TURNING. 



Tl'RXINO. 



plat*. n<l sometime* also with a micrometer screw and plate, no that 

 UM greaUt nicety ran be observed. 



It in, however, only in oonjunction with the fmrrr-latks, that the 

 full ralue of the slide-rest is exhibited. The beds, headrtook, and 

 alkie-rot of the power-lathe, fg. 10, are made in the same manner u 



;-:;;-; 



in the foot-lathe, but stronger; the mandril works in bearings to 

 allow the end B to project beyond the back puppet and carry a toothed 

 wheel ; between the beds nml aloni; their whole length is a screw, E, 

 which works in a nut nttaclied to the uiulcr |rt of the rest ; on the 

 end of the screw is placed another toothed-wheel D, which is turned by 

 the mandril-wheel B by means of the connecting wheel c. By varying 

 the sue of the wheels B and D, the rest can be made to move through 

 any required space along the beds of the lathe at each revolution of 

 the mandril. The spindle of the connecting wheel o fits in a curved 

 groove to accommodate it to the different sized wheels used on the 

 mandril and rest-screw ; when the rest is required to move in the 

 opposite direction, two connecting wheels are used. The size of these 

 connecting wheels, having no influence en the relative rates of B and D, 

 may be varied according to circumstances. The pulley, instead of 

 being fixed upon the mandril, as in the foot-lathe, is mounted upon a 

 metal tube or cannon which fits and turns smoothly upon the mandril. 

 The lathe, when set in motion, will require no more attention until a 

 fine spiral line is cut, enveloping the cylinder along its whole length ; 

 the rest has then to be shifted to where it started from, or by a simple 

 contrivance be made to work iU way back again, the tool being set out 

 a little deeper each time until the surface is completed. In screw- 

 cutting w ith the power-lathe, the point of the tool is made exactly the 

 shape of one of the spaces between the intended threads and having 

 the same rake or inclination; at each revolution of the mamhil the 

 rest must move through the distance from one thread to the next. 

 The circumference of the screw has no effect ujwm any part of the 

 arrangement but the inclination of the tool. When the screw is 

 required to be double or treble-threaded, that is, having two or three 

 intervening spirals upon the same stem, the rest must be moved 

 forward a proportionate distance at the commencement of the second 

 and third threads. In ."/. I' 1 , r r F is the iln/liny-framt, for working 

 drills and cutters, fixed in the re.-t, by aid of the pulleys a, u, and I. 

 If it U required to drill any number of holes in a plate, the drill-stock, 

 f<j. 11, is placed in the slide-rest and connected with the pulley I. By 

 drawing the drill-frame to or from the centre of the work, holes may 

 be drilled in straight lines across the centre, and. by shifting the 

 dividing-plate, in circles; by the combination of the two movements 

 the holes may le placed in curves and spirals in any direction. By 



Kir. ll. A 



Fig. 1J. 



r 



giving motion to the mandril, and connecting it with the slide-rest 

 crew, spiral groove* may be drilled upon the surfaces of plates, 

 cylinder!-. . r cone*. 



We may here notice a contrivance, introduced by Mr. Miles in 1860, 

 for turning pieced of wood no long that they would vibrate or swag if 

 operated U|mii in the ordinary way. Th- not rotate. Th. 



cutter* advance along it and turn nunil it, U-ing supported by a 

 ling carriage. Tiro dogs or pr- >pn r.r- placed hctirath the wood at certain 



points, which may be moved out of the way when the cutters 

 appro 



The cutting of toothed wheels is one of the most valuable a- 

 tioni of the lathe. [\\Y \<j.] The circular cutter u- d in 



ocess maybe employed in many other ways, such as < 

 grooves and flutes, which, except for sudden curves, it perform! bettor 

 and much more rapidly than the drill. Fur cutting straight groove! 

 both the drill and cutter are entirely superseded by the planing- 

 machine, a modern invention of the greatest importance. It supplies 

 what was one of the greatest want of the engineer, and might appro- 

 priately be called the ttraiyht lathe. For cutting grooves or flutes in 

 c\ lindrieal work, two small puppets carrying centres are screwed to the 

 table to support the work, and the parts where the grooves are re- 

 are brought under the tool by means of a division plate fixed to one of 

 tho puppets : a revolving cutter may be used instead of a fixed tool 

 for cutting long pinions and terminating flute*. 



frit Turning. In enumerating the different chucks, we pur- 

 posely omitted the c.rcentric and oval, as they give their names to the 

 respective kinds of turning for which they are used, and may tie 

 be considered rather as jarts of the lathe itoelf than as mere Appur- 

 tenances, t'i'j. 13 represents a tingle excentric chuck. It consists of a 



strong plate which screws on the nose of the mandril ; two dove 

 pieces are screwed upon it near the edges, between which the f' 

 works. Upon the slide is fitted a circular plate, which turns upon a 

 centre, and has its edge cut into a number of teeth according to the 

 eke of the chuck ; c is a click with one or two teeth fitting b 

 the teoth of the wheel, and held in its place by a spring un<!< 

 other cud. The nose, K, for carrying the work, is fixed to the upjier 

 plate. The duii/ile excentric chuck is mn.'.e in the same manner, but it 

 has a second slide, at right angles to the first, on the back of thu 

 ground plate. In common turning the use of the excentric chuck is 

 to bring any required point in the work in a line with the centre of 

 the mandril ; thus circular holes may be cut in any part of a plate, 

 the edge may be hollowed out by any number of curves of tho same or 

 different radii, and polygons with curvilinear sides maybe pro 

 with the greatest accuracy. Fig*. 14, 15, and 16 represent three a 



Fig. 14. 



Fig. IS. 



Fig. 18. 



an infinite variety of figure* produced in this way. In ornamental 

 turning the excentric chuck is mostly used for cutting jatterns upon 

 the surface of the work without altering its general outline. Tim*, iu 

 ornamenting ivory or wood-work, circles and curves arc laid in an 

 infinite variety of positions upon the face and edges of the work. The 

 ivury-turner 1'iequently uses a small instrument called an <.< 

 colter; it is formed like the drill-stock, Ji<j. 11, and moved by a lnv ; 

 the cutting point con be fixed nt dillcrcnt distances from the centre by 

 means of a groove and screw. In conjunction with a click plate upon 

 the mandril, the cutter answers many of the purposes of the siugle 

 excentric chuck. With the single-slide excentric chuck and the 

 dril at rest, the cutter will produce patterns which would otherwise 

 the double excentric. 



'.i hen the work revolves on the lathe, and the 



excentric cutter is driven by a band in connection with the mandiil, a 

 great variety of very complicated and beautiful < piejeloidal an 

 curves may be cut. This geometric chuck is an excentric with the. 

 addition of an arrangement for giving motion to the work upon tin- 

 chuck, and independent of the mandril. Fixed to the headstoek and 

 concentric with the mandril i a toothed wheel which, as the chuck 

 revolves, drives another and smaller wheel on ito under surface : this 

 latter is connected with another toothed wheel which causes the click- 

 plate and work to revolve. The patterns may be infinitely varied by 

 altering the relative sizes of the wheels ; and by introducing an extra 

 wheel, and so causing the work and chuck to revolve in opposite 

 <ns at the same time; and lastly by changing the position of 

 the tool. The 1111 ' curves that can be produced by 



these changes nnd the great dissimilarity to ouch otb- !>) l> 



conceived. The i-.\e. ntri. a < ks arc mu 



producing patterns on plates and blocks for prinlini; and embos- 

 Oval Turning. Until the Invent i,.n ,,| the oval chuck the pro,! 1 

 of true ovals was a matter of considerable difficulty, and thu cutting 

 of them upon tho lathe an impossibility ; with it we con turn ovals of 



