Abstract: A rotary workpiece indexing apparatus including a spindle supported in a housing for rotation about a spindle axis and including a workpiece-mounting surface coaxially disposed at one axial end of the spindle. A spindle lock releasably secures the spindle against rotational motion relative to the housing and includes clamps carried by the housing in circumferentially-spaced locations around the spindle. The clamps are driven to respective clamped positions securing the spindle against rotational motion by clamping the spindle to the housing through the application of clamping forces at respective spaced-apart locations around the spindle.

Abstract: A rotary workpiece indexing apparatus including a spindle supported in a housing for rotation about a spindle axis and including a workpiece-mounting surface coaxially disposed at one axial end of the spindle. A spindle lock releasably secures the spindle against rotational motion relative to the housing and includes clamps carried by the housing in circumferentially-spaced locations around the spindle. The clamps are driven to respective clamped positions securing the spindle against rotational motion by clamping the spindle to the housing through the application of clamping forces at respective spaced-apart locations around the spindle.

Abstract: A machine tool spindle is associated with an adjustable preload mechanism for varying the preload on a bearing set for the spindle the mechanism comprising an annular piston that is selectively pressurized for loading spring(s) carried by a spring retainer that is engageable with the bearing set; and wherein the annular piston is held in an adjusted position by a position locating device including an adjustment member removably supported within a housing for the bearings and selectively engageable with the annular piston; the position locating device having a plurality of adjusted positions selectively engageable with the annular piston for fixing it in one of a plurality of positions for varying the compression of the spring(s) so as to maintain one of a plurality of preloads on the bearing set.