[sdiy] 1/4" jack drill bit size?

[Prototek]

    I wanted to mount some 1/4" jacks in a plastic case today but didnt know
what size bit I should buy. My first guess was to get a 1/4" bit but when I
saw it it looked way to small to make a hole for the jack. What size do I
need?

                    Thanks,
                    John