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arc
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A curved feature representing a portion of a circle.
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auxiliary view
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A view drawn at a right angle to an angled feature of the part. Auxiliary views show the true size of an angled surface.
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blind hole
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A hole that is closed at its bottom.
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blueprint
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A document containing all the instructions necessary to manufacture and inspect a part. The key sections of a blueprint are the drawing, dimensions, and notes.
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bolt hole pattern
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A number of holes with centers that are positioned around the circumference of an imaginary circle.
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bore gage
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A hole inspection gage that makes three points of contact within the hole. Bore gages are handheld, variable instruments that provide very accurate readings of hole sizes.
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boss
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A raised, circular peg or protrusion. A boss often has a hole in the center and is used to improve assembly.
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burr
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A rough, sharp edge remaining on a part after machining or stamping. Burrs pose an injury risk and interfere with the fitting of parts.
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casting
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A part formed by pouring molten metal into a mold until it cools and solidifies into its final shape. Castings tend to have rougher surface textures.
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center
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For circles and arcs, it is the point that is equally distant from all other points located on the circle's circumference or the arc.
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center line
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A line used to define the center of a hole, a cylindrical part, or symmetrical part. Center lines consist of alternating long and short dashes.
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chamfer
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A small, angled surface added on the end of a shaft, around the opening of a hole, or along an edge. A chamfer removes the sharp edge and helps remove burrs.
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corner radius
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A rounded internal corner located where two features meet on either a flat or cylindrical part.
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counterbore
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A larger diameter added at a hole opening, with a flat surface between the two diameters. A counterbore provides a space for the head of a bolt or other type of fastener.
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countersink
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An enlarged, angled surface added to a hole opening. A countersink differs from a counterbore because it leaves a tapered opening.
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deburring
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The removal of burrs on a part by processes such as grinding or filing.
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degrees
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A common unit of measurement used to indicate the size of an angle.
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diameter
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The distance from one edge of a circle to the opposite edge that passes through the center. Round or cylindrical features require diameter measurements.
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fillet
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A rounded internal corner. A fillet adds strength to the corner and is often easier to machine.
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go gage
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A gage on or in which a good part should fit easily.
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hidden line
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A line used to define a part feature that is not visible in a specific view. Hidden lines consist of a series of short dashes.
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ID thread
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A thread located on the interior surface of a cylindrical hole.
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knurl
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A patterned series of grooves or diamond-shaped marks formed into the part surface. A knurl is added to provide a surface for gripping.
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machining
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The process of removing metal to form or finish a part, either with traditional methods like turning, drilling, milling, and grinding, or with less traditional methods that use electricity, heat, or chemical reaction.
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microinches
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One-millionth (.000001) of the U.S. standard inch. Surface roughness is typically measured in microinches.
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neck
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A groove or smaller-diameter section between two larger diameters on a cylindrical part. A neck allows a flush or tight fit between the largest diameter and another part.
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no-go gage
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A gage on or in which a good part should not fit.
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nose radius
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The rounded tip on the cutting edge of a single-point tool. The nose radius on a tool leaves a matching corner radius on a part.
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OD thread
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A thread located on the exterior surface of a cylindrical part or feature.
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optical comparator
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An inspection instrument that projects a magnified shadow of a part feature onto a screen for measurement.
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pictorial method
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A blueprint method of specifying a thread by attempting to represent the actual two-dimensional appearance of the thread.
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pin gage
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A hardened, cylindrical gage used to inspect the size of a hole. Pin gages are available in standard diameters.
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pocket
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An enclosed recess, often in a rectangular part. Most pockets are square or rectangular with rounded corners.
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profilometer
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An inspection device that uses a stylus to trace along the surface of a part and determine its average roughness.
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radius
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The distance from the center to the edge of a circle or arc. The size of a radius determines the size of the circle or arc.
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radius gage
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A handheld gage with an accurate, rounded corner used to inspect the size of a corner radius on a part. Radius gages are available in a set that offers a range of sizes.
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roughness
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The inherent, fine, closely spaced irregularities remaining on a part surface after manufacturing.
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schematic method
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A blueprint method of specifying a thread by showing a series of parallel lines.
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section line
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A line used to identify the imaginary cut portion of a part in a section view. Section lines appear as a series of diagonal lines drawn close together.
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section view
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A view illustrating a rotated section resulting from an imaginary cut in the part. Blueprints may contain a variety of different section views.
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simplified method
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A blueprint method of specifying a thread by including pairs of solid and dashed lines drawn parallel to the thread. The simplified method is the most common method for specifying a thread.
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spotface
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A shallow, larger diameter added at the top of a hole. A spotface is most often used on castings to provide a flat surface for assembly.
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stylus
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A small, cone-shaped spherical point made of diamond that contacts the part and measures surface roughness.
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surface finish
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The degree of smoothness of a part's surface after it has been manufactured. Surface finish is the result of the surface roughness, waviness, and flaws remaining on the part.
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taper
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For a cylindrical part, it is a gradual decrease in diameter from one end to another. For a flat or rectangular part, it is an angled surface that gradually changes from a larger height to a smaller height at a constant slope or incline.
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thread
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A raised, helical rib or ridge around the interior or exterior of a cylindrically shaped object. Threads are found on screws, nuts, and bolts and are used to fit parts or provide motion.
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thread class
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A number and letter combination that indicates the degree of fit for a thread.
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thread form
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The specific shape or profile of a thread. Thread forms include V-shaped or square threads.
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thread ring gage
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A disk of heavy metal with a central, threaded hole made to match a particular OD thread. The gage is screwed onto the part being inspected as though the two are mating parts.
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thread series
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A thread designation that identifies the coarseness or fineness of a thread.
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THRU
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A hole that passes completely through a part's material.
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Unified thread system
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A standard thread form based on inches that was developed by the U.S., Canada, and Great Britain.
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