A chuck is a workholding device that grips a workpiece with jaws or another clamping mechanism while a lathe spindle or rotary axis turns. The chuck, jaws, actuator and workpiece form one system; safe capacity depends on the specific components and application.
Three-jaw self-centering chucks are common for round stock and repeat work. Independent-jaw chucks allow individual centering or irregular shapes. Collet systems can provide fast, concentric gripping over a defined size range. Power chucks use hydraulic or pneumatic actuation on many CNC lathes.
Chuck capacity is not just nominal diameter. Permissible speed and gripping force can change with jaw mass, jaw position, workpiece geometry, centrifugal force and condition. Follow the chuck and machine manufacturers' manuals; inspection content is not a substitute for a qualified workholding or safety review.
Haas Automation — Lathe Workholding provides builder guidance for workholding setup and inspection. Kitagawa — Power Chuck Instruction Manual illustrates manufacturer-specific installation, maintenance and operating limits. Always use the manual for the exact chuck and machine.
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