HSS Step Drill Bit - - Our step drill bit is mainly for drilling processing of wood and steel, including metals, aluminum, wood, plastics, etc. Superior Material - - Titanium coating 4241 (HSS) high speed steel reduces friction. They are more durable than uncoated drill bits and HSS (high speed steel) has a long service life Multi-Purpose - - According to the need to process different diameter holes, no need to replace the drill bit and hole positioning, double cutting blade design to cut faster, automatic deburring of the hole when drilling Application - - 4mm precision holes can be drilled into 32mm holes of different sizes Suitable For - - Drilling tools, bench drill. Working in water cooling, can effectively extend the life of the drill bit