First of all, I totally agree that a late night beer drinking session and the three of us would probably be burning down the world 
As long as we could keep all the SAS guys from whipping Rob's ass, then that would at least be some accomplishment (inside joke)
Ari's Burgers? For Sure!
Just to throw some information on the subject of flint and steel let me give you my findings from heavily researching the process over the past few years. I'm no scientist but I have worked a lot of metal over the years and understanding things fascinates me:
First of all we all know there is a major difference between artificial flint (ferrocerium) and true flint (a generic term used for rocks such as chert, quart, obsidian, etc.). Not only is the composition of the two flints different but what occurs to produce a spark is also different. With artificial flint, the spark is created within the ferrocerium when struck or stroked by a harder substance (steel, rock, glass, etc.). In true flint, the spark is created by the steel that is striking the flint.
This latter process is the reason a certain hardness has to be maintained within the steel for the hand strike process to work. If the steel is too soft, a couple of things happen 1) it grabs the flint instead of smoothly striking 2) the carbon levels of the steel are too low at the striking surface for a spark to be generated by a hand strike. In order for sparks to occur from lower rockwell steel with true flint, then either a larger shaving has to be removed with a greater force, or the material has to be exposed to higher friction rates such as grinding wheels and cars dragging tail pipes down the road.
When a steel has been carburized properly the carbon levels at the surface, or case, are much higher than the carbon levels of un-heat treated steel. Thus, a simple hand strike from a sharp edge of a hard stone shaves a micro-grained amount of steel and turns it into a molten piece of metal - a spark. The heat treating actually helps the flint (sharp rock) since it produces a harder surface which does not grab the flint and allows the flint to shave minute amounts without biting into the steel and breaking the flint. The high carbon coupled with smooth strokes from a sharp edge creates good constant motion friction. The higher heat treat demands that only a small amount of metal will be removed. Common sense dictates that a smaller piece of metal will go to molten stage quicker than a larger piece. It is perhaps possible, and I say this with sincere doubt, to generate a spark by hand from soft steel if it can be shaven clean with one stroke without breaking the flint at a high rate of speed. This would have to be done at a higher friction rate to cause the metal to become molten since the carbon levels would be lower. The reason it is so difficult is because soft steels grab the sharp edge of the flint, naturally wanting to take a deeper bite. The more material you try to remove then the harder the process becomes because more metal removal in one pass means slower metal removal without the help of higher carbon level for producing critical temperature. In the end, when it does happen it's going to be an uncontrollable spark incapable of catching in char unless you're lucky.
I don't know if that makes sense, but the short version is the more metal you remove (natural occurence in softer steels) then the higher the friction rate has to be to produce critical temperature in the steel. Heat treat is a friend because it raises the carbon levels which helps to bring critical temp faster, thus reducing required friction, and forces the flint to take smaller bites thus increasing speed of minute particle removal, thus increasing constant motion friction, thus making a nice hot spark.
With that said, properly hardened carbon steels such as C steels have a nice smooth edge to strike a sharp piece of flint. Simple smooth motion produce showers of sparks each time.
Damn, how's that for a scientific evaluation of the process ?
Jeff
As long as we could keep all the SAS guys from whipping Rob's ass, then that would at least be some accomplishment (inside joke)Ari's Burgers? For Sure!
Just to throw some information on the subject of flint and steel let me give you my findings from heavily researching the process over the past few years. I'm no scientist but I have worked a lot of metal over the years and understanding things fascinates me:
First of all we all know there is a major difference between artificial flint (ferrocerium) and true flint (a generic term used for rocks such as chert, quart, obsidian, etc.). Not only is the composition of the two flints different but what occurs to produce a spark is also different. With artificial flint, the spark is created within the ferrocerium when struck or stroked by a harder substance (steel, rock, glass, etc.). In true flint, the spark is created by the steel that is striking the flint.
This latter process is the reason a certain hardness has to be maintained within the steel for the hand strike process to work. If the steel is too soft, a couple of things happen 1) it grabs the flint instead of smoothly striking 2) the carbon levels of the steel are too low at the striking surface for a spark to be generated by a hand strike. In order for sparks to occur from lower rockwell steel with true flint, then either a larger shaving has to be removed with a greater force, or the material has to be exposed to higher friction rates such as grinding wheels and cars dragging tail pipes down the road.
When a steel has been carburized properly the carbon levels at the surface, or case, are much higher than the carbon levels of un-heat treated steel. Thus, a simple hand strike from a sharp edge of a hard stone shaves a micro-grained amount of steel and turns it into a molten piece of metal - a spark. The heat treating actually helps the flint (sharp rock) since it produces a harder surface which does not grab the flint and allows the flint to shave minute amounts without biting into the steel and breaking the flint. The high carbon coupled with smooth strokes from a sharp edge creates good constant motion friction. The higher heat treat demands that only a small amount of metal will be removed. Common sense dictates that a smaller piece of metal will go to molten stage quicker than a larger piece. It is perhaps possible, and I say this with sincere doubt, to generate a spark by hand from soft steel if it can be shaven clean with one stroke without breaking the flint at a high rate of speed. This would have to be done at a higher friction rate to cause the metal to become molten since the carbon levels would be lower. The reason it is so difficult is because soft steels grab the sharp edge of the flint, naturally wanting to take a deeper bite. The more material you try to remove then the harder the process becomes because more metal removal in one pass means slower metal removal without the help of higher carbon level for producing critical temperature. In the end, when it does happen it's going to be an uncontrollable spark incapable of catching in char unless you're lucky.
I don't know if that makes sense, but the short version is the more metal you remove (natural occurence in softer steels) then the higher the friction rate has to be to produce critical temperature in the steel. Heat treat is a friend because it raises the carbon levels which helps to bring critical temp faster, thus reducing required friction, and forces the flint to take smaller bites thus increasing speed of minute particle removal, thus increasing constant motion friction, thus making a nice hot spark.
With that said, properly hardened carbon steels such as C steels have a nice smooth edge to strike a sharp piece of flint. Simple smooth motion produce showers of sparks each time.
Damn, how's that for a scientific evaluation of the process ?
Jeff
