THE YOTJNG SCIENTIST. 
143 
fine white Washita stone, nicely fitted in 
a walnut-wood box, which parted in the 
centre when opened for use. "Oh," said 
i]llwood, "that will be bully to sharpen 
Fig. 15. 
my jack knife on." " All right," said his 
father; "you may sharpen your knife on 
the stone, but you must be very careful 
^ind only use the ends of the stone, for if 
you rub your knife in the centre it will 
soon wear away, and become hollow, and 
then plane irons or other edge tools can- 
not be sharpened on it with any degree of 
satisfaction." 
Mr. Carpenter warned the boys against 
using inferior oil on the stone. " If pos- 
sible," he said, "always use pure sperm 
oil; lard or olive oil answers very well, 
lout when used the stone sliould be fre- 
Fig. 16. 
quently cleaned off, or it will get hard and 
full of dirt. Kerosene is excellent for 
•cleaning an oil stone, and may be used oc- 
<;asionally for sharpening with. If at any 
time you want to sharpen a chisel or a 
lield together by the screw, s, which is "tapped" 
into the boss, t, formed on the cap-iron, which is 
shown separately in Fig. 15. 
The cutting iron is shown disconnected from 
the cap-iron in Fig. 14. The long slot, m, admits 
of the iron being adjusted longitudinally, and 
also, to a slight extent, sideways. The round 
hole, h, is a little larger than the head of the 
screw s, which permits of the irons to be taken 
apart without taking the screw, s. out entirely. 
Fig 16 shows the method of holding the plane- 
iron during the process of sharpening, o is the 
iron, p the stone, and n the box in which the stone 
is cased. 
plane iron, or other tool, and have no oil 
to use on the stone, you may use a little 
castile soap and warm water. This merely 
answers a purpose, and should not be re- 
sorted to oftener than can be helped. 
" When sharpening a plane-iron, you 
should grasp it in the right hand, and 
place the fingers on the surface and the 
thumb underneath. The fingers of the 
left hand should be lapped over those of 
the right, and the thumb should be placed 
underneath to support the iron, which 
should be held at a constant angle of 
about thirty-five degrees, and kept square 
across the face of the stone. If, as may 
sometime happen, you have an iron that 
is wider than the stone, you must work it 
from side to side, so as to make the 
corners uniform with the middle. When 
the edge of an iron is required to be a 
little rounding, as is sometimes wanted in 
a jack-plane, a light roll must be given to 
the blade edgewise. You must not press 
too heavily on the iron while sharpening, 
as the edge will be liable to bend over, 
and become what is called 'wire edge.' 
•When you think your iron is sharp enough 
you must turn the fiat side down, keeping 
it quite fiat on the stone, and gently rub a 
few times to remove the wire edge, if any 
has formed. 
"If you hold the iron too upright, the 
edge will be too quickly produced, and 
will wear off much sooner than if the iron 
had been held, during the sharpening 
process, at a lower angle. You can easily 
see that if an iron is sharpened at an angle 
of forty-five degrees, which is the pitch 
at which it is fixed in the plane, the cham- 
fer formed by the oil-stone would rest on 
the work, and would, consequently, pre- 
vent the edge from cutting. On the other 
hand, if the angle be too acute, the edge 
will be too thin to be durable ; therefore, 
the angle of thirty-five degrees is probably 
the best angle for planes, chisels, and 
similar tools. 
" Itis always well to take the corners off 
the iron, for if they are left on they will be 
apt to leave marks on the work, and this 
will not be very nice." 
Fred, under his father's immediate su- 
pervision, tried his hand at sharpening up 
the plane irons, and considering that this 
