How many forging books do you know of that delve info dressing your hammer?
How many classes are taught without discussing hammer preparation?
The simple answers are; too many.
The is not an article on how to do it. This is a quick introduction into why to do it.
Take a look at the picture attached to this article.....those edges/corners look sharp to me. Hammer meets anvil at the right angle and a chisel mark appears in your anvil. Anvils are generally considered harder to replace.
When i get a chance to talk to folks over the phone, via email or in person, and they are purchasing a hammer, I make sure to show them the differnce between a new forging hammer and a dressed one. There are a few that are predresses but this is not the norm for commercially made forging hammers. Why? Most of these hammers come from over sees and there it would be an insult for a manufacturer to decide what is the correct radius a master blacksmith should want on thier forging hammer.