What characteristic of tool steel allows it to sustain shocks and major impacts?

The characteristic that allows tool steel to sustain shocks and major impacts is its toughness. Toughness is the ability of a material to absorb energy and deform plastically without fracturing. This property is crucial for tool steels, as they are subjected to various forms of stress during machining operations. When a tool encounters a sudden impact or shock, a tough material will deform and absorb that energy, preventing catastrophic failure.

While stiffness refers to a material's resistance to deformation under stress, it does not directly relate to a material's ability to withstand shocks. Ductility is the capacity of a material to undergo significant plastic deformation before rupture, which, while important for certain applications, does not specifically address impact resistance in the same way toughness does. Machinability, on the other hand, pertains to how easily a material can be cut and shaped, which is not related to its ability to handle shocks and impacts.

Thus, toughness is the critical property that enables tool steel to endure the demands of applications where it faces shock and impact, making it ideal for tools and dies in manufacturing processes.