What is a normally closed pneumatic chuck?

A normally closed pneumatic chuck is a clamping mechanism that relies on internal mechanical springs to maintain its holding force when no compressed air is applied. In this default state, the chuck remains locked onto the drawbar, spigot, or pull stud, consuming zero compressed air throughout the entire machining cycle. Compressed air is supplied only during setup to overcome the internal spring force, lifting the piston to open the chuck and release the pallet. This spring-actuated architecture operates as a mechanical fail-safe, ensuring the fixture stays clamped even if shop air lines lose pressure or fail completely.