So one day some time ago our iron stair railing going from the sidewalk to the stoop rusted through at the base of the posts and fell right over. I had a welder friend cut off the rusted portion and add a new section of 1" stock to both posts.
Now I need to figure out how to reinstall the railing. The existing holes are 1-1/2" to 1-3/4" wide at the top, but taper down. One hole is cleaned out to about 2", and the other to 1", the rest of the hole being filled with concrete and iron. From some research it seems a 2" wide and 4" deep hole should be secure enough, which I can then install the railing in, and fill with anchoring cement.
So my question is how do I enlarge and deepen the holes? Research seems to indicate a 2" core drill would be the best solution, but how would I keep the bit from jumping all over the place, especially considering I'm overlapping an existing hole? The bottom hole is only 2" from one edge and 3" from the other, so if possible I'd want to shift the center of the hole so I don't get any close to the edge.