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Mill hand dies when drill was thrown from shattered hardened steel tool extension and strikes him in chest.
Michigan State University
Morgantown, WV: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, FACE 04MI180, 2005 Aug; :1-6
On November 18, 2004, a 23-year-old male mill hand died when a drill was thrown from a shattered hard steel tool extension and struck him in his chest. He was operating a high-speed computerized numerical control (CNC) machining center. The CNC programmer asked the victim to determine if a 3/4-inch drill that was 10 inches in length "ran true". The drill's three-inch long, 1/2-inch outside diameter (O.D.) tool was placed in a purchased six-inch long, one-inch O.D. hardened steel tool extension. The hardened steel tool extension was threaded onto an in-house manufactured soft steel tool extension that was 10-inches long and had a one-inch O.D. Two inches of the soft steel tool extension was inside of the tool holder. The victim attached this tooling to the tool holder and pressed the "clamp" button on the computer console. The machine was operating in manual data input mode. The victim entered 3000 revolutions per minute (rpm) for the spindle rotation instead of entering 300 rpm. The machine doors were wide open and the machine was in override mode. The victim pressed the start button, and because the over ride was set 110%, almost instantaneously the machine reached 3300 rpm. The victim was standing near the open door looking at the spinning tooling that was in the "home" position. He nodded to the programmer and indicated that everything was working appropriately. His left side was facing the open machine doors as he turned to stop the spindle rotation at the control panel. At that moment, the soft steel tool extension bent approximately 90 degrees. As a result, the hardened steel tool extension struck a part of the automatic tool changer and the extension shattered. The drill was thrown from the hardened extension. Both the shattered extension pieces and drill struck the victim. The programmer hit the emergency stop button. A supervisor who heard the tool break went to the location and attempted first aid measures. Emergency response was called and the victim was taken to the hospital where he died. Recommendations: 1. Conduct a job safety analysis when performing non-routine tasks or using non-routine tools. 2. Use only equipment manufacturer-approved components when conducting work operations. 3. Employee training should include confirming entered program values on a CNC machine prior to initiating the machine cycle. 4. Employers should consider reviewing their standard operating procedures to include keeping machine doors closed when possible. 5. Employers should evaluate whether providing additional reinforcement for machining window areas is appropriate. 6. Employers should ensure equipment is maintained according to manufacturer's instructions.
Region-5; Accident-analysis; Accident-potential; Accident-prevention; Accidents; Injuries; Injury-prevention; Safety-education; Safety-equipment; Safety-practices; Safety-measures; Traumatic-injuries; Work-practices; Work-analysis; Work-environment; Work-operations; Work-performance; Equipment-operators; Machine-operators; Training; Machine-operation; Machine-operators; Machine-tools; Manual-controls; Computer-aided-manufacturing
Field Studies; Fatality Assessment and Control Evaluation
NTIS Accession No.
National Institute for Occupational Safety and Health
Michigan State University
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division