A shop-built system that supports extended bar stock, aiming to enhance the machine’s productivity by allowing higher volumes of material to be loaded. Allowing bar stock to be unsupported presents a potentially fatal workplace hazard. The author emphasized that employers who develop their own support systems should work with engineers or other specialists to ensure the system is functional and safe.
On January 29, 2010, a 27-year-old machinist was fatally injured when he was struck by a piece of round stainless steel bar stock that he was machining in a computer numerical control (CNC) lathe. A coworker explained that the victim was machining washers for a gill net reel frame from the round bar stock. The machinist had placed a 6-foot piece of round bar stock into a Haas TL-3W model lathe. Approximately three feet of unsupported bar stock extended past the spindle.
As the victim monitored the lathe operation, the unsupported portion of the bar protruding through the spindle bent to an 80-degree angle.
The shop general manager speculated that the victim heard the noise generated by the rapidly rotating round bar stock, and went to inspect it. As he stepped to the back of the machine to inspect the source of the noise, the manager further surmised, the machinist was struck by the bent piece of bar stock. The coworker and a contractor heard a crash sound in the vicinity of the lathe and, upon responding, found the victim unconscious.
What went wrong — The circumstances are simple to imagine, but there are series of errors in this situation that should be understood, and avoided.
1) The three-feet length of bar stock extending out past the spindle of lathe was unsupported.
2) There was no system in place to support the length of bar stock extended past the spindle.
3) There was no formal safety plan that addresses hazards regarding operation of lathe with bar stock extending beyond the spindle.
Also, CNC lathes’ ability to continue operating with unsupported bar stock extending past spindle is a problem that should be addressed in a general way. To prevent similar incidents from happening in the future the Washington State Fatality Assessment and Control Evaluation Team (FACE) recommends:
• Employers should ensure that machinery hazards are abated with engineering controls.
• Employers should develop and enforce machine and hazard specific safety policies and procedures that address and abate hazards.
• Employers should develop a mandatory checklist for each set-up procedure to ensure that all steps are properly completed before machines are started.
In addition, FACE recommends that CNC lathe manufacturers should design machines with multiple safety systems, including interlocks and “fail safes.”