TWO MAINTENANCE WORKERS WERE REMOVING A FLYWHEEL OFF WASH SCREEN TO REPLACE BEARING BEHIND IT. FLYWHEEL JAMMED AND WORKER USED COME-A-LONG AND HAMMERS TO FREE FLYWHEEL. INJURED MAN HIT SIDE OF FLYWHEEL AND INSTEAD OF MOVING A SMALL AMOUNT THE FLYWHEEL FLEW OFF THE SHAFT. INJURED MAN JUMPED BACK, SLIPPED, FALLING TO HAND & KNEES AND FLYWHEEL LANDED ON RIGHT HAND, THUMB & FOREFINGER.