If using a mid carbon steel for hammer heads (1045 or 4140) would leaving it normalized but not otherswise hardened by heating and differntlial quenching (heat treating the face and peen end) result in a usable soft face hammer? Do folks ever use hammers that are left only in an annealed state or is that too soft? Would that be roughly equivalent to a brass hammer? Still learning all this stuff so sorry if this is a dopey question.....I have lots of them!

What are you planning to use this for? If you're thinking a hammer for striking punches & chisels, you should be fine. If you want to use it for straightening twisted sections of stock (or something similarly detailed that you don't want to mess up), a brass hammer (or better yet, a wood mallet on a wood block) is probably your better bet. Suit the tool to the task.

I guess I’m asking a more general question: is simply normalizing a mid carbon steel hammer head the proper way to make a “soft faced” hammer? And, as a follow up inquiry, would annealed mid carbon steel be too soft to be useful? Thanks in advance for your input. 

You certainly could normalize a medium carbon steel hammerhead; you could also just use mild steel. My soft hammer is an old stonecutter's hand sledge with a head made from wrought iron. It mushrooms, but I don't have to worry about it chipping the striking end of my punches and chisels.

You say, "...too soft to be useful" -- well, what use? If you suit the tool to the task, it's going to be useful for some things and not for others.

Appreciate the info. May try an annealed head just to see how it compares to my brass hammers. 

I have a French crosspeen that evidently was in a burned out factory from one of the world wars---lynch collection----it's dead soft and *very* useful. Particularly for students who can't hit the workpiece and so might ding the anvil face with a hard hammer.  Of course being so soft I have to make them use a different hammer when using a hardy to avoid deep grooves in the face...

Thomas, love to see a picture of that historically rich hammer. 

I use soft hammers for people who are learning like Thomas said also for hitting my hardened hammers if I need a different set hammer for some reason. I normally just do not heat treat them, normalizing would be better. It should end up harder than brass.

Funny you should mention that...I was reading the Sword and the Crucible at breakfast today and in Chapter 2 where they discuss the introduction of iron and it has a lovely graph of the hardness of normalized steels vs the hardness of various bronzes both annealed and work hardened---the vertical axis is VPH hardness and the horizontal is doubly set up with the percentage of tin for the bronzes and percentage of C for the steels.  The hardness of normalized steels tracked between the hardness of work hardened bronze and the hardness of anneal bronze.

Now the hardness of quenched steels started very much higher and headed to the stratosphere!