Apply and Analyze questions extend your learning and help you analyze and apply knowledge. Summary ■ The earliest forms of machining were either human- or animal-powered. ■ Many forms of manual machining were developed in the late 1700s. These developments led to the industrial revolution of the early 1800s. ■ The development of inspection equipment, like micrometers, coincided with the development of machine tools. ■ Manual machines were used exclusively from the early 1800s until around 1980. ■ Milling machines were designed to machine rectangular or irregularly shaped parts. They operate by fixing the material in place while the tool rotates in a spindle. ■ Manual lathes were designed to use a fixed tool to machine a spinning piece of material. This configuration creates round or cylindrical parts. ■ Both lathes and mills can be configured in multiple ways, either vertically or horizontally. The defining characteristic for a mill or lathe is whether the material is fixed or rotating. ■ Saws can be configured in both horizontal and vertical designs. They are primarily used to reduce large stock size to a size suitable for machining. ■ The primary function of a machinist has changed as the industry has changed. Machinists began as machine builders and machine service technicians, but as the need for production increased, manual machinists were necessary in production environments. With the development of new computerized machines, CNC machinists evolved to meet the needs of modern machine shops. Now, the industry is seeing highly specific machining specialists who operate sophisticated machinery. 10. True or False? The band saw uses a thin blade that is stretched over a set of wheels or pulleys and tensioned to secure it in place. 11. _____ operations are done after the primary machining is completed. A. Mill B. Lathe C. Saw D. Secondary 12. A _____ is used to secure a workpiece in a specific location and orientation, ensuring that all parts produced using the fixture maintain conformity. A. drill fixture B. lathe chuck C. light fixture D. machine vise 13. True or False? At its most rudimentary form, we use grinding to spin a stone at high speed and cut material. 14. The term hardened steel refers to materials that are naturally extremely _____. A. expensive B. heavy C. light D. wear-resistant 15. A(n) _____ is simply a person who operates a machine. A. designer B. engineer C. machinist D. miller 16. True or False? Speeding up the process and accuracy in manufacturing required computers. 17. As transportation, electrification, and industrial improvements swept across the country, so came the need for production _____. A. analysts B. machinists C. tooling D. workshops Chapter Review Review Questions Answer the following questions using the information provided in this chapter. Know and Understand 1. The earliest tales of machine tools can be traced all the way back to _____, around 2500 BC. A. South America B. Egypt C. Greece D. Rome 2. True or False? John Parsons is widely regarded as the father of machine tool technology. 3. Production could not have happened without the ability to _____ and fit pieces together. A. cut B. grind C. measure D. mill 4. True or False? Manual machines are best described as machines that are operated by physically moving the machine, material, or cutter to shape a desired part. 5. True or False? Mills are defined as machines that fix a workpiece in position while the cutter rotates to remove material. 6. What are some components of a milling machine? A. Motor, blade, elbow, and ram B. Motor, chuck, vise, and ram C. Motor, head, knee, and ram D. Motor, tool, wheel, and ram 7. True or False? The word lathe comes from the Dutch language, meaning “to machine.” 8. The lathe chuck secures the _____ before cutting. A. chuck key B. material C. turret D. vise 9. The saw _____ is typically a thin piece of metal with a series of sharp teeth. A. blade B. pulley C. tensioner D. wheel 18. A manual machine controlled by a computer drive and servo motors was first known as numerically controlled (NC), or later as a _____ machine. A. completely numerically controlled (CNC) B. computerized number controls (CNC) C. computer numerically considered (CNC) D. computer numerically controlled (CNC) 19. True or False? Numerical control (NC) is the automation of machine tools by use of computers. 20. In 1950, John Parsons joined forces with IBM and MIT to develop _____ and servo drives. A. servo controls B. servomechanisms C. servo meters D. servo tooling Apply and Analyze 1. What design changes did James Watt implement to improve the efficiency of the steam engine? 2. What is the main difference between mills and lathes? 3. Describe the basic configuration of a band saw. 4. Differentiate between outside diameter (OD), inside diameter (ID), and surface grinders. 5. What additional equipment did John Parsons use to create the first numerically controlled machine? Critical Thinking 1. Briefly outline the major historical breakthroughs in machine tool technology. How do today’s manufacturing advances compare with earlier innovations? 2. Though the term machinist has evolved over time and can refer to various jobs, as discussed in this chapter, what qualities or defining features do you think are shared by all machinists? 3. Briefly describe the relationship between machine development and the availability of inspection equipment. How do advances in each area spur advances in the other? Summary feature provides an additional review tool for you and reinforces key learning objectives. Know and Understand questions allow you to demonstrate knowledge, identification, and comprehension of chapter material. Thinking Green notes highlight key items related to sustainability, energy efficiency, and environmental issues. From the Shop presents additional information related to the topic being discussed to deepen understanding. Critical Thinking questions develop higher-order thinking and problem- solving skills. 116 CNC Manufacturing Technology 6.5 Micrometers A micrometer, also known as a micrometer screw gage, is a measuring device that uses a rotating scale on a high-precision screw thread to precisely mea- sure objects. The micrometer has been in use for over 150 years, and forms a cornerstone of modern manufacturing. Because micrometers are precise and portable, they can make extremely accurate measurements right at a machine with repeatable results. Like other tools, micrometers come in mul- tiple configurations, including the outside micrometer, inside micrometer, and depth micrometer. All micrometers work in essentially the same way, off a rotating scale of a precision thread, and share common parts, Figure 6-10. ■ Frame. The main single-piece body of the micrometer. ■ Anvil. A fixed stop that contacts one side of the piece being measured. ■ Spindle. Rotating part that screws up and down to secure the second side of a piece being measured. ■ Locknut. Prevents the spindle from rotating. ■ Barrel. Fixed in place and provides measurement scale. ■ Thimble. Rotates around the barrel and has a secondary measuring scale numbered 1 to 24 in US Standard micrometer. ■ Ratchet. Indicates (“clicks”) when tension is applied to the spindle to create even and repeatable force when measuring. From the Shop The Indispensable Micrometer The micrometer needs to be your best friend in the shop. Practice mea- suring with it, and get really comfortable holding it in your hand. It is a very accurate tool that can measure everything from material thickness to drill diameters. Check calibration frequently with a gage block or pin gage, and take care of it like your part depends on it—because it does. Often, machinists refer to these tools as “mikes,” short for micrometer. “You can never check the quality back into a scrap part.” Goodheart-Willcox Publisher Figure 6-10. A 0–1″ micrometer and its components. The edge is exactly on the number 5, and the thimble is lined up with 0 on the centerline. The reading on this micrometer is .500″. Anvil Spindle Locknut Centerline Edge Thimble Ratchet Barrel .100 .200 .300 .025 Frame Chapter 6 Semiprecision and Precision Measurements 125 When attached to its own granite base stand, Figure 6-35, a drop indi- cator can be mobile enough to use near a machine and give accurate read- ings of dimensions that are often difficult to measure, such as while a part is mounted into a machine. Reading a drop indicator is similar to reading a dial indicator. The difference is the overall travel distance and accuracy level, Figure 6-36. The “10” on the face refers to .010″ and the small lines between the larger numbers each represent .001″. The numbers on the inner circle count the revolutions of the dial. Each revolution is .100″, so if the needle rotates completely around, the small needle will count the .100″ revolutions of travel. Thinking Green Resurfacing Granite Plates Machine shops often use solid granite plates to perform inspections because of their wear resistance and the ability to manufacture them extremely fl at. Granite plates that have become worn can be resurfaced through a hand “lapping” process. This process restores the granite plate back to original specifi cations and saves the costs and use of natural resources in replacing it. 6.11.3 Coaxial Indicators Coaxial is defined as having a common axis or two or more coincident axes. A coaxial indicator is a special indicator used in machining that spins around the spindle centerline and is used to find bore or boss fea- tures. Coaxial indicators provide an extremely fast way to find the center of a round feature, but they are not particularly accurate. These indicators should not be used if the accuracy level needs to exceed ± .002″. Often, coaxial indicators are used to find an approximate center. Then, a dial indicator is used for final adjustment. Goodheart-Willcox Publisher Figure 6-35. A common configuration of a drop indicator with mounting arm and small granite plate. .010″ .100″ Goodheart-Willcox Publisher Figure 6-36. Getting readings from a drop indicator face. Goodheart-Willcox Publisher Figure 6-37. A coaxial indicator with accessories.