1) Presumably commercially made 1045 carpenters/claw hammers are heat treated in some special way to optimize their hardness. What is that process?

2) Just curious, does the surface of a 1045 hammer get harder or tougher over time from regular/repeated use? 

It would make a good claw hammer for carpentry, but you might heat treat the head and claw separately. leaving the eye normalized.

The face of a 1045 forging hammer gets a "hard temper" of straw or dark straw. It will not get harder in use.

Thanks. Not having the best luck getting a nail worthy face on my hammers but still very much just beginning to learn about heat treating. 

Quality framing hammers are differentially tempered. Such tempering is most probably discussed on this site. (many times I suspect). Check it out.

I would post a ' u.r.l.' but I'm in the midst of preparing a biryani for "She Who Must Be Obeyed". (a.k.a. the Lovely Margaret).

Framing hammers are generally not tempered as hard as ball pein and smithing hammers. Nails are generally made of soft steel. Chipping is not desired by the construction folks.

But, then again, they use pneumatic guns these days.

Back to the kadei!

SLAG.

I’ve been doing the differential hardening/tempering. Just not yet getting terribly hard faces. 

So how are you hardening the faces?

Thomas, I’m heating the heads to non-magnetic and then quenching the face/peen ends in either heated canola oil or water. Typically, I’ve tempered in the oven at 400 degrees for two hours, although today I tried the method of heating a drift and trying to draw out the color to a dark straw before quenching (today was 1045 in water....I put the whole head in the water once the color came out but maybe that was a mistake). As an aside, found this intersting video with a pretty neat quenching approach to a large sledge (they start with a massive billet!): 

 

Just so you know more, the hammer I’m currently finishing is a funny little experimental hammer made for a friend who is involved in a project making many windowed doors for a library room. He wants a curved small hammer (8 oz. head) to help drive in the nailed moldings or mullions that hold in the window panes. The face got to a nice light straw color using a heated drift but seems rather easy to dent. It is not handled yet so I can re-harden/temper. Any thoughts or advice would be most appreciated.  

Because of the mass involved many hammer smiths just quench in water with lots of agitation.  For a knife cross section that would generally be too quick of a quench, but the hammer heads take so long to cool that it works for them.  You have to quench the whole hammer head IMO.  Otherwise there is plenty of heat in the hammer body to resoften the faces.  For a softer temper at the eye it can be tempered more... but I harden the whole head to begin with.  The hot drift tempering that you are trying is intended to soften the eye of the hammer.  Try leaving the faces fully hardened, as with 1045 and given the mass that has to be cooled that might just be about right for you.  

Yes just immersing in a quenchant is not going to do it for a good sized hammer, you will need someway to get around the Leidenfrost effect.  

As for your second question: what alloy was used? What temperature was it quenched at (was it still magnetic?) What quenchant did you use?

The piece in question is a little 8 ounce 1045 head. I heated to non-magnetic and quenched the peens yesterday. Then tried drift tempering. Not good results.

Today I did a new 10 minute normalizing cycle, then heated to non-magnetic (dark orange). After a good slow heating cycle I did a fast, vigorous quench in water. Definitely felt harder under a file this time. Tempering at 420 in the oven for two hours. 

Got a very good dark straw color on this little hammer made for installing small brads and glazing points on cabinet doors with windows. 

Handle is 140 year old mahogany from floorboards taken from an old Milwaukee building.