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Accuracy Conformity of an indicated
value to the true value i.e., an actual or
an accepted standard value.
Allowance The degree of variation
permitted from a nominal specification;
the total tolerance.
Axis A designated line on a drawing,
machine, gage or part used to denote
a linear direction for measurement or
reference.
Calibrate To graduate a measuring
instrument into appropriate units. To
determine accuracy of a gage at given
points over its gaging area.
Clearance The space between two
mating parts. On a cutting tool, the
angle between the cutting edge and
the perpendicular axis of the work.
Concentricity The amount of
conformity with one another between
the centers of two circles.
Datum A point of reference.
Deviation Error, variation, or
departure from a standard.
Dimension Any measurable extent
or magnitude, as length, breadth, or
thickness.
Discrimination (see resolution)
Division A mark or graduation
denoting an incremental value of a
scale, dial or gage.
Eccentricity The deviation of the
centers of two circles from each other.
Fit The type and closeness of
contact between two surfaces,
usually in reference to mating parts.
Flatness The degree of conformity of
a plane or axis to a master or to a
specified standard (mean or reference
plane).
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Graduate To mark in a regular manner the
increments of measurement, as on a rule,
scale or dial.
Graduation One of the marked increments.
Interchangeable Sufficiently alike in size as to permit replacement without modification.
Limit A specified dimension beyond which
variation in size is not permissible for accep- tance as conforming to size.
Mean An average. An intermediate value
between two or more values.
Master Any type of gage that is used to check
the accuracy of other gages.
Precision The quality of being sharply or clearly
determined; strictly accurate, exact. In a gage,
usually one capable of discrimination to .010" or smaller.
Resolution The smallest increment into which
a gage is divided. Used interchangeably with
Discrimination. Also, the least Interval between
two adjacent discrete details which can be
distinguished one from another.
Squareness The degree of conformity of a plane or axis to a corresponding perpendicular plane or axis.
Standard Any established measure of extent,
quantity, quality or value. An accurate example
for comparison; a master.
Straightness The degree of conformity of an axis along its length to a standard.
T.I.R. (total indicator reading) The difference
between the maximum and minimum indicator
readings obtained, usually in measurement of
roundness.
Tolerance The total permissible amount by
which a dimension may vary above or below a
specified size, usually expressed as plus
and/or minus an amount greater or less than
the specified dimension.
(courtesy of Brown&Sharpe)
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