https://alexnld.com/product/drillpro-4pcs-1-4-inch-hex-shank-hss-titanium-coated-step-drill-bit-set-3-12-4-12-4-20-4-32mm/?hilite="Drillpro 6.35mm Hex Shank HSS 4241 Titanium Coated Spiral Step Drill Bit For Hole Drilling Metal"