 



The effential properties of a lathe for outfide work are, 

 firft, that it fhall have two points which will firmly fuftaiii 

 the work at each end, by penetrating into the ends of the 

 work, and, at the fame time, allow it to turn freely round 

 upon the points : there muft be a reft or fupport to hold the 

 tool upon, and alfo fomc means of turning the work round 

 upon the points. A lathe to turn hollow or infide work will 

 not admit of a point of fupport at each end of the piece, and 

 therefore the work is firmly fixed to the extremity of a fpindle, 

 which is called a mandrel; when the mandrel is turned round, 

 the work revolves with it, and the tool can be applied at the 

 end of the work, to excavate or turn it hollow withinfide, or 

 to turn it on the outfide, as required. 



Lathes are made in a great variety of forms, and put in 

 motion by different means : they are called centre lathes, where 

 the work is fupported at both ends ; and mandrel, fpindle, or 

 chuck lathes, when the work is fixed at the projefting extremity 

 of a fpindle. 



From the different methods of putting them in motion, 

 they are called pole lathes, and hand-iuheel lathes, ox foot-tvheel 

 lath.'i. For very powerful works, lathes are turned by horfes, 

 lleam-engines, or water-wheels. 



The lathes ufed by wood-turners are generally made of 

 wood, in a fimple form, and are called ied lathes : the fame 

 kind will ferve for the common turning of iron or fteel, but 

 the beft work in metal is always done in iron lathes, which 

 are fometimes made with a triangular bar, and are called 

 6ar lathes, (fuch an one is defcribed in the article Lathe) ; 

 fmall ones, for the ufe of watch-makers, are called turn-benches, 

 and turns ; but there is, in faft, no proper diftinftion between 

 thefc and the centre lathes, except in regard to fize, and that 

 they are made of iron and brafs inftead of wood. 



The centre lathe is the moft fimple of all others. Two 

 beams of wood are fixed horizontally upon legs, like a bench, 

 and form what is called the bed. The two beams are fixed to- 

 gether, parallel to each other, and at a fmall diftance afunder, 

 lo as to leave a fpace or narrow groove between them, nearly 

 the whole length of the bed. This groove is to receive the 

 tenons at the lower ends of the puppets, which are ftjort pofts 

 rifing perpendicularly from the bed, and firnrJy fixed thereto 



by means of crofs wedges, put through the tenons bene.ith the 

 bed ; for the tenons arc of fufficicnt length to defcend quite 

 through the groove in the bid, and projeft beneath fuffi- 

 ciently to receive the crofs wedges, which being driven in, 

 draw the bafes of the puppets or pofts fo firmly down upon 

 the furface of the bed, that they will ftand firmly ereft upon it ; 

 or by withdrawing the wedges, the puppets become loofe, and 

 can be fixed in another part of the bed, in order that the dif- 

 tance between the two puppets may be made to correfpond 

 with the length of the piece of work to be turned. One of 

 the puppets has a pin orpikeoi iron fixed into it, and the other 

 one has at the fame level the centre J'creiu, working through 

 a nut fattened in the puppet : both the fcrew and pike have 

 Iharp points made of fteel, hardened and tempered, that 

 they may not wear away. They muft be exaftly oppofite, 

 and in a hne with each other. The piece of work, iuppofe 

 for inftance it is a roller of wood, is fupported by its ends 

 between the points of the pike and the fcrew, that it may 

 turn round freely. The rejl for the fupport of the tool is a 

 rail or bar, extending from one puppet to the other ; it lieS 

 in hooks, projefting from the faces of the puppets. 



The work is put in motion by means of the treadle, 

 which is worked by the turner's foot ; a firing or catgut is 

 fattened to the treadle, and pafling two or three turns round 

 the work, it is fattened to the end of an elaftic pole, fixed to 

 the ceiling over the turner's head. 



The workman ftands before his lathe, having one of his 

 feet on the treadle to give it motion ; he places a fharp 

 gouge or ch'ijj'el on the reft, and approaches the edge of it 

 gently to the piece of work ; then prcfiing the treadle down 

 by his foot, the ftring turns the work round, and the chiflel 

 or gouge being held firm upon the reft, and fo as to touch 

 the wood, it will cut it to a circular form. When he has 

 brought the treadle to the ground, he releafes the weight of 

 his foot, and the elafticity of the pole draws up the treadle, 

 turning the work back again ; during which retrograde 

 motion, he withdraws the chiflel from the work, as it would 

 not cut in this direction, though it might impede the motion 

 of the wood, and would injure the edge of the tool. He 

 mull perform his work gradually, without leaving ridges ; 

 and when he meets with a knot in the wood, he muft go on 

 ftill more gently, otherwife he would be in danger both of 

 fplitting his work and breaking the edge of his tool. For 

 turning hght work, a bow, fuch as is ufed for ftiooting 

 arrows, is fufpended by its middle over the lathe ; the ftring 

 is then tied to the middle of the bow-ftring, in lieu of the 

 pole, and afts in the fame manner. 



The common centre lathe is a very imperfeft machine, 

 when worked in this manner ; yet its fimplicity is a great 

 recommendation, efpecially among country workmen, who 

 ufe it to make various forts of common articles of houfehold 

 furniture in foft wood, as ftool and table legs, ftair-cafe rails, 

 &c. 



In centre lathes, the work is fometimes put in motion by 

 means of a large wheel, turned by one or more labourers ; the 

 wheel Ihould be heavy, that its momentum maybe fufficicnt to 

 overcome anv moderate obttacle in the work ; and the frame 

 in which it is mounted muft be of fufficicnt weight to ftand 

 fteadv, and not be liable to move, by the exertions of the 

 man turning it. An endlefs line is ufed, to communicate the 

 motion of the wheel to the work ; it paftes round a groove 

 in the circumference of the wheel, and after croffmg, like a 

 figure of 8, goes round a fmall pulley, fixed upon the work. 

 By this means, when the great wheel is turned, it gives a 

 rapid rotatory motion to the matter to be turned, and with 

 a much greater power than can be obtained from the treadle, 

 with the additional advantage of the work turning always 



the 



