Years ago I did a lot of rock cutting and shaping to make jewelry as a hobby. I tried making my own flints, using a diamond wheel rock cutter. I could cut them to any size and shape I wanted, but they sure did frustrate me trying to use them on my rifles...as the fractures could be running any direction. Some of them did okay, but some would split in any direction. I had some that actually split into two pieces on the first firing ! I think a guy is better off doing the more common pressure flaking.