If the flint is mounted at the correct angle, it will knapp itself each time it strikes the frizzen, and you will have no need to sharpen it. To square the edge to the face of the frizzen, when you put a new flint in the cock, first always put the flint in the gun when the cock is in the Half-Cock position. In that position, you can move the flint in the jaws, before running the cock screw down, so that you can see even daylight between the entire length of the flint, and the face of the frizzen when its closed. The distance should be about 1/16" inch, but this varies from lock to lock, and even with some flints, as they are not always cut to exact dimension lengthwise. I do like to lower the cock, after mounting the firzzen, and turning the screw enough to hold the flint in place, so the cock is all the way forward, and look to see where the front edge of the flint is located in relation to the center of the flashpan, and the touch hole. ( vent ). You will have to open the frizzen to do this. Then I draw the cock back to the half cock notch, and close the frizzen again. I then release the cock and lower it so I can see exactly what my angle is to the face of the frizzen. Rarely, but it does happen, I am already square to the face, and I can screw in the cock screw hard to lock the flint in place. I always out a thumb and forefinger on both sides of the flint and top jaw of the cock, so I can feel any movement in the flint when I turn that screw down tight. Often there is some movement, which moves the edge a few degrees one way or another from square. If you try to shoot the gun now, only the small edge of the flint that now touches will cut steel, and it may not throw sparks in the pan.
To fix this, open the frizzen up from the closed position just enough to allow the edge of the flint to strike the lower edge of the frizzen. Then, use the side of your thumb( left thumb for you RH shooters) to hold that frizzen in that open position, while you cock the gun with your right hand. Cock it to full cock. Pointing the gun in a safe direction. go ahead and pull the trigger to release the cock. When it falls the edge of the flint will strike the bottom of the frizzen at a steep angle, breaking off a very small, but even part of the edge to square it with the face of the frizzen. Draw the cock back to full cock again, and this time lower the frizzen, and remove your thumb. Now pull the trigger and watch the sparks to see where they go. Sometimes you will have to turn the gun to the side so you are looking at the full lockplate and flashpan from the side of the gun. You want the sparks to land either in the center of the flashpan, or just a little forward. As the flint wears down, the sparks will land further and further to the rear, until they are not landing in the pan at all. That will be when you want to move the flint forward, turn it around to get a new edge, or replace it. Each time you remount the flint, do this same routine to square the edge, and check where the sparks are hitting.
If your lock is not designed properly, and you don't correct the angle so that the flint scrapes down the front of the frizzen, and instead gouges ruts in the face, so that after a couple of months, the frizzen begins looking like an old washboard, you will find sparks going anywhere but in the pan, flint life will be very short, and misfires from failure to ignite common. The flint should strike the frizzen between half way up the length of the frizzen, and 60% up. The angle where the flint touches the frizzen should be 55-60 degrees. You can use a plastic protractor to check this angle on your gun. When the flint strikes at this angle, the striking edge will break off with each shot, a little at a time, and you can expect to get many shots out of each flint. If the springs are balanced properly, and all the surfaces that meet in the lock are polished, and moving freely, you can get as many as 125-150 shots per flint.
As for positive ignition, I always recommend using a vent pick to clear the touch hole, and open a path or hole in the main charge in the barrel so that the flame and heat of the burning prime can enter the barrel and ignite several graules of powder at once. Experiments, and chronograph results show that you get the most consistent velocity and accuracy if you use FFg powder in a flintlock and if you don't compress the powder in the barrel when you load the ball. Just push the ball down until it just touches the powder, and mark your rod when you settle on a load. Then always load to the mark for consistent performance, and accuracy. You can get slightly more velocity if you compress the powder, but you also get a wider SDV if you do so, and it is the wider SDV that spoils group size. You can get that same increase in velocity by adding a few more grains of powder, and not lose the low SDV. This is different than how you load and shoot a percussion gun, which benefits from compacting the powder, and using FFFg powder.
Paul
