Impact of Workpiece Materials 391
Impact of Workpiece Materials gives a detailed overview of the various types of workpiece materials, how they can be processed, and the challenges posed by each. Ferrous and nonferrous metals are the most common workpiece materials, and each metal has different properties and cutting tool compatibility. Non-metallic materials, such as carbides, ceramics, plastics, and composites, may require machining processes. These materials have very unique qualities, and thus have specific requirements regarding cutting tools and cutting conditions.
A working knowledge of the different varieties of workpieces, their properties, and how to process them, is indispensable. In addition to understanding cutting tool properties, familiarity with the properties and demands of workpieces ensures that operators can capably run any operation. Optimizing cutting conditions leads to better products, higher output, and reduced manufacturing costs.
Number of Lessons 23
- Workpiece Material Properties
- Basic Types of Workpiece Materials
- Cast Irons
- Properties of Cast Irons
- Review: Workpiece Materials
- Plain Carbon and Alloy Steels
- Stainless Steel
- Tool Steels
- Review: Steels
- Magnesium and Titanium
- Copper and Copper Alloys
- Review: Nonferrous Metals
- Ceramics and Cermets
- Cutting Plastics
- Cutting Composites and Plastics
- Review: Non-Metallic Materials
- Describe the material properties that are important to consider in cutting operations.
- Distinguish between ferrous metals, nonferrous metals, and non-metallic materials.
- Describe the properties and machinability of the different types of cast iron.
- Describe the properties of the various types of cast iron.
- Describe the properties, uses, and machinability of plain carbon and alloy steels.
- Describe the properties and machinability of stainless steels.
- Describe the properties, uses, and machinability of tool steels.
- Describe the properties, uses, and machinability of superalloys.
- Describe the properties, uses, and machinability of aluminum and aluminum alloys.
- Describe the properties, uses, and machinability of magnesium and titanium.
- Describe the uses, properties, and machinability of copper and copper alloys.
- Describe the uses, properties, and machinability of nickel.
- Describe the uses, properties, and machinability of graphite.
- Describe the uses, properties, and machinability of carbide.
- Describe the uses, properties, and machinability of ceramics and cermets.
- Describe the different types of plastics as well as their properties.
- Describe the cutting conditions and challenges for cutting plastics.
- Describe the properties, uses, and machinability of the various types of composites.
Damage or wearing away caused by repeated rubbing or scraping. Hard materials resist abrasion.
A material or tool consisting of hard particles used to wear down, rub away, or machine material. Abrasives are often used in finishing operations.
A substance added in small amounts to another substance or material. Additives change or improve a material's performance.
The industry that covers machines or vehicles of flight. Aerospace manufacturers generally require workpiece materials with very specific properties.
A metal consisting of a mix of two or more elements, one of which must be a metal. Alloys include cast iron and different types of steels.
A group of steels that contain intentionally added elements that change the properties of the metal. Alloy steels are common workpiece materials.
A substance that is intentionally added to a metal in order to change its properties. Alloying elements are usually added to a base metal in very small amounts.
A ceramic compound of aluminum and oxygen. Alumina is also known as aluminum oxide.
A nonferrous, silvery, lightweight, soft, very ductile metal. Aluminum is highly machinable but forms continuous chips.
A ceramic compound of aluminum and oxygen. Aluminum oxide is also known as alumina.
A grouping of very light-weight, low-density, high-strength materials made from a combination of aluminum and lithium. Aluminum-lithium alloys are used widely in the aerospace industry.
austenitic stainless steel
A grouping of stainless steels that contains the greatest amounts of chromium, nickel, and other alloying elements. Austenitic stainless steels are the most corrosion resistant stainless steels.
The primary metal used in an alloy. Base metals can be either ferrous or nonferrous.
A material acting as the medium or "glue" that holds together the particles of a sintered material. Binders for sintered carbide tools are usually made of cobalt.
A white, brittle metal with a pinkish tinge. Bismuth may be added to steels to increase machinability.
Held together by a force of attraction. Bonded materials in a composite retain their individual properties or characteristics.
A nonferrous metal alloy of copper and zinc. Brass has high tensile strength and corrosion resistance but poor weldability.
A material's unwillingness to be drawn, stretched, or formed. Brittle materials tend to break or crack if subjected to these forces.
Any copper-based alloy that does not use zinc or nickel as the primary alloying element. Bronzes commonly contain tin, aluminum, or silicon.
BUE. An unwanted, rough edge on a cutting tool that is created by pieces of workpiece welding onto the tool during cutting. Built-up edge is often produced when machining soft or gummy metals.
A common cutting tool material developed by combining carbon with chromium, tungsten, titanium, or other alloying elements. Carbide is used in metal cutting tools for its hardness and wear resistance.
A common cutting tool material developed by combining carbon with usually chromium, tungsten, or titanium. Carbide is used in metal cutting tools for its hardness and wear resistance.
A non-metallic chemical element that combines readily with metallic elements. Carbon is found in steel, carbide, diamond, and other materials.
carbon tool steels
A type of steel designed with improved wear resistance, toughness, and strength. Carbon tool steels often undergo heat treatments to improve their cutting abilities.
A manufacturing process that involves pouring a liquid material into a hollow mold until the material cools into a solidified shape. Casting is one of three general methods used in manufacturing to create metal parts.
A manufacturing process that pours a liquid material into a hollow mold until the material cools into a solidified shape. Cast iron parts are made through casting methods.
An iron alloy usually containing more than 2% carbon, along with silicon and sulfur. Cast irons offer heat resistance and compressive strength.
Cubic boron nitride. A cutting tool material with hardness second only to diamond. CBN tools are very expensive.
A particulate composite usually composed of clay and limestone. Cement can be used to make mortar, concrete, or other substances depending on how it is mixed.
A material consisting of compounds formed by metallic and nonmetallic elements. Ceramics include traditional materials such as brick and clay, as well as advanced ceramics used as abrasives, cutting tools, or electronic components.
A very hard, brittle material that contains metallic and nonmetallic elements. Ceramics are often used as cutting tools and electrical insulators.
A material consisting of ceramic particles held together by a metallic binder. Cermet workpieces and tools possess the properties of both metals and ceramics.
An unwanted piece of material that is removed from a workpiece. Chips are formed when a tool cuts or grinds a workpiece.
A device located on the cutting tool or toolholder that is designed to separate and evacuate chips. Chipbreakers may be built into a cutting tool or a separate device.
Tool wear resulting in the loss of small slivers from the cutting edge of the tool. Chipping is also called frittering.
A hard gray metal that is highly resistant to corrosion and wear. Chromium is typically 15% of stainless steels.
A type or classification of a material. Classes of cast irons are based on tensile strength.
The angled relief behind the cutting edge. Clearance eliminates interference between the cutting tool and the workpiece.
An cutting tool with a tungsten carbide base and either a single or multiple layers of refractory coatings consisting of carbides, carbonitrides, nitrides, or oxides. Coated carbide tools are often used to cut many different types of materials.
A surface treatment applied to workpiece or cutting tool materials. Coatings change the mechanical properties of a product.
A metal that is added as a component of various cutting materials. Cobalt adds toughness to carbide tools and hardness to high-speed steel tools.
A relatively soft, ductile metal used as a binder in cemented carbides and as an alloy in high-speed steel. Cobalt content increases toughness and decreases hardness in carbide tools but has the opposite effect in high-speed steel.
The shaping of metal at temperatures much lower than the molten state of the metal. Cold working can increase properties such as strength and surface finish.
A material composed of two or more unlike materials that are bonded together without losing their individual properties or characteristics. The materials in composites are generally layered or suspended in one another.
The ability of a metal to resist forces that attempt to squeeze or crush it. Cast irons have good compressive strength.
computer numerical control machine
CNC machine. A sophisticated, precise machine tool run by a computer that requires a programmed speed and feed rate value. Computer numerical control machines are very rigid and are capable of fast cutting speeds.
A particulate composite usually made from a mixture of stone, sand, cement, and water. Concrete is often used in the construction industry.
A long chip that folds in on itself rather than breaking and evacuating the workpiece. Continuous chips can pose difficulties in machining.
A reddish colored metal that is very ductile, corrosion resistant, and thermally and electrically conductive. Copper is often alloyed in order to increase its strength.
A reddish colored metal that is very ductile, corrosion resistant, and thermally and electrically conductive. Copper is often alloyed.
The ability of a material to resist destruction or deterioration due to chemical or environmental exposure. Corrosion resistance is a common property of nonferrous metals.
cubic boron nitride
CBN. A type of cutting tool material offering a hardness that is second only to diamond. Cubic boron nitride tools are very effective at machining most steels and cast irons, but they are also very expensive.
An alloy of copper and nickel. Cupronickel is similar in composition to nickel silver and copper-nickel.
Any fluid used to cool or lubricate a metal cutting process. Cutting fluids, also known as coolants, can be oil- or water-based liquids, gases, or pastes.
To change or alter the shape of an object. Deformed materials have permanently lost their original shape.
A change in an object's size or shape as a result of stress. Deformation may be intentional or an accidental consequence.
Deform or degrade by breaking or separating into layers. Delaminating refers to layers of a composite peeling away.
A naturally occurring or manufactured stone made of crystalline carbon that is used as an abrasive because of its extreme hardness. Diamond is the hardest available material.
A multi-point cutting tool that machines round holes into workpieces. Drill bits have spiral cutting edges and are usually mounted in drill presses.
ductile cast iron
A type of cast iron containing round nodules of graphite that increase its ductility. Ductile cast iron is similar to malleable cast iron.
A material's ability to be drawn, stretched, or formed without breaking. Ductility generally increases as hardness decreases.
Able to return to the original shape after deformation. Elastic workpiece materials can deform during cutting processes rather than cut away cleanly.
A material's ability to act as a medium for conveying electricity. Electrical conductivity depends on the material's structure.
A multi-point milling cutter with cutting edges that spiral up the sides, resembling a drill. End mills engage the bottom and edges of the milling cutter.
A general category of metalworking processes that produces parts by adding or removing metal. Fabricating includes welding and assembly processes.
ferritic stainless steel
A grouping of stainless steels that contain high amounts of chromium and can include lead and very small amounts of nickel. Ferritic stainless steels have high hardness but low ductility.
A metal that contains iron. Ferrous metals include cast irons and steels.
A fiber-reinforced composite made of extremely fine strands of glass. Fiberglass has many different applications, including those in the aerospace, automotive, marine, and construction industries.
A composite made from fibers of a material suspended within another material. Fiber-reinforced composites are often used in the automotive, marine, and aerospace industries.
A slender, thread-like material that is longer than it is wide. Fibers are suspended in a matrix to create fiber-reinforced composites.
A customized workholding device used on machine tools to position and hold a part during various machining operations. Fixtures are built to hold a specific part design.
A general category of metalworking processes that produces parts by mechanically deforming, but not adding or removing, metal. Forming includes casting, bending, and roll forming processes.
The catastrophic failure of a material due to the separation of a large section. Fracture can happen without warning or as the result of other forms of tool wear.
A type of alloy steel with contents that have been manipulated to increase machinability. Free-machining steels often contain sulfur or bismuth.
A soft, black form of carbon that is found alone and in other materials. Graphite is brittle and has lubricating qualities.
gray cast iron
A type of cast iron containing large flakes of graphite. Gray cast iron is the least expensive and most widely used cast iron.
The use of an abrasive tool to change the shape of a workpiece by wearing away its surface. Grinding operations commonly use abrasive grains bonded into a disc or wheel.
A material's ability to resist penetration, indentation, or scratching. Hardness poses difficulty during cutting operations because hard materials tend to resist cutting forces.
A material's ability to withstand heat. Heat resistance helps a material resist degradation when exposed to extreme temperatures.
The application of controlled heating and cooling processes used to change the structure of a material and alter its physical and mechanical properties. Heat treatment is often used to adjust a material's hardness.
A device that heats a component when activated. Heating elements are sometimes made of graphite.
HSS. A common cutting tool material that is relatively inexpensive and that offers excellent toughness. High-speed steel tools are often heat-treated and coated.
A finishing process that uses abrasive stones to grind away small amounts of workpiece material. Honing is used to create high quality surface finishes and tight tolerances.
hp. A unit used for measuring power. Horsepower can describe a machine's strength or the strength of a pneumatic or hydraulic component.
High-speed steel. A common cutting tool material that is relatively inexpensive and that offers excellent toughness. HSS tools are often heat-treated and coated.
A silver-white, metallic element that is the fourth most abundant element on earth. Iron is present in all ferrous metals.
A hard, brittle compound made from iron and carbon. Iron carbide is also known as cementite.
A composite made from layers of different materials that are bonded together. Laminar composites, such as plywood, are sometimes used in the construction industry.
Drawing a metal or element out of a material through exposure to water or liquid. Leaching can be intentional or an accidental consequence of a process.
A bluish white metal that is very soft and ductile. Lead can be added to steel to improve machinability, but it is less desirable because of the risk of lead poisoning.
A substance that reduces or prevents friction, resistance, heat, and wear during a variety of manufacturing processes. Lubricants include oil, grease, and graphite.
The relative ease with which material can be removed from a workpiece by machine processes such as cutting or grinding. Machinability depends on the properties of the workpiece material.
A strong, extremely lightweight metal that is brittle and has poor wear resistance. Magnesium is often used as an alloying element.
A strong, extremely light-weight metal that is brittle and has poor wear resistance. Magnesium is used as an alloying element.
Able to be formed or shaped through impacts or pressure. Malleable materials do not break or fracture easily.
malleable cast iron
A type of cast iron containing rounded particles of graphite. Malleable cast iron is more ductile and less brittle than gray or white cast iron.
A hard, brittle gray metal that is often used as an alloying element. Manganese is added to stainless and other types of steels.
martensitic stainless steel
A grouping of stainless steels that contain low amounts of chromium and small amounts of molybdenum, nickel, and carbon. Martensitic stainless steels are the strongest stainless steels.
A material that acts as a binder, holding composite materials together. The matrix is usually a viscous material that hardens to give shape to the composite part and to protect the material components from damage.
A force that attempts to bend, stretch, break, or indent a material. Mechanical forces are created during metal cutting processes.
The shape and alignment of the microscopic components of a metal. A material's microstructure determines its hardness, toughness, and other properties.
A pair or group of atoms held together by strong primary bonds. Molecules are the smallest unit of a material or substance that can exist alone.
A hard, silvery white metal used in metal alloys. Molybdenum can add toughness, creep strength, and wear resistance to steel.
A category of high-speed steel that contains molybdenum as its primary alloying element. Molybdenum HSS is less expensive than tungsten HSS.
A silvery metal that is both tough and corrosion resistant. Nickel is often added to metals as an alloying element.
An alloy of copper and nickel. Nickel silver is similar in composition to copper-nickel and cupronickel.
A ductile metallic element that is used as an alloying element. Niobium is found in some superalloys.
A naturally occurring gas that can be used as an alloying element. Nitrogen can promote strength and resistance to pitting in stainless steels.
A metal that does not contain iron. Nonferrous metals include aluminum and copper.
The formation of valleys or fissures at the depth-of-cut line on a cutting tool. Notch wear is also known as notching.
An extremely small piece or part. Particles are smaller than fibers.
A composite made from particles of a material suspended within another material. Particulate composites are often used in the automotive and fabrication industries.
Polycrystalline diamond. A cutting tool material that is the synthetic form of diamond. PCD is very hard, very brittle, and expensive.
plain carbon steel
Steel that contains less than 3% of elements other than iron and carbon. Plain carbon steel is considered the most pure form of steel.
A varied grouping of lightweight, synthetic materials with high elasticity and corrosion resistance. Plastics are easily shaped.
To coat a material with a thin layer of a metal or other material. Plated materials may have improved corrosion resistance or a better surface finish.
A laminar composite made from layers of wooden board that have been pressed together with the grain in alternating directions. Plywood is usually used in the construction industry.
An abrasive finishing process used to improve the surface of a part. Polishing can create fine surface finish and tight tolerances.
PCD. The manufactured formation of diamond that has a hardness approaching natural diamond. Polycrystalline diamonds are used as ultra-hard cutting tools.
A long chain of very large molecules. Polymers are found in both natural materials, such as wood, and synthetic materials, such as plastics.
positive rake angles
A cutting tool orientation where the cutting edge slopes downward and away from the workpiece. Positive rake angles are often used during composite cutting operations.
A measurable quality or attribute of a specific material. Properties include aspects such as hardness, toughness, and ductility.
A multi-point cutting tool that smooths or enlarges a previously drilled hole. Reamers have straight cutting edges and are usually mounted in drill presses.
A machine or machine setup characterized by being stiff and inflexible. Improved rigidity reduces vibration and wobble during machining processes.
A multi-point cutting device that is used to rough cut a part to a certain length or shape. Saws come in many forms, such as band saws, circular saws, and hacksaws.
A metallic non-metal element found in many materials. Silicon is found in cast irons and ceramics.
A ceramic compound of silicon and carbon. Silicon carbide is colorless and often used in semiconductors, abrasives, disc brakes, bulletproof armor, and high-temperature applications.
A ceramic compound of silicon and nitrogen. Silicon nitride is highly heat resistant.
Powdered metal that has been pressed and heated to create a solid shape. Sintered high-speed steels are harder, tougher, and more wear resistant and, therefore, usually more expensive than wrought high-speed steels.
A material manufacturing process that heats pressed and shaped metal powder to create a solid shape. Sintering can be used to make both high-speed steels and carbide materials.
To break into small, thin fragments. Splintering results from the use of improper cutting variables for the material's properties.
A grouping of steels that contain large percentages of chromium, as well as nickel, manganese, and/or nitrogen. Stainless steels have very high hardness and corrosion resistance.
A metal working process that involves forming or separating sheet metal into parts with the use of dies and punches. Stamping is a common material manufacturing process.
A metal consisting of iron and carbon. Steel is the most common manufacturing metal.
A metal's ability to resist stress caused by forces attempting to break or deform the material. Strength may refer to tensile, compression, or shear strength, depending on the direction of the force.
A brittle, yellow, non-metallic element. Sulfur may be added to steels to increase machinability.
A specialized metal alloy that is designed to exhibit properties such as high strength under extreme temperatures and conditions. Superalloys are very expensive and have very low machinability.
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.
Mixed or dispersed evenly throughout a mixture. Suspended particles within a matrix create particulate composites.
A very hard, ductile metal that is highly resistant to heat and corrosion. Tantalum is often added to superalloys and carbide cutting tools.
A compound of tantalum and carbon that is commonly used as a cutting tool material. Tantalum carbide is often combined with other carbides.
A multi-point cutting tool that machines internal threads in a workpiece. Taps are usually used with drill presses.
A material's ability to resist forces that attempt to stretch it or pull it apart. The tensile strength of a material can be affected by its alloying elements.
A grouping of plastics that can be repeatedly reheated and re-shaped. Thermoplastics are the most commonly used plastics.
A grouping of plastics that, once cooled, can never be reheated and reshaped. Thermosets will char or burn if heated after they have been hardened.
A soft, ductile metal that is highly radioactive and flammable at elevated temperatures. Thorium is used as an alloying element.
A nonferrous metal that is very soft. Tin is often used as a plating metal and soldering alloy.
A soft metal with poor strength. Tin is found in various alloys.
A strong, but lightweight, metal that is highly corrosion resistant. Titanium is often added to superalloys and carbide cutting tools.
A strong, lightweight metal that is highly corrosion resistant. Titanium is often added to superalloys and carbide cutting tools.
A compound of titanium and carbon that is commonly used as a cutting tool material. Titanium carbide is often combined with other carbides.
A ceramic compound of titanium, carbon, and nitrogen. Titanium carbonitride is often used as a coating for cutting tools.
An unwanted but acceptable deviation from a given dimension. Tolerances indicate the allowable difference between a physical feature and its intended design.
The length of time that a cutting tool can function properly before it begins to fail. Tool life length impacts production rates and costs.
A grouping of alloy steels designed to be used as cutting tools, dies, punches, and other tools. Tool steels are designed for toughness, hardness, and wear resistance.
The rate at which the cutting edge of a tool wears away during machining. Tool wear rates increase with cutting materials that have low machinability.
A mechanism used to rigidly hold a cutting tool in place during machining. Toolholders are available in standardized sizes and classified so they are paired with the correct style of cutting tool.
A material's ability to withstand an impact without breaking. Toughness determines the ability of a tool to withstand a sudden stress.
A metal that is very strong at elevated temperatures and is a key alloying element for many cutting tools. Tungsten is relatively expensive.
A compound of tungsten and carbon that is commonly used as a cutting tool material. Tungsten carbide is the original carbide material.
A category of high-speed steel that contains tungsten as its primary alloying element. Tungsten HSS is more expensive than molybdenum HSS.
A machine that uses the motion or energy of moving water, wind, gases, or any fluids to produce movement in paddles, buckets, or other devices arranged in a circle. Turbines generate electricity through this mechanical motion.
Any device that uses suction. Vacuums, or similar systems, are used to remove any graphite dust from a cutting environment.
A hard, ductile metal typically used in small quantities as a high-speed steel alloy. Vanadium increases the strength of certain steels.
The changeable aspects of a given operation. Variables for cutting operations include cutting speed, feed rate, and depth of cut.
A means of cleaning or re-circulating contaminated air. Ventilation systems are necessary during certain machining operations, including those using graphite workpieces or cutting fluids.
A material's ability to resist the gradual wearing away caused by abrasion and friction. Wear resistance is an important property for cutting tool materials.
white cast iron
A type of cast iron containing carbon in the form of iron carbide. White cast iron has high hardness and wear resistance.
Increasing the hardness of a metal through deformation. Work hardening may be intentional or an accidental consequence.
The process of securely supporting, locating, and clamping a workpiece for a manufacturing operation. Workholding helps establish a relationship between the cutting tool and the workpiece.
Solid metal that has been bent, hammered, or physically formed into a desired shape. Wrought high-speed steels are less hard, tough, and wear resistant than sintered high-speed steels.
A bluish white metal that is corrosion resistant and has a relatively low melting point. Zinc is often alloyed with aluminum.
A strong, ductile metal that is flammable when in powder form. Zirconium is used as an alloying element.