Abstract: Testing of integrated circuit components of the silicon wafer type for grading purposes is accomplished by supporting the wafer matrix on a platform type work table which is indexed in an x-y coordinate fashion, with the work table being moved vertically to a test position such that the test probes make contact with a precise predetermined position corresponding to the precise location of that portion of the integrated circuit to be tested. The work table is movable vertically with reference to a predetermined axis and rotatable with respect thereto such that the surface of the table remains perpendicular to the reference axis. The chuck assembly for moving the table includes a housing having a bore whose center forms the axis, with a chuck plate mounted for sliding movement in the bore. The end of the chuck plate is in the form of a flanged spool which receives bearing-eccentric assembly for effecting vertical movement while permitting rotation of the spool and the attached chuck plate.