The instructional design includes student-focused learning tools to help students succeed. This visual guide high- lights the features designed for the textbook. Guided Tour Learning Objectives clearly identify the knowledge and skills to be obtained when the chapter is completed. Key Terms list the terms to be learned in the chapter. Tech Tips provide you with advice and guidance that is especially applicable for on-the-job. Jacomo/Shutterstock.com Learning Objec tives After reading this chapter, you should be able to: ■ Explain the benefit of insert tooling. ■ Summarize the ISO numbering system. ■ Explain the evolution of carbide tooling. ■ Describe the benefits of PVD and CVD coating. ■ Explain the possible uses for polycrystalline diamond tooling inserts. ■ Explain the possible uses for ceramic tooling inserts. ■ Describe the benefits of polycrystalline cubic boron nitride inserts. ■ Explain the different components on a twist drill. ■ Differentiate between a center drill and a spot drill. ■ Describe the benefits of insertable drilling tools. ■ Identify a spiral flute, straight flute, and bottom tap. ■ Understand the use of counterbores and countersinks. ■ Identify the cutting-edge geometry of an end mill. ■ Explain the usage of roughing end mills. ■ Explain the usage and limits of face mills. ■ Outline the difference in CAT and BT toolholders. ■ Identify the different styles of lathe toolholders. Key Terms bottom tap center drill chemical vapor deposition (CVD) counterbore countersink end mill face mill insert physical vapor deposition (PVD) polycrystalline cubic boron nitride (PCBN) polycrystalline diamond (PCD) roughing end mill spiral fl ute tap spot drill straight fl ute tap tap twist drill 8 Cutting Tools and Inserts Chap t er Ou t line 8.1 High-Speed Machining 8.2 Inserts 8.2.1 Insert Naming System 8.2.2 Carbide 8.2.3 Coatings 8.2.4 Diamond Cutter 8.2.5 Ceramics 8.2.6 PCBN 8.3 Drills 8.3.1 Twist Drills 8.3.2 Center Drills 8.3.3 Spot Drills 8.3.4 Indexable Drills 8.4 Taps 8.4.1 Straight Flute Taps 8.4.2 Spiral Flute Taps 8.4.3 Bottom Taps 8.5 Countersinks and Counterbores 8.6 End Mills 8.6.1 Edge Cutting Geometry 8.6.2 Roughing End Mills 8.6.3 Inserted End Mills 8.7 Face Mills 8.8 Toolholders 8.8.1 Milling Toolholders 8.8.2 Lathe Toolholders 8.9 Machinability Ratings Chapter Outline provides a preview of the chapter topics and serves as a review tool. Illustrations have been designed to clearly and simply communicate the specific topic. 216 CNC Manufacturing Technology The X and Z are replaced by axis substitution definitions of “U” and “W,” so your home positioning move would be G28 U0. W0. The U and W are used because no incremental command is given. 10.3.2 Program Body As in mill programming, the body of a lathe program will direct a machine through specific tools and precise movements to create a part according to the print. The code for each tool within the program will also have an opening statement, body, and closing statement. The opening statement for a particular tool might look like this: (TOOL: 1 OFFSET: 1) (OD ROUGH: 80 DEG.INSERT: CNMG-432) T0101 G97 S350 M03 G0 X7.3205 Z.2 T0101 tool changes to tool #1 and turns on the offset #1. This is dif- ferent from the mill programming format. There is no separate M code for a tool change simply calling that tool will force a change. G97 S350 M03 is the direct revolutions per minute (rpm) input, the speed is 350, and M03 turns on the spindle in a clockwise rotation. G0 X7.3205 Z.2 moves tool #1 at a rapid rate to the designated X and Z coordinates, 7.3205 and .2 in this example. The body of this tool’s program might look like this: G99 G1 Z.1 F.01 Z-3.99 X7.4375 G2 X7.52 Z-4.0313 R-.0412 G99 G1 Z.1 F.01 places the machine in feed rate per revolution and makes a feed move to Z.1 at a rate of .010″ for every complete revolution the spindle makes. Z–3.99, still in a feed rate, moves the machine to the designated Z coordinate. X–4.0313, still in a feed rate, moves the machine to the designated X coordinate. The closing statement for this tool might look like this: G0 X7.57 G28 U0. W0. M05 T0100 G0 X7.57 is a rapid feed move of the machine to a safe position. G28 U0. W0. M05 sends the machine home in X and Z and turns off the spindle. T0100 cancels offsets for tool #1. Tech Tip At the top of this section of code, a note tells the opera- tor the type of tool to use for this operation: (OD ROUGH: 80 DEG. INSERT: CNMG- 432). Any note can be added in parentheses, including programmer name, dates, print number, part revision, or any setup instructions. Safety Note When making a closing state- ment at the end of a tool, make sure you exit away from the part to a safe position. Sending the turning center all the way to its home position before a tool change is not mandatory, but it is a safer practice, especially when running a program for the first time. In larger machines this can add significant machine cycle time. Chapter 10 CNC Lathe Programming 221 10.6 Work Coordinate Offsets Early CNC turning centers did not have the same type of work coordinate system as CNC mills—the work coordinates were just the tool offsets from the home position. But creative programmers saw opportunities to make multiple parts in a single setup, and controller manufacturers implemented additional features to handle this, like a G10 work shift. The G10 allows you to make a single part and then shift all of the tools down the Z axis to make a second part. Most current machines and controllers have implemented a simpler work coordinate system, similar to the machining center. In most cases this G54–G59 work coordinate system won’t be used, unless making mul- tiple parts—but it is possible to use it to solve other machining situations. For example, it is possible to set all tool offsets at the spindle face, or any known position, and then use a G54–G59 work coordinate to shift those coordinates to the desired Z-axis starting position. This is similar to mill- ing tool offsets and can be a good technique if the lathe tools remain in the machine for multiple different parts. Figure 10-15 shows how we can make multiple parts out of bar stock. 10.7 Tool Nose Radius Compensation The G41 and G42 codes command a compensation for the tool orienta- tion and the radius on the tool tip. In milling, G41 and G42 were referred to as cutter compensation and offset for the tool diameter and cutter direction. It is similar in lathe programming, but cylindrical tools are not used in lathes. In lathe operations the controller needs to know on what side of the cut the tool is located as well as the tool nose radius. If tool nose radius is not used in a lathe program, both angles and radii will not be finished as programmed. It is similar to a milling operation, where if the tool diameter or radius is not entered, it alters the toolpath’s finished cut dimensions. G41 is tool nose compensation left. “Left” refers to the side of the machining process on which the toolholder is located, Figure 10-16. It is often used for ID features or when boring. Because of the multiple con- figurations of lathes—like dual spindle, dual chuck, vertical, or horizontal Diameter measurement Goodheart-Willcox Publisher Figure 10-14. A cut on the outside diameter can be used to establish the X-axis position. Enter the X diameter into the controller after the X Dia Mesur button is pushed. Goodheart-Willcox Publisher Figure 10-15. Variable work coordinates can be used to machine multiple parts in one operation. The tool offset page will contain each Z-axis tool position and the X-axis offsets will remain the same. G56 G55 G54 Goodheart-Willcox Publisher Figure 10-16. A G41 tool nose radius compensation indicates the tool is on the left side of the machining direction. Toolpath Tool on left side of path Safety Notes alert you to potentially dangerous materials and practices.