3 Flats Drill Bits 5/8 reduced shank drill bits are High Speed Steel Drill Bits with 1/2" shank 3 Flatted. 3 Flats Drill Bits have surface treated flutes with a reduced flatted shank. 3 Flats drill bits expand the size range capacity of a portable drill chuck. Common Flute and overall length for minimal adjustment during tool changes. Precision ground for high degree of concentricity between shank and body diameter. 3 Flats Drill Bits are ideal for drilling in low and medium tensile strengh materials. Call Bisco Tool Supply Toll Free 1-866-247-2635 for drill bit questions.