The Detroit times., 1911-04-29
KNOW ROMANCE
Of SPARK PLUG?
Its Making the Modern Development
of One of the Most Ancient
of the Arts.

Almost every motorist knows what
spark plug is. II he doesn't he Is
not much OF a motorist But compare
lively few users Of automobiles could
tell you, right of the reel. SO TO speak,
how a spark plub is made. Although
the spark plug may seem insignificant
to the uninitated, IL is highly i'm
portant adjunct 70 the mechanism OF
motor car and the processes EN-
ployed in its manufacture are most
interesting.
There are about IS manufacturers
of spark plugs in this country today
OF these only few, not to exceed 10
at the outside, make every part OF
their plugs from the raw material. II
is conservatively estimated that the
output of spark plugs in the United
States for 1911 will amount 10 $500
600, at the rate Of 81 per plug. This
is based on an estimate of 400,O cars
now in use and on an estimated out
put OF 100000 cars for 1911.
Ii is difficult 10 see where there
would be any romance about spark
plug, but there Is. The making OF the
earthenware insulations is a modern
development OF one OF the most an
cient arts, the potter's art, which
marks back to prehistoric times.
The average spark plug is composed
-ef- a she'll of steel, packing nut or
bushing, a packing ring of metal and
asbestos, porcelain insulator, brass
cap for the top of the porcelain in
sulator, binding nut, central cleo
trode and a ground electrode carried
on the she'll The shell is made from
q rod of cold rolled steel, which comes
from steel mills in round and hexagon-
al rods about IL feet long. Four rods
are placed in an automatic machine.
which transforms them into large
number of almost complete shells. A
workman gathers the shells from u
hopper and carries them TO another
machine, which cuts the external
threads.
The next operation Is the drilling or
a small hole in the end OF the shell
to admit the small piece of wire that
forms the ground electrode The shell
is then "smoothed up and sent TO the
plating department, where II is thor
oughly cleaned by immersion In sew
eral alkaline and acid baths before
being placed in the copper and nickel
plating baths. From the plating baths
the shell, after being allowed to dry
thoroughly, goes to the buffer, where
it is polished.
The packing nuts are made from the
same kind of bars as are the shells
and the process is much the same ex-
cept that they are completed on the
enc machine The nuts are then case
hardened by being packed In granu-
lated charcoal and bone In cast iron
boxes and subjected TO an intense heat
for 55 minutes. When the boxes are
removed from the oven they are dump
ed into water, churned by a blast OF
air. The packing rings, brass caps
and binding nuts are all made by ma
chimes, the processes being compare
lively simple.
IL Is in the making of the porcelain
parts of the spark plug that the great
est skill is required To begin with,
all the materials that enter into the
composition of the ware" are care
fully weighed and mixed with water
In fixed proportions AS the mixture
flows from the stirring watts a series OF
magnets, so arranged that they extend
down into the stream, remove all
traces OF metal. The mixture passes
through a vibrating sieve into watts
known as agitators. Next II Is filtered
In a powerful press and Is then trans
ferred to a plug mill where all the air
bubbles are driven out. The clay is
then stored in large bins for several
weeks. Next, when the clay Is ready
for use. comes the kneeding process
and after that III goes 10 the throw
ing room, where "jigger" forms 1t
into cylindrical blanks, from when
the porcelains are turned In series Oh
delicate operations. Baking, enamel
ing, assembling and testing operations
follow in quick succession and the
plug is ready for the market.