The Washington times., 1924-05-14

sibls. Splitting hairs u coarse work.
Splitting a hair into 500 parts, ana
then measuring one of the parts de.
scribes the fineness Of operation Of
an instrument which measures one
hundred .thouaandfh part Of an inch.
Here the amount Is so small that
both measure and article must be
ct the same temperature to avoid
error from unequal expansion.
Hands sim Useful.
To produce the result OF which
Watt was justly proud $50 years
ago, an enormous amount OF pains
taking hand work was necessary.
Only in recent years has It been
possible to get accurate results 9TH
erwise. Were 1t necessary to ut
together by hand all parts used TOR
production in four million new cars
and for replacement In fifteen mil
lion used cars, It would be at q cost
which would be economically inn
possible. Automobiles are today
within reach Of the great majority
who can practically use them.
Standardization through precision 10
the key which has opened the way.
Back in 1907. before the Royal
Automobile Club Of England, three
Cadillac cars were completely dis
mantled and the parts thrown into
Q confused heap. Some parts were
taken away and others substituted
from a stock supply. Three cars
were assembled from the heap with
out any fitting Of the parts, and
I'll ran perfectly. This performance
was an absolute revelation to Eu-
ropean engineers and resulted in
the award to the Cadillac Of tho
Dewar trophy for the most signifi-
cant automobile development In the
year-complete Standardization and
lnterchangeability Of parts.
The precision with which the
principle is illustrated by the Cadil.
lac piston pins. which are held to
limits OF three ten.thousandths of an
inch. That is, the outside variation
allowable from the given standard,
either larger or smaller, Is one.half
that amount, one and one-half ten
thousandths, or one-twentieth of a
hairs thickness. Not only is the
correct clearance 90 maintained, but
tnterchangeability as the result Of
precise standards Is so perfect that
a piston sent from the factory to-
day for replacement in q single
cylinder engine built twenty one
years ago, fits the cylinder exactly
and without hand fitting.
Old Style Superseded.
In Europe, hand methods of fit.
ting are still largely in use. A bolt
is made slightly larger or the hole
slightly smaller than required.
Then, by filming and roaming, bolt
and hole are made to fit.
To European visitors at the Cadil.
lac factory, 1t has been a matter OF
wonder + to see q complete engine
assembled without use of a file or
any other tool for the fitting OF
parts. To achieve this result on
certain parts. a. many as 1875 In
spections are required before the
part is allowed to pass from manu-
featuring to assembly division.
Each operator IL expected to hold
his work to the close limits pres
cribed. After he has finished, each
individual part Is inspected by 9
man who does nothing else except
to inspect, and see that the standard
is maintained. The outside limit OF
accuracy Of one-thousandth part OF
an inch Is required on more than
$4,000 dimensions, and many are
measured intenths of thousandthe
Of an inch. To check the parts sc
manufactured and to see that the
high standards are always main
tanned, in this one factory alone
more than 500 men are constantly
employed wholly on inspections.