[Bill Harsey]

Hollis, A file will make a knife but it's a tough way to go.
Most files are designed to cut steel and have a very high carbon content for maximum hardness. This makes them hard to work (make into a knife) and they tend to be brittle in hard use.

I'd rather go with the spring.

Edited to add: Hollis, by a good source of knife steel, around here that means a steel I can work with in a timely and resource effective manner. Sometimes "free' can cost you a lot of time and money.

A better answer is yes they will make a good knife for some applications but the difficulty of working the file into a usable knife blade would put it down on my list of materials to use.