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boring
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The process of using a single-point tool to enlarge a preexisting hole.
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boring tool
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A long bar used to position a single-point tool for boring operations. Boring is used to enlarge a preexisting hole and ensure that it is concentric to the part's centerline.
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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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center drilling
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A process in which a rigid drill precisely locates a hole in the center of a workpiece. The purpose of center drilling is to establish a true centerline diameter.
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chasing
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Another term for "threading" on an engine lathe. Used when repairing damaged threads.
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chatter
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The development of surface imperfections on the workpiece caused by vibrations of the cutting tool. Chatter occurs if the machine does not have a sufficient rigidity or if the cutting tool is applied in an incorrect manner.
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chip load
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The thickness of the chips that come off the part during a cutting operation.
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cross-slide
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The device supported by the carriage that positions the turret toward and away from the workpiece.
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dial indicator
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A measuring device used to indicate linear movement. A dial indicator with a magnetic base is an efficient way to measure the distance between the carriage and headstock when cutting parts to exact sizes.
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drill chuck
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A device mounted in the tailstock of a manual lathe or in a manual drill that has jaws and a collar that are tightened to grip and hold a drill bit.
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drilling
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A process in which the workpiece is held stationary, while a rotating cutter (the drill) makes a round hole into the workpiece to a certain depth.
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engine lathe
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A machine tool commonly used to create cylindrical forms. A lathe holds a cylindrical workpiece on one or both ends. The cutting tool is gradually passed along the surface of the rotating part.
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external threads
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Threading that has been cut in the outer diameter of a workpiece.
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facing
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An operation performed on a lathe that feeds a single-point tool into the end of a cylindrical workpiece to create a flat surface.
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flex
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The amount that a part bends due to pressure from the cutting tool.
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inner-diameter operations
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Cutting or turning operations performed on the inner surface of a cylindrical workpiece.
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internal threads
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Threading that has been cut in the inner diameter of a hole in a workpiece.
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ISO threads
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Metric threading that conforms to the specifications of the International Organization for Standardization.
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knurling
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An outer diameter turning operation that displaces material rather than cutting, resulting in a slightly increased workpiece diameter. The result is a textured, rough pattern that has been embedded into the part's surface.
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magnetic base
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A device attached to the back of a dial indicator that is mounted either in front or back of the carriage.
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micrometer
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A measuring device that consists of a fixed anvil and movable spindle, usually with a digital readout or Vernier scale accurate to 0.0005 inch.
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Morse taper
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A hole in the sleeve of the tailstock that narrows to a point and holds tools or a center. A Morse taper allows the tool to lock in place and be easily removed.
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offset turning
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Machining on a lathe during which the workpiece is not in continuous alignment with the spindle centerline axis. Examples include turing tapers or irregular-shaped objects such as a camshaft.
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outer-diameter operations
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Cutting operations performed on the outer surface of a cylindrical workpiece.
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parting
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Also called cutoff, a cutting operation that separates a finished part from bar stock.
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pin gage
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A type of go-no go gage that determines whether the internal features of a part are within specified limits.
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pitch
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The distance from one thread groove to the next measured from crest to crest. For inch-based threads, pitch is expressed as "1" over the number of threads per inch. For metric threads, pitch is expressed in millimeters.
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reaming
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The process of using a cutting tool with straight cutting edges to enlarge or smooth holes that have been previously drilled.
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single-point tool
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A cutting tool that has a single cutting edge. Generally, single-point tools remain in constant contact with the part surface during operation.
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tapping
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The process of cutting internal threads in a workpiece with a multi-point tool.
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telescope gage
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A measuring instrument with a spring-loaded device used to check the inner diameter of a part. Telescope gages are then measured with a micrometer to get the proper value.
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threading
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The process used to machine a long, spiraling ridge down the outer or inner surface of a workpiece.
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turning
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An operation performed on a lathe that feeds a cutting tool along the length of a cylindrical part to reduce its diameter.
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unified threads
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A screw thread standard measured in inches that conforms to specifications of ASME/ANSI.
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walk off
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The tendency of a drill to wander off-center of the intended hole at the beginning of the drilling operation. Walk off is solved by center drilling prior to the drilling operation.
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