What I learned about drilling concrete

Forty years ago (hard to believe that) when I was studying to be a mining engineer I was on the mine competition team which consisted of jack-leg drilling, hand mucking, track laying and and hand steeling which was using a "single-jack" hammer (2 to 4 lbs) and a chisel tool to drill holes in rock. You were timed and then they would measure the depth of the hole. Hit, turn chisel tool and repeat. After doing that for a couple of minutes as fast and hard as you can that hammer felt like it weighed 100 lbs.