Full Flat Grind Versus A Hollow Grind
Posted 13 January 2010 - 12:23 PM
Each grind style has it's strengths. For me a full flat grind is the champion when it comes to slicing things like meat and vegetables. A hollow grind tends to be much better for shaving type operations like fleshing and whittling.
I wonder what some of the observations are that the rest of you have noted.
Posted 13 January 2010 - 03:00 PM
Posted 14 January 2010 - 09:48 AM
Posted 14 January 2010 - 04:40 PM
I make both full flat grinds and hollow grinds. As has already been stated, the end use of the knife determines the grind used. All of the knives that I have made for competitors in the Iditarod Sled Dog challenge have had Hollow grinds. This is due in part to the fact that the knives would be used as "Pry Bars". Let me explain what I mean by "Pry Bars". All of the competitors have to drop ship the meat that they use for feeding the dogs to the next checkpoint and the meat is one big frozen block of pieces of raw meat. Upon arriving at the checkpoint and getting ready to feed the dogs, the frozen meat has to be pried from the block and then thawed out to feed the dogs. A full flat grind does not have a strong enough cross section for this type of use unless the knife is at minimum a 1/4 inch thick. The hollow grind provides a stronger/stiffer spine for this type of use. There is a reason that a sword with a full length fuller is "stiffer" than a sword with a full flat grind. All a fuller is, is a hollow grind in the middle of the blade but it improves the stiffness/strength of the cross section of the blade. Think about an "I" beam as opposed to a flat piece of steel. I know this is an exaggerated example but it is the same concept, a hollow grind on a knife blade is like a "T" beam, it will be stiffer/stronger than a flat piece of steel. A full flat grind is the best for slicing and all around caping or cooking duties. A full flat grind is more flexible than a hollow grind could ever be, which is why you won't see a hollow grind used in a fillet knife.
From an engineering standpoint what you are referring to is the "area moment of inertia" or "second moment of area". This value can be calculated. In a nutshell, when comparing two dissimilar profiles made of the same material the profile that yields the highest value second moment of area is the stiffest.
Width also has an effect on stiffness but not nearly as much as thickness does. In general, stiffness increases linearly to width and cubically to thickness. So if you want a stiffer flat grind knife a little thicker and wider "leaf" type profile really helps.
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