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The trick to the operation is to have your tool bit centered. This is easier with a quick change tool holder as you can bring the tool bit up and down with an adjustment screw. If your tool is held in a solid block you may have to put shims under the tool bit to bring it to center. A good sharp tool bit on center can run flat across the face of a piece of material. To make sure your hole is centered it is always a good idea to use a center drill before drilling. The only way to get a hole truly concentric, assuming that the OD is centered, is with a single lip cutting tool (boreing bar).