An article on an Australian safety website described the tragic death of a worker whose coat was caught in a lathe and asked the question that is the title of this article: Can metal lathes be made safe? The article went on to offer the following ideas:
“How can these risks be minimised? A simple interlocked chuck guard connected via a Category 4 control system in accordance with AS 4024.1 that prevents the machine from starting while open will remove or significantly reduce most lathe safety risks…. When lathes need to be run with the guard open during set-up, for example, fit a two-hand control system that allows the operator to run the machine at a safe, low speed, rather than an interlock that can be switched off. With both hands away from the rotating hazards and ejection hazards minimised due to the safe low speed, or jog mode, the operator/setter is protected.”
I agree – partially. Innovations in safeguarding can often be incorporated when designing and building new machines. Those same innovations are often not feasible for retrofit – that’s the reason for my passion around the concepts of “Design-in Safety” and “Prevention thru Design” (PtD). The dilemma is that few engineers are even told they have a responsibility to consider occupational safety in the design of machines and systems. Then, when they get in the real world, they interface with safety people who may not have the technical acumen to deal with issues of design.
Back to lathes. Before putting on interlocked chuck guards, I would also want to know which tasks cannot be performed with the guard in place – and two hand controls may not work. When setting up a part in a lathe, you typically bring the tool into position to find the center point/depth of cut. You must have line of sight and need to move the tool by hand. It has been a long time since I’ve done that task but I would like someone to show me how two-hand controls could be used during lathe setup! This is the reason for my constant use of Task Based Risk Assessment (TaBRA). This methodology identifies when power is needed and those steps where employees may, of necessity, have close contact with equipment.
The problem with work-arounds
Many of the fatalities (over 80 during my career) and serious injuries I have investigated involved a task where the employee had to “work around” the safeguarding to accomplish the task. Sometimes there is a failure to comprehend all the variables of the work during design of the equipment and/or safety procedures. Perhaps it is for this reason that ANSI B11.6, the US National Standard for Manual Turning Machines with or without Automatic Control, is mute on the ideas offered in this article.
The ANSI B11 family of general industry machine safety standards is based upon achieving acceptable risk through the good faith application of the hierarchy of controls. The B11 Committee understands that there is no such thing as zero risk and that employee intervention is necessary for specific tasks that may force use of training, warnings, procedures, administrative controls and PPE to achieve acceptable risk. Feasibility of engineering safeguards is always a key consideration.
If you think it’s a good idea to never allow a worker to be around moving equipment/machinery, tell that to your mechanic the next time you take your automobile in for troubleshooting or a tune-up.