NIMS Core Measurement and Materials Skills 211

acceptable quality limit

AQL. A type of random sampling plan where a percentage of a product is inspected. Acceptable quality limit is representative of the quality of the entire production lot.

allowance

The difference between the smallest permissible hole and the largest permissible shaft. An allowance creates a certain kind of fit between mating parts.

alloy steel

Steel that contains added materials that change the property of the metal. Common alloy elements include chromium, manganese, molybdenum, and nickel.

ANSI

American National Standards Institute. A private, nonprofit organization that administers and coordinates voluntary standards and systems. ANSI provides a tool classification system that details characteristics such as size, shape, and tolerance.

bastard cut

A file cut in which there are roughly 30 teeth per inch that is between a middle cut and a second cut. Bastard cut is the third-coarsest cut overall, but is the coarsest cut widely used by machinists.

blade

The long flat part of a file that contains the cutting surface. The blade can be blunt or tapered.

blunt

Having sides that remain parallel in both width and thickness. A blunt file has a cross section that remains the same in size along its entire length.

calibration

The comparison and adjustment of a device with unknown accuracy to a device with a known, accurate standard. Calibration eliminates any variation in the device being checked.

carbide

A compound developed by the combination of carbon, usually with chromium, tungsten, or titanium. Carbide materials are very hard and wear resistant.

chips

A piece of metal that is removed form a workpiece during cutting or grinding. Chips are tiny curls, shards, fragments, shavings, or particles of metal.

clearance

A fit that allows intentional space to exist between a hole and the shaft inserted into it. For a clearance fit, the shaft diameter is designed to be slightly smaller than the hole.

consumer

A person who purchases products. A consumer takes on risks when sampling is used as bad parts might be accepted by not inspecting 100% of the parts in a lot.

cross section

A surface or shape that is exposed or would be exposed by making a cut at a right angle to the object's axis. The cross section of a file may be rectangular, square, triangular, circular, or semi-circular.

curved cut

A file cut in which the rows of teeth are parallel to each other but form curved rather than straight lines. Curved-cut files are often used to shape and smooth body panels in the automotive industry.

cuts

The patterned size and shape of a file's teeth. The three main cuts of a file are bastard, second cut, and smooth.

data

A collection of numbers or facts that is used as a basis for making conclusions. Data is collected by manufacturers about their facilities.

dead-smooth cut

A file cut in which there are roughly 100 teeth per inch. Dead-smooth cut is the smoothest file cut.

destructive testing

A form of testing that places parts under harsh conditions that could lead to product failure. Acceptance sampling is desirable when destructive testing is required.

double cut

A file cut in which there are two sets of parallel rows of teeth that intersect at an angle, resulting in diamond-shaped cutting teeth along the file blade. Double-cut files are best for removing larger quantities of material in a single pass.

draw filing

A type of filing in which the machinist pulls the file across the workpiece toward their body. Drawing filing is most often used for finishing.

edges

The line along which two surfaces intersect. The edge of a file blade occurs where its two faces meet.

equilateral triangle

A triangle with three equal sides and three equal interior angles. The cross section of a three square file may be either an equilateral triangle or an isosceles triangle.

faces

The flat surface of a file blade. The face contains the teeth of the file, though one face of a file can be smooth and free of teeth.

ferrule

A metal ring on the end of a file handle. A ferrule strengthens the area where the handle meets the file.

file card

A wire brush with short bristles that is used to remove chips from file teeth. Using file cards helps prevent chips caught in a file from scratching a workpiece surface.

file cleaner brush

A stiff-, short-bristled brush used to aid in the removal of chips from a file. Using file cleaner brushes helps prevent chips caught in a file from scratching a workpiece surface.

files

A flat metal cutting tool with a large number of very small teeth. Files wear away workpiece material through abrasion.

filing

A type of benchwork operation that involves manually removing small amounts of workpiece material with a tool that has small, sharp teeth. Filing can smooth workpiece surfaces, remove sharp edges, and add a chamfer.

finishing

A metal-cutting process in which a small amount of material is removed to achieve tight tolerance and good surface finish. Finishing is usually achieved with second-cut to dead-smooth-cut and single-cut files.

fit

A designation of how much space or lack thereof is allowed between mating components. There are three main types of fit: clearance, transition, and interference.

flat file

A type of file with a rectangular cross section that is blunt or lightly tapered and either single or double cut. A flat file is used to file flat surfaces.

force fits

FN. A type of fit in which pressure must exist between the parts. Force fits are a type of interference fit.

fraction

A math expression with two numbers placed above and below a division line. A fraction indicates the number of divisions or portions and the size of each division or portion.

gage block

A hardened steel block manufactured with highly accurate dimensions that is used to measure part dimensions after a part is made. Gage blocks are available in a set of standardized lengths.

half round file

A type of file with a semi-circular cross section that is either blunt or tapered. A half round file is used to file contoured workpiece surfaces.

hand file

A type of file with a rectangular cross section that is parallel in width and tapered in thickness with one smooth face and one cutting face. Hand files are used to cut a surface without cutting any adjacent surfaces.

heel

The smooth part of the file located on the blade where the blade meets the tang. The heel does not contain any cutting teeth.

inspection

The examination of a part during or after its creation to confirm that it adheres to specifications. During inspection, defects may be identified and corrected.

interference

A tight fit designed where the smallest permissible shaft is larger than the largest permissible hole. Force is required to assemble parts with an interference fit.

isosceles triangle

A triangle with two equal long sides and one shorter side. The cross section of a three square file may be an isosceles triangle or an equilateral triangle.

lapped

Polished with an abrasive paste to remove the last bit of unwanted material. Gage blocks are lapped by hand or machine.

lathe

A machine tool that holds and supports a cylindrical workpiece at one or both ends and rotates it while a single-point cutting tool removes material. Lathes are commonly used to perform turning operations.

lathe filing

A type of filing in which the machinist pushes a file against a workpiece as it rotates on a lathe. Lathe filing can be used for roughing and finishing.

length

The measurement of a component from end to end, rather than along its side. The length of a file runs parallel to its edges and perpendicular to its point.

locational clearance fits

LC. A type of fit in which the parts in an assembly are not meant to move relative to each other. Location clearance fits are loose compared to locational interference and locational transition fits.

locational interference fits

LN. A type of fit that requires assembly components to lightly or heavily press against each other. Locational interference fits are tight compared to locational clearance and locational transition fits.

locational transition fit

LT. A type of fit in which the parts in an assembly are not meant to move relative to each other and require a slight pressure between them. Locational transition fits are tight compared to locational clearance fits and loose compared to locational interference fits.

lot tolerance percentage defective

LTPD. The quality level that assigns a percentage of defects within a given lot that are acceptable to the customer. Lot tolerance percentage defective is a type of random sampling plan.

mastering

A quick check of a measuring device against a known standard reference, such as a gage block, to determine if the device is reading the measurement correctly. Instruments should be mastered on a regular basis.

middle cut

A file cut in which there are roughly 25 teeth per inch. Middle cut is the second coarsest cut after rough cut.

mill file

A type of file with a rectangular cross section that is blunt or lightly tapered and always single cut. A mill file is used to sharpen tools or finish surfaces.

out-of-round

An irregularly shaped circle that is not totally round. Out-of-round workpieces can occur during lathe filing if the workpiece is over-filed.

percentage

An amount expressing what portion of a whole is present. Percentages are similar to fractions or decimals expressed in hundredths.

pining

The process of a file’s teeth becoming clogged with chips from a workpiece. Pining can be prevented by covering the teeth in chalk.

point

The end of the blade of a file. The point is opposite the tang and is usually squared rather than pointed.

probability

The likelihood that a particular event will happen in the future. Probability can be expressed as a fraction, ratio, or percentage.

producer

A provider of products or services. A producer takes on risks when sampling is used, as good parts might get rejected based on outliers.

random sampling

The process of collecting and analyzing only a small representative portion of a larger group. Random sampling dictates that each item must have the same likelihood of being selected.

rasp cut

A file cut in which the teeth are formed into individual, raised triangular shapes along the surface of the file blade. Rasp-cut files are used on wood and other soft materials.

ratio

A numerical expression representing a part of a larger whole or proportion. A ratio consists of two numbers separated by a colon.

rough cut

A file cut in which there are roughly 20 teeth per inch. Rough cut is the coarsest file cut.

roughing

A metal-cutting process in which a large amount of material is removed to shape the workpiece. Roughing operations prioritize removing material over improving part quality.

round file

A type of file with a circular cross section that tapers toward the file point. Rounds files are used to enlarge or finish holes, round slots, and curves.

running and sliding clearance fits

RC. A type of fit in which the part is meant to move in the assembly. Running and sliding clearance fits are abbreviated as RC for running clearance.

sample

A representative part or small group of parts from a larger group. A larger sample increases accuracy.

scrap part

Any part that does not meet drawing requirements. A scrap part means increased waste for the manufacturer.

second cut

A file cut in which there are roughly 40 teeth per inch. Second cut is the third-smoothest cut overall, but is considered the middle-grade between bastard and smooth cut, the coarsest and smoothest cuts widely used by machinists.

shrink fits

FN. A type of fit in which one part in the assembly is heated to expand and fit onto another, where it cools and shrinks to create a pressured fit. Shrink fits are a type of interference fit.

single cut

A file cut in which there are parallel rows of teeth set at an angle from the centerline of the file blade. Single-cut files are best for sharpening and finishing a workpiece surface.

smooth cut

A file cut in which there are roughly 60 teeth per inch. Smooth cut is the second smoothest cut overall, but it is the smoothest cut widely used by machinists.

square file

A type of file with a square cross section that gradually tapers. Square files are used to enlarge and finish rectangular holes, slots, and angles.

statistical process control

SPC. The use of statistics and control charts to measure key quality characteristics and control how the related process behaves. In statistical process control, sample data allows predictions of the overall process.

statistics

The science of collecting, summarizing, and analyzing numerical information, which is often used to make good decisions with confidence in an otherwise uncertain environment.

straight filing

A type of filing in which the machinist pushes the file across the length of a workpiece on a straight or slightly diagonal path. Straight filing can be used for roughing or finishing.

surface finish

The measured surface profile characteristics of a completed workpiece. Surface finish can be improved with filing.

tang

A tapered extension at the end of a file opposite the point. Tangs are the part of the file onto which a handle is secured.

tapered

Gradually decreasing in size from one end of the object to the other. A tapered file has a width, thickness, or both that decreases in size along its entire length.

teeth

The cutting points of a tool. Teeth can either be molded or cut into a tool.

thickness

The measurement of a component from top to bottom. The thickness of a file measures the distance between its two faces and runs perpendicular to both the point and blade edges.

three square file

A type of file with a triangular cross section that tapers toward the file point. A three square file, or triangular file, is used to finish corners and angles.

tolerances

An acceptable deviation from a given dimension. Measuring part features after a successful first part run is done to determine if the part is within tolerance.

transition

A fit toleranced for an allowance that permits both a clearance and an interference fit. For a transition fit, a clearance fit occurs with the smallest shaft diameter and the largest hole diameter, but an inference fit occurs with the largest shaft diameter and the smallest hole diameter.

triangular file

A type of file with a triangular cross section tapers toward the file point. A triangular file, or three square file, is used to finish corners and angles.

vise

A workholding device with two jaws, usually one fixed and one movable, that grip and hold a workpiece in place. Vises hold a workpiece in place during filing operations.

wear

The erosion of material as a result of friction. Wear occurs to the teeth of a file if excessive force is used on the tool.

width

The measurement of a component along its side, rather than from end to end. The width on a file occurs parallel to the point and perpendicular to the length.

wring

To twist and rub together so that the two surfaces cling to one another. Gage blocks are wrung together in various combinations to form any length.