Originally Posted by
eight
I have done this many times and I think only once with good results. Seems the large bits usually like to jump around instead of just drilling straight down the pilot hole.
Here is my recommendation. Drill a pilot hole, 3/8" or so. Then get a unibit that goes to 7/8". Use this unibit, slowly, with lube, to get the 7/8" hole started. Then switch to a 7/8" bit and finish the hole.
The unibit will start a good hole and the 7/8" bit will follow it through. Otherwise, when just stepping up bit sizes, I find that the large bit doesn't like to just follow the pilot hole. It chatters and you end up with a larger hole than you wanted.