An employee was working on a manual clamp. He was holding the clamp with his left hand and holding a cylinder with his right hand. His right index finger was inside a slot on the cylinder housing when the clamp arm slipped out of his left hand and fell. When the unit fell, his right index finger was still in the slot and the top portion of the cylinder came down and amputated his finger. The equipment was not locked out at the time of the incident.