This is a piece of round stock into which I have drilled a hole that is perfectly on center. I could have made the hole as deep as my drill bit is long, but left it shallow. I did this on my radial arm saw. What I am demonstrating in this Instructable was inspired by a chapter in the Foxfire Books on boring the barrel for a Kentucky flintlock rifle.
Step 1: Features of a radial arm saw
My radial arm saw has a 1/2 x 20 threaded shaft on the backside of the motor. Not only can I attach a saw blade on the front side of the motor, but I can attach a drill chuck or a sanding drum on the backside end. Further, I can swivel the motor so the shaft runs parallel to the saw arm. Because the motor moves along the arm on a suspension track, I can pull the motor into something I want to drill. That would move the motor and bit nearer to the left side of the photo.
I cut a piece of wood 2 x 3 inches a little over 5 inches long and aligned it under the drill bit so it is parallel to the drill bit.