In my shop and at my modeling workspace I often have the need to drill holes in various dowels and rods.. My usual temporary solution is to cut a "V"-shape in a block of wood, then locate the center of the "V" under the drill. This 3D-printed V-Block is nominally sized with a 5" X 8" base. However, with scaling, it can be printed to any size that you may require.

Step 1:

To locate top dead center of your workpiece on a drill press, you need only locate the 1/16" locating hole under a drill bit mounted in the drill chuck. Clamp the V-Block to the drill press base and you are ready to drill. You will notice there is no clearance channel at the intersection of the V. I intentionally omitted this feature so that I can scale the part down for drilling small diameter rod. Careful plunge drilling of 1/4" diameter and larger stock will prevent any damage to the V-Block. Nevertheless, it's just as easy to print another if the block suffers any damage.

Step 2:

To save material, yet provide a strong and stable base, I shelled the underside with a wall thickness of .200". The holes in the base provide attachment points for a larger base.