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accuracy
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The difference between a measurement reading and the true value of that measurement.
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alloy steel
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Steel that contains added materials that change the property of the metal. Common alloy elements include chromium, manganese, molybdenum, and nickel.
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axes
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Imaginary lines perpendicular to one another that are used to define the position of objects in three-dimensional space.
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blade micrometer
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A type of micrometer with flattened tips on the anvil and spindle. It is primarily used to measure narrow external grooves.
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calibration
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The comparison of a device with unknown accuracy to a device with a known, accurate standard to eliminate any variation in the device being checked.
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caliper
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A measuring instrument with two pairs of jaws on one end and a long beam containing a marked scale of unit divisions. One pair of jaws measures external features; the other pair measures internal features.
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carbide
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A compound developed by the combination of carbon with usually chromium, tungsten, or titanium. Carbide materials are very hard and wear resistant.
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chromium
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A shiny, hard, steel-gray metal used to add hardness and wear resistance to steel. Many gages are plated with chromium.
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contour
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A curved surface or feature of a workpiece.
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coordinate measuring machine
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A sophisticated measuring instrument with a flat polished table and a suspended probe that measures parts in three-dimensional space.
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depth micrometer
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A type of micrometer with a spindle perpendicular to a flat base. It is primarily used to measure the depth of holes.
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English measurements
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A standard system of measurements based on the inch, second, pound, and Fahrenheit degrees. English measurements are primarily used in the United States and England.
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gage block
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A hardened steel block that is manufactured with highly accurate dimensions. Gage blocks are available in a set of standardized lengths.
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gaging
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The physical inspection of part features using a device with an established standard size. Gaging results in a pass/fail decision.
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go-no go gaging
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The use of a gage to determine whether a part feature simply passes or fails inspection. No effort is made to determine the exact degree of error.
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granite
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A dense, hard type of rock that exhibits excellent wear resistance and stability. Granite tables are used for various measuring applications.
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groove micrometer
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A type of micrometer with a long stem and two small discs at the end. It is primarily used to measure the width and position of internal grooves.
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inspection
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The examination of a part during or after its creation to confirm that it adheres to specifications.
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lapped
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Polished with an abrasive paste to remove the last bit of unwanted material.
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metric measurements
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A standard system of measurements based on the meter, second, kilogram, and Celsius degrees. The metric system is internationally recognized.
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micrometer
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A U-shaped measuring instrument with a threaded spindle that slowly advances toward a small anvil. Micrometers are available in numerous types for measuring assorted dimensions and features.
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optical comparator
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A sophisticated measuring instrument that projects an image of a part onto a screen to compare the shape, size, and location of its features.
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plug gage
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A hardened, cylindrical gage used to inspect the size of a hole. Plug gages are available in standardized diameters.
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precision
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The degree to which an instrument will repeat the same measurement over a period of time.
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ring gage
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A hardened, round gage with a hole used to inspect the size of cylindrical parts or features.
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rule of ten
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The inspection guideline stating that a measuring instrument must be ten times more precise than the acceptable tolerance of the inspected part feature.
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sensitivity
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The smallest change in a measurement that an instrument is capable of detecting.
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snap gage
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A U-shaped gage with hardened, adjustable anvils on opposite ends used to inspect the length of part features.
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standardization
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The development of universally recognized units of measurement. Standardization ensures that parts of the same size are interchangeable.
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steel rule
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A simple measuring instrument consisting of a long, thin metal strip with a marked scale of unit divisions.
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stock
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Raw material that is used to make manufactured parts. Stock is available in standard shapes such as long bars, plates, or sheet.
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thread gage
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A hardened, threaded gage used to inspect the internal threads of a part.
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tolerance
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The unwanted but acceptable deviation from a desired dimension.
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variable inspection
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The inspection of part features using an instrument calibrated in standard measurement units. Variable inspection reveals the degree of variation from a given standard.
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vernier scale
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A type of scale consisting of two opposing line markings with different divisions. Vernier scales appear on both manual calipers and micrometers.
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wear allowance
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The slight amount of material intentionally remaining on a gage to prevent the passing of defective parts over time.
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wring
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To twist and rub together so that the two surfaces cling to one another.
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