Cnc glossary

anandengg's version from 2018-03-23 09:06


Question Answer
Accurate– Conforms to a standard or tolerance.
Acme thread– A screw thread having a 29 degree included angle. Used largely for feed and adjusting screws on machine tools.
Acute angle– An angle that is less than 90 degrees.
Adapter– A tool holding device for fitting together various types or sizes of cutting tools to make them interchangeable on different machines.
Addendum– That portion of a gear tooth that extends from the pitch circle to the outside diameter.
Allowance– The prescribed difference in dimensions of mating parts to provide a certain class of fit.
Alloy – A metal formed by a mixture of two or more different metals.
Annealing– The controlled heating and cooling of a metal to remove stresses and to make it softer and easier to work with.
Apron– That portion of a lathe carriage that contains the clutches, gears, and levers for moving the carriage. It also protects the mechanism.
Arbor– A shaft or spindle for holding cutting tools; most usually on a milling machine.
Arbor press – A hand-operated machine tool designed for applying high pressure for the purpose of pressing together or removing parts.
Assembly– A unit of fitted parts that make up a mechanism or machine, such as the headstock assemble of a lathe.
Automatic stop– A device which may be attached to any of several parts of a machine tool to stop the operation of the machine at any predetermined point.


Question Answer
Babbitt– An antifriction metal alloy used for bearing inserts; made of tin, antimony, lead, and copper.
Back Gears– Gears fitted to a machine to increase the number of spindle speeds obtainable with a cone or step pulley belt drive.
Back Rake– The angular surface ground back from the cutting edge of cutting tools. On lathe cutting tools. the rake is positive if the face slopes down from the cutting edge toward the shank, and negative if the face slopes upward toward the shank.
Backlash– The lost motion or looseness (play) between the faces of meshing gears or threads.Bandsaw – A power saw. the blade of which is a continuous, narrow, steel band having teeth on one edge and passing over two large pulley wheels.
Bar Stock– Metal bars of various lengths, made in flat, hexagon, octagon, round, and square shapes from which parts are machined.
Bastard-Threads, parts, tools, and sizes that are not standard, such as ‘bastard nuts,’ “bastard plus,” “bastard fittings,’ and so forth. The term also refers to a standard coarse cut file.
Bearing-Rollers, and balls placed between moving parts to reduce friction and wear.
Bed– One of the principal parts of a machine tool, having accurately machined ways or bearing surfaces for supporting and aligning other parts of the machine.
Bell Mouth– The flaring or tapering of a machined hole, usually made at the entrance end because of misalignment or spring of the cutting tool.
Bench Grinder– A small grinding machine for shaping and sharpening the cutting edges of tools.
Bench Lathe– A small lathe mounted on a bench or table.
Bench Work– Work done primarily at a bench with hand tools. occasionally supplemented by small power-driven tools.
Bevel – Any surface that is not at right angles to another surface. Also, the name given a tool used for measuring, laying out, or checking the accuracy of work machined at an angle or bevel.
Bit, Tool (cutter) – A hardened steel bar or plate that is shaped according to the operation to be performed and the material to be machined.
Blind Hole – A hole made in a workpiece that does not pass through it.
Block, Jo – Shop name for a Johannson gage block, a very accurate measuring device.
Blowhole – A defect in a casting caused by trapped steam or gas.
Blueprint– A pen or ink line drawing reproduced (printed) on sensitized paper by direct exposure.
Bond– The material that holds the abrasive grains together to form a grinding wheel.
Bore– To enlarge and finish the surface of a cylindrical hole by the action of a rotating boring bar (cutting tool) or by the action of a stationary tool pressed (fed) against the surface as the part is rotated.
Boring Bar (cuffer bar) – A combination tool holder and shank.
Boring Tool– A cutting tool in which the tool bit’. the boring bar and, in some cases, the tool holder are incorporated in one solid piece.
Boss L– A projection or an enlarged section of a casting through which a hole may be machined.
Brass– A nonferrous alloy consisting essentially of copper and zinc.
Brazing– Joining metals by the fusion of nonferrous alloys having a melting temperature above 800 degrees F, but below that of the metals being joined.
Brine– A saltwater solution for quenching or cooling when heat treating steel.
Brinell Hardness– A method of testing the hardness of a metal by controlled pressure of a hardened steel ball of a given size.
Broach– A long, tapered cutting tool with serration’s which, when forced through a hole or across a surface, cuts a desired shape or size.
Bronze– A nonferrous alloy consisting essentially of copper and tin.
Buff –To polish to a smooth finish of high luster with a cloth or fabric wheel to which a compound has been added.
Bull gear – The large crank gear of a shaper.
Burnishing –The process of finishing a metal surface by contact with another harder metal to improve it. To make smooth or glossy by or as if by rubbing; polish.
Burr – The sharp edge left on metal after cutting or punching-, also, a rotary cutting tool designed to be attached to a drill.
Bushing– A sleeve or a lining for a bearing or a drill jig to guard against wear.[/tab]


Question Answer
Tailstock– That part of a machine tool. such as a lathe or cylindrical grinder which supports the end of a workpiece with a center. It may be positioned at any point along the way of the bed, and may be offset from center to machine tapers.
Tang– The flat on the shank of a cutting tool, such as a drill, reamer or end mill, that fits a slot in -the spindle of a machine to keep the tool from slipping. Also, the part of a file that fits into a handle.
Tap– A tool used to cut threads on the inside of a round hole.
Taper– A uniform increase or decrease in the size or diameter of a workpiece.
Tapping– The process of cutting screw threads in a round hole with a tap (an internal thread cutting tool).
T-bolt– Term for the bolts inserted in the T-slots of a worktable to fasten the workpiece or work-holding device to the table.
Tempering– A heat-treating process to relieve the stresses produced when hardening and to impart certain qualities’, such as toughness-, sometimes called “drawing.”
Template– A pattern or a guide for laying out or machining to a specific shape or form.
Tensile Strength– The property of a metal which resists force applied to pull it apart.
Thread– A helical projection of uniform section on the internal or external surface of cylinder or cone. Also, the operation of cutting a screw thread.
Thread Angle– The angle formed by the two sides of the thread (or their projections) with each other.
Thread Axis– A line running lengthwise through the center of the screw.
Thread Crest– The top surface joining the two sides of a thread.
Thread Depth – The distance between the crest and the root of a thread.
Thread Pitch – The distance from a point on one screw thread to a corresponding point on the next thread.
Thread Pitch Diameter– The diameter of a screw thread measured from the thread pitch line on one side to the thread pitch line on the opposite side.
Thread Root– The bottom surface joining the sides of two adjacent threads.
Throw– The crankpin on a crankshaft. Also, the length of the radius of a crank, an eccentric, or a cam.
Tolerance– The allowable deviation from a standard size.
Tool Steel – A general classification for high-carbon steel that can be heat treated to a hardness required for metal cutting tools such as punches, dies. drills. taps’, reamers, and so forth.
Traverse– One movement across the surface of the work being machined.
Truing– The act of centering or aligning a workpiece or cutting tool so that an operation may be performed accurately. Also, correcting the eccentricity or out of round condition when dressing a grinding wheel.
T-Slot– The slots made in the tables of machine tools for the square-head bolts used to clamp the workpiece,, attachments, or work-holding fixtures in position for performing the machining operations.
Tumbler Gears– A pair of small lever-mounted gears on a lathe used to engage or to change the direction of the lead screw.
Two-Lip End Mill– An end milling cutter designed with teeth that cut to the center so that it may be used to feed into the work like a drill.
Universal Grinder– A versatile grinding machine designed to perform both internal and external grinding operations. including straight and tapered surfaces on tools and cutters.
Universal Milling Machine– A milling machine with a worktable that can be swiveled for milling helical work. It is always supplied with attachments, including an indexing fixture.
Universal Vise– A vise designed for holding work at a double or compound angle. Also, a toolmaker’s vise.


Question Answer
Ways– The flat or V-shaped bearing surfaces on a machining tool that guide and align the parts which they support.
Wheel Dresser– A tool or device for dressing or truing a grinding wheel.
Working Drawing– A drawing. blueprint, or sketch of a part, structure, or machine.
Worm– The threaded cylinder or shaft designed to mesh with a worm gear.
Worm Gear– A gear with helical teeth made to conform with the thread of the mating worm.
Wrought Iron– A commercially pure form of iron with minute slag inclusions which make it soft, tough, and malleable.