actually you will need more than just a bit...you will also need a morticing jig...which holds the square chisel part of the bit square while the drill bit on the inside spins...

just about every vendor of drill press makes a morticing jig for their units...you will want to go online and look at the website for the maker of your drill press and find out which model will work for your tool

If you have a delta Drill Press they make an excellent mortising attachment for it.

Craftsman makes a nice set-up for this application but it only fits selected drill presses so you need to check the detail first. It runs about $70. Good luck!