object being measured by a measuring instrument during the act of measurement. Measurement force is an important factor used in the calculations of elastic deformation.
mwroinch: one millionth of an inch, i.e., 0.000001 inch, I in., or 25.4 nanometers.
micrometer: one millionth of a meter, i.e., 0.000001 meter, 1 pm, or approximately 39.37 microinches.
mm. (minimum) master ring: an internal diameter standard used to set other gaging equipment. Mm. master rings are manufactured to a unilateral Plus tolerance on the part tolerance low limit.
modulus of elasticity: the ratio of unit stress to unit deformation for a particular material, within the limit of pro.portiortality, i.e., E = o/e.
NOTE: The modulus of elasticity is sometimes known as Young’s modulus.
NoGo ring: an internal diameter gage manufactured to the part tolerance low limit with a unilateral plus tolerance, therefore accepting the manufactured part when in tolerance by not fitting on the part.
nominal coefficient of thermal expansion: approximate value (ISO VIM: 1993 Section 5.3) for the coefficient of thermal expansion over a range from a temperature, T, to 20°C and denoted a for the part and a, for the reference standard. Estimated values for a and a,, may be obtained from experiments on like objects or from published data.
out-of-roundness: is the term used to describe a deviation from being round and its value is defined as the minimum radial separation between two concentric circles within which all points on the circular cross section lie.
out-of-straightness: the deviation of the straightness of a line is the minimum distance between two parallel lines, which contain the line profile.
point contact: the single point of contact when using a sphere or section of a sphere in a measurement.
NOTE: The idealized point becomes an area of contact under the measurement force.
Poisson’s ratio: the ratio of the transverse unit deformation of a body to the unit deformation in length, within the limit of proportionality.
ring gage: an internal diameter standard used for setting other measuring instruments or checking the manufactured parts as Go/NoGo gages.
roundness: (see circularity).
resolution (of a displaying device): smallest difference between indications of a displaying device that can be meaningfully distinguished.
(1) For a digital displaying device, this is the change in the indication when the least significant digit changes one step.
(2) This concept applies also to a recording device.
straightness: the minimum distance between two parallel lines which contain the line profile.
surface texture: repetitive or random deviations from the nominal surface, which form the pattern of the surface. Surface texture includes roughness, waviness, lay arid flaws.
taper: for the purposes of this Standard, taper is defined as the gradual increase or decrease in diameter over the full length of the gage.
thermal gradients: the rate of change of temperature as a function of another parameter.
(1) Temporal thermal gradient is the variation of temperature as a function of time, denoted by Tft, °C/hour (or °F/hour).
(2) Spatial thermal gradient is the variation in temperature as a function of length, denoted by 1T/M., °C/m (or °F/in.).
uncertainty of measurement: parameter, associated with the result of a measurement, which characterizes the dispersion of the values that could reasonably be attributed to the measurand.
(1) The parameter may be, for example, a standard deviation (or
a given multiple of it), or the half width of an interval having a stated level of confidence.
(2) See NIST Technical Note 1297 for additional information.
unilateral tolerance: the entire gage tolerance is applied unidirectionally at the extreme limits of the part tolerance. This applies to Go/NoGo min./max. ring gages.