Chuck jaws are inserts that fit into a chuck and grip the workpiece. There are three types of chuck jaws: base jaws, hard jaws, and soft jaws. Base, or master, jaws are attached to the body of the chuck jaw and are the component that the top jaw is mounted to. Base chuck jaws move radially, toward, and away from the work being chucked. These types of chuck jaws carry the top jaws with them.

Hard chuck jaws and soft chuck jaws are also available. Hard jaws are top chuck jaws made to final size from hardened steel. Top jaws clamp the workpiece and are mounted to the base jaw. Unlike hard jaws, soft top chuck jaws can be machined to specified dimensions. Soft top jaws are usually manufactured from steel, aluminum, or cast iron.

Chuck jaws are manufactured to fit specific chuck brands, but some may be interchangeable with many different manufacturers’ chucks. Several standard mounting configurations exist for chuck jaws including fine serrated (1.5mm x 60° and 1/16" x 90°), serrated (3.0mm x 60° and 3/32" x 90°), ACME key, American standard tongue & groove, metric tongue & groove, dovetail tongue & groove, and square key.

Several shapes are also manufactured to clamp the part, including: 60° pointed, 90º pointed, 120° pointed, pie-shaped, standard or square nose, single-step and two-step.  Pointed chuck jaws are used for smaller as well as larger diameter parts.  Standard or square nose, chuck jaws are soft jaws with a square face that can be machined to final size.  Pie-shaped jaws (also round jaws) are full grip jaws used for maximum surface contact on large diameter, thin section and non-cylindrical parts. Single-step jaws are hard top jaws with one locating step to rest the work on.  Two-step jaws are hard top jaws with two locating step to rest the work on.  Single-step and two-step jaws are usually reversible.