INJURY FROM PORTABLE GRINDER
On one my ships the fitter was grinding with a portable grinder. Between grinding he changed the grinding stone to a new one. As soon as he resumed grinding again the grinding stone broke into many pieces one of which hit him on his leg.
Later it was found that the wheel he used did not match the R.P.M of the machine. Lesson: Always check the replacement wheel for R.P.M. suitability of the machine.