An employee was testing and adjusting a valve assembly. As he was walking towards the valve assembly, that was mounted in a bench vise, his foot caught the air hose in front of the bench, causing him to lurch forward with his hands extended to catch himself. His right index finger entered the one-inch port of the valve as his left hand forced the 24 VDC supply leads connected to the solenoid operated valve to contact one another and short. When they shorted, the valve cycled and amputated the tip of his finger.