TURNING. 
turning round in the direction where the lathe works, the 
chuck screws itself fast on against the shoulder 5 but if the 
iathe is stopped, and the chuck is turned in the opposite 
direction, it will unscrew and come off, and a different chuck 
may be put on. In some lathes, the neck of the mandrel is 
perforated, and cut withinside, with a female screw adapted 
to receive a male screw on the chuck: the effect is just the 
same as the above described. In general, the mandrel is 
made with a point at one end; and the other end, which has 
the screw to fix the work to it, is formed with a neck, pro¬ 
per to run in the collar, and with a shoulder on the neck, 
to stop the neck from going through the collar. When the 
mandrel is made with a pointed end, the point must be re¬ 
ceived in the end of a screw tapped through the part D of 
the frame of the mandrel, just in the place of the end a 
of the mandrel. By turning the screw, the mandrel can 
be adjusted to run very correctly in length; and to pre¬ 
vent the screw from turning back when the lathe is in 
motion, a nut is placed on the screw, beyond the part 
d; this causes such a pressure upon the threads of the 
screw, that it is in no danger of it turning back, as it would 
otherwise do with rough work. The mandrel, by this 
means, runs very steadily and accurately in the bearings, and 
it is plain that any piece of work, which is firmly attached 
to the end of it by means of the screw before mentioned, may 
be turned by a tool held over the rest, in the same manner as 
if it were mounted between centres, but with the advantage 
that it may be turned at the end, to ma)ce hollow work when 
required. 
The mandrel is turned round by a bjind of catgut passing 
round the pulley h, and also round the large foot-wheel H, 
which is made of cast-iron, and fixed on the end of the axis 
I. This axis is bent in the middle, as in the figure, to form a 
crank, which crank is united, by an iron link K, to the trea¬ 
dle L, on which the workman presses his foot. This treadle 
is affixed by three rails to an axis M, on which the treadle 
moves. The wheel H is of considerable weight in the rim, 
and being fixed fast on the axis I, turns round with it: the 
momentum acquired by the wheel is the power that conti¬ 
nues to turn the work while the crank and treadle are rising, 
and consequently while the workman exerts no power upon 
them. 
When the crank has passed the vertical position, and be¬ 
gins to descend, the workman presses his foot on the treadle, 
to give the wheel a sufficient impetus to continue its motion 
until it arrives at the same position again. The length of the 
iron link K, which connects the crank with the treadle, must 
be such, that when the crank is at the lowest position, the 
board L of the treadle, to which the link is hooked, should 
hang about two or three inches from the floor. To put 
the lathe in motion, the turner gives the wheel a small 
turn with his hands, till the crank rise to the highest, and 
passes a little beyond it: then by a quick tread he brings 
the crank down again, putting the wheel in motion with a 
velocity that will carry it several revolutions: he must ob¬ 
serve to begin his next tread just when the crank passes the 
highest point, and then it will continue running the same 
way with a tolerable regular motion, if he is punctual in the 
periods of his treads. The foot-wheel, by means of the 
band, causes the mandrel to move very rapidly, so that it 
will perform its work very quick, and the workman must 
acquire a habit of standing steady before his work, that he 
may not give his whole body a motion when his foot rises 
and falls with the treadle. 
The rest N of this lathe is fixed on the bed of the lathe 
by its foot, which is divided in the manner of a fork, to re¬ 
ceive a screw-bolt: this bolt passes down through the lathe- 
bed, and fastens the rest at any place along the bed, by 
a nut k beneath. The groove in the foot is for the 
purpose of allowing the rest to be moved to and from 
the centre of the work, to adjust it to the diameter of the 
work which is turning. The height of the rest is a mat¬ 
ter of some importance in turning, and in some work it 
should be fixed higher than others; therefore the piece upon 
which the tool is laid, is made with a shank of the form of 
199 
the letterT. This shank is a round pin, and is received 
into a socket at the foot of the rest, and can be held at any 
height by a clamp-screw. As the socket and shank are 
cylindrical, the edge of the T of the rest can be placed 
inclined to the axis of the work when turning cones, or 
other similar work, though the same purpose may be accom¬ 
plished by the screw, which holds the foot of the rest down 
to the bed of the lathe, admitting the fork to stand in an 
oblique direction across the bed. 
The wood turner employs gouges of all sizes, and chissels 
of different forms: the gouges are used in the first instance 
to rough out and form the wood, as they cut very rapidly, 
because ihey can take a very strong chip, and the angles will 
not stick in, as would be the case with the chissels. The 
latter are used to smooth the work, and to reduce it exactly 
to shape and size. 
The lathe should be fixed in a place very well lighted; 
it should be immoveable, and neither too high nor too 
low. 
The piece of wood to be turned should be partly rounded, 
before it is put in the lathe, either with a small hatchet made 
for the purpose, or with a plaue or rasp. Before putting it 
in the lathe, it is necessary to find the true centres of its two 
end surfaces, so that they shall be exactly opposite to each 
other, in order that, when the centre points of the puppets 
are applied to them, and the piece is put in motion, no one 
side may project out more from the centre line than another. 
To find these two centres, lay the piece of wood to be turned 
upon a plank, open a pair of compasses to almost half the 
thickness of the piece, lay one of the legs on the plank, 
and let the point of the other mark on one of the ends of 
the piece when laid flat on the plain with the plank, like a 
roller, from which plank the point of the compasses stands 
up at a given height above the plane on which the piece 
lies. Describe four marks or arcs on that end at equal dis¬ 
tances from each other round the circumference of the end, 
by laying the piece successively on four different sides; which 
arcs intersecting one another, the point within the inter¬ 
sections will be the centre of the end. In the same manner, 
the centre of the other end must be found. 
After finding the two centres, make a small hole at each 
of them, into which insert the centre points of the back 
centre and the mandrel, and screw up the back centre, to fix 
the piece so firmly as not to be shaken out, and yet loose 
enough to turn round without difficulty. 
This is the manner of fixing the work when it is to be 
turned between centres; but if it is required to be hollowed 
out, the back puppet is removed, and the work must be 
fixed in a chuck at the extremity of the mandrel. For this 
purpose, a chuck is selected which has a hole in it nearly 
the size of the piece of wood, the diameter of which being 
taken in the callipers (fig. 8), the chuck is screwed to the 
mandrel: the rest is fixed in a convenient position, and the 
hole in the chuck turned out by a proper tool to the size 
measured by the callipers: the hole should be rather conical, 
and the wood, being rasped to the same figure, is driven in 
fast by a hammer. By turning the mandrel slowly round, it 
will be seen if the wood is fixed straight in a line with the 
mandrel, and if not, a blow or two of the hammer, properly 
directed, will rectify it. 
If the-piece of wood is not very long, the chuck will be 
sufficient to hold it firm whilst it is turned; but if it is not, 
then a small centre hole must be made in the extreme end, 
and into this the point of the back centre screw must be in¬ 
serted to steady the work, until the rough part of the turning 
is done, and then it may be removed; but it is much more 
convenient to turn without the back centre, and therefore the 
turner fits the chuck to the wood with care, so that it will 
fix fast in the chuck. 
The work being thus chucked, or fixed in the lathe, the 
rest is set, so that its edge is close to that part of the work 
which is required to be turned, and the top of the rest being 
raised considerably above the level of the centre of the work, 
it is there screwed fast. 
The turner now puts the lathe in motion by treading with 
his 
