Abstract: A collet chuck has separable jaws which are freely slidable in a housing and have inner and outer faces engageable by inner and outer sleeves respectively, to urge the work-engaging ends of the jaws radially outwardly or radially inwardly. The jaws are readily replaceable by others of different effective gripping diameters, without the need for replacement of other chuck parts. The inner sleeve and a thrust element for moving the jaws relative to the inner sleeve are added to the assembly only when outward movement of the jaws is required.