Abstract: An economical rotary index table holds workpieces on machine tool beds and tables, changing rotational position in angular increments with precision. Accurate angular indexing is achieved by a curvic coupling with meshing radial teeth disengageably connecting an axially movable locking plate to the juxtaposed facing rotational worktable member, separate and apart from the drive system. An annular, axially expansible pneumatic chamber is employed to engage and disengage the curvic coupling teeth, alternately locking the worktable in the desired angular orientation, and unlocking it for angular indexing movement. In the preferred embodiment, the movable angular indexing apparatus of the present invention incorporates automatic counting means for precisely determining the degree of rotation and automatic stop means for preventing further rotation when the desired position has been reached.