Inspecting a Cylindrical Part 331

actual local size

An unrelated size dimension that indicates the measurement of an imaginary plane that intersects a feature. The actual local size, also called the cross-sectional dimension, is often measured with calipers or a micrometer.

actual mating envelope

AME. A geometrically perfect shape that is a 'best fit' around a feature. The actual mating envelope is the smallest possible cylinder contacting a shaft at its highest points or the largest possible cylinder contacting a hole at its highest points.

ASME Y14.5-2018

The standard for Geometric Dimensioning and Tolerancing published by the American Society of Mechanical Engineers (ASME). The 2018 revision is the most recent version of the standard.

bonus tolerances

Additional tolerance applied to a feature as its size shifts from a stated material condition. Bonus tolerance is permissible as a hole deviates from MMC to LMC.

calipers

A measuring instrument with a pair of jaws on one end and a long beam containing a marked scale of unit divisions. Caliper jaws can measure both internal and external features.

callouts

Information on a print that refers to a specific part feature rather than the whole part. Callouts, or local notes, communicate specifications such as chamfer angle and hole diameter.

circular runout

A two-dimensional geometric tolerance that controls the form, orientation, and location of multiple cross sections of a cylindrical part as it rotates. Circular runout is one of two types of runout tolerances.

circularity

A two-dimensional form tolerance that describes the allowable variability in the shape and appearance of a circle. Also known as roundness, circularity is an individual tolerance.

CMM

Coordinate measuring machine. A sophisticated measuring instrument that uses a suspended probe to measure parts in three-dimensional space. CMMs operate using either contact or noncontact methods.

coaxial

Sharing a common center between two cylindrical features. Circularity requires any two-dimensional cross section of a feature to remain within two theoretical coaxial circles.

concentricity

A three-dimensional locational tolerance that describes the location of opposing points in cylindrical features with respect to a datum reference. Concentricity is no longer used in prints adhering to ASME Y14.5-2018.

coordinate measuring machines

CMM. A sophisticated measuring instrument with a flat polished table and a suspended probe that measures parts in three-dimensional space. Coordinate measuring machines can measure using either contact or noncontact methods.

cross section

A section of a feature that is formed by an intersecting theoretical plane. Circularity requires any two-dimensional cross section of a feature to remain within two theoretical coaxial circles.

cross-sectional dimension

An unrelated size dimension that indicates the measurement of an imaginary plane that intersects a feature. The cross-sectional dimension, also called the actual local size, is often measured with calipers or a micrometer.

cylindricity

A three-dimensional form tolerance that describes the allowable variability in the shape and appearance of a cylinder. Cylindricity is an individual tolerance.

datums

A point of reference for machine tools, programs, and fixtures from which measurements are taken. A datum can be a hole, a line, or any three-dimensional shape.

dial indicators

A measuring instrument with a contact point attached to a spindle and gears that move a pointer on the dial. Dial indicators have graduations that show different measurement values.

functional gages

A gage representing a worst-case mating part that provides a simple pass/fail assessment of the inspected part. Functional gages often can quickly inspect several features at once.

geometric dimensioning and tolerancing

GD&T. An international standard for communicating instructions about the design and manufacturing of parts. Geometric Dimensioning and Tolerancing uses universal symbols and emphasizes the function of the part.

go gage

A gage on or in which a good part should fit easily. A go gage quickly checks a part's features without providing a measurement value.

go/no-go gage

An instrument with an established standard size that determines whether a part feature passes or fails inspection. Go/no-go gages do not determine the degree of variation.

height gage

A measuring device with a unit and extending arm that slide up and down a vertical column that is mounted on a base such as a granite surface plate, and a unit with an extending arm that slides up and down along a main scale beam. Height gages may use a standard scale beam, a vernier scale, a dial indicator, or a digital display to measure vertical dimensions and other distances.

inside micrometer

A type of micrometer that is placed in a hole to measure its inside diameter. An inside micrometer is primarily used to measure holes but can sometimes be used to measure hole features, such as counterbores and spotfaces.

inspection

The examination of a product during or after its creation to confirm that it adheres to specifications. Inspection allows manufacturers to identify and correct product defects.

lobing

A condition in which the manufacturing process creates a rounded projection out from what would otherwise be a circular feature. A hole may have more than one lobe.

material condition modifier

Defines the tolerance of a feature in relation to its acceptable size limits. The three material condition modifiers in GD&T are maximum material condition, least material condition, and regardless of feature size.

maximum material condition

MMC. The point at which a feature contains the greatest amount of material within its acceptable size limit. Maximum material condition examples include the smallest acceptable hole and the largest acceptable shaft.

micrometer

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.

no-go gage

A gage purposely designed to not fit with correctly sized parts. No-go gages are often combined with go gages to form a go/no-go gage.

nominal

The ideal measurement of a part or part feature that is specified in the part print. Nominal dimensions are geometrically perfect and are used to establish tolerance values.

optical comparators

A sophisticated measuring instrument that projects an image of a part onto a screen so that the shape, size, and location of its features can be compared to measurement markings. Optical comparators can be used to inspect both surface and profile features in two dimensions.

pin gage

A hardened, cylindrical gage used to inspect the size of small holes. Pin gages are available in sets of different sizes that range from 0.011 in. (0.279 mm) to 1.000 in. (25.400 mm) in increments of 0.001 in. (0.0254 mm).

plug gage

A hardened, cylindrical gage used to inspect the size of a hole. Plug gages are available in standardized diameters.

position

A three-dimensional geometric tolerance that controls how much the location of a feature can deviate from its true position. Position is a related tolerance.

print

A document containing all the instructions necessary to manufacture a part. A print, or blueprint, includes a part drawing, dimensions, and notes.

regardless of feature size

RFS. A modifier indicating that the stated tolerance for a feature applies regardless of its actual size within an acceptable size limit. Regardless of feature size does not permit bonus tolerance.

roundness machine

A sophisticated inspection device with a precision spindle that measures various circular and cylindrical features. A roundness machine is necessary for inspecting such tolerances as circularity, cylindricity, circular runout, and total runout.

runout tolerances

A geometric tolerance that simultaneously limits the form, location, and orientation of cylindrical parts. Runout tolerances are related tolerances requiring a datum axis.

size dimensions

A linear measurement across two opposing points, lines, planes, or surfaces. A size dimension is a required characteristic of a feature of size.

specifications

A description of the essential physical and technical properties of a finished part. Specifications outline important information including finished part dimensions and acceptable tolerance ranges.

tolerance

The amount of permitted variation from a specified dimension of a part. A part within tolerances will meet specifications and pass inspection.

total indicator reading

TIR. The absolute value of the total deviation of a dial indicator's movement. TIR is calculated to inspect the total runout of a cylindrical part or the flatness of a prismatic part.

total runout

A three-dimensional geometric tolerance that controls the form, orientation, and location of the entire length of a cylindrical part as it rotates. Total runout is a related tolerance.

unrelated actual mating envelope

Unrelated AME. A geometrically perfect shape that is a 'best fit' around a feature. An unrelated actual mating envelope is not constrained by other part features or datums.

vernier caliper

A type of caliper with a main graduated scale along the beam and a vernier scale on the movable jaw. Vernier calipers are accurate to within 0.001 in. (0.0254 mm).