Machine Tools VOCABULAR

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OverviewMetal removal fluids (MRF) are used in machine tools to provide lubrication, cooling of the tooling and parts, and to provide chip removal to the filtration systems. What exactly is a machine tool? It is simply a powered device used to fabricate metal components. Machine tools perform a wide range of operations as follows:

Boring1. Broaching (gear and spline)2. Cutting/milling3. Drilling (gun drilling)4. Grinding (centerless, OD, ID, double disc, CBN)5. Reaming6. Sawing7. Shaving8. Tapping (roll and cut)9. Threading10. Turning11.

Understanding various aspects of the machine tool will help you better identify areas where corrosion protection, lubrication, residues and other similar issues could impact the metal removal fluid and the machine tool. This very general introduction to machine tools will help you get started.

DefinitionMachine tools are powered devices that create metallic parts by exerting forces on the parts using tools to cut the metal. The types of metals vary and will be impacted by the MRF. The same goes for the cutting tools. In order to cut, the tool has to be harder than the metal being cut. The forces provided by the machine tool are typically controlled by a detailed program from a computer. These units are referred to as a CNC (computer numerically controlled).

Descriptions of ComponentsSome machine tools operate vertically and others horizontally. Many machine tools have multiple axes of operation.

However, they all tend to have the following sections:

Bed the whole machine tool sits on the bedTable sits on the bed and guides the part to/from the toolingWays the table and headstock slide back/forth on ways that are lubricated from withinHeadstock holds the spindle and tooling to perform the cuttingColumn the headstock is attached to the column; this is generally the back of the machine toolSpindle holds the toolingSaddle an internal table that moves with the parts

In general, the machine tool operator and/or the maintenance manager will know quite a bit about the different machine tools and their operations and lubricant requirements.

FluidsMany of these sections move and require lubrication. Most times the lubrication is provided by a separate non-water soluble lubricant. They are referred to as rail lubricants or way lubricants. Some machine tools rely upon the MRF to provide some of the lubrication. The interaction between the MRF and the lubricant can create problems when it comes to tramp oils. Tramp oil is any undesirable, non-soluble lubricant that gets into the MRF. The buildup of tramp oils can create issues with stickiness, dermatitis, staining and other issues. The removal of these oils is very helpful in preserving the life of the MRF.

The tramp oils can also carry the suspended solids and fines that are created by the MRF doing its job. The buildup of these solids and fines can impact workers hands as well as the surface finish of the final part.

Some machine tools may be set up to use straight oil machining fluids while others are set up to use water dispersible fluids. The machine set up, cleaning procedures and maintenance will be different for these two types of fluids. It is important to understand why a certain type of fluid is used in the machine tool. Most of the comments below are applicable to machine tools containing water dispersible fluids.

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Metal Removal Fluid SectionsThe MRF is part of the life blood of the machine tool. The sections that are most critical for the MRF are the sump, the filtration, the tramp oil removal devices and the water supply.

Many machine tools have small sump sizes that are hidden underneath the machine tool. These dark, cramped spaces are perfect breeding grounds for microorganisms. Tramp oils also build up easily if the sump is out of sight with no one monitoring its status.

Filtration is important for removing metallic contaminants as the parts are produced. These contaminants are the chips and fines that are removed from the metallic parts during the metal removal operation. The buildup of these contaminants will also impact the growth of microorganisms if left alone too long. Most machine tools have some type of conveyor belt that drags across the bottom of the sump to remove the contaminants. Some machine tools also have magnetic separators. Other units utilize some type of positive filtration in the form of a filter bag or filter cartridge. Of course, these devices have to be monitored to remove the bag or cartridge when it becomes full of debris.

There are many manufacturers of tramp oil devices. There are belts, hairy ropes, skimmers and coalescers. They are all designed to grab as much of the floating oil as possible and pull it into a separate device for later removal.

Water supply is important for water soluble products. The water hardness impacts the stability of the dilution. Some machine tools have premix devices in place that permit the mixing of the water soluble product with the water. The premixing helps to guarantee that the mixed product is ready for use.

Spindles, Chucks and QuillsThe tooling is generally held in a spindle or quill that rotates to provide the cutting action. Some of these devices are air actuated while others are lubricated by standard oil-based lubricants. The interaction of the MRF and these devices

can impact the security and accuracy of the tooling if debris builds up. Many large CNCs can contain a large carousel holding multiple tools, each in its own spindle. As the part proceeds through its multiple operations, the machine tool grabs the necessary spindle/tool combination for the next application.

Chucks are devices that hold parts in place. Some chucks are more open than others and have a tendency to gather chips and debris from the cutting action. The chips and debris can buildup and create problems with parts sticking if not cleaned out on a regular basis.

Ways and GibsWays are the sliding surfaces for the sections of the machine tool that slide over one another as the tables extend and contract. Many of these sliding surfaces are stainless steel or some other form of steel. The tolerances are tight so that the MRF does not penetrate beyond the sliding steel surfaces.

Gibs are guiding posts that help align the parts to be machined with the tooling. There are generally a number of gibs for each direction (X, Y and Z). They are adjustable for many different part configurations.

Hydraulic Systems and GearboxesJust about all machine tools maintain some type of hydraulic system or gearbox to provide the lubrication for the motion to all of the moving parts (tables, ways, slides, heads, etc.). These fluid systems help provide that lubrication. On some machine tools, the hydraulic fluid can easily leak into the MRF and create tramp oil problems. In this type of setup the fluid supplier should make sure that the customer has some type of tramp oil removal in the sump. Most gearboxes have little interaction with the MRF but there can be some spillage of the MRF into the gearbox.

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High Speed MachiningHigh speed machining (HSM) is gaining more momentum in the industry as it permits precision cutting in a shorter period of time. HSM tools are much more rigid than older machine tools. This stiffness helps to maintain the precise cuts that are required by the rapid changes of the tooling. Many of these HSM tools are coming out of Germany and Japan but other manufacturers are in this business as well.

One of the main issues with HSM is that of foam control. Many of these machine tools operate at higher pressures to help force the MRF into the cutting zone for proper lubrication and chip removal. Some of these machine tools will operate at 1,000 psi or higher.

GrindingGrinding is a finishing process whereby small amounts of metal are removed with a rotating wheel. In most grinders, the grinding wheel is fixed and the part moves past the wheel. Centerless grinding utilizes a regulating wheel to help control the position of the part that is being ground and the speed of the grinding wheel.

Inner diameter (ID) grinding utilizes a smaller wheel. The arbor/shaft that holds the grinding wheel must be very rigid in order for the grinding wheel to perform properly. Outer diameter (OD) grinding is used for cylindrical parts. The wheel must be properly balanced or the issue of concentricity will become a concern. Concentricity is the degree to which a given dimension resembles a perfectly round circle or cylinder.

Most grinding wheels require dressing and truing. Used wheels become dull as the cutting edges become worn down. Dressing is the process of grinding the very outer part of the wheel to return it to its sharp status again. Truing is making sure that the grinding wheel is straight and round.

SummaryHaving a better understanding of a machine tool permits you to communicate more effectively with your customer when discussing problems or strategies.

A more in depth study of specific machine tools and related terminology would be useful to further understand this subject. Attached is an Appendix of terms used with machine tools. It is derived from www.toolingu.com with some minor changes.

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Abrasion - The physical wearing away of material through friction.

Abrasive - A material consisting of hard particles used to wear down, rub away, or machine material.

Accuracy - The exactness of a measurement produced compared to the desired result.

Aluminum oxide - Al2O3. A common coating element for carbide tools because it reduces abrasive wear of the tool.

Arbor - The bar attached to the spindle in a horizontal milling machine. The arbor holds the milling cutter.

Automatic bar machine - A turning machine that continuously cuts a number of parts from a piece of bar stock, one after an-other. The bar stock advances through the spindle and is held by the collet during the operation.

Axis - The imaginary line around which a part rotates as it is turned.

B-1112 - A particular grade of steel that acts as the norm for machinability ratings. B-1112 steel has a 1.00 machinability rating.

Backstroke - The return motion of a saw blade that cuts with a back-and-forth movement.

Ballscrew - A long, threaded device with reciprocating ball bearings that rotates to move components on a CNC machine. Ballscrews are powered by servomotors.

Band saw - A long, continuous cutting blade with serrated teeth that is looped around two or more wheels.

Bar stock - Raw material purchased from metal manufacturers in the form of long bars.

Base -The foundation of a machine that supports all the other machine components.

Bearing - The device within a spindle that supports the rotating shaft and reduces friction. Common bearings consist of spheri-cal balls that travel within a race.

Bed - The main supporting structure upon which the operating parts of the machine are mounted and guided.

Bed-type milling machine - A type of milling machine used to mill flat surfaces that has a large bed, which only moves along a horizontal axis.

Bismuth - A white, brittle metal with a pinkish tinge that is added to steel to improve machinability.

Boring - The process of using a single-point tool to enlarge a preexisting hole. Boring is commonly performed on a lathe but is also possible on a mill.

Brasses - A nonferrous alloy containing copper and zinc.

Brazing - A joining process that is used to combine dissimilar metals at temperatures lower than welding.

Brittle - Difficult to bend, stretch, or form without breaking. Brittle metals tend to produce discontinuous chips.

Broach bar - A multi-point cutting tool with a series of progressively changing teeth that can both remove metal and finish the surface of a workpiece in one pass.

Broaching - The use of a cutting tool with a series of teeth that is used to change the shape or dimensions of a hole. Broaching can also be used to remove material from a workpiece surface.

Broaching machine - A machine that uses a multi-point cutting tool to shape and finish either the interior of a hole or the surface of a workpiece.

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Built-up edge - Deformed metal that adheres to the cutting edge of the tool under high pressures and temperatures.

Burr - A sharp, unwanted bit of material remaining on an edge after machining. Burrs can potentially cut individuals and often interfere with assembly.

Carbide - A common cutting tool material that is used to make both indexable inserts and solid cutting tools. They provide a cutting edge that is very hard and wear resistant. Carbide tools are often coated.

Carbide insert - A cutting bit made of hard material that has multiple cutting edges. Once a cutting edge is excessively worn, it can be indexed to another edge, or the insert can be replaced.

Carbon tool steel - A type of steel designed with improved wear resistance, toughness, and strength.

Carriage - The section of the lathe that slides back and forth along the ways and supports the cross-slide and cutting tool.

Case hardening - The heating of a metal within a carbon-rich environment to increase carbon levels on the metal surface. Case hardening creates a hardened exterior shell.

Cast - Metal that has been poured as a liquid into a mold and cooled into a solid shape.

Casting - A metal part that is formed by pouring molten metal into a mold. The metal then cools and solidifies into its final shape.

Center - The device located in the tailstock that holds in place the end of the workpiece opposite the spindle.

Centerless grinding - A common grinding operation in which a cylindrical part is supported on a work rest blade and guided between a grinding wheel and a regulating wheel.

Centrifugal force - A force that attempts to pull an object traveling in a cylindrical path away from the center of rotation.

Ceramic - A hard, brittle material that can withstand high temperatures. Ceramic cutting tools require high cutting speeds and rigid machinery.

Cermet - Any cutting tool material consisting of ceramic particles in a metallic binder. Cemented carbide tools are a type of cermet.

Chamfering - Machining an angled edge around the end of a cylindrical workpiece.

Chemical vapor deposition - A special process that uses chemical reactions to coat a cutting tool at the atomic level with fine layers of coating material. Carbide tools are coated by chemical vapor deposition.

Chip - An unwanted piece of metal that is removed from a workpiece. Chips are formed when a tool cuts or grinds metal.

Chip breaker - A device located on the cutting tool or toolholder that is designed to prevent chips from forming into long pieces.

Chipping - Tool wear resulting in the loss of small slivers from the cutting edge of the tool. Chipping is often caused by an excessive feed.

Chromium - A shiny, hard, steel-gray metal used in ferrous alloys to add hardness and wear resistance to steel.

Chuck - A device that holds a workpiece in place as it rotates. The chuck commonly has three or four jaws that can be adjusted to fit various sizes.

Circular saw - A power saw that cuts with a toothed or abrasive disk rotating at high speed.

Circular sawing - The use of a round saw blade with teeth around its perimeter.

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CNC machine - A machine controlled by a computer that runs special programs to manufacture a workpiece. CNC machines are very rigid and are capable of fast cutting speeds.

CNC machining center - A sophisticated CNC machine that can perform multiple machining operations in the same setup with a variety of tools.

CNC turning center - A sophisticated CNC machine that specializes in turning, boring, drilling, and threading operations, all at the same location.

Coated abrasive belt - A flexible belt composed of abrasive grains that are adhered to a backing material with an adhesive.

Cobalt - A hard, gray, brittle metal that is a key alloying element in many nonferrous cast alloys.

Cold working - The shaping of metal below its recrystallization temperature. Steel is cold worked at room temperature.

Collet - A slitted device that holds a workpiece in place as it rotates. A collet has a hole through which the workpiece passes, and it is designed to hold specific dimensions. Collets can also be used to hold cutting tools.

Column - The vertical support, or backbone, of a machine.

Compound rest - The part of the lathe on the carriage that allows for angular adjustment of the cutting tool.

Computer numerical control - The use of computers, programs, and precise motors to automatically control tool movement and carry out sequences of machining operations.

Continuous chip - A chip that does not break apart and instead continues to fold in on itself. Ductile metals tend to create con-tinuous chips.

Contour - A curved surface or part feature that is cut into a workpiece. / A cutting process that creates a curved, non-linear dimension.

Counterboring - An operation that enlarges the end of a predrilled hole to allow room for the head of a screw or nut.

Countersinking - The cutting of a beveled edge at the end of a hole so that the head of a screw can rest flush with the work-piece surface.

Crater - A depression that forms on the face of a cutting tool above the cutting edge during machining.

Crater wear - Tool wear that creates a concave depression in the face of the cutting tool above the cutting edge.

Creep feed grinding - A grinding operation in which the depth of cut is increased while the feed rate is decreased compared to normal grinding. It is used to remove thick layers of material.

Crystalline structure - The arrangement or pattern of molecules in a metal. Each metal has a specific crystalline structure that determines its unique properties.

Cubic boron nitride - A type of cutting tool material offering a hardness that is second only to diamond. CBN tools are very ef-fective at machining most steels and cast irons, but they are also very expensive.

Cutoff - For grinding, the use of a thin grinding wheel to cut through material and separate it into two pieces.

Cutting - The use of single- or multi- point tools to separate metal from a workpiece in the form of chips.

Cutting off - A cutting process, also known as parting, that cuts a finished part from bar stock.

Cylindrical grinding - A common grinding process that holds a cylindrical part on each end and rotates the part as a grinding wheel is guided along its length.

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Deform - The forming of a metal into a distorted shape. Deformed metal has permanently lost its original shape.

Depth of cut - The thickness of material removed by one pass of the cutting tool. / The distance that the cutting tool is plunged into the workpiece. Depth of cut is typically measured in millimeters or inches.

Diamond - A special formation of carbon that is the hardest known substance.

Dielectric fluid - A fluid that does not conduct an electric current under normal circumstances. For EDM, the dielectric fluid insu-lates and cools the electrode and workpiece, conveys the spark, and flushes away the removed metal.

Direct drive motor - A motor that fits within the spindle assembly and directly powers spindle rotation. Direct drive motors do not use a gearbox.

Discontinuous chip - A chip that easily fractures from the workpiece into small, separate pieces. Brittle materials tend to create discontinuous chips.

Drill press - A machining tool that uses a drill to penetrate the surface of a workpiece and make a round hole. Drill presses can be used for a variety of hole-making operations.

Drill press - A machine tool that rotates a cutting tool with enough force to cause it to penetrate the surface of the workpiece and make a round hole to a certain depth.

Drilling - The process of using a multi-point tool to penetrate the surface of a workpiece and make a round hole.

Drive - The main device that powers the rotation of the spindle.

Ductile - Able to bend, stretch, or form without breaking. Ductile metals tend to produce long, continuous chips.

EDM - Electrical Discharge Machining. EDM uses a rapid series of electrical sparks to vaporize and remove metal.

Electric discharge machining - The most common nontraditional machining process that removes metal through the use of an electric current. The workpiece is immersed in a dielectric fluid.

Electrochemical machining - A nontraditional machining process that removes metal by pumping a mixture of salt and water at a high pressure into a small gap between the workpiece and a formed tool.

Electrode - A device used to convey an electric current, which can either leave or enter the electrode. EDM machines generate an electric spark between an electrode and the workpiece.

End mill - A thin, tall mill cutter with cutting edges that wind up the sides. Both the bottom and side of the end mill are used dur-ing milling operations. End mills resemble drills.

End milling - A milling process that uses the sides and end of an end mill to cut a variety of shapes.

Engine lathe - The original and most basic type of lathe.

Etching - The use of a chemical solution to dissolve metal.

Face mill - A flat mill cutter with multiple cutting teeth surrounding the tool. The bottom of the face mill is primarily used during milling operations.

Face milling - A cutting process that uses a mill to cut a flat surface by positioning the tool at a right angle to the workpiece.

Facing - An operation performed on a lathe that feeds a cutting tool across the end of a cylindrical workpiece to shorten its length.

Feed - The rate that the cutting tool as a whole travels along the surface of the workpiece. / The rate at which the cutting tool and the workpiece move in relation to one another.

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Ferrous metal - A metal that contains iron.

Finishing tool - A single-point cutting tool used to make a very light cut for final touches to achieve precise tolerances or im-proved finishes.

Fixed centerline spindle - A secondary spindle with its own power source that fits into the original spindle of a machine tool. Both spindles rotate simultaneously to increase spindle speed.

Fixture - A customized workholding tool used on machine tools to position and hold a part during various machining opera-tions.

Flank wear - Tool wear resulting in the gradual wearing away of the cutting edge. Flank wear is mostly caused by abrasion, and it is the most desired form of tool wear.

Flute - The passageways that twist up the length of the drill and allow for the exit of chips and cutting fluids. / The curved recess that winds up the length of a drill. Flutes provide an opening for chip clearance. / The spiral grooves in a tool that create a path for the removal of chips during cutting.

Forging - A metal working process that involves forming or shaping bulk metal into parts at elevated temperatures.

Form mill - A type of milling cutter that is designed in an irregular shape in order to mill contours.

Form milling - A milling process that uses a mill with a unique shape that is imparted to a workpiece.

Free-machining steel - A particular grade of steel that has small amounts of additional alloying elements to improve machin-ability.

Grain - A small, hard particle or crystal of abrasive material.

Graphite - A soft, black formation of carbon. If diamond is subjected to high temperatures, it may revert to graphite.

Grinding - The use of an abrasive to wear away at the surface of a workpiece and change its shape. Grinding operations com-monly use abrasive grains bonded into a wheel shape.

Grinding wheel - A wheel made of a bonded abrasive used to grind the surfaces of parts.

Grooving - The process of cutting a narrow channel or passageway into the outside diameter of a cylindrical workpiece.

Gummy - Excessively soft and difficult to machine. Gummy metals produce long, stringy chips.

Hacksaw - A saw that contains a blade made of high-speed steel, molybdenum, or tungsten alloy steel that cuts in one direc-tion.

Hacksawing - The use of a long blade mounted in a bow-shaped frame. Cutting takes place using a reciprocating, or back-and-forth, motion.

Hardness - The ability of a metal to resist scratching and penetration.

Head - The part of a drill press that contains the spindle and the motor.

Headstock - The end of a lathe that holds the spindle and the drive that rotates the workpiece.

Heat treatment - The heating and cooling processes used to change the structure of a material and alter its mechanical prop-erties.

High-speed machining - An approach to metal cutting using recent speed technology that allows machining centers to do more work. HSM uses small diameter tools to perform multiple, rapid, light cuts.

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High-speed steel - A material used in cutting tools to machine metals at high cutting speeds. High-speed steel stays hard at high temperatures, has great hardness, and is resistant to abrasion.

High-velocity machining - Another term used for high-speed machining. Some manufacturers prefer this term because it em-phasizes other variables besides spindle speed.

Honing - A process that uses abrasive stones to reshape dimensions from a previous operation. Honing can also be used to achieve a certain surface finish. \ A precision abrasion process in which a relatively small amount of material is removed from a surface by means of abrasive stones. The goal is to obtain a desired finish or extremely accurate features.

Hot working - The shaping of metal at temperatures above its recrystallization phase. Hot working typically leaves a tough, scaly surface on the metal.

HSK toolholder - A type of toolholder with a short, hollow taper that contacts the spindle on two surfaces. HSK toolholders pro-vide improved rigidity during HSM operations.

Hybrid bearing - A bearing that consists of ceramic balls that travel within a steel race.

Hydrostatic bearing - A bearing that uses pressurized fluid to support the rotating shaft.

Inclusion - A substance that is unintentionally present in a metal and that often has undesirable properties.

Indexable insert - A cutting bit that has multiple cutting edges. Once a cutting edge is excessively worn, it can be indexed to another edge, or the insert can be replaced.

Inner diameter - The interior surface of a hole in a workpiece.

Insert - A cutting bit that has multiple cutting edges. Once a cutting edge is excessively worn, it can be indexed to another edge, or the insert can be replaced.

Interrupted cutting - Any machining operation involving a cutting edge that enters and exits a workpiece. Milling operations involve interrupted cutting.

Keyway - A rectangular slot or groove that is machined down the length of a hole.

Knee - The device supported by an elevating screw that raises and lowers and guides the back and forth motion of the saddle.

Knurling - A forming process that adds a pattern on the exterior of a workpiece, either for cosmetic reasons or better handling.

Lapping - An abrasive process that removes the last bit of unwanted material. A lapping process sometimes uses an abrasive paste that is rubbed across the part to gradually smooth it.

Lathe - A machine tool that holds a cylindrical workpiece at one or both ends and rotates it while various cutting tools remove material. Turning is a common operation performed on the lathe.

Lead - A bluish white metal that is very soft and ductile. Though lead can be added to steel to improve machinability, it is less desirable because of the risk of lead poisoning.

Leadscrew - The long, threaded device that controls the precise movement of the carriage on a lathe.

Linear motor - A flat motor that uses a magnetic field instead of mechanical force to power the motion of machine tool compo-nents.

Machinability - The relative ease with which material can be removed from metal by machine processes such as cutting or grinding.

Machine tool - A power-driven machine that uses a cutting tool to create chips and remove metal from a workpiece.These tools include cutting tools, workholding devices, punches, and other manufacturing tools.

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Machining - 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.

Magnetic bearing - A bearing that uses magnetic forces to support the rotating shaft.

Mandrel - For honing, the rotating shaft on which honing stones are mounted.

Manganese - A hard, brittle, gray-white metal used in ferrous alloys to add strength and hardness to steel and other metals.

Maskant - A material that protects a metal surface during the etching process.

Metalworking - A material manufacturing process that produces parts by mechanically deforming metal into parts. Stamping and forging are two major types of metalworking processes.

Mill - A rotating multi-point cutting tool that is guided along a workpiece to create flat surfaces or slots. The term also refers to a machine tool used to perform milling operations on a workpiece.

Milling - The use of a rotating multi-point cutting tool to machine flat surfaces, slots, or internal recesses into a workpiece. Mill-ing includes a wide range of versatile metal cutting operations.

Milling cutter - A rotary cutting tool with teeth around its periphery that is used on milling machines.

Milling machine - A machine that uses a multi-point tool to remove metal from the surface of a workpiece. Milling machines are most often used to produce flat or rectangular workpieces.

Molybdenum - A hard, silvery white metal used in ferrous alloys to add toughness, creep strength, and wear resistance to steel. Molybdenum is an effective substitute for tungsten.

Multiple spindle drill - A drilling machine that contains two or more spindles, which perform multiple cutting operations at the same time.

Multi-point cutting tool - A machining tool that has two or more cutting edges.

Multi-point tool - A machining tool that has two or more cutting edges.

Nonferrous alloy - An alloy that does not intentionally contain iron.

Nonferrous cast alloy - A type of cutting tool material that is relatively expensive and that must be directly cast into shape. Non-ferrous cast alloy tools have largely been replaced by carbide.

Nontraditional machining - The use of chemical, thermal, or electrical processes to machine a workpiece and remove material. Nontraditional machining includes a wide range of operations used for special purposes or unique workpieces.

Offhand grinding - A form of rough grinding used to remove excess material without regard to surface finish. The workpiece is generally held in the operators hand and placed against a moving abrasive tool.

Outer diameter - The outer surface of a cylindrical workpiece or feature.

Overarm - The device on a horizontal milling machine that reaches over the workpiece and supports the spindle or arbor.

Physical vapor deposition - A special process that bombards the surface with coating particles to produce fine layers of coating. HSS and carbide tools are coated by physical vapor deposition.

Pain carbon steel - The basic type of steel, which contains less than 3 percent of elements other than iron and carbon.

Plain mill - A cutting tool for the milling machine with cutting surfaces on the periphery. It is used to mill flat surfaces.

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Planer-type milling machine - A very large type of milling machine that often contains numerous milling heads.

Plastic deformation - Metal deformation that is permanent. During metal cutting, plastic deformation results from the forces that shear the chip from the workpiece surface.

Plate stock - A flat piece of raw material that is used to make manufactured parts.

Polycrystalline diamond (PCD) - The manufactured formation of diamond that has a hardness approaching natural diamond.

Profiling - An operation performed on a lathe that feeds a cutting tool along a non-linear path to create conical or curved fea-tures in a cylindrical workpiece.

Race - The track within a bearing that guides the motion of the balls.

Radial drill - A drilling machine that can accommodate large workpieces by maneuvering an overarm in place over the work-piece.

Rake angle - An angle the front of the cutting tool is tilted either forward or backward from its perpendicular position. Positive rake angles reduce cutting forces and encourage chip removal.

Reaming - The use of a cutting tool with straight cutting edges to enlarge or smooth holes that have been previously drilled.

Reciprocating - The back-and-forth motion of a hacksaw in which only one motion actually contacts and cuts the workpiece.

Regulating wheel - A wheel, usually made of plastic or rubber bond, used during centerless grinding to rotate the workpiece and pull it through the operation. The regulating wheel is opposite the grinding wheel.

Relief angle - The angle that is formed by the surface of the workpiece and the bottom end of the cutting tool.

Rough cutting - The quick removal of metal from a workpiece without regard to tolerances or finish.

Roughing tool - A single-point cutting tool used to make very heavy cuts and remove metal as quickly as possible.

Saddle - The device supported by the knee that slides back and forth on the knee and guides the left and right motion of the worktable.

Saw - A multi-point cutting tool that is used to rough cut a part to a certain length.

Sawing - A basic metal cutting process that uses a blade with a series of teeth on its edge to cut a narrow opening in a work-piece. Sawing may be used to produce slots or grooves or to separate the workpiece into two pieces.

Scrap - Any material not used to create the final part. During most machining operations, scrap appears in the form of chips.

Servomotor - A motor used in CNC machines that turns the ballscrew to move parts with precision.

Shear force - A force that attempts to cause the internal structure of a material to slide against itself.

Shear strain - The deformation that occurs due to forces that attempt to cause the internal structure of a material to slide against itself.

Shell mill - A type of milling cutter that has cutting edges around its periphery and can be mounted on an arbor.

Shrink fitting - An assembly process that involves heating a component, fitting components together, and then cooling the component to create a tight fit.

Side mill - A narrow type of milling cutter that has cutting edges on both its end and periphery.

Silicon - A dark gray metal with a blue tinge that is added to alloys to improve hot-forming properties.

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Single-crystal diamond - The natural formation of diamond that is the hardest known material. Single-crystal diamond is ex-tremely brittle.

Single-point cutting tool - A machining tool that has one single cutting edge.

Single-point tool - A machining tool that has a single cutting edge.

Sintered - Powdered metal that has been pressed and heated to create a solid shape. Sintered metals create very uniform contents.

Slab broach - A flat-shaped broach that is used to remove metal from the workpiece surface.

Slab milling - A milling process that uses the slab mill that rotates on an axis parallel to the workpiece. Slab milling produces flat surfaces.

Slotting - A milling process that uses a mill to cut a narrow ridge into the surface of a workpiece.

Speed - The rate at which the cutting edge of the tool moves past the workpiece surface at the point of contact. For turning, speed describes the rotation of the workpiece. For milling and drilling, speed describes the rotation of the cutting tool.

Spindle - The part of the machine tool that spins. On the mill, the spindle holds a cutting tool. On the lathe, the spindle holds the workpiece.

Spindle speed - The rate at which the machine spindle rotates. Spindle speed is typically measured in rpm.

Spot drilling - The use of a shorter, sturdier drill to locate a hole for drilling. Spot drilling often uses a drill size slightly larger than the hole diameter to leave a chamfer after the hole is drilled.

Stamping - A metal working process that involves forming or separating sheet metal into parts with the use of dies and punches.

Stock - Material available in the form of sheets, plates, or long bars that is used to make parts during manufacturing.

Strength - The ability of a metal to resist forces that attempt to break or deform the metal.

Superalloy - An alloy consisting of numerous alloying elements that is very expensive and designed to exhibit certain mechan-ical properties at elevated temperatures.

Surface grinding - A common grinding process generally used on flat surfaces that feeds a workpiece beneath a rotating grinding wheel.

Tailstock - The part located at the end of a lathe opposite the headstock that supports the end of longer workpieces.

Tap - A multi-point tool that is used to cut internal threads into a hole.

Taper turning - An operation performed on a lathe that feeds a tool at an angle to the length of the workpiece in order to create a conical shape.

Tapping - The process of cutting internal threads in a round hole with a multi-point tool.

Threading - The process of cutting a long, spiraling groove into a workpiece with a single-point tool. Threading processes are essential for the creation of fasteners.

TiAlN - Titanium aluminum nitride. TiAlN coatings help improve the wear resistance of carbide inserts at elevated tempera-tures.

Titanium carbide - TiC. A more recent material used to make carbide cutting tools that offers improved chemical stability and crater resistance.

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Titanium nitride - TiN. A compound used to coat high-speed steel and carbide tools to reduce friction.

Tolerance - The unwanted but acceptable deviation from the desired dimension.

Tool chatter - The development of surface imperfections on the workpiece caused by vibrations of the cutting tool.

Tool failure - The point at which a cutting tool is no longer useful for machining. Flank wear, chipping, and cratering all eventu-ally lead to tool failure.

Tool life - The length of time that a cutting tool can function properly before it begins to fail.

Tool wear - The rate at which the cutting edge of a tool wears away during machining.

Torque - The ability of a machine to exert a torsional force at a particular speed. The torque of a machine will vary across its speed range.

Toughness - The ability of a metal to absorb energy without breaking or fracturing.

Traditional machining - The group of machining operations that use single- or multi-point tools to remove material in the form of chips.

T-slot cutter - A type of milling cutter that is used to machine a portion of a T-shaped slot into a workpiece.

T-slotting - A milling process that uses a T-shaped milling cutter to machine a ridge or slot the shape of an inverted T into the surface of a workpiece.

Tungsten - A gray metal that is very strong at elevated temperatures and is a key alloy for many cutting tools. Tungsten is relatively expensive.

Tungsten carbide - The original material used to make carbide cutting tools.

Turning - A machining operation that rotates a cylindrical workpiece while a single-point tool is guided along the length of the part. Turning is performed on a lathe.

Turret - The component of a lathe that holds a number of cutting tools. The turret rotates to place tools in the cutting position.

Turret lathe - A lathe with a mounted device that holds multiple cutting tools. The turret rotates to position a specific cutting tool in place.

V-flange toolholder - A type of toolholder with a long, conical taper that contacts the spindle only on the taper surface. V-flange toolholders are very popular for conventional machining processes.

Vise - A workholding device with one fixed jaw and one moveable jaw. Vises are often used to hold simple rectangular or cubic workpieces on a mill or machining center.

Ways - Two precisely measured, parallel tracks that support and guide the movement of the carriage and cross slide.

Wear resistance - The ability of a metal to resist the gradual wearing away caused by abrasion and friction.

Work hardening - The hardening of a metal that occurs due to the bending or shaping of a metal.

Workpiece - A part that is being worked on during manufacturing. The workpiece may be subject to cutting, welding, forming, or other operations.

Worktable - The part of a machine tool that supports the workpiece and any workholding devices.

Wrought - Solid metal that has been bent, hammered, or physically formed into a desired shape.

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