There are many threads on this subject. I've searched and read quite a few of them. I know tool steel is best but right now all I have is truck coil spring. My punches mushroom or mushroom and bend on the working end. I anneal, quench in water, polish and heat treat with a propane torch to bronze. Seems like I might be getting a little better, last one only mushroomed slightly but only punched 2 holes ( 3/4" , my 1/2" punch does the same ).
Any suggestions
Billy