Overheard a guy in the union hall say he never uses a hammer drill for anchor bolts

I used to think you had to use a hammer drill for every bolt hole on a baseplate job. Then I'm sitting in the union hall waiting for a dispatch and this old boilermaker says he only uses a rotary hammer for concrete over 4000 psi and a standard drill for anything softer. He showed me pictures of a refinery job he did in Gary where he ran 80 bolts with no hammer drill, just a corded DeWalt and good carbide bits. I tried it on a small water tank pad last week and it cut my setup time by almost half. Has anybody else switched drills based on psi?

2 comments

2 Comments

the_zara1d ago

Are you really trusting whatever random number the concrete truck driver yells at you to set your drill speed? I've had 3000 psi pour that felt like granite after 28 days.

abbyg141d ago

Jumped into a job once where the engineer swore up and down the slab was 3500 psi and it turned out to be closer to 5000 after we busted a corner. Had to switch from a standard drill to a rotary halfway through because the bits were just smoking. So yeah @the_zara, that guy yelling a number out the truck window isn't exactly a lab report. But I've found if you take a small chipping hammer and tap a divot in a hidden spot near the edge, you can get a feel for how hard the concrete really is. Saves you guessing and burning up bits.