An accident occurred at XXXXXXXXX power station construction project involving a 100mm grinder. The operative had cut metal cable tray with the grinder and was trying to turn the machine off with his thumb. When the switch would not move he adjusted his grip to look at the switch and in doing so, caught the tip of his finger on the cutting disc resulting in an injury to the right index finger. The injury though painful was not too severe, but could have been much worse had the finger become entangled between the disc and the guard. The investigation has revealed that there had been an unauthorised adjustment to the machine that could be easy to miss.