I've never heard of tightening the chuck in each of the three holes, but I'll try that next time. I also measured the shank to make sure it's not tapered. Right at the shoulder, it measures 0.437". But right above that, and all the way to the end of the cut down shank, it measures 0.434". Next time, I'll make sure to leave a gap between the shoulder and shank when I chuck it up.