screw on the spindle end or 'nose' of the lathe, or into the female screw of the spindle. Chucks are not only necessary for giving motion to the work, but in some cases for firmly fastening and holding the material in a convenient position for allowing the tools to be applied to it. As the articles to be chucked vary greatly in size, shape, and material, the chucks must be constructed variously. Many will, however, answer equally well for hard and soft woods, and ivory. A few can be used indiscriminately for these materials and metals, but, as a rule, metals require chucks of greater strength and different construction. The drill-chuck,

Fig. 12, is made either of brass or cast or wrought iron. The dotted lines denote that it is fitted with a female screw for screwing on the spindle end. It also has a taper square, or taper round hole to receive a set of drilling tools, and also the two drivers, Figs. 13 and 14. Fig. 13 is the prong driver for the softer varieties of wood. Fig. 14 is the cross kerf driver. Both are made of steel, and the latter is used mostly for the hard woods, ivory, bone, and small work in metals. When these drivers are used, the work is always supported at the other extremity by the screw centre. The taper-screw chuck, Fig. 15, is made of metal, and screws on the male screw of the mandril. The taper-screw itself is

made of steel, and is fastened to the body of the chuck by a screw thread, so that if the screw be broken off or damaged, another can be substituted. This chuck is used for either soft or moderately hard woods. It is not well adapted for hard wood or ivory, although it is occasionally made to answer for them. Any attempt to chuck metals with it would result in the breaking or spoiling of the screw. Generally, this chuck is used for holding pieces of wood from half an inch to six inches in thickness. Thinner pieces have not sufficient substance to give the thread the requisite amount of

holding power. When the wood exceeds six inches in length, it must be supported at the other extremity by the centre, or by a proper bearing or stay. This chuck may be very conveniently used when it is required to turn any recesses in moderately thick pieces of wood; but when this has to be done in the case of very long pieces, it is inconvenient to support the other end by the screw centre, as that centre would then be in the way of the tool. In cases such as this, the exterior should be turned, whilst the end is supported by the centre. This, of course, can be done without inconvenience; the centre is then removed, and the

work supported by a wooden bearing, whilst the interior is being operated upon, and the required recess or cavity turned out. A piece of wood is then made. to fit the mouth of this cavity, and to form an abutment for the centre while the outside is being finished. If the cavity be sufficiently large to allow the centre and the spindle to enter, the former may be forced into the wood at the bottom of the cavity. In this case no stopper is required.

Sometimes, after the cavity is made, it is required to remove the work from the chuck, and change ends with it, in order to get at the end which hitherto has been against the chuck. In this case, remove the work, and on to the same chuck screw a piece of thin flat wood, which turn down to the size of the mouth of the cavity, or to fit the cavity rather tightly. The article being then gently pushed on to this stopper, and the centre forced into the hole made by the taperscrew, the work may be finished with ease. When this plan is followed, the end of the article on the stopper or chuck, as well as the cavity, is certain to run as 'true' as may be required.

The five-pin or plate-chuck, Fig. 16, is also of metal. It screws on the mandril end, and its body or 'boss is of the same shape as the chuck last described, only instead of being furnished with a taper-screw, it has five steel pins or points projecting from its face. These pins are arranged as is shown in the figure. This chuck is used almost wholly for holding thin pieces of soft wood.

The cone-chuck is made of metal and screwed on the spindle end. Its construction will be understood

by referring to Fig. 17. The projecting pin a is of steel, and has a screw cut upon it to receive the nut b. The cone c is also of metal, but sometimes for temporary use it is made of hard wood: it slides on the pin a. This chuck is used for turning pieces of wood of large diameter, and having a hole through them. Articles of this sort are by its means chucked true or concentric with their central holes. The universal mandril, Fig. 18, is used for the same description of object as the last, than which for many purposes it is somewhat better.

The mandril a is of steel, the ends are carefully hardened, and are furnished with centre holes for running between the ordinary lathe centres. It is driven by means of a carrier or driver. The mandril is screwed throughout almost its whole length, and is fitted with a nut b, and washers c c. When it is required to turn any article having a hole through it of a size for which the operator has no mandril, a piece of hard wood is taken and bored through with a hole rather smaller than the mandril thread. This wood being then twisted on the mandril, a thread is formed

D

FIG. 18.

in the hole which holds the piece firm enough to allow the wood to be turned, to the size required to fit the hole in the article requiring the mandril. This wooden socket should fit the hole nicely, otherwise the work turned out on it will be out of truth,' or eccentric with its hole. The article is forced on the wooden socket, and the nut b screwed up so as to hold it firmly between the two washers. It is, of course, necessary that the length of the wooden socket should be somewhat less than the length of the hole in the article to be turned upon it; otherwise the washers will tighten up against the socket, and will not exert any holding or gripping

19, are of metal: A is the male, B the female chuck. The male chuck is made to screw on the mandril end. The projection in front is cut with a fine screw thread, such as is used for the covers of fancy boxes. The