VIDEO: Watch Glass Explode!

This really cool video, in which Destin from Smarter Every Day explains the scientific process of glass hardening when it is cooled quickly, reminded me of the effects work hardening has in metalworking operations. The video demonstrates (with high speed, slow motion footage) how putting glass that is in a molten state into cold water forms what is referred to as Prince Rupert’s Drop—a tadpole-shaped formation that can withstand a blow from a hammer on the bulb end, but becomes explosive with only slight damage to the tail end.

As with the bulb portion of the glass, metals are also strengthened as they are hardened. But this is not necessarily a desired effect. Often during machining, early passes of the cutting tool can harden the surface of the workpiece to the point that the tool is not equipped to cut the material effectively in later passes. Some alloys are more likely to harden than others, and shops need to be prepared to handle the situation. The article “Machining Exotics” details how a shop can adjust to the challenges of smaller-run parts that use difficult to machine materials, including the challenges brought on by work hardening. “Considerations for Machining Exotics” helps to define exotic materials through specification of their excellent wear characteristics, durability and service life in high heat, extreme cold or corrosive environments. But this article also notes additional undesirable effects of work hardening.