along the axis takes only a few seconds. Since you are only drilling for about 1/4-inch, keeping the hole centered (more or less) usually is not a problem. If the hole is a little off center, just ream it out a little
with the drill fl utes when you part it off; absolute precision is not required here. Now mark off the required length of the thimble with a #11 scalpel blade, making a shallow guide cut all the way around