Feature: ? Drill 19 hole sizes. ? This compact set replaces 31 individual drill bits. ? Titanium nitride coating for cooler running. ? Quick-change 1/4" hex shank. ? High Speed Steel for long service life. ? They also help to enlarge existing holes. ? Two-flute design gives you faster, smoother cutting The drills are titanium coated for cooler running. With 3 pcs sets 9 stage + 9 stage + 15 stage step drills.Drill 19 hole sizes. 9 stage: 4-12mm(4, 5, 6, 7, 8, 9, 10, 11, 12mm) 9 stage: 4-20mm(4, 6, 8, 10, 12, 14, 16, 18, 20mm) 15 stage: 4-32mm(4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32mm)
USAGE SUGGESTION: ?To avoid step drill bits become overheated and get burned up due to fast rotary friction, ?we suggest customers to use cutting fluid to keep the bits cold during usage.
