What is the difference between punching and piercing?

Answer 1

Punching is like when Mike Tyson hits you. Piercing is when he bites you on the ear.

above is true example that there is no stupid questions but aswers yes;p

now serious!

the two terms are used synonymously. mostly. it depends on context and audience.

"Techniques in Pressworking Sheet Metal" by Eary and Reed differentiate between punching and piercing by emphasizing the fact that a slug (the material punched out) is produced in punching operations but not in piercing work.