Carbon case hardening, through natural evolution, commercialism, and economics, has become a process for which the possible number of variables is so large that it is hardly ly that any two companies will process exactly the same. There will always be some difference in choice of materials, equipment, or technique, and there will often be differences in the quality of the product. There may even be conflict of opinion regarding what is good practice and what is bad, and what is a valid test and what is meaningless. For each component treated, there is an optimum material and process combination, but who knows what this is for any given component? Most conflicts stem there being too great a choice of materials or process variables and the wide range of components that are required to be case hardened.