DEEP DRILLING - BTA SYSTEM USER GUIDE Technical Information - Adjustable Counter Boring Head Diameter Settings Drill diameter is adjusted with an adjust ball for diameter ø25 - ø39.99 mm with the following method. 1. Slide the dimensional guide pad forward and then re-tighten the lock screw at the measuring position. Dimensional guide pad Head body Adjust ball Insert 2. Tighten the adjust screw. Adjust screw Wrench Drill Dia. øDc 3. As the adjust screw moves forward, insert moves in a peripheral direction. 4. Measure the diameter with a micrometer. If the diameter is larger than expected, loosen the adjust screw and insert screw, then re-tighten the insert screw. Repeat the procedure from step 2. Drill Dia. øDc 254 ISCAR