Chuck for holding precision components

An assembly for holding a workpiece, comprising:

• a mandrel portion including an extending member;
• a piston including a bore receiving the extending member, the piston mounted for supported reciprocal movement on the extending member, the piston including plurality of tabs having internal and external surfaces, the tabs being able to deflect to bring the internal surfaces into engagement with the extending member;
• and
• a set of jaws mounted for pivotal movement, each jaw of the set of jaws including a surface positioned to receive force exerted by the external surfaces of the piston, wherein movement of said piston exerts force via the external surfaces of the piston and causes pivotal movement of said set of jaws.