Depends on how you want to make them, you can start with nothing but a file, or you can have 3 or 4 72" belt grinders, an anvil and forge, a CNC machine, a mill maching a hydraulic press, a power hammer and about 903820239875 hand tools.
There's two main ways to make knives, forging and stock removal. For stock removal a good 2" x 72" belt sander is the way to go, 1" x 42" is acceptable. For forging you need a forge (fire with a blower of some sort attached) something to work as an anvil, and a hammer to start. When forging you'll want a little bit of stock removal equipment too, though you wouldn't have as pressing need of a good one if you only use it for minor cleanup to remove scale.
p.s. And some people just use the file, along with some sandpaper.