>>1529842I mean you temper everything but not all tools are tempered in order to improve the way they handle the stresses and forces they are put through. You don't temper an axe or a hammer in order to improve the way they handle impact forces, you temper their surfaces so they are resistant to wear. But you temper through high carbon steel that is to be used for milling tools, or as you said you temper through pocket knives because you need those things to be harder than the things you want to cut through. Pic related is how steel with a given amount of carbon acts under certain temps, meaning what its structure is because tempering is reshaping the crystal structure so it is "neater" (ie material gets harder). Surface tempering =/= tempering through
