Abstract: A chuck has a drive shaft extending along and rotatable about an axis and an adjacent nonrotatable housing part adjacent the drive shaft. A chuck body fixed to the shaft and formed with a plurality of guides holding respective jaws shiftable between closely spaced inner positions and widely spaced outer positions. An adjustment sleeve surrounding the body and coupled to the jaws is rotatable about the axis relative to the body to shift the jaws between their positions. A coupling sleeve engaged between the housing part and the adjustment sleeve can shift between a coupled position rotationally locking the adjustment sleeve to the housing part and a decoupled position permitting rotation about the axis of the adjustment sleeve relative to the housing part. A shield sleeve generally rotationally fixed on the housing part coaxially surrounds at least a portion of the adjustment sleeve and chuck body.