441 



TURNING. 



TURNING. 



442 



cylinder, i, to support one end of the work, must be exactly opposite 

 to the centre of the mandril. There are several methods of arranging 

 the cylinder and its screw ; but the most convenient is as in the figure, 

 with a screw J, and a winch-handle. K is a small screw with a binding- 

 piece beneath, which rests upon a flat filed on one side of the cylinder, 

 and prevents the latter from shaking during turning. The rest, H, has 

 a jointed lever binding-screw, and several tops to suit different pur- 

 poses, with a small screw to hold them steadily in the socket. 



This completes the lathe itself, but many adaptations are necessary 

 before it is in order for work. Of these the principal are the chiifks 

 used to connect the work with the lathe. The screw-chuck is a circular 

 plate of metal with a boss at the back, tapped to screw upon the nose 

 of the mandril : the face is turned perfectly true, and in the centre is 

 a coarse conical screw to hold any large piece of wood to be turned. 

 The hullow-chuck is a strong circular cup of metal with perpendicular 

 sides : the work is either driven into it with a mallet, or, if smaller 

 than the inside of the cup, held by the ends of four screws in its rim. 

 The drill-chud is a strong iron chuck about an inch in diameter, with 

 a square hole in the centre to receive drills and other tools. In drilling, 

 a mark being made with a punch where the hole is to be, the work is 

 held against the point of the drill, and the front-head being brought 

 up to the back of the work, the cylinder ia pressed forward, as the 

 drill proceeds, by turning the screw J. The universal chuck is a circular 

 disc of metal, with three narrow slits cast in it, extending nearly from 

 the centre to the circumference. The face is turned perfectly true 

 when on the mandril, and the work being laid upon the face of the 

 chuck, is fixed to it by screws which pass through the slits into nuts 

 at the back of the plate. The concentric chuck is of the same form as 

 the last described, and the face in like manner must be turned per- 

 fectly true to the mandril. Instead of three slits, it has but two, in a 

 straight line with each other, and extending nearly the whole diameter; 

 the opening of these slits is wider at the back than front. Within 

 these slits lies a spindle, having a bearing in the centre and one at each 

 extremity, with a right-hand screw upon one and a corresponding left- 

 hand screw upon the other ; these screws move two steel studs which 

 fit accurately within the slits, and have projecting heads about an inch 

 square, that move steadily and smoothly along the face of the chuck. 

 Upon the heads are fitted two other square pieces, having their sides 

 hollowed out in curves of different diameters varying from two to eight 

 or ten inches, and which can be placed with either of their sides 

 towards the centre, to fit the circumference of the work to be held 

 between them. 



All the chucks that we have described are adapted principally for 

 work which does not require supporting at both ends. When a long 

 piece of wood is to be turned, a chuck is used having a piece of steel 

 with three points standing out upon its face ; the centre of one end of 

 the work is pressed against the middle point, and the other end is 

 supported by the cylinder of the front-head. 



The carrier is used in metal-work for the same purpose as the three- 

 point chuck for wood. If the ends of the work are pointed, it is 

 supported between the hollow end of the cylinder in the front puppet 

 s, fin. 4) and the nose of the mandril, wliich is similarly shaped for the 

 purpose : if, on the contrary, the ends are hollow, the cylinder is 

 reversed and the point-chuck (./?'/. 5) screwed upon the mandril. The 

 carrier (c,fig. 4) is fixed upon the end of the work by its screw, as 

 shown on a larger scale in the side view Jig. 6 ; and motion is given to 



Fig. 4. 



Fig. 5. 



Fig. 6. 



J 



the work by the driver H, fgt. 4 and 5, either screwed upon the nose 

 of the mandril or attached to the point-chuck. 



Wood and ivory turners make use principally of box and other wood 

 chucks altered at the instant to suit their purpose. One chuck, how- 

 ever, requires notice, called the split or riny-chuck, fg.T:& piece of 



Fig. 7. 



wood is tapped and screwed on to the mandril and then turned conical ; 

 it is afterwards drilled down the centre to the bottom, and two slits 

 cut with a saw at right angles to each other, from the point of the 

 chuck to the nose of the mandril ; the work, when in the chuck, is 

 held in it* place by the ring on the outside. 



The tool* used in turning are numerous and varied. For soft wood 

 scarcely any are required besides gouges or round chisels with circular 

 points, to rough out the work, and chisels with an oblique cutting edge, 

 haqjened by being ground and rubbed at a very acute angle on each 

 side. To give the workman power to prevent the tool dipping or 

 trembling, the tools are set in very long handles, the ends of which 



the turner holds between the upper part of his arm and his side. Eor 

 hard wood, ivory, and bone, similar gouges and chisels are used ; but 

 they are smaller, and sharpened at a less acute angle. Some of the 

 work, as in gold, silver, and light brass-work, is performed by gravers 

 with straight, oblique, and curved faces, to suit different sorts or parts 

 of the work. These are sharpened by an angle on the under side only, 

 and the cutting-edge is applied nearly opposite to the- centre of the 

 work. For inside work, drills placed in angles are used to make the 

 first opening, which is afterwards enlarged by other tools with this 

 general characteristic, that the stalk is made narrower than the cutting 

 part of the tool, to allow of undercutting or making the hollow within 

 larger than the opening through which the point of the tool is intro- 

 duced. The principal tools used for turning iron are the hook-tool, 

 fig. 8 : E is the cutting-edge ; the heel, H, is placed firmly upon the top 



Fig. 8. 



of the rest and the tool held with both hands, the end of the handle 

 resting against the turner's shoulder. For finishing the work, gravers 

 of different sizes and shapes are used, similar to those for hard wood, 

 gold, silver, brass, and ivory, but stronger, and sharpened at a more 

 obtuse angle. Screw-tools are very important appendages to a lathe, 

 and, with the engineer, in constant use : they are filed up with several 

 teeth exactly the shape of the spaces between the intended threads. 

 For inside screws the teeth are cut on the side, instead of the front of 

 the tool : taps however are much more generally used. A circular saw 

 is often fitted to a lathe, particularly for ivory-turning : the saw is 

 placed upon a spindle against a projecting collar, and held in its place 

 by a washer and nut. A parallel rule is fitted upon the table by the 

 side of the saw to regulate the width of the pieces cut off. 



In the lathe, as previously described, the tool is held in the hand, 

 and is consequently subject to any unsteadiness in the workman. To 

 get rid of this imperfection in certain cases, and so arrange that the 

 tool could be withdrawn at pleasure and replaced in the same position, 

 and always be steady, was a great desideratum. This was effected by 

 the invention of the slide-real, which is now attached to all but the 

 most ordinary kind of lathes. The principle of the slide-rest is that 

 the tool is fastened to a plate, moved in the required direction by 

 means of screws, instead of being held in the hand. Fig. 9 shows a 



Fig. 9 



very usual and convenient form. T is the place for the tool, which is 

 held down by the screw above : the tools are long square pieces of 

 steel reaching beyond the edges of the plate upon which they are fixed. 

 This plate has two small slips or dovetails screwed on to its under 

 surface and fitting the sides of the plate s, which has a screw along its 

 centre, working in a nut in the upper plate : so that by turning the 

 winch-handle the tool can be moved backward or forward along the 

 plate s, which is about twice the length of the upper or tool plate. 

 Beneath the plate s is a circular piece c, divided by a line into two 

 unequal portions; the upper and thicker portion is screwed to the 

 plate s ; the lower is in fact only a circular fillet left upon the plate 

 below : in the centre of the latter is fixed an accurately-turned pin 

 fitting into a corresponding hole in the former, which turns upon it as 

 a centre, and can be set at any required angle to the lower plate (which 

 is graduated for the purpose) and fixed in its position by two binding 

 screws, shown in the figure on each side of s. Beneath are a second 

 slide and circular plate, counterparts of those above, and the whole is 

 mounted on a plate, P. The manner of using the rest will be easily 

 understood. Hollow and~spherical surfaces may be cut with the slide- 

 rest with equal accuracy as rectangular figures, either by an adaptation 

 to the common slide-rest, by which the lower slide is made to act upon 

 the other, or by one constructed for the purpose. The slide-rest is of 

 great value in producing any number of pieces of work of exactly the 

 same form, of opposite forms and fitting each other, or in any given 

 proportions ; each slide-screw is fitted with a small circular graiuated 



