Miner along with 3 others were changing 736 dragline bucket. While removing the last trunnion link pin. EE struck the pin, not hitting it hard. A piece of metal ½""W x 1/4""H broke away from the Wilcox hammer, striking the miner in the left side of belly. Leaving laceration approximately 1/2"" across. Surgery was required to remove the piece of metal. Resulting in lost work days.