What Is Cutting? 120

Transcription

1 What Is Cutting? 120 Welcome to the Tooling University. This course is designed to be used in conjunction with the online version of this class. The online version can be found at We offer high quality web -based e -learning that focuses on today's industrial manufacturing training needs. We deliver superior training content over the Internet using text, photos, video, audio, and illustrations. Our courses contain "roll -up -your -sleeves" content that offers real -world solutions on subjects such as Metal Cutting, Workholding, Materials, and CNC with much more to follow. Today's businesses face the challenge of maintaining a trained workforce. Companies must locate apprenticeship programs, cover travel and lodging expenses, and disrupt operations to cover training needs. Our web -based training offers low -cost, all -access courses and services to maximize your training initiatives. Class Outline

2 Class Outline Objectives What Is Cutting? Cutting Tools What Is a Chip? The Making of a Chip Cutting Angles Continuous and Discontinuous Chips Built-up Edge Chip Control Cutting Variables for Turning Cutting Variables for Drilling Cutting Variables for Milling The Importance of Cutting Conditions Summary Lesson: 1/14 Objectives l Define cutting. l Describe single- and multi-point cutting tools. l Identify which cutting operations make chips. l Describe how a chip is made. l Describe the significance of cutting angles. l Describe continuous and discontinuous chips. l Describe a built-up edge. l Describe methods of chip control. l Define cutting variables for turning. l Define cutting variables for drilling. l Define cutting variables for milling. l Describe the importance of cutting conditions. Figure 1. Metal chips are unwanted bits of material removed from the workpiece during the cutting process. Figure 2. During cutting, the metal workpiece deforms ahead of the cutting tool.

3 Lesson: 1/14 Objectives l Define cutting. l Describe single- and multi-point cutting tools. l Identify which cutting operations make chips. l Describe how a chip is made. l Describe the significance of cutting angles. l Describe continuous and discontinuous chips. l Describe a built-up edge. l Describe methods of chip control. l Define cutting variables for turning. l Define cutting variables for drilling. l Define cutting variables for milling. l Describe the importance of cutting conditions. Figure 1. Metal chips are unwanted bits of material removed from the workpiece during the cutting process. Figure 2. During cutting, the metal workpiece deforms ahead of the cutting tool. Figure 3. Cutting variables for turning affect how the part is cut.

4 Lesson: 2/14 What Is Cutting? Manufacturing includes an incredible range of applications. Materials are converted into parts through three general processes: l l l Machining (Figure 1) produces parts by removing material from a workpiece. Cutting processes remove material by creating chips. Casting (Figure 2) produces parts by pouring a molten metal into a mold. The casting process is completed after the cooled and hardened material is removed from the mold. A cast part often requires machining before it becomes a finished part. Metal working (Figure 3) produces parts by mechanically deforming metal. Stamping involves working metals into parts at room temperature, while forging involves working hot metals into parts. Each process has its place in manufacturing. Casting and metal working are common, especially for parts that are made in large batches. These processes require expensive molds or tooling that are economically justified only if a manufacturer is making large numbers of parts. However, for parts being made in smaller batches, machining operations like cutting are ideal because there are no expensive molds. Cutting is also very accurate, versatile, and economical. In this class, you will learn the fundamentals of cutting. You will also learn how chips are made and how cutting variables affect each type of operation. Figure 1. These parts were made by a cutting process that removed material in the form of chips. Figure 2. Casting processes create parts like this example by pouring molten metal into a mold, where it cools and solidifies. Figure 3. Stamping is a process that creates parts like these by deforming or separating sheet metal.

5 Figure 3. Stamping is a process that creates parts like these by deforming or separating sheet metal. Lesson: 3/14 Cutting Tools During cutting operations, machines use single-point cutting tools or multi-point cutting tools. A single-point tool, shown in Figure 1, cuts parts using only one edge of the tool. Inserts made from carbide that are used for turning are good examples of a single-point cutting tool. A multi-point cutting tool, shown in Figure 2, cuts parts using two or more edges of the tool. An end mill or face mill from a milling machine and a drill from a drill press are examples of multipoint cutting tools. Both types of tools remove unwanted metal from the workpiece by producing chips, which form as little metal shavings. Metal actually deforms slightly in front of the tool at the point of contact. The metal then flows up the face of the workpiece in the form of a chip. A load of chips is shown in Figure 3. Figure 1. Single-point tools perform a cut using only one edge of the tool at any given time. Figure 2. A multi-point tool such as this face mill use two or more cutting edges to remove metal. Figure 3. Metal shavings called chips are the by-product of cutting.

6 Lesson: 3/14 Cutting Tools During cutting operations, machines use single-point cutting tools or multi-point cutting tools. A single-point tool, shown in Figure 1, cuts parts using only one edge of the tool. Inserts made from carbide that are used for turning are good examples of a single-point cutting tool. A multi-point cutting tool, shown in Figure 2, cuts parts using two or more edges of the tool. An end mill or face mill from a milling machine and a drill from a drill press are examples of multipoint cutting tools. Both types of tools remove unwanted metal from the workpiece by producing chips, which form as little metal shavings. Metal actually deforms slightly in front of the tool at the point of contact. The metal then flows up the face of the workpiece in the form of a chip. A load of chips is shown in Figure 3. Figure 1. Single-point tools perform a cut using only one edge of the tool at any given time. Figure 2. A multi-point tool such as this face mill use two or more cutting edges to remove metal. Figure 3. Metal shavings called chips are the by-product of cutting.

7 by-product of cutting. Lesson: 4/14 What Is a Chip? Metal cutting is essentially a chip formation process. Metal chips, like those in Figure 1, are the unwanted bits of material that are removed from the workpiece during the cutting process. All metal cutting operations, such as turning, drilling, and milling produce chips. Both single-point and multi-point tool operations produce chips of varying types and shapes. In order to produce quality materials, you must understand the basics behind chip formation, chip handling, and chip removal. The type of metal, the type of tool, and the nature of the work all determine the way that chips will form. Figure 1. Metal chips are the unwanted bits of material removed from the workpiece during the cutting process. Lesson: 5/14 The Making of a Chip A basic model of chip formation is illustrated in Figure 1. The point contacting the metal makes the cut. Depending on the operation and the machine, the workpiece may be moving against the cutting point or vice versa. The rate at which tools and workpieces move is carefully determined by machinists. As the workpiece is moved past the cutting tool, the workpiece metal is forced along at great pressure. Just ahead of itself, the cutting tool deforms a bit of the metal, as illustrated in Figure 2. This elongates its crystalline structure, somewhat like the stretching of a plastic bag. A boundary line between the undeformed metal and the deformed metal emerges. At this boundary line, the cutting action takes place. The force of cutting deforms metal and introduces shear forces at the boundary. The shearing creates a chip. Eventually, the tool separates the chip from the part. Figure 1. The point that contacts the metal workpiece makes the cut.

8 Lesson: 4/14 What Is a Chip? Metal cutting is essentially a chip formation process. Metal chips, like those in Figure 1, are the unwanted bits of material that are removed from the workpiece during the cutting process. All metal cutting operations, such as turning, drilling, and milling produce chips. Both single-point and multi-point tool operations produce chips of varying types and shapes. In order to produce quality materials, you must understand the basics behind chip formation, chip handling, and chip removal. The type of metal, the type of tool, and the nature of the work all determine the way that chips will form. Figure 1. Metal chips are the unwanted bits of material removed from the workpiece during the cutting process. Lesson: 5/14 The Making of a Chip A basic model of chip formation is illustrated in Figure 1. The point contacting the metal makes the cut. Depending on the operation and the machine, the workpiece may be moving against the cutting point or vice versa. The rate at which tools and workpieces move is carefully determined by machinists. As the workpiece is moved past the cutting tool, the workpiece metal is forced along at great pressure. Just ahead of itself, the cutting tool deforms a bit of the metal, as illustrated in Figure 2. This elongates its crystalline structure, somewhat like the stretching of a plastic bag. A boundary line between the undeformed metal and the deformed metal emerges. At this boundary line, the cutting action takes place. The force of cutting deforms metal and introduces shear forces at the boundary. The shearing creates a chip. Eventually, the tool separates the chip from the part. Figure 1. The point that contacts the metal workpiece makes the cut.

9 Lesson: 5/14 The Making of a Chip A basic model of chip formation is illustrated in Figure 1. The point contacting the metal makes the cut. Depending on the operation and the machine, the workpiece may be moving against the cutting point or vice versa. The rate at which tools and workpieces move is carefully determined by machinists. As the workpiece is moved past the cutting tool, the workpiece metal is forced along at great pressure. Just ahead of itself, the cutting tool deforms a bit of the metal, as illustrated in Figure 2. This elongates its crystalline structure, somewhat like the stretching of a plastic bag. A boundary line between the undeformed metal and the deformed metal emerges. At this boundary line, the cutting action takes place. The force of cutting deforms metal and introduces shear forces at the boundary. The shearing creates a chip. Eventually, the tool separates the chip from the part. Figure 1. The point that contacts the metal workpiece makes the cut. Figure 2. The workpiece deforms ahead of the cutting tool. Lesson: 6/14 Cutting Angles The angle at which the tool meets the workpiece is an important chip creation variable. Important cutting angles are illustrated in Figure 1. If you change the rake angle or relief angle of the cutting tool, chip thickness and shear strain change as well. Cutting angles and tool geometry are topics that receive much discussion in the metal cutting industry. Manufacturers can use chip formation as an indicator of the ideal cutting variables for any particular cutting operation. If the tool angle is too big or too small, the chips that are produced may be unacceptable. An inappropriate angle creates more friction between the face of the cutting tool and the workpiece. Unnecessary friction generates unnecessary heat, which shortens tool life. Manufacturers want to use cutting tools Reserved. wisely to extend their useful life. Extending tool life is an Copyright 2015 Tooling U, LLC. All Rights important economical consideration. Choosing the right cutting tool for the job can also affect the quality of the finished product.

10 Lesson: 6/14 Cutting Angles The angle at which the tool meets the workpiece is an important chip creation variable. Important cutting angles are illustrated in Figure 1. If you change the rake angle or relief angle of the cutting tool, chip thickness and shear strain change as well. Cutting angles and tool geometry are topics that receive much discussion in the metal cutting industry. Manufacturers can use chip formation as an indicator of the ideal cutting variables for any particular cutting operation. If the tool angle is too big or too small, the chips that are produced may be unacceptable. An inappropriate angle creates more friction between the face of the cutting tool and the workpiece. Unnecessary friction generates unnecessary heat, which shortens tool life. Manufacturers want to use cutting tools wisely to extend their useful life. Extending tool life is an important economical consideration. Choosing the right cutting tool for the job can also affect the quality of the finished product. Figure 1. Cutting angles are an important variable for chip creation. Lesson: 7/14 Continuous and Discontinuous Chips There are three common types of metal chips created by cutting tools: continuous chips, discontinuous chips, and continuous chips with a built-up edge. As you can see in Figure 1, continuous chips are long strings of metal waste. These shiny metal ribbons generally form when machining soft or ductile metals. Ductile metals include mild steel, copper, and aluminum. The presence of continuous chips often indicates high speeds and high rake angles. The resulting surface finish is generally good, though continuous chips often get tangled in the workpiece, machine fixtures, and toolholders. Discontinuous chips, shown in Figure 2, consist of distinct chip segments that come off the workpiece in small chunks or particles. Discontinuous chips often form with hard or brittle workpiece material that cannot withstand the high shear stresses involved in cutting, such as cast iron or hard bronze. The presence of discontinuous chips often indicates very low or very high cutting speeds. A low rake angle also contributes to the creation of discontinuous chips. Since the cutting edge generally smoothes over the surface after the chips break off, a reasonably good surface finish remains after cutting. Figure 1. These continuous chips are long, tightly curled strings of metal waste.

11 Lesson: 7/14 Continuous and Discontinuous Chips There are three common types of metal chips created by cutting tools: continuous chips, discontinuous chips, and continuous chips with a built-up edge. As you can see in Figure 1, continuous chips are long strings of metal waste. These shiny metal ribbons generally form when machining soft or ductile metals. Ductile metals include mild steel, copper, and aluminum. The presence of continuous chips often indicates high speeds and high rake angles. The resulting surface finish is generally good, though continuous chips often get tangled in the workpiece, machine fixtures, and toolholders. Discontinuous chips, shown in Figure 2, consist of distinct chip segments that come off the workpiece in small chunks or particles. Discontinuous chips often form with hard or brittle workpiece material that cannot withstand the high shear stresses involved in cutting, such as cast iron or hard bronze. The presence of discontinuous chips often indicates very low or very high cutting speeds. A low rake angle also contributes to the creation of discontinuous chips. Since the cutting edge generally smoothes over the surface after the chips break off, a reasonably good surface finish remains after cutting. Figure 1. These continuous chips are long, tightly curled strings of metal waste. Figure 2. Discontinuous chips are distinct chip segments that come off the workpiece in small chunks or particles. Lesson: 8/14 Built-up Edge Besides continuous and discontinuous chips, a third type of chip forms as a continuous chip with a built-up edge (BUE). The built-up edge often forms when cutting soft, ductile metals. As you can see in Figures 1 and 2, the built-up edge forms at the cutting edge when small workpiece particles adhere to the tool due to high pressure and heat. Copyright the 2015 Tooling U, All Rights Reserved. Although formation of LLC. a built-up edge is fairly common, the welding of workpiece material to the tool face is undesirable. Sometimes the free-floating BUE material breaks up, or it becomes embedded in the machined surface or welded onto the tool point.

12 Lesson: 8/14 Built-up Edge Besides continuous and discontinuous chips, a third type of chip forms as a continuous chip with a built-up edge (BUE). The built-up edge often forms when cutting soft, ductile metals. As you can see in Figures 1 and 2, the built-up edge forms at the cutting edge when small workpiece particles adhere to the tool due to high pressure and heat. Although the formation of a built-up edge is fairly common, the welding of workpiece material to the tool face is undesirable. Sometimes the free-floating BUE material breaks up, or it becomes embedded in the machined surface or welded onto the tool point. By increasing speeds and cutting angle, you can reduce the occurrence of the built-up edge. A built-up edge usually leaves behind a rough surface finish. The shiny finish of a normal continuous chip is dulled by the built-up edge. For some ductile materials, the built-up edge may be unavoidable. Figure 1. A built-up edge forms when small workpiece particles adhere to the tool by high pressure and heat. Figure 2. Magnified image of a built-up edge that has formed on a cutting insert. Lesson: 9/14 Chip Control Smooth and efficient metal cutting depends on controlling chip formation and chip removal. Although they often indicate ideal cutting conditions, stringy, continuous chips can snarl and tangle in the tooling, possibly damaging the tool or workpiece. Rough chips may result in a bad surface finish and tool chatter on the part, which often reduces tool life. During drilling, limited space inside holes demands careful chip management. The shape of the cutting edge influences chip formation and chip removal. Tools are designed to create a certain shape of the acceptable chip. The ideal chip looks like the letter Copyright 2015curve, Toolingdirection, U, LLC. Alland Rights Reserved. "C" or the number "9" and fits within a one-inch (25mm) square block, as shown in Figures 1 and 2.

13 Lesson: 9/14 Chip Control Smooth and efficient metal cutting depends on controlling chip formation and chip removal. Although they often indicate ideal cutting conditions, stringy, continuous chips can snarl and tangle in the tooling, possibly damaging the tool or workpiece. Rough chips may result in a bad surface finish and tool chatter on the part, which often reduces tool life. During drilling, limited space inside holes demands careful chip management. The shape of the cutting edge influences chip formation and chip removal. Tools are designed to create a certain curve, direction, and shape of the acceptable chip. The ideal chip looks like the letter "C" or the number "9" and fits within a one-inch (25mm) square block, as shown in Figures 1 and 2. Many chips do not separate from the workpiece on their own. Therefore, cutting tools may have chip breakers. As shown in Figure 3, chip breakers are built into the tool insert, or into the toolholder. The chip breaker is designed to cause the chip to curl and break off. Figure 1. One type of ideal chip looks like the letter "C." Figure 2. Another type of ideal chip looks like the number "9." Figure 3. Chip breakers may be added to the toolholder, or they may be part of the tool insert design.

14 insert design. Lesson: 10/14 Cutting Variables for Turning Each type of cutting operation has its own unique characteristics. Turning operations generally cut round, symmetrical workpieces with single-point cutting tools. Turning is often performed on a lathe, as shown in Figure 1. The principle of lathe operation is the same as that of the potter's wheel. On the lathe, the workpiece is held and rotated on a horizontal axis. The cutting tool removes metal as the tool approaches the rotating part in a parallel or perpendicular orientation. Cutting variables determine how well the lathe cuts a part. These variables influence chip formation and part finish. Speed during turning is a measurement of how fast the cylindrical workpiece is rotating. Feed during turning indicates how fast the tool is moving from one end of the workpiece to the other. Depth of cut is a measurement of how far the tool cuts into the workpiece. All of these variables for turning are illustrated together in Figure 2. Figure 1. Turning is often performed on a lathe. Figure 2. Cutting variables for turning affect how the part is cut. Lesson: 11/14 Cutting Variables for Drilling Drilling operations cut parts with multi-point cutting tools. As shown in Figure 1, there is more than one point that removes metal. Drilling can be performed on a range of machines, including the lathe, mill, and drill press. In a drill press, the two cutting edges at the tip of the drill rotate into the stationary workpiece. Enough pressure is applied to the drill for it to keep moving through the workpiece. It cuts a round hole to the desired depth. The two flutes of the drill provide a channel for chip removal from the hole. Cutting variables determine howallwell thereserved. machine drills a hole in a part. The variables influence the Copyright 2015 Tooling U, LLC. Rights accuracy of the hole and the usable life of the drill. Speed during drilling is a measurement of how fast the drill is rotating. Feed during drilling indicates how fast the drill is moving into the Figure 1. Drills use more than one cutting edge to remove metal from parts.

15 Lesson: 10/14 Cutting Variables for Turning Each type of cutting operation has its own unique characteristics. Turning operations generally cut round, symmetrical workpieces with single-point cutting tools. Turning is often performed on a lathe, as shown in Figure 1. The principle of lathe operation is the same as that of the potter's wheel. On the lathe, the workpiece is held and rotated on a horizontal axis. The cutting tool removes metal as the tool approaches the rotating part in a parallel or perpendicular orientation. Cutting variables determine how well the lathe cuts a part. These variables influence chip formation and part finish. Speed during turning is a measurement of how fast the cylindrical workpiece is rotating. Feed during turning indicates how fast the tool is moving from one end of the workpiece to the other. Depth of cut is a measurement of how far the tool cuts into the workpiece. All of these variables for turning are illustrated together in Figure 2. Figure 1. Turning is often performed on a lathe. Figure 2. Cutting variables for turning affect how the part is cut. Lesson: 11/14 Cutting Variables for Drilling Drilling operations cut parts with multi-point cutting tools. As shown in Figure 1, there is more than one point that removes metal. Drilling can be performed on a range of machines, including the lathe, mill, and drill press. In a drill press, the two cutting edges at the tip of the drill rotate into the stationary workpiece. Enough pressure is applied to the drill for it to keep moving through the workpiece. It cuts a round hole to the desired depth. The two flutes of the drill provide a channel for chip removal from the hole. Cutting variables determine how well the machine drills a hole in a part. The variables influence the accuracy of the hole and the usable life of the drill. Speed during drilling is a measurement of how Copyright 2015 Tooling U, LLC.during All Rights Reserved. fast the drill is rotating. Feed drilling indicates how fast the drill is moving into the workpiece. Depth of cut is a measurement of how far the drill cuts into the workpiece. All of these variables for drilling are illustrated together in Figure 2. Figure 1. Drills use more than one cutting edge to remove metal from parts.

16 Lesson: 11/14 Cutting Variables for Drilling Drilling operations cut parts with multi-point cutting tools. As shown in Figure 1, there is more than one point that removes metal. Drilling can be performed on a range of machines, including the lathe, mill, and drill press. In a drill press, the two cutting edges at the tip of the drill rotate into the stationary workpiece. Enough pressure is applied to the drill for it to keep moving through the workpiece. It cuts a round hole to the desired depth. The two flutes of the drill provide a channel for chip removal from the hole. Cutting variables determine how well the machine drills a hole in a part. The variables influence the accuracy of the hole and the usable life of the drill. Speed during drilling is a measurement of how fast the drill is rotating. Feed during drilling indicates how fast the drill is moving into the workpiece. Depth of cut is a measurement of how far the drill cuts into the workpiece. All of these variables for drilling are illustrated together in Figure 2. Figure 1. Drills use more than one cutting edge to remove metal from parts. Figure 2. Cutting variables for drilling affect how the part is cut. Lesson: 12/14 Cutting Variables for Milling Milling operations cut parts with multi-point cutting tools. Milling is performed on a milling machine, as shown in Figure 1. On a milling machine, milling cutters with several cutting edges rotate into a stationary workpiece. Milling cutters cut with both the ends and the sides of the tool and are often used to create a flat workpiece surface. Milling cutters can also cut complex shapes and contours. During cutting, various fixtures and clamps hold the workpiece on the worktable. The worktable can be moved both sideways and up or down as the milling cutter performs the cut. Cutting variables determine how well your mill cuts a part. The variables influence the accuracy and finish of cuts, as well as the life of the tool. Speed during milling is a measurement of how fast the milling cutter is rotating. Feed during milling indicates how fast the mill moves along the workpiece. Depth of cut is a measurement of how far the mill cuts into the workpiece. All of these variables for milling are illustrated together in Figure 2.

17 Lesson: 12/14 Cutting Variables for Milling Milling operations cut parts with multi-point cutting tools. Milling is performed on a milling machine, as shown in Figure 1. On a milling machine, milling cutters with several cutting edges rotate into a stationary workpiece. Milling cutters cut with both the ends and the sides of the tool and are often used to create a flat workpiece surface. Milling cutters can also cut complex shapes and contours. During cutting, various fixtures and clamps hold the workpiece on the worktable. The worktable can be moved both sideways and up or down as the milling cutter performs the cut. Cutting variables determine how well your mill cuts a part. The variables influence the accuracy and finish of cuts, as well as the life of the tool. Speed during milling is a measurement of how fast the milling cutter is rotating. Feed during milling indicates how fast the mill moves along the workpiece. Depth of cut is a measurement of how far the mill cuts into the workpiece. All of these variables for milling are illustrated together in Figure 2. Figure 1. On a milling machine, milling cutters with numerous cutting edges rotate into a stationary workpiece. Figure 2. Cutting variables for milling affect how a part is cut. Lesson: 13/14 The Importance of Cutting Conditions Every cutting process and workpiece material has optimal cutting conditions that differ from other processes or materials. Cutting conditions impact the rate of metal removal and tool life. The machinist may adjust the cutting speed, feed rate, and occasionally the depth of cut for each operation. The resulting conditions determine the amount of metal removed, the rate of metal removal, tool life, and the quality of the part. Of the three variables, cutting speed has the greatest effect on tool life. These settings also affect what type of chip is produced, which is a good indicator of how parts will turn out. Reference

18 Lesson: 13/14 The Importance of Cutting Conditions Every cutting process and workpiece material has optimal cutting conditions that differ from other processes or materials. Cutting conditions impact the rate of metal removal and tool life. The machinist may adjust the cutting speed, feed rate, and occasionally the depth of cut for each operation. The resulting conditions determine the amount of metal removed, the rate of metal removal, tool life, and the quality of the part. Of the three variables, cutting speed has the greatest effect on tool life. These settings also affect what type of chip is produced, which is a good indicator of how parts will turn out. Reference tables, like the chart in Figure 1, provide a conservative starting point for speeds and feeds of common materials. To use these tables, you must have detailed knowledge about what you are cutting. Figure 1. Reference tables provide a conservative starting point for speeds and feeds of common materials. Lesson: 14/14 Summary Machining processes create parts by removing material from a workpiece. Cutting is a traditional machining process that removes material in the form of chips. During cutting, machines use singlepoint tools or multi-point tools. A single-point tool cuts with only one edge of the tool. A carbide insert on a lathe is an example of a single-point tool. Multi-point tools like a drill or milling cutter use two or more edges to cut a part. There are three common types of metal chips created by cutting tools. Continuous chips are long strings of metal waste. These shiny metal ribbons generally form when machining ductile metals. Discontinuous chips consist of distinct chip segments that separate from the workpiece in small chunks or particles. Discontinuous chips may form in brittle workpiece material that cannot withstand the high shear stresses involved in cutting. A continuous chip with a built-up edge forms when small workpiece particles adhere to the cutting edge due to high pressure and heat. Speed, feed, and depth of cut are three cutting variables that affect turning, drilling, and milling. These variables determine surface finishes, the time it takes to complete a job, and tool life. Every cutting operation requires a careful monitoring of these variables. Figure 1. Single-point cutting tools like this carbide insert perform a cut using only one edge of the tool at any given time.

19 Lesson: 14/14 Summary Machining processes create parts by removing material from a workpiece. Cutting is a traditional machining process that removes material in the form of chips. During cutting, machines use singlepoint tools or multi-point tools. A single-point tool cuts with only one edge of the tool. A carbide insert on a lathe is an example of a single-point tool. Multi-point tools like a drill or milling cutter use two or more edges to cut a part. There are three common types of metal chips created by cutting tools. Continuous chips are long strings of metal waste. These shiny metal ribbons generally form when machining ductile metals. Discontinuous chips consist of distinct chip segments that separate from the workpiece in small chunks or particles. Discontinuous chips may form in brittle workpiece material that cannot withstand the high shear stresses involved in cutting. A continuous chip with a built-up edge forms when small workpiece particles adhere to the cutting edge due to high pressure and heat. Speed, feed, and depth of cut are three cutting variables that affect turning, drilling, and milling. These variables determine surface finishes, the time it takes to complete a job, and tool life. Every cutting operation requires a careful monitoring of these variables. Figure 1. Single-point cutting tools like this carbide insert perform a cut using only one edge of the tool at any given time. Figure 2. Continuous chips are long strings of metal waste. Figure 3. Cutting variables for milling affect how a part is cut.

20 how a part is cut. Class Vocabulary Term Definition Axis Brittle Built-Up Edge The imaginary line around which a part rotates as it is turned. Difficult to bend, stretch, or form without breaking. Brittle metals tend to produce discontinuous chips. Deformed metal that adheres to the cutting edge of the tool under high pressures and temperatures. 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. Casting A metal part that is formed by pouring molten metal into a mold. The metal then cools and solidifies into its final shape. Chip An unwanted piece of metal that is removed from a workpiece. Chips are formed when a tool cuts or grinds metal. Chip Breaker Continuous Chip Crystalline Structure A device located on the cutting tool or toolholder that is designed to prevent chips from forming into long pieces. A chip that does not break apart and instead continues to fold in on itself. Ductile metals tend to create continuous chips. The arrangement or pattern of molecules in a metal. Each metal has a specific crystalline structure that determines its unique properties. Cutting The use of single- or multi- point tools to separate metal from a workpiece in the form of chips. Deform The forming of a metal into a distorted shape. Deformed metal has permanently lost its original shape. Depth Of Cut Discontinuous Chip Drill Press The distance that the cutting tool is plunged into the workpiece. Depth of cut is typically measured in millimeters or inches. A chip that easily fractures from the workpiece into small, separate pieces. Brittle materials tend to create discontinuous chips. 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 use of a multi-point tool to machine a new round hole into the surface of a workpiece. Ductile Able to bend, stretch, or form without breaking. Ductile metals tend to produce long, continuous chips. 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 during milling operations. End mills resemble drills. 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. Feed Fixture Flute Forging Insert The rate at which the cutting tool and the workpiece move in relation to one another. A customized workholding tool used on machine tools to position and hold a part during various machining operations. The spiral grooves in a tool that create a path for the removal of chips during cutting. A metal working process that involves forming or shaping bulk metal into parts at elevated temperatures. 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. Copyright 2015 ToolingLathe U, LLC. All Reserved. A Rights 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.

21 Class Vocabulary Term Definition Axis Brittle Built-Up Edge The imaginary line around which a part rotates as it is turned. Difficult to bend, stretch, or form without breaking. Brittle metals tend to produce discontinuous chips. Deformed metal that adheres to the cutting edge of the tool under high pressures and temperatures. 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. Casting A metal part that is formed by pouring molten metal into a mold. The metal then cools and solidifies into its final shape. Chip An unwanted piece of metal that is removed from a workpiece. Chips are formed when a tool cuts or grinds metal. Chip Breaker Continuous Chip Crystalline Structure A device located on the cutting tool or toolholder that is designed to prevent chips from forming into long pieces. A chip that does not break apart and instead continues to fold in on itself. Ductile metals tend to create continuous chips. The arrangement or pattern of molecules in a metal. Each metal has a specific crystalline structure that determines its unique properties. Cutting The use of single- or multi- point tools to separate metal from a workpiece in the form of chips. Deform The forming of a metal into a distorted shape. Deformed metal has permanently lost its original shape. Depth Of Cut Discontinuous Chip Drill Press The distance that the cutting tool is plunged into the workpiece. Depth of cut is typically measured in millimeters or inches. A chip that easily fractures from the workpiece into small, separate pieces. Brittle materials tend to create discontinuous chips. 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 use of a multi-point tool to machine a new round hole into the surface of a workpiece. Ductile Able to bend, stretch, or form without breaking. Ductile metals tend to produce long, continuous chips. 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 during milling operations. End mills resemble drills. 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. Feed Fixture Flute Forging Insert The rate at which the cutting tool and the workpiece move in relation to one another. A customized workholding tool used on machine tools to position and hold a part during various machining operations. The spiral grooves in a tool that create a path for the removal of chips during cutting. A metal working process that involves forming or shaping bulk metal into parts at elevated temperatures. 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. Lathe A machine tool that holds a cylindrical workpiece at one or both ends and rotates it while various cutting tools Copyright 2015 Tooling U, LLC. All Rights material. Reserved. Turning is a common operation performed on the lathe. remove Machining The process of removing metal to form or finish a part, either with traditional methods like turning, drilling,

22 another edge, or the insert can be replaced. Lathe Machining Metal Working Milling Milling Machine Multi-Point Cutting Tool Rake Angle 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. 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. A material manufacturing process that produces parts by mechanically deforming metal into parts. Stamping and forging are two major types of metal working processes. The use of a rotating multi-point cutting tool to machine flat surfaces, slots, or internal recesses into a workpiece. Milling includes a wide range of versatile metal cutting operations. A machine tool used to perform milling and various other cutting operations. Milling machines are most often used to produce flat or rectangular workpieces. A machining tool that has two or more cutting edges. The angle that the front of the cutting tool is tilted either forward or backward from its perpendicular position. Relief Angle The angle that is formed by the surface of the workpiece and the bottom end of the cutting tool. 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. Single-Point Cutting Tool Speed Stamping Tool Chatter Tool Life Turning A machining tool that has one single cutting edge. The rate that the cutting tool or workpiece moves at the point of contact. A metal working process that involves forming or separating sheet metal into parts with the use of dies and punches. The development of surface imperfections on the workpiece caused by vibrations of the cutting tool. The length of time that a cutting tool can function properly before it begins to fail. The machining process used to make cylindrical parts. Turning is commonly performed with a lathe.