Optimizing Tool Life and Process 381
Optimizing Tool Life and Process provides a detailed overview of the various considerations necessary for prolonging cutting tool life. This class describes the various types of tool wear and provides explanations for how each type of wear occurs, as well as ways to reduce and prevent them. Cutting tool wear types include flank wear, crater wear, notch wear, built-up edge (BUE), plastic deformation, thermal cracking, chipping, chip hammering, and fracture.
Tool cost is a significant component of overall manufacturing expenditures. Additionally, longer tool life leads to higher production rates, as it reduces the time spent indexing or changing out cutting tools. By learning to recognize, lessen, and possibly prevent tool wear, operators can prolong tool life, reduce tool cost, and improve productivity. After taking this class, users will be able to identify common types of tool wear and strategies to reduce or prevent them from occurring.
Number of Lessons 22
- The Importance of Tool Life
- Cutting Variables
- Types of Tool Wear
- Identifying and Monitoring Tool Wear
- Tool Life Basics Review
- Flank Wear
- Flank Wear Progression
- Crater Wear
- Preventing Crater Wear
- Flank and Crater Wear Review
- Notch Wear
- Built-Up Edge
- Built-Up Edge in Action
- Plastic Deformation
- Notch Wear, Built-up Edge, and Plastic Deformation Review
- Thermal Cracking
- Thermal Cracking in Action
- Chip Hammering
- Chip Hammering in Action
- Final Review
- Describe the importance of balancing tool life and production rates.
- Describe cutting variables.
- Distinguish between the various types of tool wear.
- Describe how to identify and monitor tool wear.
- Describe flank wear.
- Describe the stages of flank wear development and how to control flank wear.
- Describe crater wear.
- Describe how to prevent or reduce crater wear.
- Describe notch wear and how it can be prevented.
- Describe built-up edge and how to prevent it.
- Describe plastic deformation and how to prevent it.
- Describe thermal cracking and how to prevent it.
- Describe chipping and how to prevent it.
- Describe chip hammering and how to prevent it.
- Describe fracture and how to prevent it.
The process of an object losing material over time due to friction caused by rubbing against another object. Abrasive wear always occurs during metal cutting operations, but it can and should be controlled.
The build up of workpiece material on a tool during metal cutting. Adhesion causes notch wear.
A silver-white metal that is soft, light, and thermally conductive. Aluminum is a ductile metal prone to forming BUE on cutting tools when machined.
AL2O3. A common coating material used on carbide cutting tools that provides excellent thermal and chemical protection. Aluminum oxide coatings improve tool life.
The smallest distinguishable unit of an element. Atoms combine to form molecules.
The stage of flank wear development during which the cutting point initially wears down to allow the formation of a wear land. The break-in period, also known as the hone-in period, is the initial phase of the flank wear process.
A material's resistance to being stretched, formed, or drawn. Brittle materials fracture easily and brittleness often increases with hardness.
The formation of an unwanted rough edge on a cutting tool that occurs when pieces of the workpiece pressure weld on the tool during cutting. Build up, more commonly called built-up edge (BUE), is a common cause of tool failure when machining soft, gummy metal.
BUE. Tool wear characterized by the formation of an unwanted rough edge on a cutting tool that occurs when pieces of the workpiece pressure weld onto the tool during cutting. Built-up edge is a common cause of tool failure when machining soft, gummy metal.
A common cutting tool material created by combining carbon with a hard metal, such as titanium or tungsten. Carbide tools are the most commonly used tools in the metal cutting industry.
A common, nonmetallic element found in a number of tools. Carbon provides excellent hardness and wear resistance.
The sudden and complete breakdown of a tool. Catastrophic failure renders a tool unusable.
An imaginary line that divides a shape into two equal halves or that runs through the center of a cylindrical object. A centerline can bisect a workpiece along its length or along its width.
A material consisting of compounds formed by metallic and nonmetallic elements. Ceramic tools are very hard but also brittle, which can make them prone to fracture.
Vibrations of the cutting tool or workpiece. Chatter can cause issues such as tool chipping and poor surface finish.
An interaction between substances that changes the make up of one or more of the substances. Chemical reactions between the tool and workpiece cause softening of the rake face, which in turn leads to cratering.
The bunching of chips around the cutting tool and cutting area. Chip crowding often occurs due to high feed rates, which results in thick chips that do not flow easily.
Tool wear characterized by damage to the rake face of a tool caused by repeated impact of improperly deflected chips. Chip hammering can be prevented by selecting the proper feed and insert geometry.
The thickness of the chips created during a machining operation. Chip load is related to feed rate and is often measured by feed per tooth (fpt).
A feature or device designed to prevent chips from forming into long pieces. Chipbreakers are either indentations on the surface of the cutting insert or another wafer clamped above the insert in the toolholder.
Tool wear resulting in the loss of small fragments from the cutting edge of the tool. Chipping can be caused by a number of factors, including tool or workpiece vibration, excessive depth of cut, and improper tool material selection.
An unwanted piece of metal that is removed from a workpiece. Chips are formed when a tool cuts or grinds metal.
A component used to hold a cutting insert or cutting tool in place. Clamping mechanisms include screws and adjustable vises.
The amount of space or distance between two objects. Clearance between the tool and workpiece in metal cutting is set through tool geometry and, when used properly, can prevent tool wear such as BUE.
The measure of the space between the flank that trails the cutting edge and the workpiece. Increasing the clearance angle can reduce premature flank wear.
The angle that determines how much of the bottom edge of an insert's flank is in contact with the surface of a workpiece. Smaller clearance angles can help reduce the possibility of tool wear, such as plastic deformation.
A chip that does not break apart and continues to fold in on itself. Continuous chips are usually created when machining ductile materials and can cause chip hammering.
Tool wear characterized by the formation of concave depressions in the rake face of the cutting tool, adjacent to the cutting edge. Crater wear, also called cratering, can be prevented through proper selection of cutting speed and tool material.
Tool wear characterized by the formation of concave depressions in the rake face of the cutting tool, adjacent to the cutting edge. Crater wear, also called cratering, can be prevented through the proper selection of cutting speed and tool material.
Tool wear characterized by the formation of concave depressions in the rake face of the cutting tool, adjacent to the cutting edge. Cratering, also called crater wear, can be prevented through proper selection of cutting speed and tool material.
Tool wear characterized by the formation of concave depressions in the rake face of the cutting tool, adjacent to the cutting edge. Cratering, also called crater wear, can be prevented through the proper selection of cutting speed and tool material.
The leading edge of a cutting tool that is in direct contact with the workpiece and performs material removal. The cutting edge is subject to a number of forms of tool wear that can be minimized through proper control of cutting variables.
Any fluid used to cool or lubricate a metal cutting process. Cutting fluids can be used to optimize tool life and the quality of a finished part.
The various stresses involved in a machining process. Cutting forces are determined by a combination of speed and feed rate, tool angle, workpiece material, and other factors.
The corner of the insert where the flanks and tool face meet that performs the actual cut. The cutting point wears down quickly during the break-in phase of the flank wear process.
An adjustable component of a metal cutting operation. Cutting variables include tool geometry, tool material, and feed and speed.
An irregularity or imperfection on an object. A tool defect, such as a wear land, can eventually lead to catastrophic tool failure.
The distortion of the original shape of an object. A tool often deforms when subjected to excessive heat or pressure during a cutting operation.
The deterioration of a material. When machining, friction degrades the cutting point of a tool, which leads to flank wear.
depth of cut
The measurement of how far a cutting tool penetrates the workpiece. Depth of cut is the distance from the uncut surface to the machined surface.
DOC line. The line formed as a tool makes a pass along a workpiece. The depth-of-cut line is where the cutting point of a tool engages a workpiece, which leads to increased cutting forces that can cause a number of types of tool wear, such as notch wear.
DOC notching. Tool wear characterized by the formation of valleys on either the rake face or flank of the cutting tool at the depth-of-cut line. Depth-of-cut notching, also called notch wear or notching, often occurs when cutting hard materials such as nickel.
A device used to help operators assess wear or defects in a tool or part. Diagnostic tools include microscopes and optical comparators.
The process of spreading from an area of high concentration to an area of low concentration. Hard carbon atoms in the tool sometimes diffuse into workpiece chips and weaken the tool.
Depth-of-cut line. The line formed as a tool makes a pass along a workpiece. The DOC line is where the cutting point of a tool engages a workpiece, which leads to increased cutting forces that can cause a number of types of tool wear, such as notch wear.
Dept-of-cut notching. Tool wear characterized by the formation of valleys on either the rake face or flank of the cutting tool at the depth-of-cut line. DOC notching, also called notch wear or notching, often occurs when cutting hard materials such as nickel.
A material that can be easily be stretched drawn, or formed without fracturing. Ductile metals are easier to cut but can cause the formation of BUE on the tool.
A rounded and blunted cutting edge used to add edge strength. An edge hone decreases wear resistance.
The stage of flank wear development where the wear land has grown to the point that it could fail at any time. The failure region often indicates the end of usable tool life.
The rate at which the cutting tool and/or workpiece move in relationship to one another. Feed is often measured in inches per minute (ipm) or millimeters per minute (mm/min).
A narrow opening caused by the splitting of a material. Fissures on a tool are caused by thermal cracking and can lead to tool failure.
The flat surface of an insert perpendicular to the rake face. The flank passes over the the newly cut surface immediately after the cutting edge, which causes it to wear over time.
Tool wear characterized by the gradual wearing away of the cutting edge and flank, which is mostly caused by abrasion. Flank wear is the only acceptable form of tool wear because it is inevitable, controllable, and predictable.
The catastrophic failure of a tool due to the separation of a large section of tool material. Fracture can happen without warning or as the result of other forms of tool wear.
A force that resists the movement of two objects sliding against each other. Friction is one of the primary causes of tool degradation.
The process of using an abrasive to remove material from a tool or part. Grinding can be used to resharpen tools that have dulled during use.
The ability of a material to resist penetration, indentation, or scratching. Hard materials tend to be very wear resistant.
The accumulation of elevated temperatures. Heat is often the result of friction.
HSS. A specialized metal used to create cutting tools. High-speed steel is tougher than carbide but offers less hardness and wear resistance.
The stage of flank wear development during which the cutting point initially wears down to allow the formation of a wear land. The hone-in period, also known as the break-in period, is the initial phase of the flank wear process.
The sudden force generated when a cutting tool initially engages or reengages with a workpiece. Impact shock is most common in milling because milling involves intermittent cutting.
Rotated to expose a fresh cutting surface. Tool inserts can be indexed if flank wear progresses to the failure region on one side of the tool.
An indexable and replaceable cutting tool with a geometric shape and multiple cutting surfaces. Insert wear can be controlled through setting the correct cutting variables.
A metal removal process in which one or more edges of the cutting tool repeatedly enter and exit the workpiece surface. Intermittent cutting, sometimes called interrupted cutting, causes temperature fluctuations in the tool that can lead to thermal cracking.
A metal removal process in which one or more edges of the cutting tool repeatedly enter and exit the workpiece surface. Interrupted cutting, also called intermittent cutting, causes temperature fluctuations in the tool that can lead to thermal cracking.
The measurement of how a tool's cutting edge is tilted in relationship to a line perpendicular to the workpiece's surface in both turning and milling. The lead angle controls the severity of some cutting forces and can be adjusted, usually in the positive direction, to reduce several forms of wear.
The length of time a cutting tool is expected to be operational before it must be replaced. Tool life can be extended through optimized implementation, including using the the proper tool geometry or cutting with cutting fluids.
The amount of force or pressure placed on an object. Load on a cutting tool is a combination of several cutting variables including feed rate and DOC.
A plain carbon steel that contains less than 0.30% carbon. Low-carbon steel is prone to adhering to tools, which can cause built-up edges (BUE) or notch wear.
A stress that attempts to bend, stretch, break, indent, or otherwise deform a material. Mechanical forces are responsible for most forms of tool wear.
A machining process that uses a tool to remove metal from a workpiece. Metal cutting processes include turning, drilling, and milling.
metal removal rate
MRR. The volume of metal removed in a given amount of time. Metal removal rate is measured in cubic inches per minute (in.3/min) or cubic centimeters per minute (cm3/min).
A magnifying device used to view small objects or examine a small portion of a larger object. A microscope can be used to assess tool wear on a cutting tool.
A machine that uses a rotating multi-point tool to remove metal from the surface of a workpiece. Common types of mills include face mills and end mills.
A cutting operation in which a rotating multi-point cutting tool is fed along the surface of a part to remove material. Milling operations generally produce flat surfaces.
A multi-point cutting tool that has inserts, or teeth, around its cutting surface. Milling cutters include face and end mills.
negative rake angles
A tool position that moves the rake face toward the workpiece in both turning and milling. Negative rake angles can lead to the formation of BUE.
A metal made of a combination of nickel and at least one other metal. Nickel alloys are hard and corrosion resistant.
The degree of roundness between two cutting edges of a tool. The nose radius is described by the insert number and influences factors such as surface finish and insert strength.
Tool wear characterized by the formation of valleys on either the rake face or flank of the cutting tool at the depth-of-cut line. Notch wear, also called depth-of-cut notching (DOC notching) or notching, often occurs when cutting hard materials such as nickel.
Tool wear characterized by the formation of valleys on either the rake face or flank of the cutting tool at the depth-of-cut line. Notching, also called notch wear or depth-of-cut notching (DOC notching), often occurs when cutting hard materials such as nickel.
Tool wear characterized by the formation of valleys on either the rake face or flank of the cutting tool at the depth-of-cut line. Notching, also called, depth-of-cut notching (DOC notching) or notch wear, often occurs when cutting hard materials such as nickel.
A person trained to run a specific machine. Operators are responsible for helping ensure that a machine runs properly, efficiently, and safely.
A measuring instrument that projects an image of a part onto a screen to examine its shape, size, or other features. An optical comparator can be used to examine a cutting tool for wear or potential failure.
A chemical reaction involving the addition of oxygen, the removal of hydrogen, or the removal of electrons from a material. Oxidation weakens and degrades a material.
A chemical compound containing oxygen and one other element. Oxides are formed during oxidation and often cause material degradation.
An intersection of two lines or objects at a right angle. The fissures and cracks caused by thermal cracking form perpendicular to the cutting edge of the tool.
physical vapor deposition
PVD. A process that deposits a thin, even layer of coating on the surface of a tool. Physical vapor deposition creates tools that are tougher but less hard than other coating processes such as chemical vapor deposition (CVD).
Tool wear characterized by the warping of the tool shape that occurs due to extreme pressure and temperature and intense mechanical contact. Plastic deformation can be prevented by using a harder tool material or reducing speed or feed.
Tool wear characterized by the warping of the tool shape that occurs due to extreme pressure and temperature and intense mechanical contact. Plastic deformation, also called thermal deformation, can be prevented by using a harder tool material or reducing speed or feed.
positive rake angle
A tool position that moves the rake face away from the workpiece. A positive rake angle can help prevent the formation of BUE.
positive rake angle
Tool geometry that moves the rake face of the tool away from the workpiece centerline. A positive rake angle can help prevent tool wear, such as cratering.
The exertion of a mechanical force upon an object. In metal cutting operations, the amount of pressure is usually related to the feed rate.
The measurement of the tilt of the rake face either toward or away from the workpiece centerline when turning or the position of the cutting edge in relation to the mill when milling. Positive rake angles reduce cutting forces, encourage chip removal, and prolong tool life.
The top surface of the cutting tool. The rake face is subject to crater wear and chip hammering because chips make contact with it as they are separated from the workpiece.
A workpiece, machine, or machine setup characterized by being stiff and inflexible. Rigid machine setups can improve tool life and the quality of the finished part.
A circular indexable cutting tool. Round inserts have the greatest edge strength.
All the necessary preparation of tooling and fixturing that occurs on a machine before operation begins. Proper machine setup is an important factor in optimizing tool life.
The rate at which the surface of the workpiece rotates past the cutting edge of a tool at the point of contact. Speed is often measured in revolutions per minute (rpm).
A type of steel that contains more than 11% chromium and exhibits excellent corrosion resistance. Some types of stainless steels, such as ferritic or austenitic, are gummy and can cause BUE to form on a cutting tool.
The stage of flank wear development during which the wear land slowly progresses while the tool is in use. The steady state region should be the longest period of flank wear development.
An alloy of iron and carbon containing less than 2.0% carbon. Steel can cause cratering when cut with a pure tungsten carbide cutting tool.
The ability of a material to resist forces that attempt to break or deform it. Inserts with good strength can operate at higher feed rates and withstand tool wear such as chipping.
The measured surface profile characteristics of a completed workpiece. Surface finish begins to degrade as a tool enters the failure region of the flank wear process.
TaC. A compound of tantalum and carbon. Tantalum carbide is used as an alloy with tungsten carbide to increase a cutting tool's resistance to cratering and thermal deformation.
Tool wear characterized by small cracks and fissures caused by temperature fluctuations. Thermal cracking, also called thermal fatigue, can be prevented by using tougher tool materials or properly applying cutting fluid.
Tool wear characterized by the warping of the tool shape that occurs due to extreme pressure and temperature and intense mechanical contact. Thermal deformation, also called plastic deformation, can be prevented by using a harder tool material or reducing speed or feed.
Tool wear characterized by small cracks and fissures caused by temperature fluctuations. Thermal fatigue, also called thermal cracking, can be prevented by using tougher tool materials or properly applying cutting fluid.
TiC. A compound of titanium and carbon that can be used as the basis for a cutting tool material, added to tungsten carbide for steel cutting grades, or used as a coating. Titanium carbide offers improved chemical stability and crater resistance.
An unwanted but acceptable deviation from a given dimension defined by a blueprint. Tolerance is a key measure of tool performance and a decrease in tolerance helps indicate when a tool should be replaced.
A device made of hard, tough materials that is used to remove metal by creating chips. A tool can be protected from premature wear by utilizing them at the correct feed and speed, among other methods.
The collective angles formed by the dimensions of the cutting tool and the positioning of the tool. Tool geometry is a key factor in tool life, production efficiency, and part quality.
A device used to hold a cutting tool in place during machining. A toolholder's positioning and setup are key to preventing tool wear such as chipping.
A material that can absorb energy without breaking or fracturing. Tough cutting tools are able to withstand sudden stresses but are less hard and wear resistant.
The ability of a material to absorb energy without breaking or fracturing. Cutting tools with good toughness are able to withstand sudden stresses but are less wear resistant.
WC. A compound of tungsten and carbide that was used as the original carbide tool. Pure tungsten carbide tools are hard but prone to cratering when used to machine steels.
A machining operation where a cylindrical workpiece is rotated while a single-point tool is guided along the length of the part. Turning is a common machining operation performed on the lathe.
An assessment where an operator examines a tool, machine, or part for defects or wear without the use of an assistive device. Visual inspection is usually supplemented with mechanically-assisted inspection.
The erosion of material as a result of friction. Types of tool wear include crater wear, flank wear, and notch wear.
The worn, flattened section that forms on the flank of the tool due to abrasive wear from contact with the workpiece. The wear land can be measured to determine the rate of flank wear and the remaining service life of the tool.
The process of permanently joining two or more materials through the use of heat or pressure. Some workpiece materials can weld onto a tool and cause issues such as BUE or notch wear.
To increase the hardness of a material through the use of pressure and shaping processes. Metals that work harden may cause notch wear in tools because they resist being cut.
A part that is subjected to one or more manufacturing procedures such as welding, machining, or casting. Workpiece material is a key consideration in extending tool life.