The Rockwell hardness tester to measure the hardness of metal measures resistance to penetration like the Brinell test, but in the Rockwell case, the depth of the impression is measured rather than the diametric area. With the Rockwell tester, the hardness is indicated directly on the scale attached to the machine.
(Redirected from Apache Nation) The Apache (/ÉËpÃ¦tÊiË/; French: [a.paÊ]) are culturally related Native American tribes from the Southwestern United States, and have traditionally lived in Eastern Arizona, Northern Mexico (Sonora and Chihuahua), New Mexico, West Texas, and Southern Colorado.
The Apache is a twin-engined army attack helicopter developed by McDonnell Douglas (now Boeing). It entered service with the US Army in 1984 and has been exported to Egypt, Greece, Israel, the Netherlands, Japan, Saudi Arabia, United Arab Emirates (UAE) and the UK. The Apache was first used in combat in 1989..