THE INJURED & A HELPER WERE REMOVING BOLTS AND NUTS FROM GEAR CASE. THE INJURED WAS HOLDING THE BOLT FROM LOWER FRAME & THE HELPER WAS LOSING THE NUT WITH IMPACT WRENCH. THE VIBRATION CREATING BY IMPACT WRENCH CAUS ONE BOLT TO COME LOOS & DROPPED. THE BOLT RICOCHETED OFF XBEAM & HIT HIS LEFT EYE BETWEEN THE EYEBROW AND EYE LID.