1015 OJT 5/32" DRILL CHUCK WITH #0 MORSE ARBOR (For Tail Stock) The 5/32" chuck holds drills from 5/32" (4mm) down to #80 (.0135 or .343mm) It is designated "OJT" which stands for "Zero Jacobs Taper", because it comes with a #0 Jacobs tapered hole in the back to fit the tailstock. This chucks is useful for holding very small drills and their shorter length provides and increase of about 1/2" in working space between centers compared to the 1/4" drill chuck. 1015 Sherline #0 Morse Drill Chuck Instructions