A 
ABBE'S
LAW: 
Principle that for
maximum reliability the axis of the standard must lie along the line of
measurement. 
ABSCISSA: 
The horizontal coordinate
of a point in a plane Cartesian coordinate system, obtained by measuring
parallel to the X axis. 
ABSOLUTE
ACCURACY: 
Accuracy relative
to a specified reference measure. 
ABSOLUTE
COORDINATES: 
S, Y, and Z coordinate
values relative to the coordinate system source. 
ABSOLUTE
DIMENSION: 
A dimension expressed
with respect to the initial zero point of a coordinate axis. 
ABSOLUTE
REFERENCE POINT: 
Work piece coordinates
relative to a fixed point on the machine table. 
ABSOLUTE
VECTOR: 
Line with end points
that are measured in absolute units from a set point of origin. 
ABSOLUTE
ZERO POINT: 
Real zero for all
axes from which point all counting begins. 
ACCURACY: 
The relative amount
by which desired results are compared with undesired results. Conformity
to truth or to a standard or model; degree of conformity of a measure to
a standard or a true value. 
ACCURATE: 
Conforming exactly
to truth or to a standard exact. 
ACUTE
ANGLE: 
An angle measuring
less than 90 degrees. 
ADAPTIVE
CONTROL: 
Control method whereby
system parameters are automatically changed for the purpose of increased
efficiency. 
ADAPTOR: 
A connecting devise
used to mate parts that would not otherwise fit. 
ADJUSTABLE
CONTACT: 
A contact, usually
the reference contact, which is adjusted when setting the gage to measure
a certain Work piece. 
AGD
SPECIFICATIONS: 
Standardized designs
developed by the gage design Committee of the American Standards Association. 
AIR
GAGING: 
Measurement by means
of pneumatic metrology. 
ALGORITHM: 
Procedure for solving
a mathematical problem in a finite number of steps that frequently involves
repetition on an operation. 
ALIGN: 
To bring objects
into precise adjustment or correct relative position. 
ALLOWANCE: 
An intentional difference
in the dimensions of mating parts. It is the minimum clearance or the maximum
interference which is intended between mating parts. 
ALLOWANCE: 
The allowed dimensional
difference between mating parts of a machine; the total tolerance. 
ALTITUDE: 
Perpendicular distance
from a vertex of a geometric figure to the opposite side, or from a side
or face to a parallel side or face; vertical distance to the highest point
from the base. 
AMERICAN
SCREW GAGE: 
Standard gage for
diameter checking of machine or wood screws. 
AMPLIFIER: 
The intermediate
modifying stage of an electronic measurement system. May incorporate other
functions such as filtering of the signal and comparison of signals. 
ANALOG
INSTRUMENT: 
An instrument in
which the sizes of physical quantities correspond to numerical values. 
ANALYTICAL
GEOMETRY: 
Study of geometric
properties by means of algebraic operations on symbols defined in terms
of a coordinate system. 
ANGLE: 
Figure formed by
two lines extending from the same point, or by two surfaces diverging from
the same line. 
ANGLE
OF INCLINATION: 
Angle described
by a screw thread, relative to its axis. 
ANGLE
PLATE: 
Two plates precision
ground at right angles to each other, with facilities for fastening machinetool
work pieces. 
ANGULAR: 
Having one or more
angles, or forming an angle; sharpcornered; measured by an angle. 
ANGULAR
MEASUREMENT: 
Expression of the
relationship of two lines, based on the division of a circle into 360 sections,
with each section equalling one degree of an angle. 
ANVIL: 
Common name for
comparator reference surface. 
APEX: 
The uppermost vertex
or point of a cone, pyramid, etc.; the narrowed or pointed end of an object. 
APPROXIMATE: 
Nearly correct or
exact; located close together, to come near to or be close to in position,
value or characteristics. 
ARC: 
A continuous portion
of a curved line, as of a circle or an ellipse. 
ARC
SECOND: 
A term of clarification
used to differentiate "degree" seconds. 
AVERAGE: 
A single value or
mean that summarizes or represents the general significance of a set of
unequal values; an estimation of or approximation to an arithmetic mean. 
AXIS: 
Straight line, about
which a line, curve, or plane figure is conceived to revolve; one of the
reference lines of a coordinate system; imaginary line through a drawing
for measurement or reference purposes. 
AXIS
INVERSION: 
Reversal of plus/minus
axial values, for the purpose of lefthanded parts machining. 
AXIS
OF COORDINATES: 
The intersection
of a horizontal line (axis of abscissas), and vertical line (axis of ordinates)
through which the location of a point in a plane can be determined. 
AXIS
OF SYMMETRY: 
Invisible line representing
the center of gravity of a symmetrically balanced body or form. 
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B 
BASIC
SIZE: 
The exact theoretical
size from which all limiting variations are made. 
BAUD: 
A variable unit
of data transmission speed, usually equal to one bit per second. 
BENCHMARK: 
Point of reference
or standard from which other measurements may be made. 
BILATERAL
TOLERANCE: 
Tolerance partially
on both sides of the basic dimension. 
BISECT: 
To divide into two
usually equal parts. 
BIT: 
Unit of computer
information equivalent to the result of a choice between two alternatives
(yes/no, on/off). 
BIT
DENSITY: 
Measure of the quantity
of bits per unit of length, area, or volume. 
BIT
RATE: 
Velocity of bit
transmission, usually in units per second. 
BITANGENT: 
Straight line touching
a curve at two points. 
BLOCKS: 
A quantity, number,
or section of things dealt with as a unit. 
BORE: 
A cylindrical hole. 
BRINELL
HARDNESS: 
The hardness of
a metal or alloy measured by hydraulically pressing a hard ball under a
standard load into the specimen. 
BRIGGS'
STANDARD PIPE THREAD: 
The US standard
for wrought pipe; angle thread of 60 degrees. 
BRITTLENESS: 
Sensitivity of a
material to cracking or breaking. 
BROWN
AND SHARPE GAUGE: 
Standard US gage
for determination of wire size. 
BYTE: 
Group of adjacent
binary digits usually shorter than a word, that a computer processes as
a unit. 
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C 
CAD: 
Computeraided design. 
CALIBER: 
Diameter of a round
body; internal diameter of a hollow cylinder. 
CALIBRATE: 
To ascertain caliber;
to determine, rectify, or mark the graduations of (as a thermometer tube);
to standardize. 
CALIBRATION: 
Act or process of
calibrating; set of graduations to indicate values or positions. 
CALIBRATIONS: 
The marks on a measuring
instrument, as the marks on a rule, which divides the instrument into fractional
parts. 
CALIPERS: 
Measuring device
with two legs or jaws that can be adjusted to determine thickness, diameter,
and distance between surfaces. 
CAM: 
Computeraided manufacturing. 
CAMBER: 
To curve upward
in the middle; slightly arched. 
CARTESIAN
COORDINATE: 
Either of two coordinates
that locate a point on a plane, and measure its distance from either of
two intersecting straight line axes on a line parallel to the other axis;
any of three coordinates that locate a point in space, and measure its
distance from any of three intersecting coordinate planes measured parallel
to that one of three straightline axes that is the intersection of the
other two planes. 
CENTER: 
Point around which
a circle or sphere is described; point related to a geometrical figure
in such a way that for any point on the figure there is another point on
the figure such that a straight line joining the two points is bisected
by the original point; place or fix at or around a center or central position. 
CENTER
DISTANCE: 
Measurable distance
between the centralizes of holes or objects. 
CENTER
GAGE: 
Flat gage for threading
tool setup prior to chasing threads on a lathe. 
CENTER
HEAD: 
Part of a combination
square set that is used in determining centers of round work pieces. 
CENTER
LINE: 
Real or imaginary
line that is equidistant from the surface of sides of something. 
CENTRAL
ANGLE: 
Angle formed by
two radiuses of a circle. 
CENTRALIZATION/CENTERING: 
Positioning of the
gage so that its measuring contacts locate diametrically across the hole,
as evidenced by a maximum reading. (Not to be confused with "squaring" the gage so that the contacts are perpendicular to the axis of the hole,
as indicated by a minimum reading.) May also apply to outside diameter
measurement. 
CENTRIC: 
Located in or at
a center. 
CHAMFER: 
Flat surface formed
when a corner is cut off, usually having an angle of 45 degrees. 
CHORD: 
Straight line joining
two points on a curve; segment of a secant between its intersections with
a curve. A line cutting the circumference of a circle at two places. 
CHORDAL
PITCH: 
Measured distance
from a point on a gear tooth to the corresponding point on the next gear
tooth. 
CIRCLE: 
Closed plan curve,
every point of which is equidistant from a fixed point within the curve;
the plane surface bounded by such a curve. 
CIRCULAR
INTERPOLATION: 
Contouring control
technique that uses the date contained in a single block to generate an
arc of a circle. The speeds of the axes used to produce this arc are varied
by the control. 
CIRCULAR
PITCH: 
Measured distance
from the center of a gear tooth to the center of the next gear tooth. 
CIRCUMFERENCE: 
External boundary
or surface of a circle, round object, or figure. 
CIRCUMSCRIBE: 
To draw a line around;
to surround by a boundary; encircle. 
CLEARANCE: 
Distance by which
one object clears another or the clear space between them. 
COATING
THICKNESS: 
Measured depth of
some material such as metal, compound, etc. applied to or covering the
surface of another material. 
COMBINATION
SQUARE: 
Device incorporating
calibrated blade, center head, bevel protractor, and square head with a
level, for machine layout measurement. 
COMPARATOR: 
Device for comparing
something with a similar thing or with a standard measure. 
COMPARE: 
To examine the character
or qualities of, in order to discover resemblances or differences. 
COMPARISON
MEASUREMENT: 
Measurement by comparing
the unknown length with a known length or standard. 
COMPASS: 
Instrument for describing
circles or transferring measurements, that consists of two pointed branches
joined at the top by a pivot. 
COMPLIMENTARY
ANGLES: 
Angles which when
added together equal 90 degrees. 
COMPUTER: 
A programmable electronic
device that can store, retrieve, and process data. 
COMPUTERIZED
DATE ACQUISITION: 
The gathering, recording,
identification, and evaluation of raw data for centralized processing via
computer into usable information. 
CONCENTRIC: 
Having a common
center or common axis. 
CONJUGATE
ANGLE: 
One of two angles
whose sum is a perigon. 
CONNECTING
EXTENSION TUBES: 
That part of the
gage's handle that connects the depth extension tubes together. 
CONCAVE: 
Hollowed or rounded
inward, arched in, or curved in; a concave line or surface. 
CONSTANT: 
Number having a
fixed value in a given situation, or that is characteristic of some of
a substance or instrument; number that is assumed not to change value in
a given mathematical context; a term in logic with a fixed designation. 
CONTACT
INSTRUMENT: 
An instrument that
depends upon physical contact with the part. Hence, distortion is introduced. 
CONTACT
POINTS: 
The part of a gage
at which measurements are taken. 
CONTOUR: 
The outline of a
curving or irregular figure; the line representing this outline. 
COORDINATE: 
One line in a system
of lines by which position is located. 
COORDINATED
DIMENSIONING: 
Method of dimensioning
wherein a point is defined as being a particular dimension and space relative
to a reference point, measured with respect to defined axes. 
CUTTING
ANGLE: 
Angle described
between the cutting tool and the surface of the material being cut. 
D 
DATA: 
Factual information
used as a basis for reasoning, discussion, or calculating. 
DATA
ACQUISITION: 
Method of gathering
masses of raw data through recording equipment for the purpose of further
processing as in a computer. 
DATA
BASE: 
Collection of data
organized especially for rapid search and retrieval as by a computer. 
DATA
FILE: 
Collection of related
data records organized in a particular configuration. 
DATA
LOGGING: 
Recording of data
relative to events occurring in time sequence. 
DATA
PROCESSING: 
Converting of raw
data to machine readable form and its subsequent processing as in a computer. 
DATUM: 
Something given
or admitted as a basis for reasoning or inference. A point of reference. 
DATUM
LINE: 
Any fundamental
line from which graphic calculations are made. 
DATUM
PLANE: 
Plane in which the
reference points lie. Perpendicular to line of measurement. 
DECIMAL: 
Numbered or proceeding
by tens; based on the number ten; proper fraction in which the denominator
is a power of 10, usually not expressed but signified by a point placed
at the left of the numerator. 
DECIMAL
EQUIVALENT: 
Value of a fraction
expressed as a decimal. 
DEGREE: 
In angle measurement,
the 360th part of the circumference of a circle. 
DEPTH
EXTENSION TUBE: 
That part of the
gage's handle which is connected to accommodate longer than normal measuring
depths. 
DEPTH
GAGE: 
Instrument consisting
of a rule and cross beam that is used for measuring depth of holes and
recesses. 
DEPTH
MICROMETER: 
Depth gage capable
of very precise measurements. 
DEVIATION: 
Departure or deviation
from an established standard or measure. 
DIAGONAL: 
Joining two nonadjacent
vertices of a rectilinear or polyhedral figure; passing through two nonadjacent
edges of a polyhedron; inclined obliquely from a reference line. 
DIAL: 
A face upon which
some measurement is registered usually by means of graduations and a pointer;
to measure with a dial. 
DIAL
INDICATOR: 
Metalworking measurement
device usually found on gages. 
DIAMETER: 
A chord passing
through the center of a circle. 
DIAMETER
TAPE: 
Steel measuring
tape that provides a reading of diameter measurement when placed around
the circumference of a cylinder or round body. 
DIAMETRAL
PITCH: 
Ratio between number
of teeth on a gear and the gear's pitch diameter. 
DIE
CLEARANCE: 
Measured space between
punch and die that allows for the thickness of the Work piece. 
DIFFERENCE
MEASUREMENT: 
Differential measurement
in which one input signal is subtracted from another one. 
DIFFERENTIAL
MEASUREMENT: 
The algebraic combination
of input signals within the measurement instrument. Used to obtain concentricity,
roundness, and other measurements directly. 
DIGIT: 
Any of the Arabic
numerals 1 to 9, and usually the symbol 0. 
DIGITAL: 
Of or relating to
calculation by numerical methods or by discrete units; relating to data
in the form of numerical digits. 
DIGITAL
INSTRUMENT: 
An instrument that
uses counting methods. 
DIGITIZE: 
To arrange or put
(as data) into digital notation. 
DIHEDRAL
ANGLE: 
Figure formed by
two intersecting planes. 
DIMENSION: 
A measure in one
direction; one of three or four coordinates determining a position in space
or in space and time; quality of spatial extension. 
DIRECT
MEASUREMENT: 
Measurement with
an instrument that incorporates its own standard of length. 
DISCRIMINATION: 
Line value of graduations
on a dial indicator. 
DISPLAY: 
A visual presentation
of data on some form of output device. 
DIVIDE: 
To separate into
two or more parts, areas, or groups; to subject a number or quantity to
the operation of finding out how many times it contains another number
or quantity. 
DRILL
GAGE: 
Steel plate containing
holes of standard drill sizes that facilitates determination of proper
drill bit size. 
DRILL
GRINDING GAGE: 
Device that checks
depth and lip angle of a drill. 
DYNAMICS: 
Branch of mechanics
that deals with forces and their relation primarily to the motion, and
sometimes to the equilibrium of bodies; variation and contrast in force
or intensity. 
DYNAMOMETER: 
Instrument for measuring
mechanical force; apparatus for measuring mechanical power, as of an engine. 
E 
ECCENTRIC: 
Deviation from the
center or from the line of a circle. 
ECCENTRICITY: 
Deviation of the
centers of two circles from each other. 
ELECTRONIC
MEASUREMENT INSTRUMENT: 
An instrument in
which the amplification is obtained by electronic means. (In most instruments
the initial pickup is mechanical.) 
ERROR: 
The difference between
an observed or calculated value and a true value; variation in measurements,
calculations, or observations of a quantity due to mistakes or uncontrollable
factors. 
F 
FEEL: 
The perception of
metaltometal contact in measurement. 
FEELER
GAGE: 
Instrument made
up of a series of thin steel plates, used for measuring the distance between
parts. 
FINISH: 
The character of
the surface. 
FIT: 
The relation between
two mating parts with reference to ease of assembly. The quality of fit
is dependent upon both the relative size and the quality of finish of the
mating parts. 
FIXED
CONTACTS: 
That part of a gage
measuring system that does not move. 
FLATNESS: 
Referred to as per
foot or overall, the deviation from above or below a reference plane. 
FLATS: 
Small surface plates,
usually of high accuracy. 
FLAWS: 
Irregularities in
surface finish that do not appear in a consistent pattern. 
FLOATING
CONTACT POINTS: 
Measuring contacts
that are able to move in or out of measurement taking. 
FLOATING
ZERO: 
A feature of a machinetool
numerical control device that allows for setting the zero reference point
on an axis at any point in the travel. 
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G 
GAGE: 
A device for determining
whether or not one or more of the dimensions of a manufactured part are
within specified limits. A standard of comparison between like items. 
GAGING: 
A process of measuring
manufactured materials to assure the specified uniformity of size and contour. 
GAGING
CAPACITY: 
Also referred to
as TOTAL RANGE OF ADJUSTMENT, embraces the maximum and minimum dimensions
to which the gage can be adjusted for measurement with acceptable accuracy. 
GAGING
LENGTH: 
The maximum distance
which gage contacts can enter a hole to check diameter or other condition,
often referred to a GAGING DEPTH when the entrance is vertical. 
GAUGE: 
See GAGE. 
GEAR
TOOTH CALIPER: 
Instrument that
uses the vernier technique to measure thickness and depth of gear teeth
on the pitch line. 
GO
GAGE: 
Attribute gage that
passes all parts within size limits. 
GO/NOGO
GAGE: 
Precision gage with
opposing ends sized a few thousandths of an inch apart, with one end greater
than a specified hole size, and the other end equal to hole size. 
GRADUATE: 
To mark with degrees
of measurement; to divide into grades or intervals; to change gradually;
graduated cup, cylinder, or flask for measuring. 
GRADUATION: 
Smallest division
on a scale. 
GRATING: 
System of closed
equidistant and parallel lines or bars ruled on a polished surface to produce
spectra by diffraction. 
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H 
"H"
DIMENSION (BLIND HOLE DISTANCE "H"): 
That part of the
bore which is not being measured the distance from the center of the measuring
contact to the bottom of the gage. 
HARDNESS
TESTER: 
Device or system
used in determining the hardness of heattreated steel. 
HELIX: 
Something spiral
in form; a curve traced on a cylinder by the rotation of a point crossing
its right sections at a constant oblique angle. 
HELIX
ANGLE: 
The angle which
results from a thread helix at the pitch diameter with a plane perpendicular
to the axis. 
HOKE
BLOCKS: 
Precision blocks,
designed by Major Hoke, for checking gages, dimensions, and other measurements. 
HOLDER: 
That part of a gage
which connects the measuring surface to the indicator. 
HOME
POSITION: 
Fixed location in
a machine tool's coordinateaxis system. 
HOOKE'S
LAW: 
An engineering law
stating that within elastic limit, deformation produced is proportional
to stress. 
HORIZONTAL: 
Of, relating to,
or situated near the horizon; parallel to, in the plane of, or operating
in a plane parallel to the horizon or to a base line. 
HYPERBOLA: 
Plane curve generated
by a point so moving that the difference of the distances from two fixed
points is a constant; curve formed by the intersection of a double right
circular cone with a plane that cuts both halves of the cone. 
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I 
IMPACT
TEST: 
Method of testing
a material for shock resistance. 
INCH: 
Unit of length equal
to 1/36 of a yard. 
INCLUDED
ANGLE: 
The complete angle
on both sides of the center line. 
INCREMENT: 
An increase especially
in quantity or value; one in a series of regular consecutive additions;
a minute increase in quantity; positive or negative change in the value
of one or more of a set of variables. 
INCREMENTAL
DIMENSION: 
Dimension expressed
in relation to the point before it in a series of points. 
INDEXING: 
Division of a circle
into a specified number of increments through the use of an indexing or
dividing head. 
INDICATING
GAGE: 
Instrument that
visually displays uniformity of measurements or contour; variation indicated
by a level or graduated dial. 
INDICATOR: 
An instrument that
visually displays the amount of variation between dimensions being measured.
May be either mechanical or electronic. 
INDICATOR
RANGE: 
Useful portion of
total travel. 
INDICATOR
STAND: 
Selfsupporting
contrivance providing a reference point for the indicator. 
INITIAL
LINE: 
The reference line
when two intersecting lines form an angle. 
INSPECT: 
To view closely
in critical appraisal; to look over or examine officially. 
INSPECTION: 
Examination by measurement,
gaging, or other means to verify an object's compliance with predetermined
standards. 
INSPECTION
BENCH: 
Metal or granite
surface of precise flatness and smoothness for checking the accuracy of
finished parts. 
INSPECTION
GAGES: 
Standard or custommade
instruments used in checking accuracy of finished products. 
INSPECTOR: 
A person employed
to inspect something, usually finished products, or products in process. 
INTERIOR
ANGLE: 
Any one of four
angles formed between two straight lines cut by another straight line. 
INTERPOLATION: 
The selection of
the nearest graduation when a measurement lies between them. The observational
equivalent to the rounding off process in computation. 
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J 
JOHANSSON
BLOCK: 
Rectangular block,
produced in a variety of degrees of accuracy, for use as a standard gage. 
K 
KEEP'S
HARDNESS TEST: 
Metalhardness testing
method in which a steel drill revolves at a specified rate and is applied
with standard force against the surface being tested. 
KNOOP
HARDNESS TEST: 
Hardness testing
method for use on thin metals, plated surfaces, particularly hard and brittle
materials, and shallow carburized and nitrated surfaces. 
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L 
LAY: 
The predominant
direction of surface pattern. 
LEAD: 
To direct on a course
or in a direction; position at the front; distance a nut advances on a
thread in a single revolution. 
LIMIT
GAGE: 
Instrument designed
for checking a specified dimensional tolerance. 
LIMITS: 
The extreme permissible
dimensions of a part. 
LINEAR: 
Of, relating to,
or resembling a straight line; involving a single dimension; of the first
degree with respect to one or more variables; of, relating to, or based
on linear equations or linear functions. 
LINEAL
FOOT: 
Unit of measurement
representing 12 in length. 
LINEAR
MEASUREMENT: 
Straight line, involving
a single dimension. A measure of length; a system of measures of length. 
LIQUID
MEASURE: 
Unit or series of
units for measuring liquid capacity. 
LONGITUDINAL: 
Of or relating to
length or the lengthwise dimension; placed or running lengthwise. 
LOT
SIZE: 
Quantity of materials
or products to be produced at a specified point in time. 
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M 
MAJOR
AXIS: 
The long diameter
of an ellipse. 
MAJOR
DIAMETER: 
Largest thread diameter
measured perpendicular to the axis. 
MASTER
GAGE: 
Any instrument used
to check the accuracy of other measuring instruments. 
MASTER
RING: 
A standard against
which to check measuring instruments to ensure that they remain dimensionally
stable and maintain their nominal level of accuracy. 
MASTER
TAPER: 
Gage used to check
other tapers for accuracy. 
MAXIMUM: 
The greatest quantity
or value attainable or attained; the upper limit allowed or allowable;
the largest value assumed by a realvalued continuous function defined
on a closed interval. 
MAXIMUM
READING: 
The farthest point
to which the indicator hand travels in the plus direction (usually clockwise). 
MEAN: 
Middle point between
extremes; value that lies within a range of values and is computed according
to a prescribed law; the arithmetic mean of the two extremes of a range
of values. 
MEASURE: 
A fixed or suitable
limit; dimensions, capacity, or amount of something ascertained by measuring;
an instrument for measuring; a system of standard units of measure. 
MEASUREMENT: 
The act or process
of measuring; a figure, extent, or amount obtained by measuring. 
MEASURING
DEPTH (REACH): 
The distance the
gage will enter into a bore. See also GAGING LENGTH. 
MEASURING
HEAD: 
The area of the
gage where the measurement takes place. 
MEASURING
MOVABLE CONTACT: 
See SENSITIVE CONTACT. 
MEASURING
MOVABLE CONTACT TRAVEL: 
The distance of
movement of the measuring contact. 
MEASURING
SLEEVES: 
Self centering and
the measuring part of an indicating plug gage. 
MEASURING
TAPE: 
A metal or cloth
tape graduated for linear measurements. 
MENSURATION: 
The act of measuring;
geometry applied to the computation lengths, areas, or volumes from given
dimensions or angles. 
METRIC: 
System of measurement
that is based on the meter as the standard of measurement; of or relating
to the metric system. 
METRIC
GEAR: 
A gear designed
and produced using the metric system of measurement. 
METRIC
SYSTEM: 
A decimal system
of weights and measures based on the meter and on the kilogram. 
METRIC
THREAD: 
Thread based on
the metric system of measurement. 
METROLOGY
LABORATORY: 
A laboratory for
the calibration of standards. May be a department within a company or an
outside service. 
MICROMETER: 
Instrument used
with a telescope or microscope for measuring minute distances; unit of
length equal to one millionth of a meter, also called a micron. 
MICROMETER
CALIPER: 
Caliper having a
spindle moved by a finely threaded screw for making precise measurements. 
MICRON: 
One millionth of
a meter, 0.001mm or 0.0000 50". Abbreviated lum. 
MICROSECOND: 
One millionth of
a second. 
MIL: 
0.001 INCH. (1,000
MILS = 1 INCH = 2.54 CM) Unit of length equal to 1/1000, used especially
for the diameter of wire; unit of angular measurement equal to 1/6400 of
360 degrees. 
MILLISECOND: 
One thousandth of
a second. 
MINIMUM: 
The least quantity
assignable, admissible, or possible; the least of a set of numbers, specifically
the smallest value assumed by a continuous function defined on a closed
interval; the lowest of degrees or speed. 
MINIMUM
READING: 
The farthest point
to which the indicator hand travels in the minus direction (usually counterclockwise). 
MINOR
AXIS: 
The chord of an
ellipse passing through the center and perpendicular to the major axis. 
MINOR
DIAMETER: 
Smallest screwthread
diameter, measured across the roots and perpendicular to the axis. 
MINUTE: 
One 60th part of
a degree. One 21,600th part of a circle. 
MOHS'
SCALE: 
A scale of hardness
for minerals developed in 1839 by Friedrich Mohs. 
MONOMIAL: 
Mathematical expression
consisting of a single term. 
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N 
NANOSECOND: 
One billionth of
a second. 
NO
GO: 
Attribute gage that
rejects all parts out of size limits. 
NOMINAL
(BLUEPRINT): 
The specified size
(the named size), not the size plus or minus some tolerance. 
NOMINAL
SIZE: 
A designation given
to the subdivision of the unit of length having no specified limits of
accuracy, but indicating a close approximation to a standard size. 
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O 
OUTOFROUND: 
Variations of the
distance from the true center of an object to the circumference. 
OBLONG: 
Deviating from a
square or circular form through elongation; rectangle with adjacent sides
unequal; rectangular, with the normally horizontal dimension the greater. 
OBTUSE
ANGLE: 
An angle greater
than a right angle. 
OCTAGON: 
Polygon of eight
angles and eight sides. 
ODD
LEG CALIPER: 
Caliper device with
legs curved the same way, used for measuring shoulder distances. 
ODONTOGRAPH: 
Instrument that
facilitates the correct layout of gear teeth. 
OFF
CENTER: 
Two or more circumferences
not having the same center or axis. 
OFFSET: 
An abrupt change
in the dimension or profile of an object or the part set off by such change;
to serve as a counterbalance. 
ON
CENTER: 
The placement of
center lines in line. 
OPTICAL
INSTRUMENTS: 
Device for inspection
and measurement that utilizes lenses, prisms, mirrors, and other optic
related components. 
ORDINATE: 
Line applied in
an orderly manner; the Cartesian coordinate obtained by measuring parallel
to the Y axis. 
ORTHOGRAPHIC: 
Characterized by
perpendicular lines or right angles. 
OUTOFROUND: 
Variation of the
distance from true center to the circumference. 
OUTPUT: 
Something produced;
information fed out by a computer or accounting machine. 
OUTSIDE
CALIPER: 
Caliper device for
measuring outside diameters or dimensions. 
OVAL: 
Having the shape
of an egg; broadly elliptical; an oval figure or object. 
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P 
PANTOMETER: 
Instrument for measuring
angles, elevation, etc. 
PARABOLA: 
A plane curve generated
by a point moving so that its distance from a fixed point is equal to its
distance from a fixed line; the intersection of a right circular cone with
a plane parallel to an element of the cone; something bowl shaped. 
PARALLAX: 
The apparent displacement
or the difference in apparent direction of an object as seen from two different
points not on a straight line with the object. 
PARALLEL: 
Extending in the
same direction, everywhere equidistant, and not meeting; having parallel
sides. 
PARALLEL
RULERS: 
Drafting tool made
up of two straight edges connected so that they remain parallel regardless
of the distance between them. 
PARALLELS: 
Blocks used in matched
pairs for machine alignment. 
PARAMETER: 
An arbitrary constant
whose value characterized a member of a system; a quantity that describes
statistical population; any of a set of physical properties whose values
determine the characteristics of something. 
PERPENDICULAR: 
Standing at right
angles to the plane of the horizon; being at right angles to a given line
or plane; an extremely steep face. 
PITCH
DIAMETER: 
Relative to a gear,
the pitch circle diameter of the gear wheel; relative to a thread, the
major thread diameter minus the depth of one thread. 
PLANE: 
A surface of such
a nature that a straight line joining two of its points lies wholly in
the surface; a flat or level surface. 
PLANE
ANGLE: 
Angle formed by
two intersecting lines each of which lies on the face of a dihedral angle
and is perpendicular to the edge of the face. 
PLANOMETER: 
A surface plate. 
PLATE
WORK: 
General term for
measurements made from a surface plate. 
PLATEN: 
A flat, wide reference
surface, sometimes referred to as a reference table. Term frequently used
for anvil. 
PLUG
GAGE: 
A precision metal
plug used for holesize gaging. 
PNEUMATIC
GAGING: 
Measurement by means
of pneumatic metrology. 
PNEUMATIC
METROLOGY: 
Measurement in which
amplification is achieved by a system using air or other gases. 
PRECISION: 
The quality or state
of being precise or exact; degree of refinement with which an operation
is performed or a measurement stated; the accuracy with which a number
can be represented; held to low tolerance in manufacture. The quality of
being sharply or clearly determined; strictly accurate; exact. Closeness
of agreement among repeated measurements of the same characteristic by
the same method under the same conditions. 
PRECISION
INSTRUMENT: 
The proficient amplification
of the natural senses of sight and touch. 
PRESET
TOOL: 
Cutting tool clamped
in position so that a specified geometrical relationship will exist with
a gage point. 
PROBE: 
The mechanical measuring
part of a gage that is inserted into a bore, having a round disc contact
that is split in two halves. 
PROFILOMETER: 
Instrument for measuring
surface roughness. 
PROTRACTOR: 
Instrument used
for laying down and measuring angles in drawing and plotting. 
PYROMETER: 
Instrument for measuring
temperatures especially when beyond the range of mercurial thermometers,
usually by the increase of electric resistance in a metal, by the generation
of electric current by a thermocouple or by the increase in intensity of
radiated light. 
PYTHAGOREAN
THEOREM: 
Theorem in geometry
which states the square of the length of the hypotenuse of a right triangle
equals the sum of the squares of the lengths of the other two sides. 
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R 
RADIUS: 
A line segment extending
from the center of a circle to the curve or surface; the circular area
defined by a stated radius. 
RADIUS
GAGE: 
Instrument used
to check the size of radiuses and fillets. 
RANGE: 
A sequence, series,
or scale between limits; the limits of a series; distance or extent between
possible extremes; to set in a row or in the proper order. Total area/distance
of measurement. 
REACH: 
The maximum distance
a gage will enter or extend into a bore for measuring. 
READOUT: 
The data that the
measurement system presents to the observer. 
READABILITY: 
The relative ease
with which the measurement can be distinguished. 
RECTANGLE: 
A parallelogram
all of whose angles are right angles. 
RECTANGULAR
COORDINATE: 
A Cartesian coordinate
of a Cartesian coordinate system whose straightline axes or coordinate
planes are perpendicular. 
REFERENCE: 
Constituting a standard
for measuring or constructing; to put in a form as in a table adapted to
easy reference; source of information. 
REFERENCE
CONTACT: 
The point or surface
from which a dimension is measured or a comparison of dimensions is made. 
REFERENCE
DIMENSION: 
A Dimension without
tolerance that is used for information purposes only. 
REFERENCE
GAGES: 
Instruments used
for testing the accuracy of inspection gages. 
REFERENCE
PLANE: 
Plane in which reference
points lie. Perpendicular to line of measurement. 
REFERENCE
POINT: 
Point defined within
the limits of travel to locate the spindle relative to the Work piece. 
REFLEX
ANGLE: 
Angle greater than
a straight angle. 
RELIEF
ANGLE: 
Angle between the
front of a cutting tool and the face of the Work piece. 
REPEATABILITY: 
Closeness of agreement
of repeated position movements to the same indicated location and under
the same conditions, dispersion of repeated readings. (Over 99% of all
readings will fall into the zone.) 
RESISTANCE: 
An opposing or retarding
force; the opposition offered by a body or substance to the passage through
it of steady electrical current. 
RESOLUTION: 
Process of reducing
to simpler form; the process or capability of making distinguishable the
individual parts of an object, closely adjacent optical images, or sources
of light. OR The ratio of the width of one scale division (one output unit)
to the width of the hand (the readout element). 
REVERSAL
PROCESS/TECHNIQUE: 
Method for detecting
or canceling of small changes by comparing a variable with itself but with
reversed algebraic sign. 
RHOMBOID: 
Parallelogram in
which the angles are oblique and adjacent sides unequal; shaped somewhat
like a rhombus or rhomboid. 
RHOMBUS: 
Equilateral parallelogram
usually having oblique angles. 
RIGHT
ANGLE: 
Angle bounded by
two lines perpendicular to each other. 
RING
GAGE: 
Ringshaped gage
used for checking outside diameters. 
RING
SEGMENT: 
Part of the gage's
measurement transfer mechanism. 
RING
THREAD GAGE: 
Ringshaped gage
used for checking outside screw threads. 
ROCKWELL
HARDNESS TESTER: 
Machine that measures
hardness by determining depth of penetration into a specimen under fixed
testing conditions. 
"ROCKING": 
Movement imparted
to a gage to determine the point at which its measuring contacts are correctly
aligned with the dimension being checked, as evidenced by a minimum reading. 
ROOT
DIAMETER: 
Same as minor diameter. 
ROUGHNESS: 
Finelyspaced surface
irregularities, in a consistent pattern produced by machining or processing. 
ROUNDNESS: 
The characteristic
that all parts of a circle are identical. 
RULE: 
Instrument made
with a straight edge for measurement applications or for scribing a line. 
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S 
SCALE: 
Something graduated,
especially when used as a measure or rule, as a series of spaces marked
by lines and used to measure distances or to register something; an instrument
consisting of a strip with one or more sets of spaces graduated to and
numbered on its surface for measuring or laying off distances or dimensions;
to pattern, make, regulate, set, or estimate according to some rate or
standard. 
"SCALED" (MARKINGS): 
See CALIBRATIONS 
SCALENE
TRIANGLE: 
Triangle in which
no two sides are equal. 
SCLEROMETER: 
Instrument for determining
the relative hardness of materials. 
SCLEROSCOPE: 
Instrument which
measures Work piece hardness in terms of elasticity. 
SCREW
PITCH GAGE: 
Gage for determining
the amount of threads per inch on screw, nut, bolts, etc. 
SECOND: 
One 60th part of
a minute. One 3600th part of a degree. One 1,296,000th part of a circle. 
SECTOR: 
Geometrical figure
bounded by two radiuses and the included arc of a circle. 
SEGMENT: 
A portion cut off
from a geometrical figure by one or more points, lines, or planes; the
finite part of a line between two points in the line; to separate into
segments. 
SELFCENTERING
BASE: 
That part of the
gage that aligns it to the center of the bore. 
SENSITIVE
CONTACT: 
That contact point
of a gage which is free to respond to the size of the Work piece being
measured and from the response is transferred to the indicator dial. Also
known as MOVABLE CONTACT. 
SENSITIVITY: 
Minimum input that
produces a discernible output. 
SERRATED
ANVIL: 
Anvil having large
number of closely spaced grooves to reduce surface area. Used to minimize
effect of air film. 
SHEET
METAL GAGE: 
Instrument used
in determining the thickness of sheet metal. 
SHRINK
RULE: 
Rule used for representative
measurement rather than actual measurement. 
SINGLEDIMENSION
GAGE: 
A gage designed
to check on particular dimension. Some are adjustable, but only over a
narrow range to compensate for wear. 
SINGLEPURPOSE
GAGE: 
A gage designed
for one type of measurement, e.g. inside diameter. Gage may be either adjustable
or made to check a single dimension. 
SLEEVE: 
See MEASURING SLEEVE. 
SLIDE
CALIPER: 
Caliper device made
up of a calibrated slide held in a rule type beam for rapid inside and
outside diameter reading. 
SLIDE
RULE: 
Instrument consisting
in it simple form of a ruler and a medial slide that are graduated with
similar logarithmic scales, labeled with the corresponding logarithms and
used for rapid calculation. 
SNAP
GAGE: 
Nonadjustable inspection
gage. 
SOLID
ANGLE: 
The threedimensional
angular spread at the vertex of a cone measured by the area intercepted
by the cone on a unit sphere whose center is the vertex of the cone. 
SPC: 
An abbreviation
for Statistical Process Control. A method of ensuring the quality of the
output of any process by means of statistical sampling to determine whether
the process itself is functioning within its established range of parameters. 
SPHERE: 
A solid that is
bounded by a surface consisting of all points at a given distance from
a point constituting its center; natural, normal, or proper place; field
or range of influence. 
SPHERICAL
ANGLE: 
Angle between two
intersecting arcs of great circles of a sphere measured by the plane angle
formed by the tangents to the arcs at the point of intersection. 
SPREAD
PROBE (Split ball): 
Part of the gage's
measurement transfer mechanism. 
SQUARE: 
Instrument having
at least one right angle and two straight edges used to layout or test
right angles; a rectangle with all four sides equal; the product of a number
multiplied by itself; to make square to rectangular. 
SQUARE
MEASURE: 
Unit or system of
units for measuring area. 
STANDARD: 
Something setup
and established by authority, custom or general consensus as a model or
example, something setup and established as a rule for the measure of quantity,
weight, extent, value, or quality; constituting or conforming to a standard. 
"A" STANDARD: 
A copy traceable
to THE STANDARD. 
"THE" STANDARD: 
The ultimate physical
embodiment of the unit of length. 
STEEL
RULE: 
Rule made of steel. 
STERADIAN: 
Unit of measurement
for solid angles which encompasses a surface equivalent to the square of
the radius. 
STRAIGHT
ANGLE: 
Angle whose sides
lie in opposite directions from the vertex in the same straight line and
which equals two right angles. 
SUM
MEASUREMENT: 
Differential measurement
in which one input signal is added to another one. 
SUPPLEMENT
OF AN ANGLE: 
Difference between
a given angle and 180 degrees. 
SUPPLEMENTARY
ANGLE: 
One of two angles
or arcs whose sum is 180 degrees. 
SURFACE
GAGE: 
A Noncalibrated
instrument used primarily for layout work. 
SURFACE
PLATE: 
Granite or iron
inspection plate whose surface is ground to a precise degree of smoothness. 
SUPPLEMENT
OF AN ANGLE: 
Difference between
a given angle and 180 degrees. 
SUPPLEMENTARY
ANGLE: 
One of two angles
or arcs whose sum is 180 degrees. 
SURFACE
GAGE: 
A Noncalibrated
instrument used primarily for layout work. 
SURFACE
PLATE: 
Granite or iron
inspection plate whose surface is ground to a precise degree of smoothness.
A horizontal reference plane of sufficient strength and rigidity that measurement
operations may be supported on it. 
SWIMMING
CONTACT POINT: 
See FLOATING CONTACT
POINTS. 
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T 
T
SQUARE: 
Ruler with a crosspiece
or head at one end, used in making parallel lines. 
TAPE: 
Narrow flexible
strip or band sometimes used for measuring. 
TAPER
GAGE: 
Instrument for taper
degree and accuracy testing. 
TENTOONE
RULE ("RULE OF TEN"): 
General rule that
instrument should be capable of dividing part tolerance into ten parts. 
TENSIMETER: 
Instrument for measuring
differences of vapor pressure. 
TENSIOMETER: 
Device for measuring
tension. 
TENTH: 
Engineering term
meaning 1/10 of 1/1000 or 0.0001. 
TERMINAL
LINE: 
The measured line
when two intersecting lines form an angle. 
THICKNESS
GAGE: 
Fixed leaftype
gages for clearance checking between mated parts. 
THREAD
GAGE: 
Plug or ringtype
device for checking thread fit. 
THREADS
PER INCH: 
Number of screw
threads in an inch of length. 
THREE
DIMENSIONAL: 
Of or relating to
three dimensions; giving the illusion of depth or varying distances. 
THREEPOINT
MEASURING SYSTEM: 
The gage has three
measuring contacts. 
THREEWIRE
METHOD: 
Screw thread pitchdiameter
measurement technique. 
TIR: 
Total indicator
reading. Difference between maximum and minimum indicator readings obtained. 
TOLERANCE: 
Allowable deviation
from a standard; range of variation permitted in maintaining a specified
dimension in machining a Work piece. 
TOTAL
RANGE OF ADJUSTMENT: 
See GAGING CAPACITY. 
TRACEABILITY: 
Documentation to
establish that standards are known in relation to successively higher standards
until the National Bureau of Standards is reached. 
TRAMMEL: 
Instrument for drawing
ellipses. 
TRANSFER
CALIPER: 
Caliper device that
allows return to measured Work piece setting after that setting has been
changed as a result of removal from the Work piece. 
TRANSFER
OF MEASUREMENT: 
Operation between
taking a measurement and reading the value of the measurement. 
TRANSVERSAL: 
Line that intersects
a system of lines. 
TRIANGULAR
SCALE: 
Threeedged drafting
tool, with each edge having two sets of calibrations  one for actual measurement
and the other for representative measurement. 
TRUE: 
Conformable to a
standard or pattern; on center; the quality or state of being accurate. 
TRUE
DIAMETER (BORE): 
See DIAMETER 
TRY
SQUARE: 
Instrument used
for laying off right angles and testing whether work is square. 
TWOPOINT
MEASURING SYSTEM: 
The gage has two
measuring contacts. 
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U 
UNIFIED
THREADS: 
Screw thread standard
adopted by the United States, Great Britain, and Canada. 
UNILATERAL
TOLERANCE: 
Allowable deviation,
in only one direction, from a basic dimension. 
UNITED
STATES FORM THREAD: 
Screw thread having
the same shape as the USS National Coarse, but with different pitch. 
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V 
VANISHING
POINT: 
Point at which receding
parallel lines seem to meet when represented in linear perspective; point
at which something disappears or ceases to exit. 
VARIABLE: 
Able or apt to vary;
subject to variation or changes; having the characteristics of a variable;
something that is variable; a quantity that may assume any one of a set
of values. 
VARIANCE: 
The fact, quality,
or state of being variable or variant; state of being in disagreement;
the square of the standard deviation. 
VECTOR: 
A quantity that
has magnitude and direction and that is commonly represented by a directed
line segment whose length represents the magnitude, and whose orientation
in space represents the direction; course or compass direction. 
VERNIER: 
A short scale made
to slide along the divisions of a graduated instrument for indicating parts
of divisions; small auxiliary device used to obtain fine adjustment. 
VERNIER
CALIPER: 
Caliper device that
consists of a main scale with a fixed jaw and a sliding jaw with an attached
vernier. 
VERTEX: 
The point opposite
to and farthest from the base of a figure; the termination or intersection
of lines or curves; a point where an axis of an ellipse, parabola, or hyperbola
intersects the curve itself; highest point. 
VERTICAL: 
Situated at the
highest point directly overhead or in the zenith; perpendicular to the
plane of the horizon or to a primary axis; located at right angles to the
plane of a supporting surface; lengthwise. 
VERTICAL
ANGLE: 
Either of two angles
lying on opposite sides of two intersecting lines. 
VICKERS
HARDNESS TEST: 
Similar to the Brinell
hardness test. 
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W 
WAVINESS: 
An irregular surface
condition of greater spacing than roughness. Usually caused by deflections
or vibrations, not by the cutting edge. WAVINESS HEIGHT: Surface irregularities
spaced too far apart to be considered characteristics of roughness. 
WHITWORTH
THREAD: 
Standard English
thread with included angle of 55 degrees. 
WIRE
GAGE: 
Notches plate, with
each notch representing a standard sheet metal and wire size. 
WORKING
DEPTH: 
Gear tooth depth
from addendum line to clearance line. 
WORKING
GAGE: 
Gage used exclusively
by a worker as opposed to inspection gages, master gages, etc. 
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Z 
ZERO: 
The point from which
all coordinate dimensions are programmed in an absolute system. The arithmetical
symbol 0 denoting the absence of all magnitude or quantity; the number
between the set of all negative numbers and the set of all positive numbers;
the lowest point. 
ZERO
OFFSET: 
Numerical machinetool
control feature that allows the shifting of the zero point over a specified
range on an axis. 
ZERO
OFFSET POSITION: 
Point to which zero
on the machine is shifted to absolute zero. 
ZERO
SETTING: 
Bringing the zero
position of the instrument into correspondence with a reference of the
measurement. 
ZYGLO: 
Fluorescentpenetrant
inspection method for detection of flaws in nonmagnetic metals. 
