Cracks are part of the game. Knife making is all about finding the balance between sharpness/thinness and durability. For kitchen knives, you usually want to go as thin as possible, but the thinner you go the more likely you are to get a warp or crack during heat treatment. Today, a got a warp in my quench and was trying to straighten it out during the temper. But I went a little too far and it cracked. Gonna see if I can pivot and still make a functional blade out of it by shortening it to where the crack is and switching from full tang to through tang.