quent requisition, and are indispensable to the turner in metals.

The centre-punch, Fig. 74, is of steel: its FIG. 78. point a is made with the same angle as the lathe-centres, and is carefully hardened and tempered. The indent-punch is similar to the last, but its point b is ground to an angle much more acute than the last. The centering cone, Fig. 75, is in two parts, the box or cone a and the sliding punch b. The former is made. of iron or brass, and the latter of a straight cylindrical rod of steel, pointed with the same angle as the lathe-centres, and carefully hardened. This rod is free to slide up and down the hole in the cone box. The illustration will sufficiently explain the instrument.

The driving chuck at Fig. 76 is usually of cast iron the driving pin or arm is of wrought iron or steel, and is fastened to the plate by passing through a hole and having a nut behind. The plate has a boss fitted with a screw thread for screwing on to the spindle of the lathe. A very good form of driver is that known as Clement's driver, seen at Fig. 11, on in place. This driver has two arms attached to a separate plate, on the face of the main plate, and capable of moving so as to cause both driving arms to bear equally against the lathe carrier. The die-chuck, Fig. 77, is made of iron, with steel screws. It is screwed on to the lathe-spindle.

The round mandril, Fig. 78, is merely a round bar of steel, carefully turned to a standard size; its ends

FIG. 79.

are drilled with small holes, countersunk to fit the lathe-centres, and afterwards carefully hardened. The shape of the mandril end is shown enlarged at Fig. 79. It must run perfectly true, and should be either quite parallel or very slightly tapered. Many sizes are required. The screw mandril, Fig. 80, is of steel, and has a true standard thread cut upon it. This thread may be either right or left handed, or both, as seen in the figure.

The mandril ends are made of the same

shape as the last, and are hardened. Screw mandrils of various sizes and pitches of thread are in frequent request. The tool-rest, Fig. 82, is of wrought iron,

FIG. 80.

and its shank is turned to fit the socket of the restholder of the lathe. Other shapes than that shown are occasionally required for peculiar work.

Fig. 81 is the ordinary hook tool used for roughing wrought iron, steel, cast iron, and malleable iron; a is the case or holder and b the tool, which, fitting a groove the whole length of the holder, can be slid farther out as the tool wears away. It will be noticed that the tool passes through a sort of staple, so that by twisting the handle c in one direction the tool is firmly fastened between the staple and the bottom of the groove in the holder; and by twisting the handle in the contrary

from its place There
are two sorts of this
hook tool: one has its
cutting edge ground
off to a round shape
as at B, the other has
a pointed or angular
cutting edge as at A.
The tool having a
round cutting edge is
used entirely for
roughing; the angular
tool is used for rough-
ing down any small
works in metal, and
for trueing up the
ends of articles, the
sides of collars, and
flat shoulders. Both
tools are held in the
same manner, and the S
position in which they
cut is shown at Fig.
83, a being the work,
and b the tool. The

rest or support for the
tool is that shown at
Fig. 82.

The handle c of the tool-holder is grasped by the right hand of

FIG. 1

the operator; the extremity of the holder farthest from the point of the tool is laid on the shoulder, the left hand

FIG. 82.

being placed upon the holder between the handle, c Fig. 81, and the shoulder, and the point of the tool held about level with the centre of the work.

This is a very effective tool, but its use is not easily learnt. Beginners find it difficult to prevent the tool 'catching in' and taking a much deeper bite out of the metal than is necessary or desirable. When this occurs, the work, the tool, or the lathe-centre is certain to receive some damage; and in certain cases the operator is lifted off his feet before he knows what the matter is. After the use of the tool is learned, it is one of the easiest

FIG. 83.

to manage. It will cut off the metal in large deep shavings, and may be held and guided by a couple of fingers. All workmen should be able to use this tool from either shoulder.

These hook-tools should vary in shape according to the height of the user, as will be evident to all who examine the illustration, Fig. 83. The difficulty of using increases with the angle of the tool; the tool being a lever of the first order, of. which the 'heel' or point bearing on the rest is the fulcrum. The weight is applied at the cutting edge, and the power at the other end of the handle. It will therefore be understood that the nearer the cutting edge is to being

in a vertical line passing up through the fulcrum or heel of the tool, the less will be the force required at the other end to counterbalance this weight on the cutting edge. The weight, of course, is the resistance of the metal to being cut.

There are other varieties of this tool in which the cutting part is shaped so that the handle has to be placed under the shoulder, instead of on it; they are used in

the same manner as the first mentioned, but I do not consider them equal in efficiency, and facility of using. Both sorts, however, may be manipulated with very little exertion, the workman only having to guide the tool, all the weight of the cut being borne by the tool rest. I have nevertheless seen illustrations of a workman using a tool of this sort, and hanging on to it as though his life depended on the amount of force he could expend upon the tool. Such illustrations are not true to good practice.