Cutting Tool Materials 321

"Cutting Tool Materials" provides an in-depth discussion of various cutting tool materials and their properties. Effective cutting tools combine a handful of valuable properties: hardness, toughness, and wear resistance. Cutting material selection is based primarily on the workpiece material, machine tool, and cutting operation, and involves an appropriate balance of properties. Available cutting tool materials have expanded and improved over the years, ranging from the very tough and inexpensive to the very hard and expensive. Other tool modifications, such as heat treatment and tool coatings, can also improve cutting tools.

Selecting the proper cutting tool material is essential for a successful machining operation. The tool material dictates the material removal rate, surface finish and tolerance, and expense to the manufacturer in the form of reduced scrap, extended tool life, production rates, and part quality.

Class Details

Class Name:
Cutting Tool Materials 321
Version:
2.0
Difficulty:
Advanced
Number of Lessons:
21
Related 1.0 Class:
Cutting Tool Materials 220

Class Outline

  • The Importance of Cutting Tool Properties
  • Balancing Cutting Tool Properties
  • Early Cutting Tools
  • Tool Materials Review
  • High-Speed Steel
  • HSS: Heat Treatment
  • HSS: PVD Coatings
  • HSS Properties
  • Interrupted Cutting
  • High-Speed Steel Review
  • Carbide Cutting Tools
  • Carbide Tool Use
  • Coated Carbides
  • Carbide Coatings
  • Solid Tools vs. Indexable Inserts
  • Carbide Review
  • Cermet
  • Ceramics
  • Cubic Boron Nitride
  • Diamond
  • Other Cutting Tool Materials Review

Objectives

  • Describe cutting tool properties.
  • Describe the balance or trade-off of properties involved in selecting tool materials.
  • Distinguish between early cutting tool qualities and modern cutting tool qualities.
  • Describe high-speed steel.
  • Describe the treatment processes used to improve HSS properties.
  • Identify the advantages provided by HSS tool properties.
  • Describe carbide cutting tool composition.
  • Describe the advantages and disadvantages associated with carbide tool use.
  • Distinguish between CVD and PVD processes.
  • Distinguish between indexable inserts and solid tools.
  • Describe cermet cutting tool properties and use.
  • Describe ceramic cutting tool properties and use.
  • Describe cubic boron nitride tool properties and use.
  • Describe diamond cutting tool properties and use.

Job Roles

Certifications

NIMS
  • CNC Milling Programming, Setup, & Operation
  • CNC Turning Programming, Setup, & Operation
  • Drill Press I
  • Job Planning, Benchwork, & Layout I
  • Milling I
  • Turning Operations: Turning Chucking Skills

Glossary

Vocabulary Term Definition
alloying elements An element that is intentionally added to a metal in order to change its properties. Common alloying elements include chromium, manganese, nickel, and silicon.
alumina Al2O3. A common coating element for carbide tools that has excellent resistance to abrasive wear, crater wear, and notching. Alumina is also known as aluminum oxide.
aluminum A metal that is silvery white in color and light-weight. Aluminum resists corrosion and is a good conductor of electrical and thermal energy.
aluminum oxide Al2O3. A common coating element for carbide tools that has excellent resistance to abrasive wear, crater wear, and notching. Aluminum oxide is also known as alumina.
arc The area in which electricity jumps from an electrode to the workpiece. Arcs generate a high level of heat.
atoms The smallest distinguishable unit of a material that maintains the same characteristics of that material.
binder 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.
brass A nonferrous alloy containing copper and zinc. Brass has high tensile strength and corrosion resistance.
brazed Joined using a process in which a filler metal is melted at a lower temperature than can melt the base metal. Brazing differs from welding because only the filler metal is melted.
brittle A material's unwillingness to be drawn, stretched, or formed. Brittle materials tend to break or crack if subjected to these forces.
bronze An alloy of copper and tin. Bronze offers a balance of strength, wear resistance, and corrosion resistance.
built-up edge An unwanted, rough edge on a cutting tool that is created by pieces of workpiece welding onto the tool during cutting. Soft or gummy metals often produce a built-up edge.
carbide A common cutting tool material developed by combining carbon with chromium, tungsten, or titanium, among other materials. Carbide is used in metal cutting tools for its hardness and wear resistance.
carbide substrate The base material that makes up the majority of a coated carbide cutting tool. A carbide substrate is an uncoated carbide cutting tool.
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.
cast iron A metal consisting of iron, over 2.11% carbon, and 1 to 3% silicon. Cast iron offers heat resistance and compressive strength.
catastrophic failure The sudden and complete loss of tool performance. Catastrophic failure can be the result of gradual wear and intermittent failure.
ceramic cutting tools A group of cutting tools that are made from a hard, brittle material consisting of compounds formed by metallic and nonmetallic elements. Ceramic cutting tools require high cutting speeds and rigid machinery.
ceramics 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.
cermet A material consisting of ceramic particles held together by a metallic binder. Cermet cutting tools possess the properties of both metals and ceramics.
chemical vapor deposition A cutting tool coating process that uses chemical reactions at elevated temperatures to deposit a thin film of hard materials onto the tool's surface. Chemical vapor deposition coatings provide improved abrasion and crater resistance.
chips An unwanted piece of material that is removed from a workpiece. Chips are formed when a tool cuts or grinds a workpiece.
chromium A hard metal used in ferrous alloys to add hardness, hardenability, and wear resistance. Stainless steels contain large amounts of chromium.
coated carbide tools A cutting tool insert with a tungsten carbide base and either a single layer 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 steel.
coating The application of surface treatments to a material. Coating processes change a material's mechanical properties.
cobalt 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.
computer numerical control machine CNC machine. A machine controlled by a computer that runs special programs to manufacture a workpiece. Computer numerical control machines are very rigid and are capable of fast cutting speeds.
crater wear Tool wear that creates a concave depression in the face of the cutting tool above the cutting edge. Crater wear is also called cratering.
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.
diamond 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.
drill bits A multi-point cutting tool that machines round holes into workpieces. Drill bits have spiral cutting edges and are usually mounted in drill presses.
electron beam A narrow stream of electrons that create focused thermal energy. Electron beams are sometimes used in cutting tool coating processes.
end mills A milling cutter that performs a mix of peripheral and face milling with its bottom and side cutting edges. End mills can be used to machine grooves, slots, circular slots, and pockets, among other features.
ferrous metals A metal that contains iron. Ferrous metals include cast irons and steels.
fiberglass Reinforcement material made from extremely fine strands of glass. Fiberglass is the most commonly used reinforcement material in composites.
finishing A final metal cutting pass performed to obtain tight tolerances and smooth surface finish. Finishing cuts often require faster speeds and a lighter depth of cut.
fracture The catastrophic failure of a tool due to the separation of a large section. Fracture can happen without warning or as the result of other forms of tool wear.
gradient technology A modern carbide tool manufacturing process that allows for a higher or lower concentration of particles in different areas of the tool. Gradient technology allows for areas of concentrated hardness and toughness.
graphite A soft, black form of carbon that is found alone and in other materials. Graphite is brittle and has lubricating qualities.
hardness A material's ability to resist penetration, indentation, or scratching. Hard materials tend to be very strong and wear resistant.
heat treatments 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.
high-speed steel 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.
hot working The shaping of metal at temperatures close to the metal's molten state. Hot working typically leaves a tough, scaly surface on the metal.
HSS High-speed steel. A common cutting tool material that is relatively inexpensive and that offers excellent toughness. High-speed steel tools are often heat-treated and coated.
indexable inserts A cutting tool that has multiple cutting edges. An indexable insert's cutting edge that is excessively worn can be rotated to another new, unused cutting edge.
interrupted cuts A cutting operation where the cutting edge alternately enters and exits the workpiece. Interrupted cuts subject the tool to shock and require tools with improved toughness.
manganese A hard, brittle, gray-white metal that increases the ability of steel to be hardened. Manganese also increases strength and hardness.
metal alloys A solid combination or mixture of two or more materials, one of which must be a metal. Metal alloys include tungsten high-speed steel and molybdenum high-speed steel.
milling A cutting operation in which a rotating multi-point cutting tool is fed along a part's surface to remove material. Milling operations are very versatile and generally produce flat surfaces.
molybdenum A hard metal that increases the toughness, wear resistance, and hardenability of steel. Molybdenum is an effective substitute for tungsten in many high-speed tool steels.
molybdenum high-speed steel A category of high-speed steel that contains molybdenum as its primary alloying element. Molybdenum high-speed steels are less expensive than tungsten high-speed steels.
nickel alloys A metal that contains nickel, which is a hard, malleable, silvery white metal, combined with other metals to improve its properties. Nickel alloys often have increased strength, toughness, and impact resistance.
niobium A platinum gray ductile metal used as a stabilizing alloying agent in stainless steel. Niobium is also known as columbium.
nonferrous alloys A metal alloy that does not contain iron. Nonferrous alloys include aluminum alloys.
physical vapor deposition PVD. A cutting tool coating process that deposits a thin film of evaporated hard materials onto a tool's surface at moderate temperatures. Physical vapor deposition methods are used to coat carbide and HSS tools.
plain carbon steel The most basic type of steel. Plain carbon steel's contents are altered very little from the original iron ore.
polycrystalline diamond The manufactured formation of diamond that has a level of hardness that approaches that of a natural diamond. Polycrystalline diamonds are used as ultra-hard cutting tools.
PVD Physical vapor deposition. A cutting tool coating process that deposits a thin film of evaporated hard materials onto a tool's surface at moderate temperatures. PVD methods are used to coat carbide and HSS tools.
quenching The controlled cooling of a metal after it has been heated to very high temperatures during heat treatment processes. Quenching rates are determined by the metal type.
reamers 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.
saws 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.
scale A flaky film of oxide coating that forms on heated or rusted metals. Scale on a workpiece surface can increase cutting tool wear.
silicon A metallic element found in many materials. Silicon is sometimes added to alloys to improve hot-forming properties.
single-crystal diamond The natural formation of diamond that is the hardest known material. Single-crystal diamonds are not recommended for cutting ferrous materials because they tend to react chemically and break down.
sintered 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.
stainless steels A type of steel that contains more than 15% chromium. Stainless steel exhibits excellent corrosion resistance.
steel A metal consisting of iron and carbon, usually with small amounts of manganese, phosphorus, sulfur, and silicon as well. Steel is the most common manufacturing metal.
superalloys A complex metal alloy designed to perform under intense conditions. Superalloys consist of numerous alloying elements and often exhibit high strength and heat resistance.
taps A multi-point cutting tool that machines internal threads in a workpiece. Taps are usually mounted in drill presses.
tempering The reheating of hardened steels to intermediate temperatures followed by a gradual cooling process. Tempering is usually done to improve toughness.
titanium alloys A mixture of metal containing titanium, which is a silver-gray, strong, and lightweight metal known for its corrosion resistance, and another metal. Titanium alloys are very difficult to machine.
titanium carbide TiC. A material that is used to make carbide cutting tools and that offers improved chemical stability and crater resistance. Titanium carbide can be added to tungsten carbide and can also be used as a coating.
titanium carbonitride TiCN. A surface coating that has intermediate hardness properties. Titanium carbonitride has good balance of abrasion resistance and toughness and is applied by CVD or PVD processes.
titanium carbonitride TiCN. A surface coating that has intermediate hardness properties. Titanium carbo-nitride has good balance of abrasion resistance and toughness and is applied by CVD or PVD processes.
titanium nitride TiN. A common coating element for high-speed steel and carbide tools used to reduce friction. Titanium nitride also increases surface hardness, wear resistance, and insulation against heat.
titanium nitride TiN. A common coating element used to reduce friction for high-speed steel and carbide tools. Titanium nitride coatings increase surface hardness, wear resistance, and insulation against heat.
tolerance The unwanted but acceptable deviation from the desired dimension. Tolerance indicates the allowable difference between a physical part and its intended design.
toughness The ability of a material to withstand forces or sudden impacts that attempt to break it. Toughness determines the ability of a tool to withstand a sudden stress.
tungsten A metal that is very strong at elevated temperatures and is a key alloying element for many cutting tools. Tungsten is relatively expensive.
tungsten carbide WC. The original carbide tool material. Tungsten carbide offers excellent hardness, but it is somewhat expensive and craters when machining.
tungsten high-speed steel A category of high-speed steel that contains tungsten as its primary alloying element. Tungsten high-speed steels are more expensive than molybdenum high-speed steels.
uncoated carbide tools A carbide insert without any added coating layers on its surface. Uncoated carbide tools are often used to cut certain nonferrous alloys.
vanadium A hard, ductile metal typically used in small quantities to increase the strength of a metal alloy. Vanadium is often used in high-speed steels.
wear resistance The ability of a material to resist the gradual wearing away caused by abrasion and friction. Wear resistance in a tool refers to the tool's ability to withstand stresses that cause it to wear during cutting.
wrought 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.
zirconium oxide ZrO2. A crystalline oxide of zirconium that is used as a cutting tool coating material. Zirconium oxide is also added to alumina to increase fracture toughness.