Each different blade steel has a recommended Rockwell range by steel industry standards. For both 8-A and 440 steel this is a perfect range for field use. From a practical standpoint, blade material that tests below Rockwell C52 is too soft to offer any protection against edge deterioration. Blade material that tests above C60 is approaching the edge of brittleness and is very difficult to attain an edge during sharpening. Heat-treating of knife blades is performed to reduce blade brittleness and increase hardness.
Carbon is the main alloying element that creates edge-holding ability.
All Pardner knives will feature 8-A steel. However, considering the amount of water and fish fluids that are common when using a fillet knife, the 440 stainless steel that is used for the Kingfishers is aptly suited for that series. The proper grind rids the blade of unneeded steel which causes a drag, especially when dressing game. The benefit of this feature is that the blade is kept clean and out of your work area, plus it makes picking up and handling the knife safer and easier. Brass is a softer metal than steel and resists oxidation.