It seems that the unibit is for drilling holes in conduit boxes, but works quite well for other metal applications. You can find them at HD.
You probably used normal bits to drill the holes. If so, even in a drill press, the bits will wander and flex.
I got the unibit because I needed to drill 1" holes and I could not find a big enough bit.
It drilled pretty clean big holes so I touched up the smaller ones as well with it.