STEP DRILL 9 STEPS NO3 1/4in.-3/4in. HSS ZIRCONIUM COATED STEP DEPTH 1/8in. SHANK 3/8in. - STEP DRILL BITS HIGH SPEED STEEL. CENTURY STEP DRILLS ARE FOR CUTTING IN FERROUS AND NON-FERROUS METALS AND PLASTICS UP TO 1/8in. THICK. DOUBLE FLUTE DESIGN REDUCES CHATTER AND DEBURRS HOLES. ZIRCONIUM COATING REDUCES WARE FOR A LONGER TOOL LIFE. 3-FLAT SHANK REDUCES CHUCK SLIPPAGE. SELF-STARTING TIP.