[mactec54]

My experience with spring steel is that milling it with carbide is fine. It will burn up HSS drills tho, you will need to use carbide drills. (If you have small holes, cheap PCB drills work).
Other than that it's not special, just slow and steady. I used mist, I did not have flood coolant at the time. It worked out.

Quality HSS drills will drill it without any problem it is only 50Rc