54 
THE YOUNG SCIENTIST. 
taper, having round corners, hollow 
sweeps, true curves, and moulding beads 
Tig. 3. 
of any kind. It requires no forging, and 
will cut at a very quick speed. The end 
Fig. 4. 
face requires to be very true ; hence when 
ground it is held as shown in Fig. 6. It is 
Fig. 5. 
made very hard, and oilstoned for a pol- 
ished finish, water being used when cut- 
ting wrought iron or steel. 
When used with one point resting as a 
fulcrum upon the face of the lathe rest, that 
point should be pressed firmly to the rest 
to prevent the tool from slipping. Here 
it becomes necessary to caution the be- 
ginner against leaning the cutting edge 
too far over, as this is an error into which 
he is very liable to fall, and it invariably 
results in his losing control of the tool, 
and allowing it to rip into the work. Sup- 
Fig. 6. 
pose, for example, that in Fig. 7, A is a 
sectional view of a graver, B is the part 
receiving the pressure of the cut, and C is 
the lathe rest; the leverage of B is the 
distance between the vertical lines D and 
E, and the whole pressure of the cut at 
that leverage has to be resisted by a coun- 
teracting twisting pressure exerted by the 
hands upon the handle. The leverage of 
the cut as shown in Fig. 2 is, it will be 
Fig. 8. 
