Dave wrote on 08/20/16 at 04:27:13:There was a time when I was not so lucky, and I did not get the hole right down the center. I still was able to make it work by drilling with as large or drill as I could without hitting the threads on the close side - then using a Dremel grinder and a stone made for sharpening chain saws.......it is a small diameter and long stone and works well for grinding ins small spaces, and it can even grind away a broken drill bit or taps. They do wear rather quickly as they are small, and you may need to use several of them - but they can work if you are careful and go slowly. Once you have most of the bolt/stud ground away, it can usually be collapsed with a punch/chisel/ice pick and removed.
A word on drilling this particular bolt straight, The downtube of the frame is in the way slightly, not so much that you can't get the bit straight on through the bolt, but enough that it is easy to nick the frame paint with the chuck on your drill. I put a few wraps of electricians tape around the frame near where the drill needed to run, and yes I bumped it a few times that would have scuffed paint. I didn't have any specialty long bits so I ran the ones I had long in the chuck, leaving about a 1/4" at least in the jaws of the chuck. This helped keep the chuck even farther away from the frame.
For alignment and getting my best guess on the first pilot hole I drilled I used a long bolt threaded into the opposite exhaust bolt hole. Using the long bolt I could easily see if my drill was misaligned in the slightest. I keep my bits sharp and that's critical too, this isn't the time or project to be fighting poor equipment. Dull bits make you strain and wiggle and shake and you will not be drilling a straight hole like that. With a sharp bit, slow speed on the drill, and a steady hand you can get the pilot hole started straight and that is the most critical moment. Once you have drilled a 1/4" or so it is difficult to change direction, so getting it right in that first effort is important. After that you can relax and just let the drill work.
If you get misaligned it's not the end of the world. As you drill your pilot hole it is a good idea to check your progress every 1/4" or so. This helps you keep from making a big mess and also keeps your drill bit nice and cool. Look in the hole with a flashlight and see if you see any threads appearing in the
sides of the hole. Usually you can see the bolt/stud threads giving way before you damage the threads of the hole. If you spot threads appearing and you know there's quite a bit more bolt left, you may be able to start at the entrance of the hole with a high misalignment on your drill and
walk the hole over away from the threads you found. Usually this is the time to jump up a bit size because trying to get the pilot bit to just scoot over can be nearly impossible.