Complex sentence: The tough metal and thick blade of a cleaver also make it a suitable tool for crushing with the side of the blade-wheras some hard, thin slicing knives could crack under such repeated stress.
Split into simpler sentences: The tough metal and thick blade of a cleaver also make it a suitable tool for crushing with the side of the blade. This contrasts with certain hard, thin slicing knives, which should not be used for crushing because they can crack under such repeated stress.