CU of man operating milling machine bevelling piece of metal. CU of emery wheel of machine grinding metal. Front CU of emery wheel, sparks flying when wheel grinds metal. Various shots of undercarriage of plane being tested in plant. Front CU of man operating precision emery grinder. CU of precision machine in operation. CU of man's hands testing controls of airplane, lights on control panel going off in background. CU of sign "KEEP OUT - Entry must be authorized by crew chief" on door.