A chuck mounted center finder is handy for drilling through round stock. The tool’s pivoting section rests on the stock and a rigid shank mounts in the drill press or mill chuck. The work piece is moved until the center finder’s two reference lines match. With this particular model, the back of the pivoting part is the middle of the shank. Match up the back of the center finder with a line scribed at a desired distance, match up the reference lines, spot drill, and drill to size. If all has gone well, you’ll have a hole drilled through the middle of the work piece at a desired distance.
I encountered only two inconveniences. The shank is rigid and a drill press spindle wants to be in its own position. The tool seems delicate and could not on its own rotate a the spindle. A small improvement may be to have a pivoting shank, as long as accuracy remains. The second small inconvenience comes when trying to line up a work piece line with the back of the center finder. A small change could have the front of the center finder be the middle of the shank, where the tool’s references lines are visible.
The tool came at just the right time as I needed to add a set screw to a collar nut, and the center finder made the job easy. This particular model is made in the USA by PEC Tools and is easy to find online. I got mine from eBay seller thetaylormk.