Copyright Goodheart-Willcox Co., Inc. Chapter 2 The Skills to Compete 25 bones, Figure 2-6. In the last 50 years, medical advances have led to joint implants and artificial limbs. Medical machinists contribute to everything from hip and knee replacements to artificial heart valves and structural pinning for bone repair. 2.2.3 Aerospace Applications The term aerospace refers to human efforts in design and engineering to achieve flight in the earth’s atmo- sphere or in space. It is truly one of humankind’s greatest achievements and adventures. Some of the most impressive advances in machining were spurred by aviation and space travel. For example, solid car- bide or insertable cutters were developed to machine exotic aircraft alloys, such as titanium and molyb- denum, Figure 2-7. Conversely, some of the greatest advances in flight could only have been achieved using precision machining and radical machining tech- niques. The first computer-controlled machines were developed to make helicopter rotors that were bal- anced with repeatable precision. Today’s multi-axis machines were designed to machine the extremely complicated geometry of today’s aerospace industry, Figure 2-8. Critical components in aerospace applications range in size from as small as a grain of rice to as large as a car. It takes a wide variety of machines and skills to produce the critical pieces that fulfill the requirements of the aerospace industry. Aerospace continues to push the limits of preci- sion and human ability to machine exotic materials. The key to faster flight is increasing speed, or thrust, and decreasing weight, or mass. However, faster travel puts more stress on the materials. This added stress has pushed engineers to use exotic materials, such as tita- nium and high-strength aluminums. Many old machin- ing techniques cannot be used for these tough materials. Instead, machinists must employ high-speed spindle feeds and develop new cutting tool technology. The result is that the aerospace industry can be one of the most challenging and exciting machining fields. 2.2.4 Defense Manufacturing has always played a massive role in national defense. Between 1885 and 1914, the United States experienced tremendous manufacturing growth and prosperity. As World War I (WWI) started, this growth meant that the United States initially was the largest supplier of weapons and ammunition to Euro- pean war efforts. The US capability to machine and Praisaeng/Shutterstock.com Figure 2-6. X-ray view of medical plate and screw placement for bone repair. Anatoliy Lukich/Shutterstock.com Figure 2-7. USAF F-22 Raptor in flight. Castleski/Shutterstock.com Figure 2-8. NASA space shuttle orbiting Earth.