In order to explain normalizing we must first spend a few minutes discussing "grain". No, I'm not interested in if you've got enough fiber in your diet. Metals, just like wood, have grains that run throughout the material.
In their "normalized" state, the grain in metals is aligned and tightly packed. However, after continual heating and cooling cycles combined with massive quantities of hammer blows, the grains become severely disrupted and are in bad need of some stress reduction. This is accomplished by a series of stress relieving heating and cooling cycles (which we call "normalizing").
Normalizing the blade is an essential step in the process of creating a strong and useable tool. When the grains are enlarged and out of alignment within the metal, they are not packed together as tightly. Until some metallurgist tells me differently, I assume this to mean that each metal molecule (or crystal as the case may be) has less surface area bonded to it's neighbor, thereby weakening the basic structure of the metal.
This phenomenon can only be observed through testing, so in the spirit of gathering empirical data we sacrificed a few blades by putting them to the bending test and eventually breaking them to examine the grain structure.
Videos: Breaking metal before (33.4 MB) and after (26.1 MB) normalizing.
A forged blade that has not been normalized displays a large and disrupted grain structure as follows:
Another section of the exact same blade after normalization demonstrates a much tighter grain structure:
Here is a Super High Resolution version.
The process we learned to normalize the blade involves three heat cycles. If one were fortunate enough to own a heat treat oven, such as the ones used for pottery, it would substitute for this process.
Seth demonstrates the proper way to slowly and evenly heat the blade. (Video: 63.3MB ~4 mins. long)
Finally, allow the blade to cool completely and move on to the Grinder.
First of all, don't ask silly questions. If Mike Williams says it will work, just do it! :-)
Beyond that, the only way to know you've done it right is to try it a few times and break the metal to observe the grain growth. If you do it a few times you'll be able to get a feel for it and you'll learn to be able to trust that you've done it right.
More information on Annealing (closely related to normalizing) from the 1924 edition of Machinery's Handbook
Beginning - Definitions - Forging - Normalizing - Grinding - Hardening - Tempering - Summary
This page last updated 12/30/2004
Copyright 1996-2005© John Pozadzides. All rights reserved.