4340 is a top notch steel for hot-working tools that still need to be hit with hardened hammers, such as top tools, punches, and drifts. It is superior to 4140 both in its resistance to deformation under heat, and its strength when heat treated. It is also an oil quenching steel, so unlike H13 or S7, it is more forgiving and the tools can be cooled in oil as you use them.

2 inch diameter hot rolled.