I will let you in on a little trick though, even though I didn't use it today due to the 10 ft length of pipe I'm doing.....
If you get a piece of PVC that the pipe slides snugly through, it will keep the bit from walking and cut down on broken bits when not center punching the holes. I just knew if would be hard to keep everything level enough to guide the pipe smoothly with that 10 ft length, so I just made a cradle to keep the pipe centered under the bit, and hung a piece of 1/2" by 4" x 2ft flat bar on the pipe to act as a counterweight to keep the holes in line.
If you get a piece of PVC that the pipe slides snugly through, it will keep the bit from walking and cut down on broken bits when not center punching the holes. I just knew if would be hard to keep everything level enough to guide the pipe smoothly with that 10 ft length, so I just made a cradle to keep the pipe centered under the bit, and hung a piece of 1/2" by 4" x 2ft flat bar on the pipe to act as a counterweight to keep the holes in line.