speeds of 25,000 to 40,000 rpm. Routers are normally used with a template to define a smooth regular cut with the depth of the cut set and locked. Hole saws are good for removing small areas of damage on laminates, although they have a tendency to damage honeycomb rather than cut it. Hole saws also easily clean up damages, providing a good surface for repairs. Backup plates should be taped to the backside of the material being sawed to prevent backside breakout. Fine tooth metal or diamond saws work the best for sawing laminates. HAZARDS AND SAFETY PRECAUTIONS Learning Objective: Recognize the different safety precautions peculiar to working with advanced composites materials. The issue of personal health and safety is paramount when working with composite materials. With the rapid development of the new material systems, the full effect of hazards to personnel has not been determined; however, sensible shop practices and procedures have to be employed to prevent problems now and those that may appear later. Following these safety precautions may prevent future health problems, such as those encountered in the case of asbestos fibers. PERSONNEL HAZARDS Airborne dust and fibrous particles are the principal source of hazards. These particles are generated by drilling, sanding, routing, or sawing the composite structures. Fine, lightweight fiber particles are easily circulated into the atmosphere, causing skin irritation and inflammation, eye irritation, respiratory system inflammation, pulmonary diseases (black lung), cancer of the lung, and abdominal disorders. Respiratory protection is required in those operations where dust exists or is generated. Eye protection, consisting of safety goggles or a face shield, is also recommended for use in work involving any operation where the likelihood of airborne fibers exist. Broken fibers can penetrate the skin. The fibers may become lodged beneath the skin. These fibers are so brittle and difficult to remove that they generally have to be cut out and the wound disinfected to prevent infections. Personal hygiene includes washing your hands before and after working with composites, and your hair should be washed at the end of each day. Wash dust-contaminated clothing separate from other clothing. Do not eat, drink, or smoke in the composite repair area. EQUIPMENT HAZARDS Graphite dust and particles are conductors and can cause shorts in electrical motors and avionics circuity. Also, these dust particles can affect the aircraft’s fluid systems. In the hydraulic system where contamination is critical, actuating cylinder rods can draw the dust particles into the system, causing premature seal failures. The abrasiveness of these dust particles can also cause failures to valves, pumps, and other close tolerance parts. In the fuel system, these particles can be introduced during wet wing repairs, causing clogged filters and erroneous readings in capacitance fuel quantity probes. The abrasiveness of these dust particles can cause failures to fuel controls and other close tolerance fuel valves. SOLVENTS Because of the necessity to use solvents while accomplishing bonded repairs, potential health and fire dangers must be given special consideration. Solvents dissolve natural skin oils and result in drying and cracking of the skin, rendering it susceptible to infection. Additionally, these solvents may cause irritation and allergic reactions to individuals. If the vapors are inhaled during prolonged and repeated exposure to moderate concentrations, solvents can cause headache, fatigue, nausea, or visual and mental disturbances. Extreme exposure may result in unconsciousness and even death. Solvent vapors may also act as an anesthetic or cause irritation of the eyes or respiratory system. In addition, they can result in blood, liver, and kidney damage. Therefore, adequate ventilation should be provided during mixing and use of adhesives, solvents, and cleaning solvents. To minimize or eliminate the danger of tire and subsequent destruction of life and property, flammable solvents should be used only in approved areas and with methods recommended by local fire safety authorities.    Composite material fire hazards are usually limited to solvents and resins. Flashpoints of solvents and resins vary, but are usually around 14-28