The Boy Mechanic: Volume 1 | Page 6

half of the
design will be traced on the second side. With the metal shears, cut out
four pieces of copper or brass of No. 22 gauge and with carbon paper
trace the shape and decorative design on the metal. Then cut out the
outline and file the edges smooth.
Cover the metal over with two coats of black asphaltum varnish,
allowing each coat time to dry. Cover the back and all the face except
the white background. Immerse in a solution of 3 parts water, 1 part
nitric acid and 1 part sulphuric acid. When the metal has been etched to
the desired depth, about 1-32 of an inch, remove it and clean off the
asphaltum with turpentine. Use a stick with a rag tied on the end for
this purpose so as to keep the solution off the hands and clothes. The
four pieces should be worked at the same time, one for each corner.
It remains to bend the flaps. Place the piece in a vise, as shown in Fig.
2, and bend the flap sharply to a right angle. Next place a piece of metal
of a thickness equal to that of the blotter pad at the bend and with the
mallet bring the flap down parallel to the face of the corner piece, Fig.
3. If the measuring has been done properly, the flaps
[Illustration: Manner of Forming the Plates]
ought to meet snugly at the corner. If they do not, it may be necessary
to bend them back and either remove some metal with the shears or to
work the metal over farther. All the edges should be left smooth, a
metal file and emery paper being used for this purpose.
If a touch of color is desired, it may be had by filling the etched parts
with enamel tinted by the addition of oil colors, such as are used for
enameling bathtubs. After this has dried, smooth it off with pumice
stone and water. To keep the metal from tarnishing, cover it with
banana-oil lacquer.

** Boring Holes in Cork [8]
The following hints will be found useful when boring holes in cork. In
boring through rubber corks, a little household ammonia applied to the
bit enables one to make a much smoother hole and one that is nearly
the same size at both openings. The common cork, if rolled under the
shoe sole, can be punctured easily and a hole can be bored straighter.
The boring is made easier by boiling the cork, and this operation
insures a hole that will he the desired size and remain the size of the
punch or bit used.

** Self-Lighting Arc Searchlight [9]
A practical and easily constructed self-lighting arc searchlight can be
made in the following manner: Procure a large can, about 6 in. in
diameter, and cut three holes in its side about 2 in. from the back end,
and in the positions shown in the sketch. Two of the holes are cut large
enough to hold a short section of a garden hose tightly, as shown at AA.
A piece of porcelain tube, B, used for insulation, is fitted tightly in the
third hole. The hose insulation A should hold the carbon F rigidly,
while the carbon E should rest loosely in its insulation.
The inner end of the carbon E is supported by a piece of No. 25
German-silver wire, C, which is about 6 in. long. This wire runs
through the
[Illustration: Arc in a Large Can]
porcelain tube to the binding post D. The binding post is fastened to a
wood plug in the end of the tube. The tube B is adjusted so that the end
of the carbon E is pressing against the carbon F. The electric wires are
connected to the carbon F and the binding post D. A resistance, R,
should be in the line.
The current, in passing through the lamp, heats the strip of

German-silver wire, causing it to expand. This expansion lowers the
end of the carbon E, separating the points of the two carbons and thus
providing a space between them for the formation of an arc. When the
current is turned off, the German-silver wire contracts and draws the
two carbon ends together ready for lighting again. The feed can be
adjusted by sliding the carbon F through its insulation.
A resistance for the arc may be made by running the current through a
water rheostat or through 15 ft. of No. 25 gauge German-silver wire.
--Contributed by R. H. Galbreath, Denver, Colo.

** A Traveler's Shaving Mug [9]
Take an ordinary collapsible drinking cup and place a cake of shaving
soap in the bottom ring. This will provide a shaving mug always ready
for the traveler and one that