THE YOUNG SCIENTIST. 
87 
to be applied is spread upon a level sur- 
face ; a rod or stick is put through the 
hole in the wheel as a means of turning it ; 
glue is then applied smoothly and evenly 
to the leather surface. Take an end of 
the stick or rod in each hand, with the 
wheel between them, and roll it in the 
emery until an even coating is retained on 
the glue-covered surface. Lay it aside to 
dry, being careful that nothing scratches 
or mars the freshly-coated surface. If the 
emery be applied warm by spreading it 
upon a warm board, or an iron plate also 
warmed, there will be no danger of the 
glue being chilled while the emery is ap- 
plied, and a more lasting surface will be 
the result. 
The grades of emery may range from 
No. 60 to 90, according to the work to be 
done. The coarser is used for cutting- 
down a surface, and the finer for finish- 
ing and polishing. 
In putting on the leather, some persons 
prefer to put the hair side of the leather 
to the wheel, giving as a reason that the 
flesh side is softer, and makes a more 
elastic wheel. In doing this the hair side 
must be thoroughly scraped before being 
glued to the wood. If it be desired to 
make a wheel elastic, two thicknesses of 
leather may be used, putting on one and 
letting it dry, turn it off, and put on a 
second one over the first ; turn it off and 
coat with emery. 
Wheels of hollow or round form can be 
easily made. Turn the w^ood to the re- 
quired slope, and then go to a harness 
maker and have the leather rolled to the 
desired form by running it between the 
rolls that are used to shape leather in a 
hollow or round form for harness making. 
Apply the leather, and fasten to the wheel 
in the same manner as in making a flat 
wheel. 
It is necessary to have emery wheels 
balanced. That is, one side must not be 
any heavier than the other. To ascertain 
where this balancing is required, put the 
wheel on the spindle on which it is to run, 
or on a tight-fitting wood rod inserted in 
the spindle hole. Have two straight edges 
of iron prepared, and fastened perfectly 
true and horizontal— wooden straight i 
edges may be used, with the edges made I 
pretty sharp, and these sharpened edges> 
set uppermost. They must be placed 
parallel to one another, and at a distance 
apart to receive the wheel between them. 
On placing the wheel with its spindle on 
these straight edges, if one side be heavier 
than the other it will slowly revolve until 
this heavy side is at the bottom. Mark 
the side that is uppermost, bore a hole 
there, and drive in a rifle or pistol bullet. 
Try it again, and so continue until it will 
lie at rest on the straight edges. Where 
access can be had to an iron lathe bed, 
with the opening in the shear wide enough 
to receive the wheel, it is a very good sub- 
stitute for the straight edges. 
Wheels, can also be covered with canvas 
or common sail cloth in place of leather. 
If several thicknesses are put on it will 
give an elastic wheel. Probably the most 
elastic wheel that can be made is by cover- 
ing the wheel with stout cotton cloth, put- 
ting it on loosely, and stuffing cotton be- 
tween the cloth and the wheel. Take care 
to put in the cotton evenly and alike all 
around. The cloth can be fastened to the 
wheel by using smooth-headed tacks, 
driven through it into the wheel at the 
sides near the periphery. 
When the coating of emery wheels be- 
comes worn by using, and is " dull " as it 
is termed, another coating may be put on 
over the first. A third may be put on 
over the second one. But when it gets 
uneven, it is best to soak off the old coat- 
ings with warm water. This may be done 
by putting a wet cloth around the glued 
surface, changing it occasionally until the 
glue can be scraped off. The scraping 
can be done with a knife that is not sharp 
enough to cut the leather. When dry 
apply a new coating. In places where 
many wheels are used, when the old coat- 
ings require to be removed they are re- 
volved with the coated surface just touch- 
ing the water. They can also be placed 
over a pan of water, and turned occa- 
sionally by hand until the surface is suf- 
ficiently softened to admit of its being, 
scraped off. ^ 
— When the inscription on a coin is il- 
legible, heat it gradually as hot as it will 
bear, and the letters will come out quita 
plainly. 
