An employee was fixing a grinder. The space was limited and he could not open the grinder electrical door all the way. After checking voltage and replacing a fuse, he stood up to shut the main disconnect off and the cabinet door shut slowly, pushing his hand inside and shocking him. He was then held to the grinder. He was shocked, resulting in the amputation of his left pinky and ring fingers, as well as a thumb injury that required a skin graft.