An employee was removing a spent reel that had slipped off one of the eject rails from an unwinder. He went to push the core and dislodge it from the ejection rail. The employee began to raise his hands to warn other employees to stand clear and not enter the area. His right ring finger slipped into a hole in the chuck. The chuck closed and fell off the rails, crushing the employee's right ring finger between the chuck and spacer, resulting in a fingertip amputation.