I use leather to tighten my flints. Also I have a diamond muzzy wheel that fits my dremel tool. With that I shape the top and bottom of my flints (wear goggles) and then they fit the jaws real nice and snug. I go through them and take the humps off the backs.

It is not uncommon for a new flint to flake. Especially if the flint is too large for the frizzen. For instance I have 3/4 flints I use in my Lyman. The T/C on the other hand and the Traditions I shoot are 5/8th. Many times I have had the outside edge break on them and lay in the pan. Especially after they have struck the frizzen a few times.

When you set your flint, square it to the frizzen face. Often the back end of a napped flint is not square. If you them square to the hammer then the front will be a little off. Hit that front right, at an angle and you are basically napping all over again. Set it square and you get a longer and there for hotter spark. And they don't break or dull as fast.

After you have set the flint and fired a couple times, take a screw driver and check the flint locking screw. That flint will move from striking the frizzen and often times come loose. And then you suddenly look down and no flint.

Have fun.