Heat Generation With a Hammer

Background - where this project comes from

I am a blacksmith.  Any time I make something with a hammer and forge, I am working with high temperatures.  In order to avoid serious injury, focus and attention to detail are required.  This focus can result in noticing things that I never expected to see.  Many people, I contend, do not notice even obvious things because they don't expect to see them.  Most of the time, for most people, this is not a problem.  As a blacksmith, I have to notice things or I will get burned.  Again.

When I start working, I like to do one or two simple things before I get into more precise work.  This helps me to "warm up" my arms and I think of it being similar to a runner stretching before he or she starts running.  One of the "warm-ups" I do when I am going to start a long session of forging is making nails. 


photo and nails by Patrick Woolery

There are several reasons that I enjoy nail making, but they are not really relevant to the discussion at hand.  The point is that making a nail, like any blacksmith work, is a matter of balancing the available heat with the work still to be done.  The colder the iron is, the less it will deform with a hammer blow.  At some time, the iron will be cool enough that effective work is no longer worth the effort and the iron has to be heated up again.  Back to the forge, in other words.

Since I work iron in the temperature range where it is glowing red to yellow, I use the color of the material to judge the available heat and therefore working time.  Every blacksmith does this.  It is part of the basic skill set.  I have less than a minute to work on a rod of 1/4 inch iron before it has to go back in the fire. 

Heat is lost to the surface of the anvil, the face of the hammer, and the surrounding air. 

A couple of years ago, I was fascinated to notice that as I hammered the point of a nail to shape, it appeared to get hotter, rather than cooler. 

I'm going to say that again.  Bold and in big letters.  Against expectation, the iron was getting hotter on the anvil rather than colder. 

Not for very long, just for a couple of hammer blows in a very localized area, but it was enough to make me pay much closer attention to details of something that already had my focus.  And it eventually inspired this project. 

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