I needed to drill and tap a 1/4-20 hole in the end of a piece of 3/8" diameter steel rod stock. It didn't need it to be too accurate so I came up with this quick and dirty method. If you don't need a lot of accuracy and you don't own a metal lathe this is a simple way to get your hole reasonably on center. I simply slipped a 3/8" hex socket with 1/4" drive over the end of the rod stock. Then I drilled a countersink into the end of the rod stock with a 1/4" diameter twist drill.
Step 1: Results
Next all I needed to do was slide the socket off and drill a hole with the tap drill. Of course this method will also work on other sizes of rod stock as long as you have a corresponding hex socket.